02 gsmp&o b-en-gsm radio network planning principle-word--201009

GSM Radio network planning principle

Course Objectives:

·Understand capacity planning and calculation methods

·Understand principles for SDCCH and LAC planning

·Grasp link balance calculation

·Grasp various frequency multiplex methods and common

anti-interference technologies

·Understand dual-band networking and parameter settings

i

Contents

1 Capacity Planning ...................................................................................................................................... 1

1.1 Basic Concepts.................................................................................................................................. 1

1.1.1 Traffic Volume and BHCA..................................................................................................... 1

1.1.2 Call Loss Probability and Erlang B........................................................................................ 2

1.2 Capacity Predication ......................................................................................................................... 5

1.2.1 Overview................................................................................................................................ 5

1.2.2 Methods.................................................................................................................................. 5

1.2.3 Traffic Distribution Prediction ............................................................................................. 14

1.3 Capacity Planning Process .............................................................................................................. 15

1.3.1 Work Flow............................................................................................................................ 15

1.3.2 Prerequisites of Capacity Planning ...................................................................................... 16

1.3.3 Calculation of Capacity Planning......................................................................................... 16

1.4 Channel Capacity Planning ............................................................................................................. 17

1.4.1 SDCCH Capacity Planning .................................................................................................. 17

1.4.2 CCCH Configuration Principle ............................................................................................ 20

1.4.3 Recommended CCCH and TCH Allocation......................................................................... 20

1.5 Optimization of Capacity Planning ................................................................................................. 21

1.6 Improvement of Network Capacity................................................................................................. 22

1.6.1 Methods for Improving Network Capacity .......................................................................... 22

1.6.2 Analysis of Methods for Network Capacity Improvement................................................... 23

1.7 Location Area Planning................................................................................................................... 24

1.7.1 Determining LA Edges......................................................................................................... 25

1.7.2 LA Paging Capacity ............................................................................................................. 26

ii

1.7.3 LA Capacity Calculation.......................................................................................................29

1.7.4 Affect of SMS on LA Paging Capacity ................................................................................31

2 Link Budget and Coverage Planning......................................................................................................33

2.1 Purposes of Link Budget .................................................................................................................33

2.2 Calculation of Uplink and Downlink Balance .................................................................................33

2.2.1 Analysis of Parameters in Uplink Budget.............................................................................34

2.2.2 Analysis of Parameters in Downlink Budget ........................................................................43

2.3 Coverage Planning...........................................................................................................................46

3 Frequency Planning..................................................................................................................................51

3.1 Cellular Structure Creation Rule......................................................................................................51

3.2 Interference Models .........................................................................................................................52

3.3 Frequency Reuse Technology and Interference Analysis ................................................................57

3.4 Frequency Reuse in Groups.............................................................................................................57

3.4.1 4 X 3 Frequency Reuse.........................................................................................................57

3.4.2 3 x 3 Frequency Reuse..........................................................................................................61



3.4.5 Multiple Reuse Pattern (MRP) .............................................................................................64

3.4.6 Concentric Cell Technology .................................................................................................68

3.5 Cell Splitting....................................................................................................................................72

3.6 Common Anti-Interference Technologies........................................................................................73

3.6.1 Discontinuous Transmission (DTX) .....................................................................................74

3.6.2 Frequency Hopping (FH)......................................................................................................74

3.6.3 Dynamic Power Control (DPC)............................................................................................78

3.6.4 1 x 3 Reuse + RF Frequency Hopping + DTX + DPC .........................................................78

3.7 Summary of GSM Frequency Allocation ........................................................................................79

iii

3.8 Neighbor Cell Planning................................................................................................................... 81

3.8.1 Planning Principles............................................................................................................... 81

3.8.2 Case Analysis ....................................................................................................................... 84

3.8.3 BSIC Planning...................................................................................................................... 86

4 Dual Band Technology ............................................................................................................................. 91

4.1 Structure of Dual Band Networks ................................................................................................... 91

4.1.1 Shared HLR/AUC, EIR, OMC and SC ................................................................................ 91

4.1.2 Shared Switching Subsystem ............................................................................................... 91

4.1.3 Shared Switching Subsystem and BSC................................................................................ 92

4.1.4 Shared Network Subsystem ................................................................................................. 92

4.2 Dual Band Network Planning ......................................................................................................... 94

4.2.1 Requirement Analysis .......................................................................................................... 94

4.2.2 Coverage Planning ............................................................................................................... 95

1 Capacity Planning

1.1 Basic Concepts

1.1.1 Traffic Volume and BHCA

The time when a user initiates a call and the duration are random but comply with a

rule in some degree. To reflect the frequencies of giving calls and call duration, the

term traffic is introduced. Traffic usually refers to the volume of calls in the given

period, often measured in Erlang (one Erlang means the traffic load where one call

circuit is occupied completely for one hour, or the traffic load where two call circuits

are occupied completely for half an hour).

The average traffic ρ of a user is calculated by the following formula:

36001÷×=

μλρ

where, λ , also called call reach rate, stands for the number of calls orginated by each

user within the unit time. μ1

stands for the average call duration of each user and the

unit is second. μ stands for the call completion rate.

The traffic of each cell, that is, A , is expressed in the following equation:

dSA ρ=

where, ρ stands for the average traffic per user (Erlang / user), stands for user

density (number of users / km2), and

dS stands for cell area (km2).

In actual situations, traffic changes over time. Even if long time changes are ignored, it

can still change over a short period, for example, by day or week.

The hour when the traffic is the largest is called busy hour. The call amount in the busy

hour is known as Busy Hour Call Attempt or Busy Hour Calling Amount (BHCA).

Busy-hour traffic is calculated by the following formula:

1

36001÷×=

μρ BHCABH


In network planning, busy-hour traffic is always used as a design index. If a GSM

network can deal with the busy hour traffic, it is sure to deal with common traffic.

Busy-hour traffic per user is also used in network planning, which is expressed in the

following formula:

360010 ÷××=

μβαρ

where, 0ρ stands for busy-hour traffic per user, α stands for the number of calls in

a day per user, and β stands for the busy hour factor (ratio of busy-hour traffic to day

traffic).

Thus, busy-hour traffic can be:

NBH

2

×= 0ρρ

where N stands for the number of users.

This formula is quite important in capacity planning. Obviously, the planned capacity

should be greater than the expected BHρ .

The average busy hour traffic per user of a system can be obtained from the statistical

data. The previous formula shows that total busy hour traffic divided by the number of

subscribers in busy hour on the VLR is the average busy hour traffic per user of the

system. In network planning, leave margins for the average busy hour traffic per user

of the system.

In China, the experience value of average busy hour traffic per user is 0.025~0.03erl /

user. In other words, 6 calls (incoming and outgoing) are allowed for each user and

each call lasts for 2 minutes in average.

1.1.2 Call Loss Probability and Erlang B

Call loss, or congested call, refers to call lost due to disconnection after all the channels

occupied in mobile telecommunications system. Call loss probability indicates the

probability of call congestions.

Grade of service (GOS), expressing the congestion level, is used to define the

congestion probability. In GSM network planning, the TCH GOS is 2% or 5%.

According to Public Mobile Telephony Network Technology Mechanism, the radio

channel loss probability should be less than or equal to 5% (in areas with high traffic

1 0BCapacity Planning

density, 5%). Generally, public mobile telephone network is a system with call losses.

Through a cell (or sector) is designed with the assumption that idle a call attempt

cannot get an idle channel at the first time and keep on originating call attempts, the

sector sharing or directed retry function guides the congested call to another sector for

idle channels and thus leave the original sector to be accessed. Therefore, for each

sector, a call is discarded once no idle channel is available. As a result, the total

congestion characteristic is close to the requirement in Erlang-B call rule.

According to the Erlang call loss formula and calculation table, a call must have the

following features:

1. Any two calls are independent of each other (The calls are random).

2. Each call has the same probability in time.

3. When a call cannot obtain idle channels, this is taken as call loss, instead of

waiting for some time for idle channels.

The Erlang-B formula is as follows:

This formula shows the relationship between call loss probability (B), traffic (A), and

number of channels (n). Traffics with different loss probability and different channels

can be calculated according to the Erlang formula and summarized into an Erlang-B

table. Then, when any two items are known, the third item can be calculated.

The following table is an Erlang-B table calculated by the Erlang formula:

N 1.0% 1.2% 1.5% 2% 3% 5% 1 0.0101 0.0121 0.0152 0.0204 0.0309 0.0526 2 0.153 0.168 0.19 0.223 0.282 0.381 3 0.455 0.489 0.535 0.602 0.715 0.899 4 0.869 0.922 0.992 1.09 1.26 1.52 5 1.36 1.43 1.52 1.66 1.88 2.22 6 1.91 2 2.11 2.28 2.54 2.96 7 2.5 2.6 2.74 2.94 3.25 3.74 8 3.13 3.25 3.4 3.63 3.99 4.54 9 3.78 3.92 4.09 4.34 4.75 5.37

10 4.46 4.61 4.81 5.08 5.53 6.22 11 5.16 5.32 5.54 5.84 6.33 7.08 12 5.88 6.05 6.29 6.61 7.14 7.95

3


4

N 1.0% 1.2% 1.5% 2% 3% 5% 13 6.61 6.8 7.05 7.4 7.97 8.83 14 7.35 7.56 7.82 8.2 8.8 9.73 15 8.11 8.33 8.61 9.01 9.65 10.6 16 8.88 9.11 9.41 9.83 10.5 11.5 17 9.65 9.89 10.2 10.7 11.4 12.5 18 10.4 10.7 11 11.5 12.2 13.4 19 11.2 11.5 11.8 12.3 13.1 14.3 20 12 12.3 12.7 1 3.2 14 15.2 21 12.8 13.1 13.5 14 14.9 16.2 22 13.7 14 14.3 14.9 15.8 17.1 23 14.5 14.8 1 15.2 15.8 16.7 8.1 24 15.3 15.6 16 16.6 17.6 19 25 16.1 16.5 16.9 17.5 18.5 20 26 17 17.3 17.8 18.4 19.4 20.9 27 17.8 18.2 18.6 19.3 20.3 21.9 28 18.6 19 19.5 2 0.2 21.2 22.9 29 19.5 19.9 20.4 21 22.1 23.8 30 20.3 20.7 21.2 21.9 23.1 24.8 31 21.2 21.6 22.1 22.8 24 25.8 32 22 22.5 23 23.7 24.9 26.7 33 22.9 23.3 23.9 24.6 25.8 27.7 34 23.8 24.2 24.8 25.5 26.8 28.7 35 24.6 25.1 25.6 26.4 27.7 29.7 36 25.5 26 26.5 27.3 28.6 30.7 37 26.4 26.8 27.4 28.3 29.6 31.6 38 27.3 27.7 28.3 29.2 30.5 32.6 39 28.1 28.6 29.2 3 0.1 31.5 33.6 40 29 29.5 30.1 31 32.4 34.6 41 29.9 30.4 31 31.9 33.4 35.6 42 30.8 31.3 31.9 32.8 34.3 36.6 43 31.7 32.2 32.8 33.8 35.3 37.6 44 32.5 33.1 33.7 34.7 36.2 38.6 45 33.4 34 34.6 35.6 37.2 39.6 46 34.3 34.9 35.6 36.5 38.1 40.5 47 35.2 35.8 36.5 37.5 39.1 41.5 48 36.1 36.7 37.4 38.4 40 42.5 49 37 37.6 38.3 39.3 41 43.5 50 37.9 38.5 39.2 40.3 41.9 44.5 51 38.8 39.4 40.1 41.2 42.9 45.5 52 39.7 40.3 41 42.1 43.9 46.5 53 40.6 41.2 42 4 3.1 44.8 47.5 54 41.5 42.1 42.9 44 45.8 48.5 55 42.4 43 43.8 44.9 46.7 49.5 56 43.3 43.9 44.7 45.9 47.7 50.5 57 44.2 44.8 45.7 46.8 48.7 51.5 58 45.1 45.8 46.6 47.8 49.6 52.6 59 46 46.7 47.5 48.7 50.6 53.6 60 46.9 47.6 48.4 49.6 51.6 54.6


5

N 1.0% 1.2% 1.5% 2% 3% 5% 61 47.9 48.5 49.4 50.6 52.5 55.6 62 48.8 49.4 50.3 51.5 53.5 56.6 63 49.7 50.4 51.2 52.5 54.5 57.6 64 50.6 51.3 52.2 53.4 55.4 58.6

1.2 Capacity Predication

1.2.1 Overview

ented on the basis of initial and future traffic

distribution obtained in various ways.

The following factors should be considered in capacity prediction:

1. Income situation

2. Distribution of users with different ages and incomes

3. Economic development level of the area

4. Service competition

5. Special offers or reduction of mobile service charges

6. Advertising and vision of the operator

1.2.2 Methods

1. Short-term prediction (1 – 2 years) and long-term prediction (3 – 5 years)

2. Popularization rate

3. Growth trend prediction

4. Growth curve

5. Quadratic curve

1.2.2.1 Growth Trend Prediction

In cellular network planning, the capacity requirement must be determined at first, as it

is the basic of the whole engineering design. Capacity requirement involves the number

of users in the system and the corresponding traffic. The purpose of capacity prediction

is to give the actual and future capacity requirement to help estimate the required

channels. Network planning is implem

Mobile communications technology, especially GSM and other 2nd generation mobile


6

communications, is developing rapidly in the whole world. In some developed

European countries, mobile phones still grows even through the popularization rate

reaches a certain level, for example, above 50% in Finland. In 1997, some countries,

such as Sweden, Norway, and Denmark, the rate was close to 30% and the annual

growth rate reached 70%-80%. In China, the number of mobile phone users doubles

the growth rate for continuous 10 years. In 1996, mobile phone numbers occupy 18%

of the allocated numbers in the whole country, 29% in 1997, and 37% in 1998. This

proves that the mobile phone market is prosperous. The following table shows the

situation of mobile users in China:

Ta wth obi scr C N rs

ble 1.2-1 Gro of M le Sub ibers in hina in ine Yea

Year 1990 1991 1992 1993 1994 1995 1996 1997 1998

Subscribers

(Unit: 10,000) 1.53 4.75 17.69 63.82 156.8 362.9 684.8 1364 2496

Annual

growth (%) 160 272 261 146 132 89 99 83

According to the prediction from related experts, the annual growth of mobile

subscribers in China will reach over 40% after 2000, and the net growth rate of

subscribers in each year will go down stably. The average growth rate of mobile

subscriber between 1998 and 2010 will be 29.28%. The prediction data are shown as

diction of the growth of mobile subscribers in China in the

near and medium terms.

Table 1.2-2 wt ob scr n C n T rs

below.

Table 1.2-2 shows the pre

Gro h of M ile Sub ibers i hina i en Yea

Year 1998 1999 2000 2001 2002 2003 2004 2005

Subscribers (Unit: 2254 3432 5053 7016 9219 11861 14582 17680

10,000)

Growth quantity (Unit:

10,000) 931 1178 1621 1963 2203 2642 2721 3098

Growth rate (%) 70.33 52.26 47.23 38.85 31.40 28.66 22.94 21.25

According to the comparison and analysis of the subscriber growth in 1998 (24.96

million) and August 1999 (33.05 million), we find that the data in Table 1.2-2 are

somewhat conservative, but the prediction results are in good line with the

development objectives specified in the Post & Telecom 1998-2002 Rolling Plan. The


7

growth is appropriate and has some values of reference.

Table 1.2-3 show

1.2-3 Growth of Subscribers of Previo rs in a Place

s the growth of mobile subscribers in an area.

Table us Yea

1992 1993 1994 1995 Place Number of

Subscribers Rate

Growth Number of

Subscribers

Growth

Rate

Number of

Subscribers

Growth

Rate

Number of

Subscribers

Growth

Rate

HX 1085 3033 180 7367 143 14539 97

1996 1997 1998 1999

31180 114 49761 60 93922 89 177659 89

In the area, the subscriber growth rate did not fall year by year during 1992 ~ 1999, but

fluctuated, without any particular reason. Therefore, we take the growth rate for 2000 is

taken as the average of 1995-1999, that is 70%, and 40% for 2001, slightly lower than

the national average of 38.85%. This matches its status as a medium-sized city. We take

mobile subscriber number for the area

according to the trend pre

Ta -4 Prediction of Mobile for the Area

the growth rate of 30% for 2002.

Table 1.2-4 shows the prediction of the

diction method.

ble 1.2 Subscribers

2000 2001 2002 Place

Number of

Subscribers

Growth

Rate (%)

Number of

Subscribers

Growth

Rate (%)

Number of

Subscribers

Growth

Rate (%)

HX 302021 70 422829 40 549678 30

1.2.2.2 Populatio

tries in the world

ing years

e area

n Penetration Rate Method

When focusing on penetration rate, consider the following factors:

1. Mobile phone penetration rate of the medium developed coun

2. Expected penetration rate in the country for upcom

3. Current penetration rate of the carrier in th

4. Economic development status in the area

5. Potential factors that affect the purchasing ability

During the mobile communication development in China, an important event is the

establishment of China Unicom. As the second telecom operator in China, its growth in


8

recent years leaves much to be desired, with still a low market share. However, it is

because of the appearance of China Unicom, China Telecom made greater efforts in

building the GSM network by greatly reducing the access charges. The building of the

GSM systems, the introduction of competition, and the decrease of the charges

contribute to the prosperity of the mobile communication industry in China. In terms of

technology, the mobile communication will evolve to the 3G mobile communication

system. In terms of service types available, it will also provide data services of various

rates in addition to global all-rounded voice services for individual subscribers. We can

see that as the charges decrease and new technologies are introduced, the future mobile

communication will be based on integrated networks bearing multiple services oriented

to individual subscribers. The expansion of services will attract more subscribers to the

f

26.61% for mobile phone, which is still growing at 43.24%, as shown in Table 1.2-5.

Table 1 Growth a f Mo Hong 98

Year Mobile Subscribers Growth Rate (%) enetration Rate (%)

wireless network.

Currently, the penetration of mobile phone has reached over 50% in Finland, but it is

still growing. In 1997, some developed counties such as Sweden, Norway, and

Denmark have penetration up to 30%, but they still grow at a high rate, with an annual

growth of 70% ~ 80%. In 1998, Hong Kong SAR of China has a penetration rate o

.2-5 nd Penetration Rates o bile Subscribers in Kong During 1992-19

P

1992 189664 3.3

1993 233324 23.02 4.02

1994 290843 24.65 4.93

1995 484823 66.7 8.03

1996 798373 64.67 12.97

1997 1143566 43.24 18.58

1998 1638010 43.24 26.61

Table 1.2-6 shows the penetration rates of mobile phone of China from 1995 to 2002.

ble 1.2-6 etra ates of fro to Ta Pen tion R of Mobile Phone China m 1995 2002

Year 1995 1996 1997 1998 1999 2000 2001 2002

Subscribers (Unit: 684.8 1364 2496 3432 5053 7016 9219

10,000) 362.9

Penetration Rate

(%) 0.302 0.57 1.14 2.08 2.64 3.89 5.40 7.69


9

According to the prediction of experts, the penetration rate of mobile phone in China

will reach 10 per 100 persons in two or three years. Lanzhou is an important city in the

northwest of China, and its economic development level is among the rank of the

medium-developed cities in China. Its penetration rate of mobile phone has now

reached 6% and the penetration rate of 10 handsets/100 persons is to be achieved two

or three years earlier. In other words, the penetration rate will reach 10% in 2000. Table

1.2-7 shows the penetration rates of Gansu and China as a whole in recent years.

Table 1.2-7 Penetration Rates of Mobile Phone in an Area

1996 1997 1998 1999 Place Number of

Subscribers

Penetration

Rate (%)

Number of

Subscribers

Penetration

Rate (%)

Number of

Subscribers

Penetration

rate (%)

Number of

Subscribers

Penetration

Rate

GL 31180 1.13 49761 1.77 93922 3.25 177659 6.12

The penetration rate of the area has reached and exceeded the national average ever

since 1998. This matches the status of the city as a provincial capital city. In 1999, the

penetration rate of the area is nearly three times higher than the national average.

According to this percentage, the penetration rates of Lanzhou in 2000-2002 will reach

10%, 15%, and 20% respectively.

The penetration rates of Shanghai and Beijing have exceeded 15%. As a medium-sized

city, it is possible for its penetration rate to lag behind Beijing for two years (15% for

2001). Therefore, the penetration rates for the future three years for the area can be

taken as 10%, 15% and 20%.

Currently, China Unicom has a market share of about 10% throughout the country, and

its objective is 20-30%. After the splitting of China Telecom, China Mobile will take

on a new look in meeting the competition from China Unicom. It is estimated that the

growth in market share of China Unicom will slow down. Therefore, we predict that

the market share of China Unicom in the area will be 10%, 15% and 20%. In addition,

as the market develops, the government will gradually remove its support for China

Unicom, and the market will become normalized. In future, what attract subscribers are

service quality and new services available. Table 1.2-8 shows the population

development of the area in 2000-2002.


Table 1.2-8 Population Development of Lanzhou in 2000-2002

1996 1997 1998 2000 2001 2002

No. Place Population

(10,000

persons)

Population

(10,000

persons)

Population

(10,000

persons)

Natural

Growth

(‰)

Population

(10,000

persons)

Population

(10,000

persons)

Population

(10,000

persons)

1 Lanzhou 276.09 280.46 288.56 5.90 291.98 293.70 295.43

According to the population estimation data and the market share of China Mobile in

the area, the population penetration method is used to predict the number of mobile

subscribers for three prefectures/cities in the province for 2000-2002, as shown in

Table 1.2-9.

Table 1.2-9 Development of Mobile Subscribers of Three Prefectures/Cities of Lanzhou for 2000-2002

2000 2001 2002

Place

Population (10,000

persons)

Penetration Rate (%

)

Market Share (%

)

Num

ber of Subscribers

Population (10,000

persons)

Penetration Rate (%

)

Market Share (%

)

Num

ber of Subscribers

Population (10,000

persons)

Penetration Rate (%

)

Market Share (%

)

Num

ber of Subscribers

GL 291.98 10.0 90 262778 293.70 15.0 85 374465 295.43 20.0 80 472689

GW 192.42 0.8 98 14448 194.50 1.1 92 20564 196.59 1.5 88 26510

DX 293.63 0.5 100 13236 296.40 1.0 98 29459 299.19 1.8 90 47336

1.2.2.3 Growth Curve Method

The research on prediction methods finds that the development of equipment and

growth of market demands has similarities in some degree. For example, during the

development of the local calls, when the penetration reaches a certain level, it gradually

reaches saturation, instead of increasing simply in the exponential or linear trend. For

such saturation curve, common equations are Gompertz curve equation and Logistic

curve equation. For this prediction, the Gompertz curve equation is used.

ktbet LeY

−−=

10


The shape of the Gompertz curve is as follows:

t

Yt

L

t

Yt

L

The parameter can be determined in the following ways:

1. Determine the saturation peak L.

2. Perform logarithm operations to both sides of the equation, which is then changed to lnln (L/Yt) =lnb-kt. Take A=lnb, yt’= lnln(L/yt), then the equation becomes a

linear expression: yt’=A+Bt. With the least square method, user can resolve A and

B of the linear equation.

Step 1: Determine the saturation peak L.

Mobile phones have ready mobility. Population mobility is related to ages. The

population in the 15-64-age range may have higher mobility, and is more likely to use

mobile phones. On the other hand, the population within 0-14 ages and above 65 ages

is less mobile, and fixed telephone is nearly enough to meet their communication needs.

Therefore, when user predict the number of subscribers, user should focus userr

attention to the needs of the persons in this age range. According to the trend in the

change of the population age structure in China (错误！未找到引用源。), the

population of 15-64 ages accounts for 67.7% of the total in 2000. We can take this

percentage as the saturation value (L) of mobile phone penetration..

The following table shows the trend of age structure change in China from 1995 to

2020:

Total Population 0-14 Ages 15-64 Ages 65 Ages and Above

Year Population

Percentage

Population

(10,000

persons)

Population

percentage

Population

(10,000

persons)

Population

percentage

Population

(10,000

persons)

Population

percentage

Population

(10,000

persons)

1995 100 121121 26.7 32303 66.6 80727 6.7 8091

1996 100 122248 26.4 32273 66.8 81662 6.8 8313

1997 100 123385 26.1 32203 67 82668 6.9 8514

1998 100 124532 25.8 32129 67.2 83686 7 8717

11


Total Population 0-14 Ages 15-64 Ages 65 Ages and Above

Year Population

Percentage

Population

(10,000

persons)

Population

percentage

Population

(10,000

persons)

Population

percentage

Population

(10,000

persons)

Population

percentage

Population

(10,000

persons)

2000 100 126859 25.3 32105 67.7 85841 7 8913

2005 100 131438 22.9 30099 69.5 91350 7.6 9989

2010 100 136183 20.7 28248 71.1 96799 8.2 11136

Step 2: Calculate the values of A and B. Take the city GL as an example:

Year SN (t) Number of

Users (Yt)

Yt'=lnln(L/Yt) Ytt'=t*Yt' t2

1996 1 31180 1.422966 1.422966042 1

1997 2 49761 1.303444 2.60688764 4

1998 3 93922 1.114066 3.342198523 9

1999 4 177659 0.879344 3.517377014 16

Sum ∑ 10 352522 4.719820 10.88942922 30

Use the least square method to get the values of A and B and set up a mathematical

model:

5.24

10,4 === tn

te 182024.0129540. −

12954.5== Ae

t ey 51976705 −=

,182024.0=−= bBK

63502.1*' =−= tByA t

182024.0*

***22

''

−=−−

=∑

∑tnt

ytnytB tt

471982.4' =ty

Estimate the user quantity in GL in 2000. Introduce t=5 into the above formula to obtain y2000=250804. Introduce t=6 to the formula to obtain y2001=353629. Introduce

t=7 to the formula to obtain y2002=470899.

Use the growth curve method to predict the number of mobile subscribers for the GL

area in 2000-2002.

12


Number of Users No. City

Year 2000 Year 2001 Year 2002

1 GL 250804 353629 470899

Any telecom service involves four stages: initiation, growth, saturation and decline.

For the services with this feature, user can use the growth curve method for prediction.

This method is very suitable for medium-term prediction.

1.2.2.4 Curve of Second Order Method

Many engineering problems need several groups of experimental data of two variables

to find their relation represented by an approximate expression, called as empirical

formula. After an empirical formula is set up, users can combine their experiences in

production process or experiments with the theory during analysis. When forecasting

mobile users, users can set an empirical formula based on the situations in the past

years and use the formula to forecast the future trend.

For the growth of mobile users in a city, the empirical formula can be:

y ax bx c= + +2

where, x- is the year and y- is the number of mobile communications users.

Input the number of mobile users in the past years. Use the least square method to

select the constants a, b, and c.

σ 2 2 2

1

= − + +=∑ [ ( )]y ax bx ci

N

Obtain the values of a, b and c according to the following formulas:

∂σ ∂2 2 2

1

0a y ax bx c xi i i ii

N

N

= − + + ==∑[ ( )]

∂σ ∂

∂σ ∂

2 2

1

2 2

1

0

0

b y ax bx c x

c y ax bx c

i i i ii

i i ii

N

= − + + =

= − + + =

=

=

∑

∑

[ ( )]

[ ( )]

Introduce the number of mobile subscribers of GL in 1996-1999 to the formula and

obtain the values of a, b and c. Then, user can predict the number of the mobile

subscribers of the city in the coming three years.

Use the curve of second order method to predict the number of mobile subscribers of

13


14

GL for 2000-2002, as shown in the following table:

Number of User SN City

Year 2000 Year 2001 Year 2002

1 GL 287371 430790 606184

1.2.3 Traffic Distribution Prediction

The traffic distribution of the mobile cellular services in China has the following

characteristics: The traffic is mainly concentrated in medium and big cities, and there

are traffic dense areas in the downtown areas of a city. In such areas, there are usually

local higher traffic hot areas. In addition, the traffic volumes in the suburbs are low. If

these factors are not considered in network building, with sites distributed evenly, the

resources in the low-traffic areas are wasted, while the capacity in the heavy-traffic

areas is insufficient, affecting the Return On Investment (ROI) of the network and the

service quality. To solve this problem, user must predict the traffic density distribution,

and deploy the sites and configure the channels according to the prediction results.

In earlier phases, use the statistical data of population distribution, income situation,

vehicle usage, and telephone usage to forecast the geographical distribution of traffic

demand. After the network is constructed, obtain more accurate traffic distribution data

of the serving area based on the traffic statistics by the OMC, which can serve as

reference in network optimization and expansion.

Three methods for forecasting traffic density are available:

1. Percentage distribution method

2. Linear forecast

3. Linear forecast in conjunction with manual adjustment

Percentage distribution method:

This method divides the serving area into high density area, medium density area, and

low density area (for example, high density district, common district, and suburbs), and

allocate the forecasted percentage of mobile users to each density area. Then, get the

number of users in the density area by multiplying the forecasted number by the

percentage, and get the user density by equally dividing the area.

Linear forecast: Use the planning software and electronic map to distribute the existing

busy hour traffic to each cell. Input the total traffic of the target year in the system.


15

Then, the planning software generates the traffic distribution graph of the target year

based on the existing traffic distribution.

1.3 Capacity Planning Process

From the previous prediction on the capacity and traffic distribution, the total traffic

demand and the traffic distribution and area of each special district in the serving area

can be obtained.

Correctly predict the user development in the planned area. Select an appropriate

frequency multiplexing method based on the available band resources. In combination

of the configuration capacity of the wireless products and features of wireless

environment/user distribution in the planned area, determine the site types of different

areas. At last, get the number of sites that meet the capacity requirement.

The result of capacity planning is as follows:

1. Number of base stations that meet the traffic requirement in the planned area

2. Site configuration of each base station

3. Number of TCHs provided by each sector, traffic, and user quantity

4. Number of TCHs provided by each base station, traffic, and user quantity

5. Number of TCHs provided by the entire network, traffic, and user quantity

The previous procedure is an initial planning. In later radio coverage planning and

analysis, some sites may be added or reduced. Then, the number of bases stations and

site locations can be finally determined.

1.3.1 Work Flow

Work flow is as follows:

Predict capacity → Analyze traffic distribution → Determine site configuration →

Determine site quantity → Determine site lausert

1. In initial phase of network development, less capacity is required. Consider the

basic coverage. The site is generally small and the network structure is simple.


16

2. In middle phase of network development, comparatively more capacity is required

and higher coverage requirement must be met. This can be realized through site

expansion and cell splitting. The network structure is comparatively complex.

3. In the advanced phase of network development, large capacity is required and no

blind spots are allowed in the coverage. This can be realized through adding micro

cells and deploying dual band networks. The network structure is complex.

1.3.2 Prerequisites of Capacity Planning

1. Total traffic of the planning area and traffic distribution prediction

2. GOS, that is, congestion rate or loss probability

3. Available band resource and sequence multiplexing mode

1.3.3 Calculation of Capacity Planning

1. Estimate the number of base stations, site types, and capacity in the capacity limited

districts.

Estimate the largest site types of various districts based on the frequency

resources and frequency multiplexing mode

Get the capacity of each base station based on the traffic model

Get the number of base stations required by dividing the total traffic by the

maximum capacity (sum of each cell)

2. Estimate the number of base stations, site types, and capacity in the coverage limited

districts.

Based on the district type, divide the area by the corresponding coverage area

(estimated) to get the total number of base stations that meet the coverage

requirement.

Multiply the cell coverage area (estimated) by the corresponding traffic

density to get the traffic that meets the cell requirement.

Estimate the number of required voice channels and control channels by

referring to the Erlang-B table.

Divide the sum of the two numbers by 8 to get the frequency required by the

cell.


17

3. Output the result: number of base stations, site type.

1.4 Channel Capacity Planning

1.4.1 SDCCH Capacity Planning

1. SDCCH structure and bearing service type

The SDCCH has two types of structure: SDCCH/4 (used in mixed control channel

structure) and SDCCH/8 (used in separate control channel structure).

In a GSM network, the cell broadcast service can be activated to broadcast the

short messages in the SMS center to all users registered in the location area. After

the broadcast service is activated, each cell broadcast cell (CBCH) must seize one

SDCCH.

Combined channel:

BCCH + CCCH + SDCCH/4 (TS0)

Non-combined (separate) channel:

BCCH+CCCH (TS0) + X x SDCCH/8 (1 – 7 timeslots of BCCH frequency or

timeslots of any other frequencies)

In network planning, configure X according to the number of frequencies (that is,

number of TCHs), and the ratio of TCH traffic to SDCCH traffic.

The SDCCH mainly bears the following services:

1. Location update, periodic location update

2. IMSI attach/detach

3. Call setup

4. SMS

5. Fax and supplementary services

The seizure time of above events vary depending on the network structure and

traffic model.

2. SDCCH GOS and capacity ratio of SDCCH to TCH

When defining the number of SDCCHs, the congestion rate of both SDCCHs and


TCHs must be considered. The reason is that during a conversation, the SDCCH is

required to transfer call connection signaling and the TCH is required to transfer

voice and data messages. For the setup of a conversation, the SDCCH and TCH

are of the same importance. However, the SDCCH can use the physical channel

more effectively. In such a case, the congestion rate of SDCCH should be lower

than that of TCH.

The principle for determining SDCCH congestion rate is that the congestion rate

of SDCCH should be 25% of that of TCH. If the actual ratio is greater than 25%,

more SDCCHs should be defined. For the SDCCH/4 configuration, the congestion

rate of SDCCH should be 50% of that of TCH.

The SDCCH/8 GOS is 1/4 of that of TCH. The SDCCH/4 GOS is 1/2 of that of

TCH.

For example, if the TCH GOS is designed to be 2%, then:

SDCCH/4 GOS = 1%

SDCCH/8 GOS = 0.5%

According to the BSC channel assignment algorithm, signals can be transferred on

TCH, and messages of early assignment and dynamic SDCCH allocation can also

be transferred on TCH. This function of immediately assigning TCH to transfer

call connection signals during the call setup process can reduce call losses and

improve the GOS.

3. SDCCH capacity prediction

SDCCH traffic is predicted on the basis of common traffic model. The SDCCH

traffic model varies from network to network and from traffic model to traffic

model. During SDCCH planning, use the traffic model provided by the operator.

In case that the traffic model is known, the traffic per user of different mobile

phone acts can be calculated.

The calculation formula is as follows:

18

(mE/user) 3.6

durationuserrateesectuiontimbusytimeexTraffic × ×=

The calculation process (considering only location update, SMS, and call setup) is

as follows:


19

Known conditions:

Location update factor: L

Ratio of SMS to calling amount: S

Average call duration: T

Cell traffic: Acell

Location update duration: TLU

Call setup duration: TC

SMS duration: TSMS

SDCCH clear-down protection duration: TG

Then:

Number of cell calls in busy hour: λCALL =Acell x 3600/T

Number of location updates in busy hour: λLU =L x Acell x 3600/T

Number of SMSs in busy hour: λSMS =S x Acell x 3600/T=6Acell

Then, the traffic that the SDCCH needs to bear is as follows:

ASDCCH=[λCALL x TC +λLU x (TLU + TG)+ λSMS x (TSMS +TG)]/3600

After the traffic that the SDCCH needs to bear is obtained, refer to the Erlang-B

table according to the GOS and acquire the number of SDCCHs.

4. Recommended SDCCH configuration

TRX

Quantity

Channel

Quantity

SDCCH

Structure

SDCCH

Quantity

TCH Quantity TCH Traffic

(GOS=2%)

1 8 SDCCH/8 1 6 2.28

2 16 SDCCH/8 8 14 8.2

3 24 2*SDCCH/8 16 21 14.9

4 32 2*SDCCH/8 16 29 21

5 40 2*SDCCH/8 16 37 28.3

6 48 2*SDCCH/8 16 45 35.6

7 56 3*SDCCH/8 24 52 43.1

8 64 3*SDCCH/8 24 60 49.6

9 72 3*SDCCH/8 24 68 57.2

10 80 4*SDCCH/8 32 75 64.9


20

1.4.2 CCCH Configuration Principle

1. CCCH structure

a. CCCH consists of Access Grant Channel (AGCH) and Paging Channel (PCH),

Random Access Channel (RACH).

b. Uplink channel sends channel request message. The downlink channel sends

access granted (that is, immediate assignment) message and paging message.

c. All the TCHs of each cell share the CCCH.

2. CCCH configuration

CCCH-CONF Meaning Number of CCCH Message

Blocks of a BCCH Multiframe

1 basic physical channel used for CCCH 0

Not combined with SDCCH

9


Combined with SDCCH

3



18



27



36

1.4.3 Recommended CCCH and TCH Allocation

In combination with SDCCH recommended configuration and CCCH channel structure,

suppose that the average busy hour traffic is 0.025Erl/user and call loss GOS of radio

channel is 2%, refer to the Erlang-B table to acquire the maximum traffic provided by

each cell configured with different number of frequencies. Use this value to calculate

the maximum number of users supported by each cell, and get the maximum number of

users supported by the system.

CCCH Capacity

(Erlang)

Frequency

Quantity

Channel

Quantity

Channel Structure

CCH

Quantity

(SDCCH)

TCH

Quantity

GOS=2%1 8 (1BCCH+9CCCH)+SDCCH/8 1 6 2.28 2 16 (1BCCH+9CCCH)+SDCCH/8 1 14 8.2 3 24 (1BCCH+9CCCH)+2*SDCCH/8 2 21 14.9 4 32 (1BCCH+9CCCH)+2*SDCCH/8 2 29 22


CCCH Capacity

(Erlang)

Frequency

Quantity

Channel

Quantity

Channel Structure

CCH

Quantity

(SDCCH)

TCH

Quantity

GOS=2%5 40 (1BCCH+9CCCH)+2*SDCCH/8 2 37 28 6 48 (1BCCH+9CCCH)+2*SDCCH/8 2 45 35.5 7 56 (1BCCH+9CCCH)+3*SDCCH/8 3 52 42.12 8 64 (1BCCH+9CCCH)+3*SDCCH/8 3 60 49.64 9 72 (1BCCH+9CCCH)+3*SDCCH/8 3 68 57.2

10 80 (1BCCH+9CCCH)+4*SDCCH/8 4 75 64.9

Based on the traffic model and GOS, obtain the channel configuration and traffic by

referring to the configuration recommended in the above table.

1.5 Optimization of Capacity Planning

The initial capacity planning is performed on the basis of prediction and assumptions.

With the implementation of the plan and network construction, the traffic model may

change, which has a direct effect on the capacity planning. Therefore, the initial plan

should be adjusted and optimized according to the actual situation. This can help future

network optimization and reduce investment cost.

The recommended calculation method of traffic model is as follows:

Adjust and optimize the capacity planning in any of the following situations:

1. User behavior change: It refers to the user capacity deviation because of user

movement in the local network. User behaviors can be classified into user traffic

behaviors and user movement behaviors, which respectively result in the

deviation of user traffic from macroscopical and microcosmic aspects. The

fluctuation factor (generally 1.05 - 1.1) is used to measure the degree of affect of

traffic deviation on the network. The network margin resulted from the deviation

cannot be saved in network construction.

2. Channel configuration nonlinear effect: Channel configuration is calculated by

frequency amount rather than linear configuration based on requirements, which

leads to channel wastage. For example, if only 9 TCHs are required for a cell

after the calculation, 2 TRX (14 TCHs) must be configured. According to the

21


22

research result, the nonlinear configuration reduces the network utilization by

20% - 25%, with 20% for provincial capitals, 25% for common cities, and 30%

for backward districts with many single carrier cells.

3. At initial phase of network construction, if large numbers of traffics are

congested, the traffic added for solving congestion should be taken into

consideration when predicting the traffic model.

4. For different phases of network construction, periodically analyze and predict

the traffic model.

5. Take the user activation ratio (make sure the value is reasonable) into

consideration. This can reduce the traffic module value of each user, reduce cost,

and remedy the effects resulted from uncontrollable factors.

6. Other factors

1.6 Improvement of Network Capacity

In the initial phase of GSM network construction, configuring little number of base

stations and small site type can meet the requirement of limited users. The prediction

focus is coverage. With the increase of user quantity and promotion of new services,

the cell congestion is more and more serious. To improve network quality, the network

capacity must be improved. The sequence of capacity design priority is as follows:

Compact base station → base station expansion&cell splitting → micro cells for hot

areas → dual band network → half rate

1.6.1 Methods for Improving Network Capacity

Split cells

Use aggressive frequency reuse pattern

Add micro cell devices

Expand frequency band

Half rate


23

1.6.2 Analysis of Methods for Network Capacity Improvement

1.6.2.1 Cell Splitting

1. During the initial phase of GSM network construction, the coverage is the main

problem, with large antenna mount height, spaces between base stations, and cell

coverage radius.

2. With the development users, the original cells can be split into smaller cells with

less coverage area.

3. Cell coverage radius can be reduced by minimizing the space between base

stations and lowering antenna height or enlarging antenna downtilt.

4. After cells are split, the numbers of bases stations, frequencies, and channels are

increased and thus the traffic capacity and user quantity are increased.

The methods to split cells are as follows:

1. Add a new base station in the middle of the existing two base stations.

2. Split the cell with the radius being1/2 of the existing cell. The antenna directions

are not changed.

3. A cell cannot be split infinitely. The space between macro-cellular base stations

should be at least 400 m.

4. Antenna height cannot be excessive. In medium cities, the height is recommended

to be around 25 m.

5. For base stations with high antenna height, better reduce the height when splitting

cells.

1.6.2.2 Aggressive Frequency Reuse Pattern

If network capacity cannot be improved through cell splitting, use aggressive

frequency reuse (AFR) pattern can be used to improve band utilization. Add the site

types supported by the network, and thus improve the entire network capacity.

Common AFR patterns are as follows:

1. Multiple Reuse Pattern (MRP)

2. 1 x 3 (or 1 x 1) multiplexing technology

3. Concentric Cell


24

1.6.2.3 Adding Micro Cell Devices

1. Micro cells are used to reduce coverage holes, and solve the problem of traffic

overflow in traffic hot spots.

2. The comparison between macro cells and micro cells are as follows: Macro cells are

in the lower layer and covers larger areas. They absorb the main traffic. Micro cells

are in the higher layer and supplement the coverage of macro cells by mainly

improving indoor coverage. They absorb hot spot traffic and improve network

quality.

1.6.2.4 Expanding Band

1. Add the number of carriers by expanding the band. This can add system capacity.

2. After 900M resources are assigned to GSM, introduce 1800M band to build dual

band network which can absorb traffic to improve network capacity.

3. The dual band network of the same manufacturer can use the co-bcch technology to

save one CCCH.

1.6.2.5 Half Rate

1. The frequency resources are limited. The expansion method by adding frequencies is

not applicable. Adding frequency points also increases the cost.

2. Traffic Channel/Half-rate Speech (TCH/HS) enables the channel that can bear one

TCH/FS or TCH/EFS to bear two TCH/HSs. That is, the channel capacity is

doubled.

3. TCH/HS uses the VSELP coding. To adapt to the half rate bandwidth, the coding

rate is reduced to 5.6 kbps. Compared with the 13 kbps of full rate speech coding,

the speech quality is a little reduced.

1.7 Location Area Planning

Location area (LA) is an important concept in GSM. As defined by the GSM protocol,

the entire mobile telecommunications network is divided into different service areas

according to location area identity. LA is the basic unit of paging range in GSM

network. That is, messages are paged based on LA. The paging message of a mobile

user is sent to all cells in the LA. One LA may contain one or more BSCs, but it

belongs to only one MSC. One BSC or MSC can contain multiple LAs.


25

LA size (that is, the coverage of a location area code (LAC)) is a key factor in the

system. From the perspective of reducing frequent location update and saving channel

resources, large LA size is recommended. The reason is that more location updates

enlarges the SDCCH load, reduce channel resources, and add the load of MSC and

HLR. In addition, a cell update takes about 10 s and during the update, an MS cannot

make or receive calls. However, if the LA is so large that paging capacity cannot match,

the paging signaling load is excessive, which causes missing paging messages and

lowers the paging success rate. Also, low paging success rate make users call again and

thus the paging load is increased and the success rate is further reduced. Therefore, the

LA cannot be set to a too large value. In this case, when performing network planning,

consider the balance between LA capacity, channel resources, and paging capacity. Try

to reduce frequent location update to the minimum on prerequisite that the paging load

is not excessive.

1.7.1 Determining LA Edges

During the initial phase of GSM network construction, the base stations under multiple

BSCs can be set as an LA. With the increase of traffic and frequency capacity, the

traffic that a BSC bears is enlarged. In this situation, the definition of LAs gradually

evolves to division by BSC. That is, a BSC is set as an LA or multiple LAs in some

cases. If the LAs are too small, new problem may occur, such as too frequent location

updated across LAs. This increases the exchange load.

During location updates cross LAs, an MS cannot make or receive calls. However, in

high traffic areas, the MS may have frequent activities in overlapped areas. This poses

higher requirement on the determination of edges between two or several LAs. With

the network development and increase of user density, the location updates across LAs

has more and more effect on the system load. Therefore, the determination of LA edges

is more and more important. The principles of determining LA edges are as follows:

1. Determine the edges away from high traffic districts. Try to set them in low traffic

districts, such as suburbs or factories. These districts has small density and MS

locate update range is small and therefore the location update across LAs has

comparatively smaller effect on the network load. If the dense downtown cannot be

bypassed, try to set the edge in the district having users with low mobility, such as

inhabited communities.

2. Set the LA edge to be athwart to the road. Avoid setting the overlapped area n the


26

high mobility area. This can avoid large numbers of ping-pang location updates

when crossing LAs. If the setting does not obey this rule, the system may be greatly

affected.

3. Avoid setting the edges of several location areas at the same small area. This reduces

constant location updates of MSs in a small area.

4. When determining LA edges, consider the growth trend of traffic. Based on the

design of paging capacity and traffic capacity, the expansion margin should also be

considered to avoid frequent LA division and splitting.

1.7.2 LA Paging Capacity

1.7.2.1 Paging Principles

When an MS under an LAC is paged, the MSC sends a paging request to all cells of the

LAC through the BSC. Currently, two paging modes are available: TMSI paging and

IMSI paging.

In a GSM system, each user is assigned a unique IMSI, which is written in the SIM

card. Each IMSI is 8 bytes long and used to identify user ID. TMSI is temporary

number assigned by the VLR after the mobile is successfully authenticated. It is only

used to replace the IMSI on the air interface in the VLR managing scope. A TMSI is 4

bytes long and corresponds to the IMSI. Therefore, when the PCH of the air interface

uses the IMSI paging mode, the paging request message can contain only two IMSI

numbers. When the TMSI paging mode is used, four TMSI numbers can be contained.

In this case, the paging load of using IMSI mode doubles that of TMSI mode.

When the MSC obtains the location area identity (LAI) of the MS from the VLR, it

sends paging messages to all the BSCs in the LA. After receiving the paging message,

the BSC sends the paging command message to all its cells of the LA. After receiving

the paging command, the base station sends a paging request message on the paging

sub-channel to which the paging group belongs. This message carries the IMSI or

TMSI of the paged user. After receiving the paging request message, the MS request

for SDCCH assignment through the RACH. After the BSC determines that the base

station activates the required SDCCH, it assigns the SDCCH to the MS on the AGCH

through the immediate assignment command message. The MS uses the SDCCH to

send the Paging Resp message to the BSC. The BSC forwards the Paging Resp

message to the MSC. Then, a radio paging is complete.


27

1.7.2.2 Paging Policy

If the location area of the MS is known in the VLR, the first paging message is

broadcasted only within the LA registered by the MS, that is, local paging. If the MS

does not respond to the first paging, the MSC originates a second paging. The second

paging is always broadcasted within the original LA, but the message can be paged to

all cells within the MSC, that is, global paging. Global paging improves the paging

success rate. The MSs can be distinguished through TMSI or IMSI during a paging.

1.7.2.3 Paging Parameter Configuration

According to the GSM specification, the CCCH configuration has two modes:

1. Combining CCCH and SDCCH, also called combined BCCH. Each multiframe

transfers three paging groups.

2. Not combining CCCH and SDCCH, also called non-combined BCCH. Each

multiframe transfers nine paging groups.

Paging groups can broadcast paging requests as a paging channel (PCH) and respond to

the MS access requests as an AGCH. In operation, several multiframes can be

combined to form a paging period to add the number of paging groups in a cell. The

MS periodically listens to its paging groups. When the MS is called, it will detect the

paging request sent by the base station and make responses.

If many paging groups are set, the MS needs to wait for a long time before detecting

the correct paging group. This adds the paging time. If less paging groups are set, the

MS will frequently listen to the paging group and reduce the call setup duration. In this

case, the phone battery consumes fast. The number of paging groups of a cell can be

adjusted through the following two parameters:

1. Number of access grant blocks BS-AG-BLK-RES

This parameter defines the number of AGCH dedicated paging groups within each

multiframe. For cells with combined CCCH and SDCCH, the value range is 0-2. For

cells with non-combined CCCH and SDCCH, the value range is 0-7. If the cell

broadcast channel (CBCH) is used, the value range is 1-7. If the value is set to 0, it

indicates that the dedicated AGCH is not available and all the paging groups are shared

by PCH and AGCH. If the value is set to more than or equal to 1, it indicates that the

paging group is kept as the AGCH dedicated channel. The specific value depends on

the cell traffic.


28

The following table shows the number of CCCH message blocks contained in each

BCCH multiframe (containing 51 frames) under different CCCH configurations.

CCCH

_CONF

BS_AG_BLK_RES Number of Blocks for SGCH

Within Each BCCH Multiframe

Number of Blocks for PCH

Within Each BCCH Multiframe

0 0 3

1 1 2

2 2 1

1

Other (invalid) - -

0 0 9

1 1 8

2 2 7

3 3 6

4 4 5

5 5 4

6 6 3

Other

7 7 2

2. Number of multiframes of PCHs (BS_PA_MFRAMS)

This parameter defines the number of multiframes for the 51 TDMA frames of the MSs

that transmit paging messages to the same paging group. According to the GSM

specification, each mobile user (or each IMSI) belongs to a paging group. Each paging

group in each cell corresponds to a paging sub-channel. The MS calculates its paging

group according to its IMSI and then gets the paging sub-channel location of the

paging group. In actual network, the MS only listens to the paging sub-channel it

belongs to and ignores the contents of other paging sub-channels. Power off some

hardware of the MS so as to save the power overhead (that is, the DRX origin). The

number of multiframes of PCH BsPaMframs indicates the number of multiframes to

form a cycle of paging sub-channel. In other words, this parameter defines the number

of paging sub-channels that are allocated by the PCH in a cell. The MS uses this

parameter to calculate the paging group that it belongs to so that it can listed to the

corresponding paging sub-channel.

The following table shows the relation between AGCH, MFRMS, number of paging

groups, and interval.

Number of Paging Groups in

Combined Situation

Number of Paging Groups in

Non-Combined Situation

BS_PA_M

FRAMS

Interval Between

Paging Groups

(second) AGCH=0 AGCH=1 AGCH=0 AGCH=1


29

2 0.47 6 4 18 16

3 0.71 9 6 27 24

4 0.94 12 8 36 32

5 1.18 15 10 45 40

6 1.41 18 12 54 48

7 1.65 21 14 63 56

8 1.89 24 16 72 64

9 2.12 27 18 81 72

1.7.3 LA Capacity Calculation

The method for calculating LA capacity is as follows:

Number of paging blocks/s x paging messages/paging block = Max paging times per

second → paging times per hour → allowable traffic of each LA → frequencies of each

LA

1. Number of paging blocks per second

One frame equals 4.615ms. One multiframe equals 51 frames or 0.2354s. Suppose that

the number of access allowed blocks is AGB. The number of paging blocks per second

is calculated in the following way:

For non-combined BCCH: Number of paging blocks per second = (9-AGB) /

0.2354 (paging blocks/s)

For combined BCCH: Number of paging blocks per second = (3-AGB) /

0.2354(paging blocks/s)

For non-combined BCCH, the ZTE configuration is AGB=2. Then, the number of

paging blocks per second is 29.7 paging blocks/s.

For combined BCCH, the AGB equals 1, and then the number of paging blocks per

second is 8.5 paging blocks/s.

In the same LA, it is not recommended to deploy both combined BCCH and

non-combined BCCH. The number of access grant blocks should be consistent at the

same LA. Otherwise, the paging capacity may be reduced to the smallest in the LA. If

the LA does not have great capacity and the location area coding resource is

insufficient, the combined BCCH and non-combined cells can be deploying the same

LA, thus increasing the number of TCHs in 10 and S111 base stations.


30

2. Paging times per paging block (X)

When a BTS broadcasts paging requests from paging groups, the following

configurations may be available: a) 2 IMSIs, or b) 2 TMSI and 1 IMSI, or c) 4 TMSIs

Then, the average allowed paging times per paging block (X) is as follows:

X = 2 paging times/paging block If IMSI paging mechanism is used

X = 4 paging times/paging block If TMSI paging mechanism is used

3. Maximum paging times per second (P)

The calculation formula is as follows:

For non-combined BCCH: P = (9-AGB) /0.2354 (paging blocks/s) x X

(paging times/paging block)

For combined BCCH: P = (3-AGB) /0.2354 (paging blocks/s) x X (paging

times/paging block)

IMSI paging mechanism: for non-combined BCCH, when AGB=2, P=59.47 paging

times / s; for combined BCCH, when AGB=1, P=16.99 paging times / s.

TMSI paging mechanism: for non-combined BCCH, when AGB=2, P=118.95 paging

times / s; for combined BCCH, when AGB=1, P=33.98 paging times / s.

4. Allowed traffic of each LA (T)

One principle of designing LA capacity is that the LA size must not exceed the allowed

maximum paging capacity. For an operating network, the times of message paging

(C11621) sent by the BSC can be collected from the daemon and converted into paging

messages per second. The value of T must not exceed the result.

When no traffic statistical data can be referred, for example, a new network, calculate

the value by supposing a traffic model:

Average call duration: 60 s, that is, 1/60 Erl

Ratio of Times of MS terminated calls (causing paging and generating TCH

traffic) to total call times: 30%

Suppose 75% of MSs respond at the first paging, 25% of MSs respond at the

second paging. Ignore the MSs that respond at the third paging. Then, each

successful paging of an MS needs 1.25 paging.


31

Suppose after 50% of theoretical maximum paging capacity is exceeded, the PCH is

congested. That is, in the case that 50% of the maximum paging load is not exceeded,

the original paging messages will not discarded because the BTS paging queue is full.

In this case, the paging volume in one second is P*50%.

For IMSI paging mechanism, when AGB=2 and non-combined BCCH is used, the

calculation of the traffic volume allowed in an LA is as follows:

T*30%/(1/60)*1.25 = P*50% = 59.47*3600*50%

T = 4757.6 Erl (AGB=2, non-combined BCCH)

Similarly:

T= 1359.39 Erl (AGB=1, combined BCCH)

For TMSI paging mechanism, the traffic allowed by an LA is as follows:

T= 9515.72 Erl (AGB=2, non-combined BCCH)

T= 2718.78 Erl (AGB=1, combined BCCH)

1.7.4 Affect of SMS on LA Paging Capacity

Short messages can be sent through SDCCH or SACCH. According to the difference of

SMS sending and receiving, the process can be divided into SMS originating procedure

and SMS terminating procedure. The affect of SMS on LA paging capacity mainly

goes to the SMS receipt on the MS. When an MS receives SMSs, just like the case

when the MS serves as the termination, the system needs to page the MS. Therefore,

the effect of MS receiving an SMS on the network is the same as that the MS is called.

The following part calculates and analyzes the effect on the network based on a certain

SMS traffic model.

The SMS service is to receive 3 SMSs / user / day. The retransmission rate is 30%. The

busy hour factor is 0.12.

Suppose that there are 100,000 users in an LA, then the busy hour SMS paging times

are as follows:

100000 x 3 x 0.12 x (1+30%) = 46800 (times/h)

This shows that that the large amount of paging comes from SMS, which affects the

system performance.


32

In addition, SMS have bursty traffic. In peak period, for example, festivals, the burst

factor can reach 3-8. That is, the SMS quantity in festivals is 3 to 8 times of normal

situation. The paging coming from SMS can reach:

100000 x 3 x 0.12 x 8 x (1+30%) = 374400 (times/h)

This data is amazing. Also, the SMS peak accompanies traffic peak. The two peaks

lead to a large paging volume, which has great impact on the system. In this case, flow

control measures need to be taken to ensure that the network survive the SMS and

traffic peak. The measures can be setting SMS to retransmission prohibit, delaying data

processing in peak, and reducing maximum paging times.

2 1BLink Budget and Coverage Planning

2 Link Budget and Coverage Planning

This chapter describes the following contents:

System parameters and design parameters used in link budget

Parameter definitions and recommend values in link budget

2.1 Purposes of Link Budget

When performing tasks related to coverage during network planning and optimization,

link budge is an important step. Through link budget, the maximum UL/ DL path loss

is obtained, which is useful in future tasks. Link budget must be performed during the

planning phase to make the uplink signals and downlink signals balanced in the

coverage area. If uplink signal coverage is greater than downlink signal coverage, the

signals at the cell edge are weaker and thus may be “submerged” by stronger signals in

other cells. If downlink signal coverage is greater than uplink signal coverage, the MS

is forced to “perch” under the strong signals. However, the uplink signals are weak and

thus the voice quality is poor. The balance mentioned here is only a relative word.

Deviation within a certain range is allowed.

2.2 Calculation of Uplink and Downlink Balance

Figure 2.2-1 Power budget model

33


Figure 2.2-1 shows that the purpose of link budget is to analyze the power balance

between downlink and uplink through the given system parameters and design

parameters.

2.2.1 Analysis of Uplink Budget Parameters

The formula of uplink budget is as follows:

Maximum allowable path loss = MS transmission power (dBm) + MS antenna gain

(dB)–body loss (dB)–base station feeder loss (dB) + base station receiving antenna

gain (dBi)–building or vehicle penetration loss(dB)–slow fading margin (dB)– fast

fading margin(dB)–interference margin(dB)–base station receiver sensitivity (dBm)

The parameters for uplink budget can be classified into four types: system parameter,

MS transmitter parameters, base station receiver parameters, and margin reservation.

2.2.1.1 System Parameters

1. Carrier frequency

Carrier frequency affects the transmission loss. Radio waves of different frequencies

have different propagation models and different losses.

2. System bandwidth

In a GSM system, the receiver bandwidth is 200 kHz (that is, 53 dBHz)

3. Data rate

The full rate of GSM voice service is 9.6 kbit/s and the corresponding half rate is 4.8

kbit/s.

Table 2.2-1 shows the CS1–CS4 rate in GPRS data service.

Table 2.2-1 GPRS data rate

4. Background noise

34


35

Background noise, also called thermal noise, is produced by the thermal movement of

electrons. The formula is as follows:

N=kTB

where, k is Boltzmann constant, which equals 1.38 x 10-23J/K, T is absolute

temperature (K), and B is system bandwidth.

Spectral density of thermal noise is kT. It is -174dBm/Hz in room temperature (300K).

2.2.1.2 MS Transmitter Parameters

1. Max TCH transmitter power

At MS side, according to GSM protocol, the max MS transmission power is 2W

(33 dBm).

2. Adapter loss

It refers to the signal attenuation on various components on the route from

transmitter to antenna. This value is generally ignored for MSs, that is, 0dB.

3. Transmitting antenna gain

For MSs, electronically small antennas are always used. In addition, MS antennas

must receive and transmit reliably in any direction. For GSM MSs, unipole

antenna and planar inverted-F antennas (PIFA) are always used and the gain is 0

dBi.

2.2.1.3 Base Station Receiver Parameters

1. Antenna gain

Select the antenna gain based on the area to be covered.

Table 2.2-2 shows the values of base station antenna gains in different areas.

Table 2.2-2 Base station antenna gains in different areas

Area Antenna Gain (dBi)

City 15.5

Suburb 15.5 - 17

Village 17 – 18

Highway or narrow valley 18 – 21

Mountain, hill 17 - 18


36

2. Feeder, adaptor, and combiner loss

It refers to the signal attenuation on various components on the route from antenna to

transmitter. The value is generally 3 dB in link budget. In actual situation, the value

should be calculated based on the loss of cables with different lengths and types and

various connectors.

a) Adapter loss

Generally, for one path feeder, 6 adapters are needed from transceiver to antenna

input. Each adapter loss is 0.05 dB. Then, the total loss is 0.3 dB. If antenna

amplifier is required, one more adaptor is required. The loss of lightening arrester

is generally 0.2 dB.

b) Feeder loss

At the base station side, antennas and radio frequency front ends are connected

through feeders. The feeder loss varies depending on feeder type and manufacturer.

The loss of ZTE feeders is shown in Table 2.2-3.

Table 2.2-3 Feeder loss

Loss (dB/100m) Feeder Type

900 M 1800 M/1900 M

1/2 soft jumper 7.22 11.3

7/8 main feeder 3.89 6.15

15/8 main feeder 2.34 3.84

When selecting main feeders, observe the following principle:

Feeder loss should be lower than 3 dB.

If the loss exceeds 3 dB, use thicker feeders.

Therefore, for main feeders used in DCS1800 cells in open land with more than 40

m and GSM sites with more than 70 m, 15/8 cables are recommended. Otherwise,

the main feeder loss exceeds 3 dB. In normal situations, each route feeder needs 5

m 1/2 soft jumper and the loss is 0.35 dB.

3. Base station divider loss

As combiners are used in the downlink, the uplink must use divider. Thus, loss is

introduced. The loss varies depending on the dividing device. Determine the divider


37

type according to the number of frequencies of the cell.

Table 2.2-4 Divider / Combiner loss

Divider/Combiner Type 900 M Insertion Loss (dB) 1800 M Insertion Loss (dB)

CDUG 4.4 4.6

CEUG 3.5 3.6

CENG 5.3 5.5

CENG/2 5.3 5.5

ECDU 0.9~1.0 0.9~1.0

4. C/I required by TCH

Carrier-to-Interference ratio (C/I) is the SNR requirement on the air interface. The

target value varies depending on the propagation environment, mobility speed, and

coding rate. According to the GSM protocol, C/I should be greater than or equal to 9dB.

In actual situations, the C/I is greater than or equal to 12 dB with 3 dB margin added.

5. Noise figure

Noise figure is generally used to measure the following issues:

(a) Added value of environment noise received by the antenna compared with the

thermal noise

(b) Reduction in SNR after the signal passes the receiver

(c) Added value of antenna noise temperature compared with receiver noise

temperature to antenna caused by noise source from the antenna end (generally

satellite antenna)

In link budget of mobile telecommunications, noise figure includes the noise figure of

base station receiver and the noise figure of MS receiver. When signals pass a receiver,

noise is added to the signal and thus the noise figure is a method to measure the noise

addition. The numerical value is the ratio of input signal to noise ratio (SNR) to output

SNR.

When signals and noises are input to an ideal receiver with no noise, they are equally

attenuated or amplified. Thus, the SNR is changed, that is, F = 1 or 0 dB. In actual

situations, a receiver has noise and the output noise power is greater than signal power.

Thus, the SNR is worse and F > 1.

Noise figure is an attribute of a receiver. As defined in GSM protocol, the noise figure


38

of a base station receiver is 8 dB.

6. Receiver sensitivity

It refers to the minimum signal power which ensures that the receiver input can

successfully discern and decode (or retain the required FER) signals.

In telecommunications system, receiver sensitivity is given by:

Receiver sensitivity = noise spectral density (dBm / Hz) + bandwidth (dBHz) + noise

figure (dB) + C/I (dB)

Noise floor = noise spectral density + bandwidth + noise figure

C/I is the SNR requirement on the air interface. In narrowband system, C/I is the

requirement of receiver base band demodulation performance. It is generally negative.

Receiver sensitivity refers to sensitivity of MS receiver and BS receiver. Uplink is used

for BS to receive signals. Therefore, BS receiver sensitivity should be considered. For

example, for voice service, BS receiver sensitivity = noise spectral density (dBm / Hz)

+ bandwidth (dBHz) + noise figure (dB) + C/I (dB) = -174 + 53 + 8 + 9 = -104dBm.

This formula can calculate the theoretical reference value for BS receivers in different

situations. In actual situations, affected by various factors, the receiving sensitivity is

better than the theoretical value.

7. TMA Effect

Tower mounted amplifier (TMA) is actually a RF low noise amplifier (LNA). After a

TMA is installed, the receiver noise figure is reduced, as proved by the relation

between noise figures in cascaded system. Therefore, the receiver sensitivity is

improved by around 3 dB.

2.2.1.4 Margin Reservation

1. Shadow fade margin

Shadow fade is also named slow attenuation. It follows a lognormal distribution in

the calculation of radio coverage. To reach the specified coverage probability,

during network planning, certain power margin must be reserved for BS or MS

receivers to reduce the attenuation effect. Reserved power is called shadow fade

margin, whose value is associated with sector edge communication probability

and shadow fading standard deviation.


a. Shadow fading standard deviation

Shadow fading standard deviation is related to electromagnetic wave propagation

environment. In urban areas, the shadow fading standard deviation is about 8 – 10

dB. In rural areas or villages, the value range is 6 – 8 dB.

b. Edge coverage probability

To evaluate the reliability of communication links in shadow fading environment,

edge coverage probability is used to express the coverage quality. Coverage

probability refers to the probability that the quality of communication between

terminals in radio coverage edge (or inside coverage) and the base station meet the

requirement (eg. BER). Coverage probability can be classified into location

probability and time probability. For terrestrial radio communications system,

changes in time have little effect on the communications probability. Therefore,

location probability is the main factor to be considered during network planning.

Coverage probability can also be classified into area coverage probability and

edge coverage probability. The requirement defined by the former one is direct

whereas using the latter one is convenient.

Edge coverage probability is an index determining the coverage quality. It is

defined as the time percentage of edge receiving signals exceeding the receipt

threshold. In radio propagation, for a given distance, the path loss changes quickly

and can be regarded as a random variable in lognormal distribution. If the network

is designed based on the average path loss, the loss value on cell edge will be

greater than the path loss median in one 50% of the time and smaller in the other

50% of the time. That is, the edge coverage probability is 50%. In this case, users

at the cell edge will receive unsatisfactory service with a half chance. To improve

cell coverage, fade margin should be deserved in link budget. Generally, the link

budget is based on 75% edge coverage, and 90% for cities and 75% or villages.

The following part explains by taking the 75% edge coverage probability as an

example:

Suppose the propagation loss random variable is ζ , thenζ is Gauss distribution

in dB. Let the average be , standard deviation be m δ , and the corresponding

probability distribution function be function. Set a loss thresholdQ 1ζ . When

the propagation loss exceeds the threshold, signals fails to meet the demodulation

requirement of expected services. Then, at the cell edge, satisfying 75% edge

39


coverage probability can be translated into:

∫∞−

−−

=<=1

2)(

cov2

2

21)1(

ζδ

ζ

ζδπ

ζζ dePPm

rerage

For outdoor environment, the standard deviation of propagation loss random

variable is always 8 dB. Then, the margin of 75% edge coverage probability is as

follows:

dBm 4.58675.0675.01− = = × =δζ

Figure 2.2-2 and Figure 2.2-3 show the graph:

Figure 2.2-2 Attenuation margin

Figure 2.2-3 Attenuation margin—normal distribution

The previous two graphs show that during network planning and design, the 5.4

40


41

dB margin must be reserved to ensure a 75% edge coverage probability. If 90%

edge coverage probability is required, the 5.4 dB margin must be reserved.

c. Area coverage probability

In actual situation, area coverage probability is often important. Area coverage

probability is the percentage of area of the location where receiving signal

strength is greater than receiving threshold to the total area in a round region with

the radius R. This parameter corresponds to the edge coverage area. When μ=3

and σ= 8dB, the 90% edge coverage probability corresponds to 96% area

coverage probability and 75% edge coverage probability corresponds to 89% area

coverage probability.

d. Shadow fading margin

In the same radio propagation environment, the shadow fading margin is mainly

determined by coverage probability. Higher requirement on coverage probability

leads to greater reserved margin and less maximum coverage area. Thus, the

number of base stations is affected. In actual network, base station lausert is not

regular because of building blockage. The effect of coverage probability on base

station quantity is smaller than the theoretical calculation. However, it is sure that

the base station quantity grows with the increase of coverage probability.

Table 2.2-5 Common edge coverage probability and shadow fading margin

Edge Coverage

Probability (%)

70 75 80 85 90 95 98

Shadow fading

margin/dB

0.53σ 0.68σ 0.85σ 1.04σ 1.29σ 1.65σ 2.06σ

Note: σ is the standard deviation of shadow fading. The value is 6, 8, or 10

Table 2.2-6 Common area coverage probability and shadow fading margin

μ=3 μ=4

σ=8dB σ=10dB σ=8dB σ=10dB

Area

Coverage

Probability.

(%) Edge

Coverage

Probability

(%)

Shadow

fading

margin/dB

Edge

Coverage

Probability

(%)

Shadow

fading

margin/dB

Edge

Coverage

Probability

(%)

Shadow

fading

margin/dB

Edge

Coverage

Probability

(%)

Shadow

fading

margin/dB

98 95 13.2 96 17.6 93 11.8 94 15.6

95 87 9 89 12.3 85 8.3 87 11.3


42

μ=3 μ=4

σ=8dB σ=10dB σ=8dB σ=10dB

Area

Coverage

Probability.

(%) Edge

Coverage

Probability

(%)

Shadow

fading

margin/dB

Edge

Coverage

Probability

(%)

Shadow

fading

margin/dB

Edge

Coverage

Probability

(%)

Shadow

fading

margin/dB

Edge

Coverage

Probability

(%)

Shadow

fading

margin/dB

90 77 6 80 8.5 73 5 76 7.1

75 52 0.5 56 1.6 47 0 51 0.3

Note: σ is the standard deviation of shadow fading. μ is path loss index.

Generally, in urban areas, when σ= 8dB and edge coverage probability is 90%, shadow

fading margin is 10.3dB, and in rural areas, when σ＝8dB and edge coverage

probability is 75%, shadow fading margin is 5.4dB.

(2) Fast fading margin (Rayleigh fading margin)

Fast fading is a type of multipath wave interference generated because the propagation

is reflected by scattering objects (mainly buildings) or natural obstacles (mainly forest)

around the MS (within 50-100 wave length). Fast fading always produce standing wave

field. When an MS passes the standing wave field, the receiving signal is attenuated in

a short period.

Deterioration refers to the addition of receiving level in order to realize that the voice

quality in multipath propagation effect and man-made noise (mainly vehicle spark

interference) is the same as the condition when only receiver interval noise exists

In GSM system, the deterioration of voice and data are both 3 dB.

(3) Antenna density gain

Antenna density gain refers to the gain brought by the usage of density technology on

the base station. Generally, density gain can be considered in receiver sensitivity or

separately considered. The BTS uses two-way density. The density gain is 3 dB.

(4) Body loss

Body loss refers to the loss produced by the signal blockage and absorption when

hand-held mobile phones are near to the human body. The body loss is determined by

the distance of mobile phone relative to the human body. When the hand-held mobile

phone is near the waist or shoulder, compared with the case that the antenna is several

wave lengths away, the signal field strength is reduced by 4-7 dB and 1-2 dB


43

respectively.

In the link budget of voice service, the value is 3 dB. In the link budget of data service

using data card, the value is 0 dB. In the link budget of data service using mobile

phones, the value is small and can be regarded as 0 dB.

ZTE link budget always set the body loss to 3 dB.

(5) Penetration loss

Building loss is associated with building style and structure, for example, concrete

structure, brick structure, window size, and style. Determine the building penetration

loss according to the type of actual coverage area.

Table 2.2-7 Values of penetration losses in normal situations

Area Type 900 M Loss (dB) 1800 M Loss (dB)

Dense urban 18-22 23-27

Common urban 15-20 20-25

Suburb and village 10-15 15-20

(6) Interference margin

In a GSM system, the internal interference can be co-channel interference, adjacent

channel interference, cross-modulation interference, and near-end-to-remote-end

interference. Based on these factors, the interference margin is generally set to 3 dB.

2.2.2 Analysis of Downlink Budget Parameters

The formula of downlink budget is as follows:

Maximum allowable path loss = BS transmission power (dBm) + BS antenna gain

(dB)– base station feeder loss (dB) – base station combiner loss + MS receiving

antenna gain (dBi)–body loss (dB) – building or vehicle penetration loss(dB)–slow

fading margin (dB)– fast fading margin(dB)–interference margin(dB)–MS receiver

sensitivity (dBm)

Similar to uplink budget, the parameters for downlink budget can be classified into

four types: system parameter, MS transmitter parameters, base station receiver

parameters, and margin reservation.


44

2.2.2.1 System Parameters

Except carrier frequency, other parameters are the same as uplink.

2.2.2.2 BS Transmitter Parameters

(1) BS transmit power

The following table lists the transmit power.

Table 2.2-8 BS transmit power

Mode Transmit Power

GSMK 40W 46dBm

GSMK 60W 47.7dBm

GSMK 80W 49dBm

8–PSK 30W 44.7dBm

(2) BS divider/combiner loss

For further details, refer to the corresponding content of uplink.

(3) BS feeder and adaptor loss


(4) BS antenna gain


(5) Additional gain brought by new technology

In ZTE V3 equipment, new technologies are added to the RF module, which brings

additional gain to transmit signals.

The DPCT technology can provide the gain of 2.5 dB.

2.2.2.3 MS Receiver Parameters

(1) MS antenna gain


(2) MS C/I ratio


The value is determined by the protocol.

(3) Noise figure


45

For further details, refer to the corresponding content of uplink. The value is set to 10

dB as defined in the protocol.

(4) MS receiver sensitivity

MS receiver sensitivity is similar to the communication receiver sensitivity. The

difference is that the C/I value and noise figure are different from the uplink. The noise

figure is set to 10 dB. According to the C/I value defined in the protocol, the theoretical

MS receiver sensitivity can be obtained, as shown in the following table:

Table 2.2-9 MS receiver sensitivity using different GPRS coding modes

GSM 900 and GSM 850

Propagation conditions Type of channel

static TU50

(no FH)

TU50

(ideal FH)

RA250

(no FH)

HT100

(no FH)

PDTCH/CS-1 dBm -102 -101 -102 -102

PDTCH/CS-2 dBm -98 -97 -98 -98

PDTCH/CS-3 dBm -96 -95 -96 -95

PDTCH/CS-4 dBm -88 -87 -87 *

DCS 1800 and PCS 1900

Propagation conditions Type of channel

static TU50

(no FH)

TU50

(ideal FH)

RA130

(no FH)

HT100

(no FH)

PDTCH/CS-1 dBm -102 -102 -102 -102

PDTCH/CS-2 dBm -98 -98 -98 -98

PDTCH/CS-3 dBm -96 -95 -95 -95

PDTCH/CS-4 dBm -88 -84 -84 *

Table 2.2-10 Receiver sensitivity using different GPRS coding modes (actual value)

Coding Mode Static Model TU50 Model (no FH)

Voice -110 -108

CS1 -113 -107.5

CS2 -111 -104.5

CS3 -109 -103

CS4 -105 -95


46

2.2.2.4 Margin Reservation


2.3 Coverage Planning

2.3.1.1 Coverage Simulation

Coverage simulation is to use the planning software to plan the sites based on the user

distribution in a certain area. It aims to ensure the area coverage and capacity and avoid

interference. ZTE uses the AIRCOM network planning software.

The initial simulation involves coverage prediction and BS engineering data

determination.

1. Select the design indicators:

The indicators include minimum receiving power and edge connectivity rate.

2. Select design parameters.

The parameters include antenna height (from floor), antenna azimuth and gain, antenna

downtilt, BS height, BS type, feeder type, feeder antenna loss, combiner/divider mode,

transmitter output power, receiver sensitivity, BS diversity receiving type, and diversity

gain.

3. Predict the coverage of each BS cell according to the propagation model of different

districts. Give suggestions on BS site, antenna direction, downtilt, and height based on

the possible blind spots and weak signal spots to get the actual engineering data of the

BS.

2.3.1.2 Layered Coverage

Networking has the following formats: macro cell, cell, highway, multi-layer,

dual-band, as shown in the following figure:


GSM900 macro GSM1800 macro

900 micro 1800 micro

P-cell P-cell

GSM900/1800 伞形小区 macro

Figure 2.3-1 Layered coverage

2.3.1.3 Coverage Methods in Special Districts

Tunnel:

The following combinations may be used in actual situations:

Micro BTS + single antenna scheme

Micro BTS + distributed antenna system

Micro BTS + leaky coaxial cables

Repeater + single antenna scheme

Repeater + distributed antenna system

Repeater + leaky coaxial cables

Railway 450 M leaky coaxial cables can be used. But these cables have greater radial

loss (11dB/100 m). The coverage distance is relative small.

When determining whether to use micro cell or repeater as the GSM signal source of

the tunnel, consider the following factors:

(1) Whether strong GSM signals are available around the tunnel entrance

(2) Whether transmission lines are available around the tunnel

Generally, if existing signal levels around the tunnel entrance (including high space

such as hill) are lower than -80 dBm. Micro BTS is recommended. If the levels are

higher than -80 dBm, repeater or micro BTS is recommended. If the transmission

problem is difficult to solve, it is recommended to use repeaters. When using the

repeater solution, take full consideration on repeater isolation. Otherwise, use the micro

47


48

BTS solution and improve system capacity.

Offshore:

Towers of offshore base stations are always installed on the seaside mountain top, with

the height from 50 to 200 m.

Because oversea propagation has little loss, signals can be transmitted to faraway seas.

In this case, the ground should be regarded as a spherical surface. That is, the earth

curvature has effect on the signal propagation. In addition, islands, hill, and large ships

also have shadowing effect on signal propagation. Literature considers that oversea

propagation model can be regarded as a free space propagation model. But according

to the result of offshore testing, free space propagation model is not suitable for testing

offshore coverage. Also, the Okumura-Hata model and amended parameters are not

applicable to oversea propagation environment. It requires further study.

Offshore large distance overage should be measured in combination with the

technologies of cell expansion and dual-timeslot cell. These technologies are applicable

to situations with the required coverage more than 35 km.

Indoor coverage:

With the development of social economy, skyscrapters and underway architecture such

as subway, and underway carbarns emerge. In this situation, mobile phones are more

and more frequently used indoors. Users require not only excellent outdoor mobile

service but also satisfactory indoor mobile service.

The problems always exist for indoor mobile communications:

1. Coverage: Due to complex indoor structure and building protective shielding and

absorbing function, great transmission attenuation is lost in radio wave propagation.

Weak field-strength area even blind area is formed. This cause the basement,

storey 1 and storey 2 of a building to have weak field strength, even blind spots.

Because of poor indoor coverage, the problems such as call drops, no response to

paging, and user not available in the serving area are common.

2. Quality: Higher stories of a building always have radio frequency interference. The

serving cell signals are unstable. Pingpang effect always occurs. The speech

quality is poor and call drops occur.

3. Capacity: In buildings such as super market and conference center, because the


49

usage density of mobile phones is large, the LAN capacity cannot meet user

requirement. Thus, radio channels may be congested.

4. Currently, indoor coverage mainly depends on the extension mode of the existing

network coverage, for example, using repeater, outdoor large power BTS, or

mounting antenna high. However, these methods bring the following problems:

5. Due to great penetration loss, the indoor coverage effect is bad. Large amount of

blind spots are generated. Conversation fails.

6. The repeater method has high requirement on the level of the source signals. In

addition, the cross-modulation interference and co-channel and adjacent-channel

interference are all severe. The conversation quality cannot be ensured. Even the

network quality may be degraded.

7. The repeater and outdoor BTS methods does not basically solve the capacity

problem. The network capacity is limited and the connection success rate is low.

8. Mounting antenna high may cause across-boundary coverage and affects the entire

network quality.

9. When outdoor cells add frequencies, it is difficult to plan the frequencies and

expand network capacity.

51

3 Frequency Planning


Analysis of frequency reuse and interference models based on ideal cellular

structure

Common anti-interference technologies

3.1 Cellular Structure Creation Rule

In ideal conditions, the basic unit (BTS area) of the cellular structure is a hexagon

(handover edge). Several hexagons form a radio area cluster, and every two adjacent

radio area clusters constitute the coverage area of the entire mobile network.

The radio area cluster is the basic unit of frequency reuse. Inside one radio area cluster,

all the available channels are evenly distributed to each BTS area or sector cell. Two

same radio area clusters can be adjacent to each other to ensure the one-to-one

relationship between various BTS areas or sector cells. Since the channel group

allocated to each BTS area or sector cell is fixed, the corresponding BTS cells or sector

cells in any adjacent radio area clusters are co-frequency cells, thus forming a complete

co-frequency reuse pattern.

The radio area cluster must meet the following conditions:

1. The radio area clusters should be adjacent to each other.

2. The central distance between any two co-frequency reuse areas in adjacent radio

area clusters should be the same.


52

A

B

C

D

E

F

G

A

B

C

D

E

F

G R

60o

j

i

D

Figure 3.1-1 Composition of a radio area cluster

As shown in Figure 3.1-1, “i" and “j” are two parameters. Starting from one cell, user

can take different values for these two parameters (cannot be 0) to reach one cell.

According to the triangle relationship in the diagram, we can obtain the distance (D)

between two co-frequency reuse areas:

22 jijiD ++=

The radio area cluster complying with this distribution includes clusters for a number

of N :

22 jijiN ++=

Suppose the central distance between two adjacent BTS areas is 1 and the BTS area

radius is R, then:

3/1=R

Define the Dq R/= as the co-frequency reuse distance protection coefficient or

co-frequency interference attenuation factor:

NRDq 3==

3.2 Interference Models

1. Co-frequency interference protection ratio ( B )

3 2BFrequency Planning

It is defined as the minimum ratio of the useful RF signals measured on the input end

of the receiver to the un-useful RF signal, usually measured in dB, when the useful

signals of the output end of the receiver reach the specified quality.

2. Estimating the C/I Ratio in the N-Reuse Radio Area Cluster

53

A

B

C

D

E

F

G

A

B

C

D

E

F

G

A

B

C

D

E

F

G

A

B

C

D

E

F

G

A

B

C

D

E

F

G

A

B

C

D

E

F

G

A

B

C

D

E

F

G

A

B

C

D

E

F

G

A

B

C G

A

B

C

D

E

F

G

A

B

C

D

E

F

G

A

C

D

E

F

G

A

B

C

D

E

F

G

A

B

C

D

E

F

G

B

C G

A

B

E

F

G

A

B

C

D

E

F

G

AD F

E

A

B

C

D

E

Figure 3.2-1 Interference source

For the radio transmission feature, user can obtain the model mentioned above for

description:

DiffkkkHdkHkdkkPL effeff 765loglog4log3log21 ++++++=

For the radio transmission feature, user can obtain the model mentioned above for

description:

DiffkkkHdkHkdkkPL effeff 765loglog4log3log21 ++++ ++=

Since the ideal cellular system is studied, each cell has the same transmitted power and

also the same height of antenna, without diffraction loss. Thus, we can obtain the C/I

ratio as below:


∑∑

∑∑∑

=

+−

+−

=

−

−

=

−

−

=

−

−

=

==

===

M

k

dkk

dkk

M

k

PL

PL

M

k

PL

PL

M

k

PLP

PLP

M

kk

kHeff

Heff

k

kkt

t

I

CIC

1

10/log)log42(

10/log)log42(

1

10/

10/

1

10/

10/

1

10/)(

10/)(

1

10

10

10

10

10

10

10

10

Let effHkkk log42'2 += , be the cell radius (d R ), and be the

transmission distance between each interference resource to the cell ( ).

kd

D

10/'210/'2

10'2

12

1

10/2log'26

1

10/log'2

10/log'2

)2(126

1010

10

kk

lkk

Dk

k

Dk

Rk

DDR

IC

−−

−

=

−

=

−

−

+=

+=

∑∑ (4-5)

Let '2k=γ /10 (the propagation path loss slope determined according to the actual

geographical environment):

γ

γ

γγ

γ

2126)2(126 +

=+

=−

−−

− qDD

RIC

Perform logarithm operation to them to obtain:

)6log(log'2)( += kdBI 2γ

40'2

12C 10+q (4-6)

To be general, take =k , 4=γ .

Now dB5.06log10)2126log(10 4 ≈−+ .

We can see that the next most powerful interference sources on the second circle can be

ignored since they contribute to the interference far less than the most powerful

interference sources on the first circle.

Now, we have created the interference model in the ideal cellular environment. We will

use this model to examine the interference when we describe the common reuse modes

later in this document.

54


3. Co-frequency interference probability )/( BICP ≤

In fact, because of non-ideal BTS location and the landform fluctuation, the signals

received by a MS in motion are affected by Rayleigh fast fading and Gauss slow fading.

Whether it is signal or interference, when it reaches the MS, the transient value and

mean value of the filed strength are random variables. Even if a MS is still, the

transient value and mean value of its field strength are still random variables due to the

presence of various interferences, including the objects moving around it.

Therefore, the C I/ value on the input end of the receiver is not constant, but a

random variable. Only when

C I B>/ , there is no interference. Co-frequency interference occurs at a certain

frequency.

According to the CCIR740-2 report, France in 1979 put forward that multi-path fading

complies with Rayleigh distribution, and shadow fading complies with Gauss

distribution. The probability of co-frequency interference is:

∫−∞+

∞ −−−+−u 2}exp{1

= duBCP u 10/)2)/( σπ≤I BIC(101

Where, is the integral interference, and u σ is the standard deviation between signal and interference, IC σσσ −= .

BICZ p −−=

100

10-1

10-2

10-3

10-4

20 40 60dB

σ = 12

σ = 0 σ = 6 σ = 8

Figure 3.2-2 Co-frequency interference probability

Figure 3.2-2 provides the typical co-frequency interference probability.

55


To be general, take σ = 6 and interference probability )/( BICP ≤ =0.1, and find

from the table. The GSM requires that the co-frequency interference

protection ratio (B) must be less than 9 dB. However, in engineering B=12 dB is often

taken. Therefore, the

dBZ p 12=

IC / calculated in the ideal interference model is greater than:

9(12)+12=21 dB (24 dB).

William C.Y. Lee believes that the margin of 6 dB is sufficient, hence the IC /

calculated in the ideal interference model must be greater than: 9(12)+6=15dB (18dB).

3. Near-remote interference

AC

D

Bd2

d1

Cell 1 d2

d1

Cell 2

Figure 3.2-3 Near-Remote Interference

According to the interference model, let the C/I of MS B against MS A be

dBddkdB

IC 9log'2)(

2

1 −== , hence 69.11

2 =dd

. If the frequency used by

MS B is adjacent to that used by MS A, when 69.11

2 >dd

, the adjacent interference

protection ratio is not met and call drop will occur. The same case may occur in the

adjacent cell.

Let us see an extreme case: Suppose the output power of the antenna of cell 2 is 34

dBm, and the reception level at D is -85 dBm, and the BTS sensitivity is -110 dBm.

Suppose the uplink/downlink powers are balanced, the transmitted power of MS D is

-110+(34-(-85))=9dBm.

56


57

Now, MS C in a very close distance is turned on and works at its maximum transmitted

power, supposedly at 30 dBm (1W). Suppose the path loss for the signals arriving at

cell 2 is the same as MS D, then, cell 2BTS receives the interference signals of

30-(34-(-85) = -89 > -110 + 9, so call drop occurs.

3.3 Frequency Reuse Technology and Interference Analysis

Frequency reuse is a commonly used technique in GSM networks to use the same

frequency to cover different areas. There must be an appropriate distance between these

areas that use the same frequency. This distance is known as the co-frequency reuse

distance.

If omni directional antennas are used, the 4 x 3 frequency reuse pattern is

recommended. In areas with large traffic, other frequency reuse patterns such as 3 x 3

and 2 x 6 can be adopted according to the capability of the equipment. In whatever

mode, the basic principle is to consider different propagation conditions, different reuse

modes, and multiple interference factors to meet the requirements of the

interference-protection ratio, that is:

Co-frequency interference-protection ratio: C/I ≥ 9 dB

Adjacent-frequency interference-protection ratio: C/I -9 dB.

400KHz adjacent-frequency interference-protection ratio: C/I -41 dB

3.4 Frequency Reuse in Groups

3.4.1 4 X 3 Frequency Reuse

The GSM adopts many frequency reuse patterns, including 4 x 3, 3 x 3, and 2 x 6. All

frequency reuse patterns divide the limited frequencies into several groups to form a

cluster of frequencies for allocating to adjacent cells, as shown in Fig4.2-1 According

to the GSM specification, the 4 x 3 frequency reuse pattern is commonly used in

various GSM systems. This pattern divides frequencies into 12 groups and allocates

them to four sites in turn. That is, three frequency groups are available to each site.

This frequency reuse pattern can reliably meet the requirement of co-frequency

interference-protection ratio and adjacent frequency interference-protection ratio of

GSM network to have high quality and secured service, as shown in Figure 3.4-1:


A3

D2B1

D1

D3

C1B3

C2

B2

C3

A1

A2

58

A3

D2B1

D1

D3

C1B3

C2

B2

C3

A1

A2

A3

B1

B3B2

A1

A2

A3

B1

A1

A2A3

D2B1

D1

D3

A1

A2

A1

A1

A3

D2

A2 D1

B1 D3

B2 B3 C1

C2 C3

Figure 3.4-1 4 x 3 frequency reuse

Let the side length of a cellular hexagon be 1. According to Figure 3.4-1 and the

interference model described above, we can obtain:

dBdBI

18)2.7(28

log10)( 52.352.3 =+

= −−

C 2 52.3−

The result deducted by the 6 dB margin as recommended by William C.Y. Lee is

exactly 12 dB.

The following part discusses the 4 x 3 frequency reuse pattern in engineering

application:

As the name implies, 4 x 3 reuse divides the available frequency into 4 x 3 = 12 groups,

which are tagged as A1, B1, C1, D1, A2, B2, C2, D2, A3, B3, C3, and D3, as shown in

the following table:

A1 B1 C1 D1 A2 B2 C2 D2 A3 B3 C3 D3

1 2 3 4 5 6 7 8 9 10 11 12

13 14 15 16 17 18 19 20 21 22 23 24

25 26 27 28 29 30 31 32 33 34 35 36

Assign A1, A2, and A3 as a group to three sectors of a base station. Assign B1, B2, and

B3 as a group, C1, C2, and C3 as a group, and D1, D2, and D3 as a group to three

sectors of an adjacent base station. Obviously, the following frequency reuse patterns

are available:


Using the above grouping method, co-channel phenomenon does not appear among

adjacent cells. However, opposite cells may have adjacent channels (as shown by the

red arrows in the figure above):

Pattern 1: D1---A2; Pattern 2: D2---A3; Pattern 3 D1---A2;

Pattern 4: D2---A3; Pattern 5: D3---A1; Pattern 6: D3---A1.

Change a frequency grouping pattern, as shown in the following table:

A1 B1 C1 D1 A2 B2 C2 D2 A3 B3 C3 D3

1 2 4 3 5 8 7 6 9 11 10 12

13 14 16 15 17 20 19 18 21 23 22 24

25 26 28 27 29 32 31 30 33 35 34 36

Six frequency reuse patterns:

Pattern 1 and 4 do not have adjacent channel. Pattern 2: C1---A2; Pattern 3: B2---A3;

Pattern 5: C1---A2, B2---A3, D3---A1; Pattern 6: D3---A1

59


Therefore, it is recommended to use the reuse pattern 1 and 3. As the base stations of

each system are not exactly located in the grid, the former grouping pattern can also be

used, but pay attention to the adjacent channel of opposite cells.

The example table shows that the maximum configuration of the BTS is 3/3/3. The

frequency utilization is very low and cannot meet the requirement of network capacity

expansion in areas with high traffic. In some medium and large cities, the population is

dense, and site distance is not more than 1 km and some of the coverage radius is only

several hundred of meters, or even 300 m for some sites. Obviously, it is not realistic to

improve the network capacity by using massive cell splitting. To meet the requirement

of ever-increasing network capacity, there are two solutions available. One solution is

to develop the GSM900/1800 dual band network, and the other solution is to adopt the

aggressive frequency reuse pattern.

60


3.4.2 3 x 3 Frequency Reuse

A3

C2B1

C1

C3

B3B2

61

A1

A2

A3

C2B1

C1

C3

B3B2

A1

A2A3

C2B1

C1

C3

B3B2

A1

A2

A3 C1

A1

A2

A1

A3

C2

A2 C1

B1 C

B3B2

A3 C1

A1

A2

A1

AA2

B1

B2 B

Figure 3.4-2 3 x 3 frequency reuse



dBdBC 3.132log10)(4

==I )57.5(2)7(2 44 + −−

−


application:

3 x 3 reuse pattern generally uses baseband frequency-hopping. It divides the available

frequency into 9 groups, which are tagged as A1, B1, C1, A2, B2, C2, A3, B3, and C3,

as shown in the following table:

A1 B1 C1 A2 B2 C2 A3 B3 C3

1 2 3 4 5 6 7 8 9

10 11 12 13 14 15 16 17 18

19 20 21 22 23 24 25 26 27

28 29 30 31 32 33 34 35 36

The two reuse patterns are:


A1

A2 A3

B1

B2 B3

C1

C2 C3

C1

C2 C3

B1

B2 B3

A1

A2 A3

A1

A2 A3

C1

C2 C3

B1

B2 B3

A1

A2 A3

C1

C2 C3

B1

B2 B3

B1

B2 B3

C1

C2 C3

A1

A2 A3

A1

A2 A3

B1

B2 B3

C1

C2 C3

Pattern 1: No adjacent frequencies for opposite cells.

Pattern 2: C1---A2, C2---A3, C3---A1

Obviously, pattern 1 is better.


A 3

62

A 1

A 2

A 3

A 1

A 2

A 3

A 1

A 2

A 3

A 1

A 2A 3

A 1

A 2

A 3

A 1

A 2

A 1

A 2 A 3

Figure 3.4-3 1×3 Reuse



dBdBIC 43.9

)36.4(252log10)( 44

4

=+

= −−

−


application:

3 x 3 reuse pattern is the most closed pattern in frequency reuse. It is generally used in

synthesizer hopping frequency system. In addition, anti-interference technologies such

as DTX, power control, and antenna diversity also need to be used so as to rectify the

interference deterioration resulted from the reduction of reuse distance. This

technology divides the non_bcch frequency into A1, A2, and A3 groups, which

individually serve as the MA of three sectors of each base station, as shown in the


following table:

A1 1 4 7 10 13 16 19 22 25 28 31 34

A2 2 5 8 11 14 17 20 23 26 29 32 35

A3 3 6 9 12 15 18 21 24 27 30 33 36

When the hopping frequency load (cell frequencies/MA length) is less than 50%,

ensure that the MAIOs of the three cells of the same base station do not have adjacent

frequencies, MAIOs of the cells with the same direction in each base station are

consistent, HSNs of the three cells of the same base station are the same, HSNs of

adjacent base stations are different, and base stations with the same HSN should be as

far as possible.


63

A1A 2

A3A4

A5

A6

B1B2

B3B4

B5

B6

A1A 2

A3A4

A5

A6

B1B2

B3B4

B5

B6

A 1A2

A 3A4

A5

A6

B1B2

B3B4

B5

B6

A 1A2

A3A4

A5

A6

B1B2

B3B4

B5

B6

A 1A2

A3A4

A1A 2

A3A4

A1A 2

A3A4

A5

A6

B1B2

B3B4

B5

B6

A1A 2

A 1A2A6

A 1A2

A3A4

A5

A6

B1B2

B3B4

B5

B6

Figure 3.4-4 2×6 Reuse

The 2x6 reuse model is not a symmetrical model. Cell A1 and cell A4 have different

reuse distances from other cells.


interference model described above, user can obtain the C/I ratios of cell A1 and cell

A4:


dBdBIC 86.16

)64.2(1log10)( 4

4

== −

−

C/I ratio of other cells:

dBdBIC 04.12

)2(1log10)( 4

4

== −

−

3.4.5 Multiple Reuse Pattern (MRP)

MRP technology divides the whole frequency band into BCCH and TCH bands that are

mutually orthogonal by using different reuse patterns. Each segment of carrier serves

as an independent layer. Frequencies at different layers adopt different reuse patterns

and the frequency reuse becomes increasingly closer layer by layer.

One way of improving system capacity is to use closer reuse patterns. Because the

BCCH plays an important role during the access and handover of the MS, the use of

the frequency orthogonal to the TCH band to ensure BCCH quality brings about the

following benefits:

1. BCCH can use the 4 x 3 or higher reuse coefficient to ensure quality, while the TCH

can use the relatively intensive frequency reuse pattern.

2. The decoding of BSIC is independent of the load of speech channels.

3. Because the BCCH band and the TCH band are mutually orthogonal, the increase of

TCH load hardly affects the BCCH, and thus the decoding of BSIC is not affected.

In this way, the handover performance can be improved.

4. The configuration of the adjacent cell table is simplified. According to related

literature, the adjacent cell table, if too long, may reduce the handover performance.

5. Because BCCH uses a separate frequency (12 frequencies in the 4×3 pattern), the

adjacent cell table (composed of the BCCH frequencies) length can be reduced

significantly.

6. The anti-interference technologies such as power control and DTX are brought into

play. The BCCH cannot dynamically use the technologies such as power control and

DTX. The BCCH always transmits signals at the maximum transmission power.

Therefore, if the BCCH and TCH use the same frequency band, the effect of these

anti-interference technologies will be affected.

64


65

7. The BCCH and TCH are independent of each other. This makes it easy to maintain

and expand each layer individually. The addition or deletion of TRXs of sites or

cells will not affect the existing BCCH planning, which makes easier network

maintenance.

6MHz MRP Segmentation

Carrier

No. 1 2 3 4 5 6 7 8 9 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

BCCH(12) 1 2 3 4 5 6 7 8 9 11 12

TCH1(8) 13 14 15 16 17 18 19 20

TCH2(6) 21 22 23 24 25 26

TCH3(4) 27 28 29 30

The MRP is one of the important technologies in the development of frequency

planning in recent years. As mentioned in the related literature, when the MRP is used

with anti-interference technologies such as frequency hopping, DTX, and power

control, the average frequency reuse coefficient can be reduced to around 7.5, without

affecting the network quality.

Example:

Table 3.4-1 Carrier Distribution of Different BTSs

Number of Cell TRXs 2 3 4

Percentage of Such Cell 20% 30% 50%

MRP Segment 12/8 12/8/6 12/8/6/4

Average Frequency Reuse Coefficient (12+8)/2=10 (12+8+6)/3=8.7 (12+8+6+4)/4=7.5

Frequency Hopping Diversity Gains Small Medium Large

In Table 3.4-1, the number of cells with 2 TRX accounts for 20% of the total carriers,

with 3 TRX for 30%, and that with 4 TRX for 50%. Suppose that these cells are

“distributed evenly”, the average frequency reuse coefficient must be lower than the

actual reuse coefficient. For cells with 3 TRX: The cells with three or more TRXs

actually account for 80% of the total, and they are distributed evenly, so the actual

reuse coefficient of L3 TRX is 6/0.8=7.5.

Expanded MRP is the expansion of the MRP concept. After segmentation, each layer

can include the frequencies of each subsequent layer: The TCH0 layer includes various

frequencies of layers TCH1- TCHn, the TCH1 layer includes those of layers TCH2-

TCHn, and so on. First, allocate the frequencies of layer TCHn, and then those of layer


TCHn-1, and so on. However, this affects the structured feature of the MRP planning.

Table 3.4-2 6MHz Band Expansion MRP Segmentation

Carrier

No. 1 2 3 4 5 6 7 8 9 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

BCCH(12) 1 2 3 4 5 6 7 8 9 11 12

TCH1(8) 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

TCH2(6) 21 22 23 24 25 26 27 28 29 30

TCH3(4) 27 28 29 30

Example:

Take the 7.2 MHz frequency bandwidth as an example. Use the MRP to divide the 36

pairs of carriers into groups according to 12/9/8/7, as shown in Table 3.4-3:.

Table 3.4-3 Carrier Allocation Table

Channel Type Logical Channel TCH1 TCH2 TC3

Frequency Band

Number

60 61 62 63 64 65

66 67 68 69 70 71

72 73 74 75 76 77

78 79 80

81 82 83 84 85

86 87 88

89 90 91 92

93 94 95

The BCCH uses the 4 x 3 reuse (as shown in Figure 3.4-5 A), the TCH1 uses the 3 x 3

reuse (as shown in Figure 3.4-5 B), and TCH2 and TCH3 use 2 x 3 reuse (as shown in

Figure 3.4-6 A and Figure 3.4-6 B), in four groups:

60

64

62

66

7063

67

68 7161

65

69

72

75

73

76

7972

75

78 787477

80

Figure 3.4-5 (A) BCCH uses 4 x 3 reuse mode (B) TCH1 uses 3 x 3 reuse mode

66


Figure 3.4-6 (A) TCH uses 2 x 3 reuse mode (B) TCH3 uses 2 x 3 reuse mode

60728189

64 75 8391

85 93 6878

62738290

66 76 8492

70808594

63 7282 90

67 75 92 84

71 8678 94

65 77 8391

61748189

85936980

Figure 3.4-7 Schematic Diagram for 7.2 MHz Band MRP Carrier Configuration

Comparison of system capacity between group reuse and MRP technology

According to the analysis and description of various reuse patterns described above,

now we compare the increase in capacity between these four reuse patterns. Table 3.4-4

shows the BTS configuration that can be implemented of various patterns in different

bandwidths, the average capacity of each BTS, and capacity ratio (with the 4*3 pattern

as reference).

Table 3.4-4 Comparison of system capacity between various reuse patterns

Reuse Pattern BTS ConfigurationAverage Site Capacity

(Subscribers) Capacity Ratio

4 x 3 3/2/2 or 3/3/2 1440 1

3 x 3 3/3/3 1788 1.24

1 x 3 4/4/4 2640 1.83

6 MHZ

MRP (12, 9, 6) 3/3/3 1788 1.24

67


68

**

2 x 6 2/2/2/2/2/2 2160 1.5

4 x 3 4/4/4 2628 1

3 x 3 5/5/5 3384 1.29

1 x 3 6/6/6 4272 1.63

MRP (12, 9, 6)

** 6/6/6 4272 1.63

9.6 MHZ

2 x 6 3/3/3/4/4/4 4416 1.68

Note: GOS=0.02, 0.025Erl/subscriber

**( ) means the reuse pattern of each carrier.

3.4.6 Concentric Cell Technology

1. Basic Principles

By concentric cell, it means that a common cell is divided into two areas: outer layer

and inner layer, also known as overlay and underlay. The coverage of the outer layer is

the traditional cell, while the coverage of the inner layer is around the BTS. In addition

to the coverage, the frequency reuse coefficients of the outer layer and the inner layer

are also different. The outer layer usually adopts the traditional 4 x 3 frequency reuse

pattern, while the inner layer adopts the closer frequency reuse patterns such as 3 x 3, 2

x 3, or 1 x 3. Therefore, all TRXs are divided into two groups: one group is used for the

outer layer and the other for the inner layer. It is because the outer layer and the inner

layer share the same site, the same antenna system, and the same BCCH, such a

structure is called concentric cell. However, the common control channel must belong

to the channel group of the outer layer. In other words, a conversation must be

established on an outer layer channel. Figure 3.4-8 shows the structure of a concentric

cell.


Figure 3.4-8 Schematic diagram for the concentric structure

According to the implementation mode, the concentric cell is divided into common

concentric cell and intelligent underlay overlay (IUO). The major difference between

these two types of concentric cell lies in the transmission power of the inner layer and

the handover algorithm between the inner and outer layers.

The transmission power of the inner layer of a common concentric cell is usually lower

than that of the outer layer to reduce the coverage, increase the distance ratio, and meet

the requirement of co-frequency interference. The handover between the inner layer

and outer layer of a common concentric cell is usually based on the power and the

distance.

The transmission power of the inner layer (because the frequency adopts the closer

reuse pattern, this layer is called super layer) of the IUO is completely the same as that

of the outer layer (usually called conventional layer) because the transmission power is

related to the handover algorithm. The IUO handover algorithm is a handover

algorithm based upon C/I. The actual implementation process is briefly described as

below:

First, the call is established on the conventional layer, and then the BSC continuously

monitors the C/I ratio of the downlink super group channel of the call. When the C/I

ratio of one super channel reaches the available threshold (known as GoodC/Ithreshold

in the IUO), the call channel is switched over to the super channel. At the same time,

69


70

continues to monitor the C/I of the channel. If it degrades to a certain threshold

(BadC/Ithreshhold), the channel is switched to the common channel. Therefore, the

following functions must be added in order to use IUO:

A. Estimation of the downlink co-frequency C/I ratio

B. Handover algorithm related to IUO

C. Intra-cell handover from conventional layer to super layer (the measured C/I ratio

must be greater than GoodC/Ithreshold)

D. Intra-cell handover from super layer to conventional layer (the measured C/I ratio is

smaller than BadC/Ithreshhold)

2. Capacity

Because the inner layer adopts the closer frequency reuse pattern, more TRXs can be

allocated to each cell to increase the frequency utilization and the network capacity. It

should be noted that the coverage radius of the inner layer of a concentric cell is less

than that of a common cell. The traffic absorption of the inner layer is restricted by the

traffic distribution and the coverage. Table 3.4-5 shows the comparison between a

concentric cell and the traditional 4 x 3 pattern of different traffic distribution and

different coverage ranges, Where Si means the inner layer coverage, Sout means the

outer layer coverage area, and Erlang the unit of capacity:

Table 3.4-5 Comparison in Traffic Volume Between Various Reuse Patterns

Coverage Ratio

(Si / Sout) 3TRX 2TRXout+2TRXin 4TRX 3TRXout+2TRXin

0.3 14.04 10.57 21.04 20.05

0.7 14.04 20.55 21.04 28.25

Even

distribution

of traffic 0.9 14.04 21.04 21.04 28.25

0.3 14.04 15.09 21.04 21.92 Linear

distribution

of traffic 0.7 14.04 21.04 21.04 28.25

It should be noted that the coverage ratio is related to the frequency reuse type: the

closer the frequency reuse pattern, the higher the co-frequency interference, and the

smaller the inner coverage percentage. In addition, it is also related to the settings of

the handover parameters and the surrounding environment. Therefore, user should not

set the coverage radius randomly but user must consider the network quality, which can


71

seldom exceed 50%.

According to the above analysis, the concentric technology can barely increase or even

decrease the capacity when the traffic is distributed evenly. The better the effect in

increasing the capacity, the more the traffic is concentrated around the BTS. Generally,

the capacity increase is very limited. For a common concentric cell, the transmitted

power of the inner layer is low and cannot easily absorb the traffic indoors, so the

efficiency of the frequency is not high. The actual capacity increases about 10-30%.

For IUO, the transmitted power of the inner layer is not changed, it can absorb the

indoor traffic, and it can absorb the capacity flexibly for handover based on quality.

Therefore, the actual capacity increases greatly by about 20-40%.

3. Characteristics and applications

a. Common concentric cell

The characteristics of a common concentric cell include:

1. It is unnecessary to change the network structure.

2. It is necessary to add some special handover algorithms. However, the

implementation is simple as a whole.

3. There is no special requirement for the handsets.

4. The capacity increase is limited, usually within 10% to 30%, and is also related to

the traffic distribution. The power of the outer layer is low so that it is difficult for

the outer layer to absorb indoor traffic.

5. The common concentric cell is applicable to the case where the traffic is

concentrated around the BTS and distributed outdoors.

Pay attention to the following in application:

1. Perform good network planning. On one hand, it should be used in the areas with

concentrated traffic. On the other hand, user should well plan the coverage area of

the inner layer. In other words, do not allow the quality to be affected by the

interference resulting from close reuse, while adequate traffic should be absorbed.

If the planning is not good, not only the capacity is not increased, but also the

network quality may be reduced.

2. It is preferable to combine the concentric cell with the anti-interference

technologies such as power control and DTX


72

b. Intellignet underlay overlay (IUO)

The IUO has the following characteristics:

1. As a type of concentric cell, the IUO can utilize the existing site. The network change is

small and there is no special requirement for the handsets.

2. The system function requires the measurement and estimation of C/I ratio as well as

special handover algorithm additionally.

3. The capacity can be increased by 20% to 40%. The capacity increase is related to the

traffic distribution and the traffic absorbed by the super layer. The quality can be

ensured when the capacity is increased.

4. The super layer can adopt the closer frequency reuse pattern. When the frequency band

is wide enough, part of the frequencies can be reserved for micro cells.

5. The IUO is applicable to cells where the traffic is highly concentrated around the BTS.

Pay attention to the following when user use the IUO:

1. Perform network planning. Perform cell planning according to the traffic distribution

and take steps to reduce interference.

2. When user configure the cell channels, pay attention to the reasonable configuration of

the super group frequency and common group frequency. Enable the bottom layer to

absorb adequate capacity to reduce call drop. Set the cell parameters appropriately.

3. To reduce the interference, technologies such as power control and discontinuous

transmission (DTX) can be combined with the IUO.

4. Preferably C/I-based handover should also be used on the conventional layer.

3.5 Cell Splitting

At the early stage of the GSM network construction, the number of subscribers is not

large, and therefore there are usually idle channels. As the number of subscribers

increases, the channels originally assigned to each BTS cell will be congested. In this

case, new channels can be added and allocated within the original BTS. If the number

of subscribers continues to increase and all available channels are already assigned,

only the cell splitting technology is applicable to increase BTS quantity and

co-frequency reuse to meet the requirement. Usually, the radius of a split cell is only a


73

half of that of the original cell.

Radius of new cell = Radius of old cell/2 (1-5-1)

Based on formula (1-5-1), the following formula is derived:

Coverage area of new cell = coverage area of old cell/4 (1-5-2)

Let each new cell have the same maximum traffic load as the old cell, we can

theoretically obtain:

New traffic volume/unit area = 4 old traffic volume/unit area (4-3-3)

Therefore, the relationship in capacity between cell splitting and subscriber addition

can be expressed as the following formula:

Tn = 4n T (1-5-4)

Where, Tn is network capacity after "n” times of cell splitting

T0 is network capacity before cell splitting

Formula (4-3-4) is applicable to the case where a cell is split into four smaller cells

according to 1:4. In simple words, after one time of splitting, the number of subscribers

increases to four times the original, but the actual capacity is smaller than four times.

3.6 Common Anti-Interference Technologies

The GSM itself has many anti-interference technologies such as frequency hopping,

power control, and DTX based on voice activity detection. The effective application of

these technologies can improve the C/I ratio to form the closer frequency reuse pattern

and increase the frequency reuse coefficient and frequency utilization. These

parameters are described one by one as below, with purely mathematical and simulated

models to study their gains.


3.6.1 Discontinuous Transmission (DTX)

DTX codes voices at a rate of 13 kbit/s during voice activation period, and codes

comfort noises at the rate of 500 kbit/s during silent period.

DTX contributes little to interference during silent period, and it can be believed that

its power is zero (non-activated state). Suppose the activation factor of DTX is

480 ms

Voice frame

Comfort noise frame

BTS MS

TRAU BTS

p ,

then the gain is:

pCCdBIC log10log10log10)(/ −=−=ΔIpI

3.6.2 Frequency Hopping (FH)

As a type of spectrum spread communication mode, frequency hopping, when used in

the cellular mobile communication system, can enhance the immunity of the system

against multi-path fading, and can suppress co-frequency interference that may affect

the communication quality, so it is very valuable. Particularly at a time when the

frequency spectrum resource becomes increasingly insufficient, frequency hopping will

become one of the most effective means for improving the spectrum utilization.

In the GSM, the data of each logical frame are interleaved in a distributed way in eight

TDMA frames for transmission, while all these data have undergone convolutional

coding. If the code blocks of these eight bursts are partly interfered or damaged, the

good convolutional decoder can be used to restore the data transmitted. However, if too

many code blocks are damaged, it is very difficult to restore the old data. Through

frequency hopping, the bursts of one channel will not stay in the deep fading area

continuously for a long time (this is very likely occur to one MS still or in slow motion

that works on a fixed carrier), and will also not always be interfered by the same

74


75

powerful co-frequency signal. This way, the channel coding/decoding can be used to

obtain good transmission effect. This is the simple principle for using the frequency

hopping technology to improve the communication quality.

The frequency hopping sequence used by the GSM system is a Poisson pseudo random

variable sequence, which can provide up to 64 frequency hopping sequences, with the

length same as that of an ultra-high frame (lasting for 3 hours, 28 minutes, 53 seconds,

760 milliseconds), to ensure various sequences to be orthogonal between each other as

far as possible, for good frequency hopping effect. The frequency hopping sequence in

the GSM is described by two parameters: HSN (hopping sequence number) and MAIO

(mobile allocation index offset). Usually, different cells are allocated to different HSNs,

while different MAIO values are allocated to different channels in cells.

It can be seen that various channels in one cell use the same HSN, only with different

MAIOs. This ensures that the channels in one cell will not occupy the same frequency

at the same time. Different cells have different HSNs, using different types of

frequency hopping sequences. This way, the HSNs of various cells are independent of

each other as far as possible, and the powerful interference source signals are allocated

to multiple channels, ensuring the coding effect. When HSN=0, the MAIO repeats in

cycle from low to high, known as Cyclic Hopping. Because this method has a very low

gain, it is usually not used in GSM.

GSM supports baseband frequency hopping and RF frequency hopping (also known as

Synthesized Frequency Hopping). For baseband frequency hopping, multiple

transmitters work at their respective frequencies, while the signals of different channels

on the baseband are switched over to different transmitters for transmission according

to the HSN, for frequency hopping. On the other hand, RF frequency hopping means

that the transmission frequency of the transmitter hops according to the HSN.

Baseband frequency hopping is easy to implement, but it has few hopping frequencies

due to the restriction of the number of TRXs. The frequency hopping simulation

system established by ZTE CORPORATION mainly supports the RF frequency

hopping, while the baseband frequency hopping is taken as a special example of RF

frequency hopping (that is, when the number of frequencies is equal to the number of

TRXs).

The main benefit of frequency hopping is the so-called frequency diversity and

interference diversity. The former increases the coverage area of the network, while the


76

later increases the capacity of the network.

Since baseband frequency hopping has its number of available frequencies equal to that

of the TRXs, it brings about only frequency diversity gains, without interference

diversity gains. However, now the GSM operator is more concerned with capacity,

since coverage is no longer a problem in most cities. To solve the capacity problem, the

RF frequency hopping is a very effective means.

RF frequency hopping represents the application trend in network planning.

(1) Frequency diversity gain

Frequency diversity means the immunity against Rayleigh fading. Due to the

independency between the Rayleigh fading on different carriers (the larger the

frequency difference, the smaller the dependency), the bursts distributed over different

carriers will not be affected by the same Rayleigh fading. This is very valuable for the

Static MSs or in slow motion. It is said that this can provide gains about 6.5 dB. While

for MSs in fast motion, the time and location difference between two consecutive

bursts of one channel is adequate to make them independent of Rayleigh changes. In

other words, they are nearly not affected by the same fading. In this case, slow

frequency hopping can provide very small frequency diversity gain.

When an MS is moving rapidly, the number of frequencies configured for a cell has

little impact on the frequency hopping performance. On the other hand, for the case

without frequency hopping, there is about 1~2 dB frequency diversity gain. When a

MS is moving slowly (TU3), due to the frequency diversity effect, the number of

frequencies configured has a significant impact on the system performance. Once the

number of frequencies doubles, a gain of about 0.2 ~ 1 dB can be obtained, and the

load ratio increases for about 10%.

(2) Interference diversity gain

Interference diversity means the ability to suppress the interference signals from other

co-frequency reuse cells, by providing frequency hopping on the transmission path, to

improve the interference in harsh conditions so that all subscribers can evenly obtain

good communication quality. This is very important for the mobile communication

system with a great number of subscribers, particularly for increasing the

communication capacity by increasing the frequency reuse ratio. Usually, to provide

the interference diversity effect, the number of hopping frequencies should be no less


than 3.

Frequency hopping set MA {ƒ1, ƒ2, ƒ3 … ƒn}

Number of TRXs: m (m≤n)

Interference cell

Figure 3.6-1 Frequency Hopping Allocation Schematic Diagram

Suppose the MS use fk for a call at the moment “t”. Now, the probability that the

interference cell (fk) is activated is:

nmCCp mn

mn //1

1 == −−

mn

IC

pICdBIC log10log10log10)(/Gain =−=Δ

(3) Frequency hopping planning and capacity analysis

Suppose there are 10 MHz frequencies. When frequency hopping is not used, the

frequency planning and capacity analysis are described as below:

The reuse pattern of BCCH is 4X3, and that of the traffic channel is 3X3. The 10 MHz

offers 50 frequency points. In addition to one protection frequency point and 12 BCCH

points, there are 37 left. Therefore, each cell can be allocated with four traffic

frequency points ((37-1)/9). Totally, there is one frequency point left. In other words,

the maximum configuration is 5+5+5. Each cell can provide 37 channels

(1BCCH+2SDCCH+37TCH).

When the RF frequency hopping technology is used, the traffic channels can adopt 1X3

reuse. When the load is 50%, each cell can provide six traffic logical frequency points,

which are so called because they use the same 12 frequency hopping sets ((37-1)/3),

only with different HSNs and MAIOs. Similarly, there is one frequency point left,

while the maximum configuration becomes 7+7+7, providing 53 traffic channels

77


(1BCCH+2SDCCH+53TCH), increasing the capacity by 43%. At the same time, more

than 90% areas can still reach the C/I ratio of 9dB. When the DTX and the ZTE unique

fast power control algorithm are used at the same time, the capacity of the system can

increase dramatically. If the intelligent traffic control technology is used, GSM can also

obtain flexible capacity, where larger system capacity is obtained in the hot areas at the

cost of certain voice quality.

3.6.3 Dynamic Power Control (DPC)

A3

78

A1

A2

A3

A1

A2

A3

A1

A2

A3

A1

A2A3

A1

A2

A3

A1

A2

A1

A2 A3

Figure 3.6-2 Schematic Diagram for Dynamic Power Control

As shown in Figure 3.6-2, only when the interference MS under the dynamic power

control is on the edge of the cell, can the BTS work at the maximum transmitted power.

Obviously, the location of the interference MS is a probability. This case is particularly

obvious in frequency hopping.

Suppose the DPC factor is p:

pIC

pICdBIC log10log10log10)(/ −=−=ΔGain

3.6.4 1 x 3 Reuse + RF Frequency Hopping + DTX + DPC

Let us examine the “1 x 3” reuse interference to see how much the anti-interference

technology contributes to the reduction of interference and the increase of system

capacity.


79

The “1 x 3” reuse, compared with “4 x 3” reuse, brings about the following

interference degrade:

CIR 4 x 3- CIR 1 x 3 =18 - 9.43 ≅ 8.57 dB

“1 x 3” frequency hopping and 50% load can bring about the following interference

diversity gain:

10log10(2/1) = 3dB

Suppose the frequency hopping length is 12 frequency points. Then, the frequency

diversity gain brought is about: 2dB

Suppose the activation factor of DTX is 0.5, then the gain is:

-10log10(0.5) = 3dB

Suppose the activation factor of DTX is 0.9, then the gain is: -10log10(0.9) =0.5dB

The total gain is 3+2+3+0.5=8.5dB.

According to the above analysis, we can see that the anti-interference technology can

basically compensate the interference degrade brought about by closer reuse pattern.

3.7 Summary of GSM Frequency Allocation

Signals of the same base station cannot be co-channel and adjacent-channel.

Adjacent base stations should avoid co-channel (even if the antenna main lobe

directions are different, the side lobe and back lobe cause interference)

Opposite cells cannot be co-channel. Adjacent channel should be avoided,

especially the BCCH and SDCCH frequencies (generally the first and second

frequencies of a cell). When frequency hopping is used, the starting point of an

adjacent base station can be the same, but the frequency hopping algorithm

must be different.

For synthesizer frequency hopping, the algorithm (HSN) of each cell in the

same base station is consistent, but the Mobile Allocation Index Offset (MAIO)

can not be adjacent. Note that the CCB combiner does not support frequency

hopping.

BSIC = 8 x NCC + BCC and BCC ranges from 0 to 7. Therefore, the BSIC of

close co-channel and adjacent-channel cells should be inconsistent. Avoid


80

co-channel (especially BCCH) and co-BSIC in a short distance.

If a mountain exists at the cell edge, do not set the base station as the neighbor

station. If a water area exists, consider to set the base station as the neighbor

station.

Before frequency hopping, the usage range of BCCH is not limited and the

BCCH can be staggered. During frequency hopping, a band should be

segmented from the BCCH for 4 x 3 frequency reuse. If the frequencies are

sufficient, the 5 x 3 reuse mode even 6 x 3 reuse mode can be considered so

that the interference between BCCHs can be reduced.

In large and medium-sized cities, use different close frequency reuse modes

based on the functions supported by the equipment, for example, MRP, 1*3,

1*1 hopping frequencies. In addition, reserve some frequency points for micro

cells to construct layered network. The frequency reuse coefficient is

comparatively small.

In small and medium-sized cities, use different frequency reuse modes based on

the functions supported by the equipment. Determine whether to construct

layered network based on the actual situations. The frequency reuse coefficient

is a little greater than that of large and medium-sized cities.

In towns and villages, the frequency resource is rich. Use the 4 x 3 frequency

reuse mode.

For mountain sites, allocate separate frequency points.

In addition to the principles mentioned above, there is another important principle, that

is, the frequency planning must agree with the actual situations. The terrain and base

stations of each system are different and radio propagation environments are different.

This requires that the frequency planning should correspond to the actual situation

without being limited by the accumulated experience. If possible, use special planning

tools and electronic maps to predict the field strength. First observe whether the

coverage area of each cell is reasonable. Then, modify the coverage or frequency

planning for areas whose interference does not meet the requirement (the co-channel

interference is set to around 12 dB with 3 dB margin in frequency planning). After the

base station is commissioned, determine whether the coverage planning is reasonable

by using drive test and other statistical data. For severely interfered areas, adjust the


81

coverage and modify the frequency planning.

During frequency planning, the geographical area is always virtually sliced. Note that

edges between slices must reserve some frequency points (when frequencies are

sufficient) or have band plan. The determined edges should be far from hot areas or

complicated networking areas.

Generally, plan the frequency from the densest districts, for example, central business

district, to suburbs with low frequency configuration (generally O1 or S1/1/1 type).

Pay special attention to urban areas with a river or large lake and avoid interference

resulted from strong transmission of water surface.

Because base stations are irregularly distributed in actual situations, the frequencies in

the same layer are not sure to be planned as 4*3 or 3*3. Adjust the frequency planning

according to the actual situations.

3.8 Neighbor Cell Planning

3.8.1 Planning Principles

The planning of neighbor cells determines the continuous coverage of a GSM network

and the network performance. The principles for planning neighbor cells are as

follows:

1. Main cell and neighbor cell must not be co-channel.

2. The number of neighbor cells cannot exceed 32. OMCR can be configured with a

maximum of 32 neighbor cells.

To obtain the optimal planning effect, take the following factors into account: one is

quality of service and the other is system load. More neighbor cell relations lead to

more system load resulted from handover. Appropriate neighbor cell planning can

effectively reduce call drops due to handover failure.

When defining neighbor cells, pay attention to the following issues:

1. Excessive neighbor cells result in excessive handovers, and moreover, overload

signals.

2. Insufficient neighbor cells result in call drops due to handover failure, and degrade

the quality of service.


For neighbor cell planning, cells are considered to arrange regularly in a cellular

structure. Therefore, pay attention to the following issues:

a. For macro cells in urban areas, configure two-level adjacency relationship, as shown

in Figure 3.8-1:

A3

D2B1

D1

D3

C1

A1

A2

82

B3

C2

B2

C3

A3

D2B1

D1

D3

C1B3

C2

B2

C3

A1

A2

A3

D2B1

D1

D3

C1 B3

C2

B2

C3

A1

A2

A1

A3

D2

A2 D1

B1 D3

B2 B3 C1

C2 C3

Figure 3.8-1 Neighbor cell planning for urban areas

b. For suburbs or villages, each cell has a large coverage and thus the distance between

the first and second levels is comparatively large. Therefore, only one-level cells need

to be configured when configuring adjacency relationship, as show in Figure 3.8-2:

A3

D2B1

D1

D3

C1B3

A1

A2

C2

B2

C3

A3

D2B1

D1

D3

C1B3

C2

B2

C3

A1

A2

A3

D2B1

D1

D3

C1 B3

C2

B2

C3

A1

A2

A1

A3

D2

A2 D1

B1 D3

B2 B3 C1

C2 C3

Figure 3.8-2 Neighbor cell planning for rural areas


In a dual band network, cooperation of the two systems and predefined rule are

important for configuring neighbor cells. Therefore, configure the adjacency

relationship based on different network sharing schemes.

Usually, we believe that cells are arranged in good order like a beehive, but the fact is

that they are not in perfect order due to the various factors that affect site selection. The

solution to this can only be the configuration according to the data simulated in

network planning. In addition, if the BTS has a large transmitted power, the edge of the

coverage area accounts for a large portion of the total area. In this case, the adjacency

relationship cannot be obtained from the geographical location alone. Instead, user

should make site measurement or configure more adjacency relationships, as shown in

Figure 3.8-3.

Figure 3.8-3 Neighbor cell configuration

As shown in the diagram, when an MS is moving in the curve on the edge of the

coverage area, the MS theoretically chooses the service cells in the following order: A

to B to C. However, due to influence of some complicated radio propagation

environment, the signals of site B may never dominate in this moving direction. In this

case, if site C cell is not configured to be the adjacent cell of sector 1 of site A, the MS

will stay in sector 1 of site A all the time until call drop or cell reselection. The solution

is to configure sector 1 and 2 of site A and sector 1 of site C as the adjacent cells

(monitoring frequency band). However, user should not expand without limit. For

example, user cannot set all the cells such that any two are adjacent cells to each other,

as this cause many undesired cell reselections and handovers.

83


84

Unreasonable Neighbor Cell Planning:

1. Unidirectional neighbor cells

2. Excessive neighbor cells

3. Insufficient neighbor cells

Problems Resulted from Unreasonable Neighbor Cell Planning

1. Call drop

2. Handover failure

3. Frequent handovers

4. Isolated cell

5. Exceptional inter-cell handover

6. Unbalanced traffic

7. Reduced handover precision

3.8.2 Case Analysis

Case 1

[Problem Description]

The situation of the problem base station is as follows:

S333 base station configuration

GSM900 network

1*3 RF frequency hopping

A sector of this base station has continuous high handover failure rate. The original cell

A accounts for 80% of the incoming handover failure. Other indicators such as call

drop rate and voice channel allocation failure are normal.

[Reason Analysis]

The problem does not occur due to hardware faults and interference. Though the

handover failure rate is high, TCH allocation never fails. This proves that the MS can

successfully seize the TCH allocated by the BSC. Additionally, call drops never occur

and the voice quality is good. This proves that no interference exists. As the original


85

cell A, which has high incoming handover rate, is far from the cell, less handover

requests should have been originated. Therefore, the cause of the problem is isolated

cell effect.

[Fault Location]

Check the cells around the original cell A for cells co-channel and co-color with the

problem cell C and find cell B. Further research finds that a large square is established

between cell B and cell A. The open square improves the radio propagation condition

between cell B and cell A. Thus, the MS actually listens to the signals from cell B

whereas the BSC identifies that MS sends Handover Command to cell C. Actually, the

level of cell C may be low and as a result, the handover fails.

[Solution]

Modify the frequency point of cell C and add the isolated cell B to the neighbor cell list

of cell A.

[Summary]

Pay attention to environment changes when handling network problems. If the change

in environment affects or improves radio signal propagation, timely adjust the cell

parameters (for example, add, delete, or modify neighbor cells or frequencies) and

engineering parameters (for example, antenna mount height, downtilt, and azimuth).

Because GSM network frequencies are limited, the isolated cell effect is more probable

to occur with the expansion of network dimension. In addition, severe co-channel

interference may greatly affect handover success rate.

Case 2

[Problem Description]

A user living at the border of a province complains that his mobile phone does not have

roaming problems in his residence, but after receiving roaming signals from another

province, it cannot disengage from the roaming signals. The two princes have no

neighbor cell relationship.

[Reason Analysis]

The drive test finds that the network structure is as shown in Figure 3.8-4:


Figure 3.8-4 Network structure

The user location is spot P which is located in cell A. Cell A and cell B are mutually

neighbor cells and they are subscriber homing network. Cell C and cell D are mutually

neighbor cells and they are roaming network. Cell A does not have neighbor cell

relationship with cells C and D.

Because cell D has the same BCCH frequency point as the neighbor cell B of cell A,

the MS in spot P may select cell C and then select cell C through cell D. Cell A

frequency point is not defined in the neighbor cell lists of cell C and cell D. Therefore,

the MS is resides in the network of the roaming location. After the user powers on the

MS again in cell C, the MS still keeps the frequency point of the cell when it is

powered off. As a result, the MS first seeks the frequency points of cell C and its

neighbor cells and the roaming problem occurs.

[Solution]

Define the neighbor cells between provinces. If this method is not applicable, modify

cell B frequency point.

3.8.3 BSIC Planning

3.8.3.1 Definition

In the GSM system, each BTS is allocated with one local color code, known as base

station identify code (BSIC). If MS receives the BCCH carriers of two cells at a

location with the same channel number, the MS distinguishes them according to the

BSIC. In network planning, the BCCH carriers of the adjacent cells should use

different frequencies in order to reduce co-frequency interference. On the other hand,

86


the characteristics of the cellular communication system determine that the BCCH

carriers are certain to have the possibility of reuse. For these cells using the same

BCCH carrier frequencies, user must ensure that they have different BSICs, as shown

in Figure 3.8-5:

Figure 3.8-5 Schematic Diagram for Selection of BSIC

In the diagram, the BCCH carriers of cells A, B, C, D, E and F have the same absolute

channel numbers, and other cells use different channel numbers as the BCCH carriers.

Usually, cells A, B, C, D, E and F must use the same BSIC. When the BSIC resource is

insufficient, different BSICs should be first ensured for the close cells. For cell E, if

there are not sufficient BSIC resources, different BSICs should be first used for cells D

and E, B and E, and F and E, while cells A and E, and C and E can have the same

BSICs.

Its major functions are:

1. After a MS receives the SCH, it believes that it has been synchronized with the

cell. However, to correctly decode the information on the downlink public

signaling channel, the MS also needs to know the Training Sequence Code (TSC)

used by the signaling channel. According to the specification of GSM, the TSC

is available in eight fixed formats, which are represented with sequence numbers

0 ~ 7 respectively. The common signaling channel of each cell uses the TSC

determined by the BCC of the cell. Therefore, one of the functions of the BSIC

is to notify the MS of the TSC used by the common signaling channel of the

current cell.

2. Since the BSIC has participated in the decoding process of the Random Access

Channel (RACH), it can be used to prevent the BTS from sending the MS to the

RACH of the adjacent cell, for misinterpretation as the access channel of the

current cell.

87


3. When the MS is in the busy mode (during calls), it measures the BCCH carrier

of the adjacent cell and reports the results to the BTS, according to the

specification of the adjacent cell table on the BCCH. At the same time, the MS

must give the BSIC of the carrier it has measured for each frequency point in the

uplink measurement report. When in a special environment where the adjacent

cells of one cell have two or more cells use the same BCCH carriers, the BTS

can distinguish these cells based on the BSIC, to avoid incorrect handover, or

even handover failure.

4. The MS must measure the signals of the adjacent cells in the busy mode, and

report the measurement results to the network. Since each measurement report

sent by the MS only includes the contents of six adjacent cells, the MS must be

controlled to report only the cells actually with handover relationships with the

current cells. The higher three bits in the BSIC (that is, NCC) are used for the

above purpose. The network operator can use the broadcast parameter “allowed

NCC” to control the MS to report the adjacent cells with the NCCs in the

allowed range.

3.8.3.2 Format

The BSIC consists of the Network Color Code (NCC) and Base Station Color Code

(BCC), as shown in Figure 3.8-6. The BSIC is transmitted on the Synchronization

Channel (SCH) of each cell.

Figure 3.8-6 Composition of the BSIC

Format of the BSIC: NCC-BCC

Value range of NCC: 0 ~ 7

Value range of BCC: 0 ~ 7

3.8.3.3 Setting and Influence

In many cases, different GSMPLMNs use the same frequency resources, which,

88


89

however, are somewhat independent in network planning. To ensure that the adjacent

BTSs with the same frequency points have different BSICs in this case, it is usually

specified that the adjacent GSMPLMNs should select different NCCs.

It is special in China. Strictly speaking, the GSM network provided by China Telecom

is a complete and independent GSM network. Although China Telecom has numerous

local mobile offices under it, they all belong to one operator – China Telecom.

However, as China is a large country with a vast territory, it is very difficult to

implement complete unified management. Therefore, the entire GSM network is

divided into parts managed by the mobile offices (or local organizations) in various

provinces and cities. On the other hand, the mobile offices in various places are

independent of each other in network planning. To ensure that the BTSs with the same

BCCH frequencies on the borders between various provinces and cities have different

BSICs, the NCCs of various provinces and cities in China should be managed by China

Telecom in a unified manner.

As part of the BSIC, the BCC is used to identify different BTSs with the same BCCH

carrier number in one GSMPLMN. Its value should meet the above requirement as far

as possible. In addition, according to the GSM specification, the TSC of the BCCH

carrier in a cell should be the same as the BCC of the cell. Usually, the manufacturer

should maintain such consistency.

3.8.3.4 Precautions

It must be ensured that the adjacent or nearby cells with the same BCCH carrier have

different BSICs. Particularly, when one cell has two more adjacent cells having the

same BCCH carriers, it must be ensured that these two cells have different BSICs. User

must pay special attention to the configuration of the cells on the borders of various

provinces and cities to avoid inter-cell handover failure.

4 Dual Band Technology


Networking modes of dual band networks

Coverage mode of dual-band networks

Traffic sharing parameters settings

Differences between uplink and downlink transmit power

4.1 Structure of Dual Band Networks

The GSM900/1800 dual-band network may be in one of the following four structures:

4.1.1 Shared HLR/AUC, EIR, OMC and SC

This structure is also called separate MSC networking structure. GSM1800 and

GSM900 are connected to their respective BSCs and MSCs and share the HLR, AUC,

OMC, SC, and EIR. The structure of shared HLR/AUC, EIR, OMC and SMC is shown

in Figure 4.1-1:

Figure 4.1-1 Network structure of separate MSC

4.1.2 Shared Switching Subsystem

This structure is also called shared MSC networking structure. GSM1800 and GSM900

are connected to their respective BSCs and share the MSC/VLR, HLR/AUC, OMC, SC,

91


and EIR. The BSSs of the DCS1800 and GSM900 are connected to the MSC/VLR

respectively via the A interface, as shown in Figure 4.1-2:

Figure 4.1-2 Network structure of shared MSC

4.1.3 Shared Switching Subsystem and BSC

This structure is also called shared BSC networking structure. DCS1800 and GSM900

share the BSC, as shown in Figure 4.1-3. As the Abis interface is not standardized yet,

the BSSs of the DSC1800 and GSM900 should come from the same equipment

manufacturer, and the BSCs shared should have functions added accordingly.

Figure 4.1-3 Hybrid network structure of shared BSC

4.1.4 Shared Network Subsystem

This structure is also called shared BTS networking mode. DCS1800 and GSM900

share the entire network subsystem. In other words, the GSM900 and DCS1800

reception/transmission functions should be implemented in one BTS, as shown in

92

4 3BDual Band Technology

Figure 4.1-4:

Figure 4.1-4 Hybrid network structure of shared BTS

It is recommended to use the shared BSC mode and shared MSC mode. Use the

separate MSC mode with caution. The reasons are as follows:

1. Dual band network requires the incorporate planning of the radio part. The

separate MSC mode cannot ensure the planning integrity.

2. The purpose of building dual-band network is to provide a high quality network.

Therefore, the shared BSC mode is the most simple and effective mode for the

operation of a dual-band network.

3. The signals to be processed are the smallest if the shared BSC mode is used. The

handover traffic is extremely large due to mobility of users. Even if the

DCS1800 has a good coverage, large numbers of handover cannot be avoided.

The shared BSC mode enables a large portion of handovers to be complete

within the BSC. In this way, the network signaling loads are greatly reduced and

thus the investment is saved.

4. The co-sited mode is commonly used in BSS. If the shared BSC mode is used,

the base stations with low configurations can use daisy chain to solve the

transmission problem. This saves investment and simplifies the construction.

5. The shared BSC mode brings limited equipment selection, complicated planning,

and difficult network maintenance and management. However, the preliminary

task is to guarantee and improve network quality as well as reducing investment.

It is worthwhile to use the shared BSC mode. If the equipment selection is a big

93


94

problem, the shared MSC mode is an alternative. The separate MSC mode is the

last choice.

6. When using the shared BSC mode, use BSCs with as large capacity as possible.

This helps network planning, engineering construction, and O&M management

simpler.

4.2 Dual Band Network Planning

4.2.1 Requirement Analysis

1. Available Frequency Scope

The planned available bandwidth is XMHz. The detailed data is as follows:

Uplink: X∼X MHz

Downlink: X∼X MHz

Corresponding channel No.:X∼X

Whether the frequency for micro cells is reserved. If yes, get the frequency

segmentation.

Whether the frequency band is used by other operators. If yes, get the frequency

segmentation.

2. Traffic sharing requirement

Determine the ratio of traffic sharing based on the requirement of the operator.

During the early phase of dual band network construction, the main task is to

make use of new DCS1800 network to share the traffic of the GSM900 network.

In terms of traffic control, observe the following principles based on the purpose

of the DCS1800:

a. During the early phase of dual band network construction, use the DCS1800 cell

to absorb dual band users to reduce the load of GSM900 system.

b. When the number of dual band users reaches a certain degree, share the traffic

between each frequency band so as to reduce dual band switching.

In actual situation, the traffic control policies can be different by adjusting

parameter settings:


95

First, in idle mode, when an MS selects the cell after being powered on or

reselects the cell in standby status, define the system message parameters CBQ

(Cell Bar Qualify), CBA(Cell Bar Access), CRO, TO, and PT to upgrade the

priority level of the DCS1800 cell or give better neighbor cell measurement

comparison values to the CSC1800. In this way, users are more likely to reside

in the DCS1800 cell and the calls are established in the DCS1800 cell.

Second, if traffic congestion occurs to the serving cell during the process of call

establishment, use the retry function to assign the MS to the idle TCH of the

neighbor cell and adjust the traffic allocation.

Last, in the conversation status, arrange cells by layer and levels to make the

enable the traffic flow to the lower-layered lower-leveled DCS1800 cell.

Additionally, set handover parameters to make the traffic load reasonable.

3. Coverage Requirement on DCS1800

a. Outdoor coverage

The outdoor coverage is easy to realize in case of short distance. If necessary,

add sites in some places in addition to establishing DCS1800 at the original

GSM900 site.

b. Indoor coverage

To ensure a good indoor coverage of the DCS1800, the distance between base

stations in urban area should be less than 1000 m. As the buildings mainly use

reinforced concrete structure and the penetration loss is great, it is recommended

that the site spacing be around 500 m to 800 m.

c. Other requirements

Determine that the operator has no other requirements on the network planning.

4.2.2 Coverage Planning

4.2.2.1 DCS1800 Coverage Modes

1. Sparse coverage mode in hot areas

The DCS1800 absorbs the traffic of hot areas. Sparsely distribute DCS1800 base

stations. In the initial phase, the coverage planning is simple. When the

DCS1800 base station has low configuration, the SDCCH and TCH congestion


and frequency handover between the two bands should be solved in network

planning. Figure 4.2-1 is the schematic diagram of GSM1800 coverage mode.

Figure 4.2-1 Sparse coverage mode in hot areas

This coverage mode is based on the original GSM900 network. As the DCS1800

base stations are established in hot areas, the continuous coverage is not realized.

If a dual-band mobile phone is in conversation in area covered by DCS1800,

then it switches to the GSM900 cell after it leaves the DCS1800 area. This

handover is caused by coverage. Similarly, when the dual-band mobile phone is

in conversation in the area covered by GSM900, it switches to the area covered

by DCS1800 because GSM900 area has large traffic and is busy. This handover

is caused by traffic. The disadvantage of this type of coverage mode is that it

only relieves the traffic pressure in a short time. In addition, frequent handover

in frequency bands increases the signal loads and thus result in the loss of

system coverage.

2. Continuous coverage in hot areas

This mode increases the shared traffic and improves network capacity, thus

solving the problem of the sparse coverage in hot areas mode.

3. Continuous coverage

The continuous coverage in the whole planning area can share the traffic of

GSM900 at the maximum, increase network capacity, reduce switching between

network layers, and improve operation quality. The following figure is the

schematic diagram of continuous coverage:

96


Figure 4.2-2 Continuous coverage mode

This coverage mode features easy expandability and can meets the medium and

long period of coverage requirement. Compared with the sparse coverage in hot

areas mode, this mode realizes high density and large area of coverage.

Therefore, the handovers between frequency bands are greatly reduced. This

coverage mode is comparatively ideal. The difference to the sparse coverage in

hot areas is that DCS1800 is independent rather than attached to GSM900.

For the engineering design of DCS1800, take the following points into account

for the purpose of sharing as many traffic as possible:

DCS1800 antennas should be 2-3 m higher than GSM900 antennas.

DCS1800 antennas and GSM900 antennas should be in the same direction to

facilitate traffic control.

The V-plane and H-plane half-power angles should be small and close.

The DCS1800 main lobe gain should be equal to or 2-5 dBi greater than that of

GSM9002. Radio paramete

From the perspective of traffic sharing, in addition to engineering parameters,

radio parameters such as cell selection, cell reselection, and handover

parameters also need consideration. By adjusting related parameters, make the

mobile phone select the DCS1800 network on prerequisite that the conversation

quality can be ensured. This can share the GSM900 network load.

97


98

(1). Cell reselection parameter

Because signal attenuation of DCS1800 is greater than GSM900, the signals of

DCS1800 cells are weaker than GSM900. To make a dual-band mobile phone

primarily access the DCS1800 system, set the values of CBQ and CBA to

differentiate the priories of DCS1800 and GSM900. The priority of cells does

not affect cell reselection. The relationship between CBQ, CBA and cell

selection priority and reselection is as follows:

CellBarQualify CellBarAccess Cell Selection Priority Cell Reselection Status

0 0 Normal Normal

0 1 Barred Barred

1 0 Low Normal

1 1 Low Normal

Adjust the minimum receiving level allowed by DCS1800, expand the coverage

range of DCS1800 site, share the traffic in edge areas, and consider cell

reselection. For GSM900 network, maintain the parameters of existing network,

thus ensuring that the GSM900 coverage is consistent before and after the

activation of dual-band network. This guarantees the network service of

peripheral users.

Based on the previous relationship, the planning of access parameters of co-sited

and co-addressed dual band cells are as follows:

Cell Name Max

Repeat

times

Timeslots of

transmitting

distribution

Cell Bar

Qualify

Cell Access

Bar

TCH Max

Power Level

Allowable Min

Receiving Level

USERLA

BEL

MAXRE

TRANS

TXINTEGER CELLBARQ

UALIFY

CELLBARA

CCESS

MSTXPWRM

AXCCH

RXLEVACCESS

MIN

1800-1 2 14 0 0 0 12~15

1800-2 2 14 0 0 0 12~15

1800-3 2 14 0 0 0 12~15

900-1 2 14 1 0 5 10

900-2 2 14 1 0 5 10

900-3 2 14 1 0 5 10

(2). Cell reselection parameters

Cell reselection has no priority. In proper situations, the MS reselects a cell with

a greater C2 value. According to C2 algorithm, set the parameters such as CRO,


99

TO, and PT to make the C2 value of DCS1800 be greater than GSM900. In case

that DCS1800 cell signals are weaker than those of GSM900, the dual-band MS

can also be enabled to reselect DCS1800 cell through parameter settings.

Table 4.2-1 Cell reselection parameters

Cell

Name

Cell

Reselection

Delay

Additional

Cell

Reselection

Parameter

Indicator

Cell Reselection

Parameter

Indicator

Cell

Reselection

Offset

Temporary

Offset

Penalty

Time

USERL

ABEL

RESELHYST

ERESIS

ADDITIONR

ESELPI CELLRESELPI

RESELOFFS

ET

TEMPORA

RYOFFSET

PENAL

TYTIM

E

1800-1 4 0 1 6~8 1 0

1800-2 4 0 1 6~8 1 0

1800-3 4 0 1 6~8 1 0

900-1 4 0 1 0 1 0

900-2 4 0 1 0 1 0

900-3 4 0 1 0 1 0

For DCS1800 cell, C2 = C1 + CRO (12~16dB) –TO (10db) *H (PT (10s) –T)

whereas for GSM900, C2 = C1 + CRO (0db) –TO (10db) *H (PT (10s) –T) . In

this case, once an MS successfully resides in the DCS1800 network, the high C2

value enables it to stay in the DCS1800 network for a long time. Similarly, an

MS is easy to reselect the DCS1800 network and implement the traffic sharing

task. Through reselection parameter setting, in idle mode, an MS can stay in the

DCS1800 network providing effective coverage.

(3) Cell handover parameters

Dual-band networking currently is based on the existing GSM network.

Building the DCS network is to expand the capacity of existing digital mobile

network to provide better and colorful communications service. Because DCS

frequency resources are more colorful than GSM, its capacity is more than twice

of the GSM network. Therefore, ignoring the speed factor, the traffic of

dual-band MSs should be absorbed and processed by the DCS network on

condition that the conversation quality is ensured. This is the start point of dual

band handover.


100

Table 4.2-2 Parameters of DCS1800 cell handover selection

Cell

Name

Handover

Control

Whether

related

cell

Static priority

of cell

handover

Min interval

of inter cell

handover

Min

receiving

strength

level

Min

threshold

of PBGT

handover

Min

strength

handover

Min

threshold

of quality

handover

USERL

ABEL HoControl

IsRelated

Cell HOPRIORITY

HOMININTE

RVAL

RXLEVMI

N

HOMARGI

NPBGT

HOMAR

GINRXL

EV

HOMARGI

NRXQUAL

1800-1 22 0 3 10 12 36 28 28

1800-2 22 0 3 10 12 36 28 28

1800-3 22 0 3 10 12 36 28 28

900-1 22 0 3 10 15 14 28 28

900-2 22 0 3 10 15 14 28 28

900-3 22 0 3 10 15 14 28 28

These parameters are set for co-sited co-directional cells. Set the parameters normally

for non-co-sited cells.

(4) Other parameter settings

Set early classmark sending control (ECSC) to Y

The ECSC parameter indicates whether a multi-band MS can send early

classmark modification message to the BSC through the BTS. This function

enables the MSC to send the message to the target BSC once receiving messages

about multiple bands. This facilitates the call setup and allows timely handover

when necessary.

The ECSC value can be Y or N. Y indicates that an MS needs to report its

CLASSMARK3 to the network immediately after the link is set up. N indicates

that an MS does not allow actively reporting its CLASSMARK3 to the network.

Because CLASSMARK3 is mainly about dual band application, set ECSC to N

for single-band GSM application area and set ECSC to Y for dual-band GSM

application area.

Set MULTIBAND_REPORT to 3.

In a single-band GSM network, when an MS reports neighbor cell measurement

results to the network, the contents of only six cells with the strongest signals

are needed. When a network is composed of multiple bands, the operator always

has a band with the highest priority when an MS performs inter-cell handover.


101

Therefore, the MS is expected to report measurement results based on not only

signal strength but also signal band. The multiband-reporting (MBR) parameter

is used to inform the MS that neighbor cell contents of multiple bands are

required.

0: The MS needs to report the measurement results of six neighbors with

strongest signals and that are allowable and known by NCC, irrespective of the

bands of the neighbor cells.

1: The MS needs to report the measurement result of a neighbor cell with the

strongest signal and this is allowable and known by NCC on each band

(excluding the band being used by the current service area) in the neighbor cell

list, and report the neighbor cell of the current service area in all bands in the

remaining space. If there is still remaining space, report the situations of other

neighbor cells, irrespective of the band.

The value range of MBR is 0-3. In multi-band application situations, the value is

related to the traffic volume of each band. Generally, refer to the following

principles during the setting:

Set MBR to 0 when each band has equal traffic.

Set MBR to 3 when the traffic volume of each band is obviously different and

the operator has a preferable band.

Set MBR to 1 or 2 when the situation is between the previous two cases.

Activate traffic handover

The parameters of traffic handover are as follows:

Traffic handover layer control value (TrafficHoLayrCtl) = 1 (same layer)

Traffic handover frequency control value (TrafficHoFreqCtl) = 0 (or2) (0:

GSM900; 2:DCS1800)

Traffic handover threshold (TrafficThs) = actual traffic load

02 gsmp&o b-en-gsm radio network planning principle-word--201009

Business

Transcript of 02 gsmp&o b-en-gsm radio network planning principle-word--201009