OMF007001 GSM Frequency Planning ISSUE2.0

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GSM Frequency Planning


Contents

1. Frequency Planning

2. Normal Frequency Reuse Technology

3. Tight Frequency Reuse

4. Multiple Reuse Pattern Technology

5. Concentric Cell Technology

6. Frequency Hopping


Contents

1. Frequency Planning Basic

1.1 Frequency Resource of GSM System

1.2 Concept of Frequency Reuse

1.3 Reuse Density

1.4 C/I Ratio


P-GSM 900 :

DCS 1800 :

1710 1785 1805 1880

Duplex distance : 95 MHz

890 915 935 960

Duplex distance : 45 MHz

Frequency Resource of GSM System


Frequency Resource of GSM SystemFrequency

Spectrum

Range

(MHz)

Uplink

Frequency ValueARFCN

Downlink

Frequency

Value

P-GSM900890~915

935~960Fu(n)=890+0.2n 1≦n ≦ 124 Fd(n)=Fu(n)+45

E-GSM900880~915

925~960

Fu(n)=890+0.2n

Fu(n)=890+0.2(n-1024)

0 ≦ n ≦ 124

975 ≦ n ≦ 1023Fd(n)=Fu(n)+45

R-GSM900876~915

921~960

Fu(n)=890+0.2n

Fu(n)=890+0.2(n-1024)

0 ≦ n ≦ 124

955 ≦ n ≦ 1023Fd(n)=Fu(n)+45

DCS1800

1710~1785

1805~1880Fu(n)=1710.2+0.2(n-512) 512 ≦ n ≦ 885 Fd(n)=Fu(n)+95

PCS1900 1850~1910

1930~1990Fu(n)=1850.2+0.2(n-512) 512 ≦ n ≦ 810 Fd(n)=Fu(n)+80


{fi,fj..fk}

{fi,fj..fk} {fi,fj..fk} {fi,fj..fk}.. ..

Macro-cell system

d

Micro-cell system

Concept of Frequency Reuse


Example of Frequency Reuse

Frequency resource is limited. If there is 8MHz

frequency resource, 8 MHz = 40 channels × 8

timeslots = 320

Max. 320 users can access the network at the same

time.

If every frequency is reused N times

Max. 320×N uses can access the network at the same

time.


The spectrum utilization ratio can be expressed by frequency reuse density (freuse), which reveals the tightness of the frequency reuse and c

an be expressed by the following equation

NARFCN is the total number of the available channel numbers,

NTRX is the number of TRXs configured for the cell.

Reuse Density

TRX

ARFCNreuse N

Nf


Question

(1) Frequency bandwidth is 12MHZ, if frequency reuse

density is 4x3,each cell has how many TRX?

(2) Frequency bandwidth is 6MHZ, if frequency reuse

density is 2x3,each cell has how many TRX?


Looser reuse

Higher frequency reuse efficiency,

but interference is serious.

More technique is needed.

Tighter reuse

0 12 20

Little interference,

but frequency reuse efficiency is low.

Reuse Density Reuse density is the number of cells in a basic reuse cluster.

For the n x m frequency reuse pattern,

n: The number of BTSs in the reuse clusters m: The number of the cells under each BTS.

mnfreuse


4×3 Frequency Reuse

A1C1

B1

D1A2

A3B2

B3

C2

C3D2

D3

A1

C1

B1

D1A2

A3B2

B3

C2

C3D2

D3

A1C1

B1

D1A2

A3B2

B3

C2

C3D2

D3A1

C1

B1

D1A2

A3B2

B3

C2

C3D2

D3

A1C1

B1

D1A2

A3B2

B3

C2

C3D2

D3

A1C1

B1

D1A2

A3B2

B3

C2

C3D2

D3


Requirement for C/I Ratio

All useful signals CarrierAll useless signals Interference=

Useful signal Noise from environment

Other signals

C/I =


Requirement for C/I Ratio

Interference C/I

C/I in Actual Project

(3 dB margin is

needed )

Co-channel ≥ 9dB ≥ 12dB

Adjacent-channel ≥- 9dB ≥- 6dB

Carrier offset reaches 400

KHz

≥- 41dB


Exercise

Cell A fre 5

Cell C fre 4

Cell D fre 3Cell B fre 5 ?dB<

?dB<

?dB<

-70dB


Contents








Example of 4 x 3 Frequency Reuse Hereunder are several assumptions

The available bandwidth is 10MHz. The channel number is 45~94

BCCH 81~94 (14 channel numbers in total, 81~82 are

reserved)

The other channel numbers are allocated to TCH

So the maximum base station configuration is S4/4/4, and the

frequency reuse density is 12.5 (50/4 = 12.5)

Frequency group number

A1 B1 C1 D1 A2 B2 C2 D2 A3 B3 C3 D3

Channel Number of Each

Frequency Group

94 93 92 91 90 89 88 87 86 85 84 83

80 79 78 77 76 75 74 73 72 71 70 69

68 67 66 65 64 63 62 61 60 59 58 57

56 55 54 53 52 51 50 49 48 47 46 45


4 x 3 Frequency Reuse Conclusion The 4 x 3 frequency reuse pattern is a basic technology applied in frequency

planning. Which must be applied to the BCCH in frequency aggressive reuse technologies

If the network capacity needs to be further expanded, the following measures can be taken:

Split a cell into smaller cells.

Utilize new frequency resources. For example, you can establish a DSC 1800MHz network.

Under the current 900MHz network, use more tight frequency reuse technology to expand the network capacity.

At present, the tight frequency reuse technology works as the most economical and convenient way to expand the network capacity, so it is also the most popular with carriers.

The typical frequency reuse technology includes 3 x 3, 2 x 6, 2 x 3, 1 x 3, and 1 x 1.


Contents








1 x 3 Frequency Reuse Pattern 1 x 3 frequency reuse pattern is also called f

ractional reuse. For 1 x 3 or 1 x 1 frequency reuse pattern, th

e reuse distance is quite small, so the interference in the network is quite great. Therefore, to avoid frequency collision, you must use RF hopping technology and set the parameters, including MA (mobile allocation), HSN (hopping sequence number), and MAIO (mobile allocation index offset). The ratio of number of the TRXs to that of the available frequency hopping is FR LOAD (generally, it is smaller than 50%).

A1 A2

A3

A1 A2

A3

A1 A2

A3

A1 A2

A3


Example of 1 x 3 Frequency Reuse If the available bandwidth is 10MHz ,the channel numbers are 45~94

For BCCH carriers, channel numbers is 81~94, frequency reuse pattern is 4×3

For TCH carriers, channel numbers is 45~80, frequency reuse pattern is 1×3

Because FR LOAD 1 to 2, if the bandwidth is 10MHz, the maximum base station type can be configured as S7/7/7. In this case, the frequency reuse degree is 7.14

Frequency group number Channel number MAIO

A 80, 77, 74, 71, 68, 65, 62, 59, 56, 53, 50, 47 0, 2, 4,6, 8, 10

B 79, 76, 73, 70, 67, 64, 61, 58, 55, 52,49, 46 1, 3, 5, 7, 9, 11

C 78, 75, 72, 69, 66, 63, 60, 57, 54, 51, 48, 45 0, 2, 4, 6, 8, 10

space grouping


A 80, 79, 78, 77, 76, 75, 74, 73,72, 71, 70, 69 0, 2, 4, 6, 8, 10

B 68, 67, 66, 65, 64, 63, 62, 61, 60, 59, 58, 57 0, 2, 4, 6, 8, 10

C 56, 55, 54, 53, 52, 51, 50, 49, 48, 47, 46, 45 0, 2, 4, 6, 8, 10

sequence grouping


Example of 1×3 Frequency Reuse Suppose 900 band: 96 ～ 124 BTS configuration: S3/3/3 BCCH layer: 96 ～ 109 reuse pattern: 4×3 TCH layer: 110 ～ 124 reuse pattern: 1×3


TCH Consecutive Allocation Scheme

MAIO

CELL1(MA

1)

110 111 112 113 114 0,2

CELL2(MA

2)

115 116 117 118 119 0,2

CELL3(MA

3)

120 121 122 123 124 0,2

MA1

MA2 MA3

Cell1

Cell2Cell3

MA1

MA2 MA3

Cell1

Cell2Cell3

MA1

MA2 MA3

Cell1

Cell2Cell3

(110,112)

(110,112)

(110,112)

(115,117)

(115,117)

(115,117)

(120,122)

(120,122)

(120,122)


TCH Interval Allocation Scheme

MAIO

CELL1(MA1

)

110 113 116 119 122 0,1

CELL2(MA2

)

111 114 117 120 123 2,3

CELL3(MA3

)

112 115 118 121 124 4,0

MA1

MA2 MA3

Cell1

Cell2Cell3

MA1

MA2 MA3

Cell1

Cell2Cell3

MA1

MA2 MA3

Cell1

Cell2Cell3

(110,113) (110,113)

(110,113)

(117,120) (117,120)

(117,120)

(124,112) (124,112)

(124,112)


The Characteristics of the 1 x 3 The frequencies are more tightly reused, so the network capacity is great. When planning a network, only need to plan BCCH, while it’s unnecessary to r

e-plan frequencies. So the efficiency for network planning is high. Wideband combiner must be used, but the cavity combiner with frequency sele

ctivity is inapplicable. Co-channel and neighbor channel interference increases as the frequency reus

e distance decreases. RF hopping must be used, and the channel numbers participating frequency ho

pping is twice that of the number of carriers at least. In actual conditions, BCCH cannot take measures, such as RF hopping, DTX, an

d power control, therefore, in order to ensure network quality, BCCH can only use the looser 4 x 3 frequency reuse pattern.


Example of 1 x 1 Frequency Reuse One cell of one base station forms a frequency reuse cluster

If the available bandwidth is 6MHz ,the channel numbers are 96~124

For BCCH carriers, channel numbers is 111~124, frequency reuse pattern is 4×3

For TCH carriers, channel numbers is 96~110, frequency reuse pattern is 1×1

the maximum base station type can be configured as S4/3/3 under 1 x 1 frequency

reuse pattern. In this case, the frequency reuse degree is 7.25/9.67/9.67, so the

average value is 8.86.

Therefore, the maximum base station configuration under 1 x 1 frequency reuse

pattern is the same as that under 1 x 3 frequency reuse space grouping pattern, so is

the network capacity.


A 96,97,98,99,100,101,102,103,104,105,106,107,108,109,110 0,2,4

B 96,97,98,99,100,101,102,103,104,105,106,107,108,109,110 6,8

C 96,97,98,99,100,101,102,103,104,105,106,107,108,109,110 10,12


BCCH14+TCH36 ：

1BCCH+3TCH

1BCCH+3TCH 1BCCH+3TCH

1BCCH+12TCH


4×3

1×3

1×3 and 1×1

1BCCH+TCH


1×1


TRX1 TRX2 ... TRX7

TRX8 TRX9... TRX14 TRX15 TRX16...TRX21

TRX1 TRX2 ... TRX7

TRX8 TRX9... TRX14 TRX15 TRX16...TRX21

The red items are BCCH RCs

Illustration of 1×3 or 1×1


Contents








Conception of MRP Technology

According to multiple reuse pattern (MRP), the

carriers are divided into several groups.

The carries in each group work as an independent

layer, and each layer uses a different frequency

reuse pattern.

During frequency planning, configure the carriers

layer by layer, with reuse density increases layer by

layer, as shown in the next slide.


Conception of MRP Technology


Capacity increase when reuse density is multiplied: Supposing there are 300 cells Bandwidth: 8 MHz (40 frequency)

Normal 4×3 reuse: reuse density=12 Network capacity = (40/12)×300 = 1000 TRX

Multiple reuse: BCCH layer: re-use =12, (14 frq.) Normal TCH layer: re-use =10, (20 frq.) Aggressive TCH layer: re-use = 6, (6 frq.) Network capacity = (1 +2 +1)×300 = 1200 TRX

Example of MRP


Example of MRP Capacity increase when reuse density is multiplied:

Supposing there are 300 cells Bandwidth: 8 MHz (40 frequency)

Normal 4×3 reuse: reuse density=12 Network capacity = (40/12)×300 = 1000 TRX

Multiple reuse: BCCH layer: reuse density=12, (14 frequency) Normal TCH layer: reuse density=10, (20 frequency) Aggressive TCH layer: reuse density= 6, (6 frequency) Network capacity = (1 +2 +1)×300 = 1200 TRX


Contents








Conception of Concentric Cell Technology In the GSM network, concentric cell technology is used to divide

the service area into two parts: overlaid and underlaid.

Essentially, the concentric cell technology concerns channel allocation and handover, but when combining this technology with various frequency planning technologies, both expand network capacity can be improved network quality.

Overlaid-cell

Underlaid-cell


Overlaid/Underlaid Frequency Configuration

Super fn

Regular fm Regular fm Regular fm

Super fn

BCCH 15f Regular 24f Super 12f

BCCH TRX reuse density: 12

Regular TCH TRX reuse density: 12

Super TCH TRX reuse density: 6

Super fn


Conception of Concentric Cell Technology Generally, 4 x 3 frequency reuse pattern is used for the

underlaid. For overlaid, the frequency reuse patterns, such as 3

x 3, 2 x 3, or 1 x 3, are used. Therefore, all carriers can be

divided into two groups, one for underlaid, and the other one for

overlaid.

Underlaid Overlaid


Contents








Contents


6.1 Classification of hopping

6.2 Advantages of hopping

6.3 Parameter of hopping

6.4 Collocation of hopping data


Frequency Hopping


Advantages of Hopping

Get an agreeable radio environment.

Provide a similar communication quality for every

user.

Tighter reuse patterns are possible to be used for

larger capacity.


Smoothen the rapid fading (Rayleigh fading)

Frequency Diversity of Hopping


Smoothen and average the interference

Interference Diversity of Hopping


Classification of Hopping

According to implementation mode Base-band hopping RF hopping

According to the minimum hopping time unit Timeslot hopping Frame hopping


Base Band Hopping Principle

FH bus


Base Band Hopping Principle BCCH carrier attends hopping, on which TS0 can not attend hopping

No

HoppingTRX0

TRX1

TRX2

TRX3

TS 0 TS 1 TS 2 TS 3 TS 4 TS 5 TS 6 TS 7 ARFCN

5(BCCH carrier)

10(TCH carrier)

15(TCH carrier)

20(TCH carrier)

MA={5,10,15,20}MA={10,15,20}


Base Band Hopping Principle

BCCH carrier does not attends hopping

TRX0

TRX1

TRX2

TRX3

TS 0 TS 1 TS 2 TS 3 TS 4 TS 5 TS 6 TS 7

MA={10,15,20}

ARFCN

5(BCCH carrier)

10(TCH carrier)

15(TCH carrier)

20(TCH carrier)

No Hopping No Hopping No Hopping No Hopping No Hopping No Hopping No Hopping No Hopping


RF Hopping Principle


RF Hopping Principle

BCCH carrier does not attends hopping

TRX0

TRX1

TRX2

TRX3

TS 0 TS 1 TS 2 TS 3 TS 4 TS 5 TS 6 TS 7

No Hopping No Hopping No Hopping No Hopping No Hopping No Hopping No Hopping No Hopping

MA={10,15,20}

MA={10,15,20}

MA={10,15,20}

(BCCH carrier)

(TCH carrier)


Classification of Hopping

Frame hopping

Frequency changes every TDMA frame.

The different channel of one TRX uses the same MAIO.

Timeslot hopping

Frequency changes every timeslot.

The different channel of one TRX uses the different

MAIO.


Frame Hopping

f 0

Frame 0

f 1

f 2

f 3

f 4

Frame 1 Frame 2 Frame 3 Frame 4 ……

One TRX (none BCCH carrier) hopping on 5 frequencies

•RF hopping and baseband hopping without BCCH carrier


Timeslot Hopping

f 0

Frame 0

f 1

f 2

f 3

f 4


•5 timeslots on 1 TRX hopping on 5 frequencies


Hopping Parameters

All the parameters which are related to hopping

are configured in Cell Attributes/Frequency

Hopping.

Hopping mode: the mode used by the BTS

system

No hopping

Base band hopping

RF hopping


Hopping Parameters

HSN ： Hopping Sequence Number （ 0 ～ 63 ） HSN=0 ： cycle hopping. HSN≠0 ： random hopping. Every sequence number corre

sponds a pseudo random sequence.


Hopping Parameters MA (Mobile Allocation Set):

MA is the set of available RF bands when hopping, containing at most 64

frequency carriers. The frequency being used must be those of the available

frequency

MAIO (Mobile Allocation Index Offset)

MAIO is used to define the initial frequency of the hopping.

Be careful to configure the MAIO of same timeslot in all channels, otherwise

interference occurs.

MAI (Mobile Allocation Index)

At the air interface, the frequency used on a specific burst is an element in MA

set. MAI is used for indication, referring to a specific element in the MA set.

MAI is the function of TDMA FN, HSN and MAIO.


Example of MAIO

No

Hopping

0

2

1

2

2

2

3

2

0

2

1

2

2

2

0

1

1

2

2

2

3

2

0

2

1

2

2

2

3

2

1

1

2

2

3

2

0

2

1

2

2

2

3

2

0

2

2

1

3

2

0

2

1

2

2

2

3

2

0

2

1

2

TRX0

TRX1

TRX2

TRX3


5(BCCH carrier)

10(TCH carrier)

15(TCH carrier)

20(TCH carrier)

MA2={5,10,15,20}MA1={10,15,20}

MAIO 0 1 2 MAIO 0 1 2 3

MAIO MAI


Example of MAIO

No

Hopping

0

2

1

2

2

2

3

2

0

2

1

2

2

2

0

1

1

2

2

2

3

2

0

2

1

2

2

2

3

2

1

1

2

2

3

2

0

2

1

2

2

2

3

2

0

2

2

1

3

2

0

2

1

2

2

2

3

2

0

2

1

2

0

3

1

3

2

3

3

3

0

3

1

3

2

3

3

3

1

3

2

3

3

3

0

3

1

3

2

3

3

3

0

3

2

3

3

3

0

3

1

3

2

3

3

3

0

3

1

3

3

3

0

3

1

3

2

3

3

3

0

3

1

3

2

3

TRX0

TRX1

TRX2

TRX3


5(BCCH carrier)

10(TCH carrier)

15(TCH carrier)

20(TCH carrier)

MA2={5,10,15,20}

MA1={10,15,20}

MA3={510,515,520,525}

510(TCH carrier)

515(TCH carrier)

520(TCH carrier)

525(TCH carrier)

TRX4

TRX5

TRX6

TRX7


Example of MAIO

5

Frame 0

10

15

20

25


MA={5,10,15,20,25}

• 5 TRXs separately belongs to the same MA hopping on 5 frequencies, and uses same HSNs


Example of Hopping Parameters

f 0

Frame 0

f 1

f 2

f 3

f 4


• 8 timeslots of 1 TRX separately belongs to different MAs hopping on 5 frequencies, and uses different HSNs.


Example of Hopping Parameters

f 0

Frame 0

f 1

f 2

f 3

f 4


• 5 TRXs separately belongs to different MAs hopping on 5 frequencies, and uses different HSNs

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OMF007001 GSM Frequency Planning ISSUE2.0

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