UMTS Applied Radio Planning

UMTS Applied Radio PlanningP025

Course Objectives

▪ Understand the key planning parameters of the UTRAN

▪ Produce UMTS Link Budgets for various services

▪ Understand UMTS Coverage and its KPI’s

▪ Understand Capacity dimensioning in UMTS

▪ Appreciate the Coverage/Capacity relationship in UMTS

▪ Evaluate GSM-UMTS Co-location issues

1- The UMTS Air Interface

UMTS▪ Universal Mobile Telecommunication System

▪ Also called “3G”, along with other IMT-2000 technologies

▪ The evolution from GSM-GPRS-EDGE

▪ WCDMA technology, part of the CDMA family

The UMTS Air Interface

1.1- WCDMA, Processing Gain and Codes


CDMA - Direct Sequence Spread Spectrum


Frame Period (we may still need frames/timeslots for signaling)

CDMA Spreading•Essentially Spreading involves changing the symbol rate on the air interface

Identical codes

Tx Bit Stream

P

f

Code Chip Stream

Spreading

P

f

Channel

Air Interface Chip Stream

P

f

Code Chip Stream

Despreading

P

f

Rx Bit Stream

P

f


Spreading and Despreading

Rx Bit Stream


Tx Bit Stream1

-1

Code Chip Stream

XSpreading

Code Chip StreamXDespreading


Spreading and Despreading with code Y


Tx Bit Stream1

-1

Code Chip Stream

XSpreading

Code Chip Stream YXDespreading

Rx Bit Stream


Interference mitigation

▪ The gain due to Despreading of the signal over wideband noise is the Processing Gain

Rx Signal (= Tx Signal + Noise)

fP

Channel

Wideband Noise/Interference

P

f

Signal

P

f

Spreading Code

Tx SignalP

f

Spreading Code Signal

P

f


Processing Gain

▪ If the Bit Rate is Rb, the Chip Rate is Rc, the energy per bit Eb and the energy per chip Ec then

▪ We say the Processing Gain Gp is equal to:

▪ Commonly the processing gain is referred to as the Spreading Factor

b

ccb R

REE ×=

b

cp R

RG =


Visualising the Processing Gain

W/Hz W/Hz W/Hz

W/Hz W/Hz dBW/HzEb

No

Ec

Io

Eb

No

Eb/No

Eb

No

Eb/NoEb

No

W/Hz dBW/HzSignal

Intra-cell Noise

Inter-cell Noise

Before Spreading

After Spreading With Noise

After Despreading/Correlation

Post FilteringOrthog = 0

Post FilteringOrthog > 0

f f f

f f f

f f


Types of Codes▪ Channelisation Codes

▪Are used to separate channels from a single cell or terminal

▪ Scrambling Codes▪Are used to separate cells and terminals from each other rather than purely channels

▪ Different base stations will use the same spreading codes with separation being provided by the use of different scrambling codes.

S1

S2

S3

C1 C2 C3

C1 C2 C3

C1 C2 C3


Channelisation Codes

▪ Channelisation codes are orthogonal and hence provide channel separation

▪ Number of codes available is dependant on length of code

▪ Channelisation codes are used to spread the signal


Channelisation Code Generation

▪ Channelisation codes can be generated from a Hadamard matrix

▪ A Hadamard matrix is:

▪ Where x is a Hadamard matrix of the previous level

▪ For example 4 chip codes are:▫ 1,1,1,1

▫ 1,-1,1,-1

▫ 1,1,-1,-1

▫ 1,-1,-1,1

− xx

xx

Note : These two codes correlate if they are time shifted


▪ Orthogonal Variable Spreading Factor Codes can be defined by a code tree:

SF = Spreading Factor of code (maximum 512 for UMTS)

SF = 1 SF = 2 SF = 4

Cch,1,0 = (1)

Cch,2,0 = (1,1)

Cch,2,1 = (1,-1)

Cch,4,0 =(1,1,1,1)

Cch,4,1 = (1,1,-1,-1)

Cch,4,2 = (1,-1,1,-1)

Cch,4,3 = (1,-1,-1,1)

OVSF codesThe UMTS Air Interface

SF = 1 SF = 2 SF = 4

Cch,1,0 = (1)

Cch,2,0 = (1,1)

Cch,2,1 = (1,-1)

Cch,4,0 =(1,1,1,1)

Cch,4,1 = (1,1,-1,-1)

Cch,4,2 = (1,-1,1,-1)

Cch,4,3 = (1,-1,-1,1)

IN USE

IN USESF = 1 SF = 2 SF = 4

Cch,1,0 = (1)

Cch,2,0 = (1,1)

Cch,2,1 = (1,-1)

Cch,4,0 =(1,1,1,1)

Cch,4,1 = (1,1,-1,-1)

Cch,4,2 = (1,-1,1,-1)

Cch,4,3 = (1,-1,-1,1)

IN USE

IN USE

Code Usage Efficiency▪ Any codes further down the trunk of

a branch in use cannot be used

▪ Any codes further out from the branch in use cannot be reused

▪ By filling up branches of the code tree before starting new branches a greater capacity can be achieved

▪ Multiple code trees can be used from a cell but at an increased level of interference between channels


Scrambling Codes

▪ The spread data symbols are then scrambled by multiplying with a complex scrambling sequence

▪ Scrambling codes do not affect the chip rate

▪ The scrambling code is specific for a cell and thus serves to provide isolation between signals from adjacent cells

▪ There are 512 Scrambling Codes in the DL which can be allocated by Radio Planners


1.2- Ec/Io, Eb/No, NR and Loading


Interference and Noise DensitiesThe UMTS Air Interface

▪ From the point of view of a UE, every other UE’s power appears as Interference

▪ Io is the Interference Density

▪ No is the Interference + Noise Density

▪ In general, when you talk about chips, or “Ec”, you use Io. When you talk about bits, or “Eb”, you use No.

▪ “No” considers Thermal Noise at the NodeB

Ec/Io

▪ Ec/Io is the Chip Energy we obtain in the presence of the Interference generated by all other users

▪ Ec/Io of the Pilot Channel is used to:

▫ Estimate (“sound”) the channel (multipath characteristics)

▫ Decide which server is “best server”

▫ Make handover decisions

▫ Typical requirement -15 dB


Eb/No

▪ Eb/No is the Bit Energy we obtain after despreading in the presence of the Noise generated by all other users and the Noise from NodeB equipment

▪ There’s a different Eb/No requirement for UL and DL:

▫ Typical requirement 1 to 10 dB

▫ Requirement varies by Bearer, Service, Multipath Profile, Mobile Speed, and Type of Receiver.


Noise Rise▪ The effective noise floor of the receiver increases as the

number of active mobile terminals increases.

▪ This rise in the noise level appears in the link budget and limits maximum path loss and coverage range.

Three Users

Background NoiseOne User

Two Users


Effect of Neighbouring Cells

Users in other cells cause interference.

Typical ratio of power from other cells to power from

own cell, i, is 0.6 (Urban Macrocells)


The Noise Rise Equation

jb

jUL

Mj

jj

N

total

R

W

E

NL

LP

I

+=

−=

−=

∑=

=

0

11

1

11

1

1η

If we have M identical users:

jb

Mj

jj

R

W

E

N

ML

+=∑

=

= 01 1

jb

N

total

R

W

E

N

MP

I

+−

==

01

1

1 Rise Noise


Noise Rise and Loading Factor

▪ Capacity is linked to Eb/No value

▪ Maximum Path Loss tolerated is linked to maximum NR

Noise Rise Loading Factor

1 dB 20%3 dB 50%6 dB 75%10 dB 90%

( )ULη−−= 1log10Rise Noise 10


Loading Factor

( )

( )

RW

viMNE

iNE

WMvR

RM

b

b

+

=

+

=

=

1

1

Factor Loading

: rate data with users identical For

Capacity Pole

Throughput Actual Factor Loading

0

0


UL Pole Capacity

( )iNE

W

b +

≈

1

Capacity Pole

users ofnumber largeFor

0

( )( ) kbps 8535.013

3840000 Capacity Pole

0.5 3 Eb/No 3840000W

=+

≈

=== i

• 50% of this would give a Noise Rise of 3 dB.

•50% of 853 kbps = 426 kbps


DL Pole Capacity

The Downlink benefits from orthogonality between channelisation codes.

α is orthogonality factor and has a value between zero and 1.


( )iNE

W

b +−

≈

α1

CapacityPole

0

1.3- Power Control and Handovers


Power Control and Near/Far EffectThe UMTS Air Interface

▪ When a UE is near the NodeB it doesn’t need much power to reach it

▪ In the same manner, if a UE is far away it needs greater power to communicate with the NodeB

▪ Power Control is needed in the UL because a single over-powered mobile could block a Cell

▪ Power Control is also needed in the DL to provide far away userswith enough power and to keep power low for near-by UEs

Soft and Softer HandoverThe UMTS Air Interface

▪ In UMTS it is possible to have a UE connected to more than 1 NodeB. This is called Soft Handover

▪ When in Soft Handover, the RNC can combine the best signals from the NodeB’s, hence providing a Soft Handover Gain

▪ Softer Handover applies when the mobile is being served by two cells on the same site. A Softer Handover gain also occurs.

▪ However, too many mobiles in Soft or Softer Handover could impose a significant Overhead on the system

Active Set and Pilot PollutionThe UMTS Air Interface

▪ The Cells with which the UE is communicating form the UE’sActive Set

▪ This Active Set is made typically of 3 cells/pilot signals

▪ Any Pilot which is not a member of a UE’s Active Set and exceeds a certain threshold (typ. Ec/Io>-15dB) is considered a Polluter

▪ Pilot Pollution is a common WCDMA issue that needs to be sorted immediately

Summary of Key ConceptsThe UMTS Air Interface

▪ Processing Gain

▪ Channelisation and Scrambling Codes

▪ Ec/Io

▪ Eb/No

▪ Noise Rise

▪ Cell Loading

▪ Pole Capacity

▪ Near/Far Effect

▪ Soft and Softer Handover Gain

Summary of Key Formulas▪ Eb/No

( )iN

E

W

b +

≈

1

Capacity Pole UL

0


( ) pcb G

I

EdB

N

E+=

00

▪ Pole Capacity

( )iN

E

W

b +−

≈

α1

Capacity Pole DL

0

2- The UMTS Link Budget

UMTS Link Budget vs. GSM’s

▪ Interference Margin for Noise Rise

▪ Target Eb/no

▪ Processing Gain (dBs) in UMTS

= 10 log (3840000/User Rate (bps))

▪ Power Control margin

▪ Handover Gains

The UMTS Link Budget

Interference Margin

▪ An admission control parameter. Same as “Noise Rise Limit”

▪ Puts a limit to how many users can be taken in the UL

▪ Has an associated Loading Factor:

▫ NR= 3dB, Load Factor=50%

▫ NR=6dB, Load Factor=75%


Target Eb/No

▪ UMTS Link Budgets are made for Bearers

▪ A UMTS service may use one or more Bearers, with each

Bearer having a QoS Eb/No requirement

▪ A typical Voice Bearer requires an Eb/No of 5dB

▪ A typical 128 kbps Bearer requires and Eb/No of about 2dB


Processing Gain

▪ Depends on the bitrate of the Bearer

▪ Helps with the required Ec/Io at the receiver

▪ For a 12.2 kbps voice Bearer, Gp = 25dB

▪ For a 128 kbps data Bearer, Gp= 15dB


Power Control (Fast Fading) Margin

▪ It’s entered to allow for adequate Power Control to compensate

for Fast Fading

▪ It’s dependent on the Speed Profile of the Mobile

▪ At higher speeds, its smaller as the network cannot effectively

compensate for Fast Fading


Handover Gains

▪ If a UE is in Soft or Softer Handover, this will provide Diversity

Gains

▪ These gains can help the Link Budget by helping in achieving

the Target Eb/No with less power

▪ This gain is dependent on the Delta on the Ec/Io of the involved

paths


UL Link Budget

▪ Because UL power is lower than DL power coverage is

“UL limited”.

▪ Initially, most attention is paid to the UL budget.


-120 dBm Receiver Sensitivity

▪ Typical noise floor of cell receiver is -104 dBm.

▪ Considering full rate voice (12.2 kbps) processing gain is 25 dB.

▪ If target Eb/No is 5 dB and allowed Noise Rise is 4 dB then:

▫ UE must be capable of delivering (-104-25+5+4)= -120 dBm for

a successful connection.

▫ -120 dBm is effectively the receiver sensitivity for 12.2k voice.

▫ For a 128kbps service, the Rec. Sensitivity is around -110dBm


UL Link Budget - voice

▪ If the UE can transmit at powers up to +21 dBm, the maximum

link loss is: 21 - (-120) = 141 dB.

▪ The maximum air interface path loss can be calculated by

considering antenna gains and miscellaneous losses (e.g.

feeder loss, body loss)

▪ If antenna gain = 17 dBi and losses = 4 dB, then maximum path

loss = 141 + 17 - 4 = 154 dB

▪ Note: margins not considered (e.g. shadow fading, building

penetration loss). These could total 24 dB.


Link Budget - voice

Noise Floor -104 dBm Noise Rise Limit 4 dB Processing Gain 25 dB Target Eb/No 5 dB Receiver Sensitivity -120 dBm UE Tx Power +21 dBm Maximum Link Loss 141 dB Antenna Gain 17 dBi Feeder loss 3 dB Body loss 1 dB Maximum path loss 154 dB Margins 24 dB Target path loss 130 dB


UL Link Budget - VT

▪ UMTS is introduced to offer higher level services such as video

telephony (VT).

▪ VT will typically operate at 64 kbit/s.

▫ Processing gain = 17.8 dB

▪ If all other parameters remain the same, then the maximum

path loss will be 154 - 25 + 17.8 = 146.8 dB.

▪ Different service:- different range.

▪ Typically range for voice = 1.6 x range for VT


UL Link Budget- 128 kbps

Thermal Noise: -104 dBm, Noise Figure: 4 dB, Eb/No: 1.5 dB

Processing Gain: 15 dB (10 log[3840/128])

Receiver Sensitivity -113.5 dBm

Max Link Loss = 21 dBm -(-113.5 dBm) = 134.5

Antenna Gains: 20 dBi Feeder Loss: 3dB Body Loss: 0dB

Maximum Path Loss: 151.5 dB


DL Link Budget- 128 kbpsAllowable Path Loss: 151.5 dB

Receiver Sensitivity -113.5 dBm

Required Tx Power: 24 dBm per channel

Eb/No= 1.5 dB, which in linear is 10^(1.5/10)= 1.41

i = 0.5 1+i = 1.5

( )( ) Mbps36.05.0141.1

1084.3 Capacity Pole DL

3

=−+

= x

For 50% loading capacity = 1.5Mbps or 11- 128kbps channels11 channels @ 24 dBm = 34.4 dBm


Conclusions

▪ Eb/No and capacity intimately linked.

▪ Link budgets are affected by fast fading and interference margins.

▪ Uplink and downlink affected differently by increased loading.

▪ Flexibility allows high data rate services to be provided.

▪ Asymmetric traffic requirements can be designed in.


3- Coverage Planning

Coverage Objectives▪ Achieve Minimum Pilot Coverage on Service Area

▪ Minimum Coverage dependant on:▫ ALP▫ Services to be provided▫ Loading

▪ KPI’s▫ RSCP (Ec)

▫ RSS (Io)▫ Ec/Io▫ Pilot Pollution (Scrambling Code overlapping)

Coverage Planning

Factors affecting Coverage▪ ALP is a function of:

▫ Clutter Type

▫ Shadow Fading Margin

▪ Services:▫ The higher the bitrate the lower the coverage

▫ Different Eb/No requirements

▪ Loading:▫ The higher the loading the lower the coverage

▫ Loading factor tied to Noise Rise Limit

Coverage Planning

3.1 Network Dimensioning

Coverage Planning

Dimensioning Inputs

Environment

Site Configuration

GeographicDemographic

Service

Coverage Planning

Simple Coverage▪ Link Budget based

▫ i.e. simple numerical calculation

▪ Firstly a link budget is created

▪ The maximum path loss is used to calculate the cell range using a propagation model

▪ The cell range is used to calculate the site area

▪ Site Numbers = (Total Area)/(Site Area)

Create Link Budget

Calculate Range

Calculate Site Area

Calculate Number of Sites in a given Area

Max PL

Max Range

Max Area

Coverage Planning

Shadow Fading and Building Penetration

▪ Building Penetration

▫ Mean and standard deviation per environment

▪ Shadow Fading▫ Typically calculated using ‘Jakes’

▫ This assumes an isolated omni directional site…

( )

−−

−+−=b

aberf

b

abaerfFu

11

21exp1

2

12

( )2

0

σα−= x

a

=2

log10 10 σe

nbWhere: ;

x0-α = Fade Marginσ = Standard Deviation of Model

n = Propagation Model Exponent

x0 - α

x0 - α

P(connect)

P(connect)

5.6

0

50%

76% 90%

75%

Point Location Probability

Area Location Probability

Coverage Planning

Environment Distribution

▪ Spreadsheets don’t deal with topology or morphology accurately▫ Hills, parks and distributed

target areas

▫ Interference and traffic captured by sites will vary

▪ Margins for site acquisition and overlap are required

Urban Area Site Numbers

Suburban Area

Site Numbers?

Coverage Planning

3.2 Planning using Software Tools

Coverage Planning

Pilot Power as an Indicator Coverage Planning

If pilot power is 33 dBm, the pilot strength on the ground is an

indicator of link loss.

113 dB loss: -80 dBm pilot

120 dB loss: -87 dBm pilot

Popular indicator as drive test measurements report on pilot

strength.

•> -80 dBm

•> -87 dBm

Pilot Power as an Indicator -issues

Coverage Planning

▪ Pilot powers not necessarily equal deployment of MHA at selected sites will alter target pilot values.

▪ Even if MHAs are universally deployed, their effect will depend on feeder loss.

▪ Generally, MHAs have a different effect on UL to DL, therefore DL measurement not a reliable indicator of UL performance.

•> -80 dBm

•> -87 dBm

Letting the tool do the work Coverage Planning

▪ It is possible to define:

▫The UE: in particular Tx Power

▫The bearer: bit rate and Eb/No.

▫Cell receiver: noise floor; noise rise; feeder loss; MHA characteristics.

▫Margins required.

▪ This allows maximum path loss to each cell to be determined and UL coverage to be calculated directly.

•VT coverage achieved

•Voice coverage achieved

Assessing Interference with a Static Analyser - Ec/Io

Coverage Planning

▪ Pilot Ec/Io indicates pilot power as a ratio of total wideband power (including the pilot itself).

▪ Not terribly “scientific” but it corresponds directly to measurement reported by the UE in drive tests.

Assessing Interference with a Static Analyser - Pilot SIR

Coverage Planning

▪ Pilot SIR gives the quality of the pilot.

▫ Effect of orthogonality on own-cell interference is considered.

▫ Pilot power not considered as interference.

▪ Pilot SIR is always better than Ec/Io.

3.3 Overcoming Coverage Problems

Coverage Planning

Limiting mutual interference

• Downtilt antennas.• Consider mounting antennas on the side of buildings.

Coverage Planning


Controlling the backlobe can produce a small but significant improvement in capacity.

0º

0ºElec 6ºMech

0º0º

6º

6º

6º

6ºElec 0ºMech

0º

6º6º0º

6ºElec -6ºMech

0º

-6º

12º

0º

Coverage Planning


• Key parameter: Frequency Re-use Efficiency (FRE).

(W) ceinterferen cell-inter theis

(W) ceinterferen cell-intra theis

FRE

Inter

Intra

InterIntra

Intra

N

N

NN

N

+=

Coverage Planning

▪ Used to lower the Noise Figure of the receiver

▪ Can “offset” feeder losses

▪ MHA used to increase coverage range

▪ Typ. 1.6 dB Noise Figure (NF)

▪ Typ. Gain of 12dB (adjustable)

▪ Increase uplink capacity

▪ Adds Insertion loss on DL (~ 1.3 dB)

AntAntBiasBias--TT

DCDC

TMATMAby passby pass

Mast Head Amplifiers (TMA’s)Coverage Planning

Uplink Receive Space Diversity

▪ Common to have two receive antennas per sector at the base station.

▪ Even if highly correlated, coherent combination should yield ~3 dB

improvement.

▪ In practice a gain of 4 dB or more is expected from antennas spaced 2-3

m apart.

Receive antenna 1

Receive antenna 2

Coverage Planning

Uplink Receive Space Diversity

▪ This is not “conventional” space diversity.

▪ Each antenna is connected to a separate finger of the Rake receiver.

▪ This is possible due to the synchronisation and channel estimation derived from the Pilot channel.

▪ Thus Eb/No is improved, rather than simply an effective power gain.

▪ Very low individual Eb/No will probably mean a very low pilot level which will lead to poor coherence and little gain - process becomes “self-defeating”.

Coverage Planning

3.4 Coverage in the Real World

Coverage Planning

Typical vendor values▪ Pilot Power = 5-10% of Total Power (30-35 dBm)

▪ Control Channel Powers = 3-5 dB below Pilot (27-33 dBm)▫ CCPCH’s

▪ Other signalling Channels = 3-5 dB below Pilot (27-33 dBm)▫ PICH, AICH, SCH’s

▪ Summary: Total Non-Traffic Channels = 20-25% of total power

Coverage Planning

Some additional constraints▪ GSM existing coverage

▪ GSM legacy sites

▪ Antenna limitations: height, azimuths, etc.

Coverage Planning

4- Capacity Planning

Capacity Objectives▪ Manage effectively predicted Load on Service Area

▪ Capacity dependant on:▫ Number of users

▫ Position of users relative to the cell

▫ Services demanded

▫ UE Power Control

▪ KPI’s▫ Cell UL Load Factor

▫ Cell DL Power

Capacity Planning

Factors affecting CapacityCapacity Planning

▪ Number of Users: The more users the more noise

▪ Position of Users: The farther away, the more noise

▪ Services demanded: The more high-bitrate users on the cell, the less overall number of users possible

▪ UE Power Control: Imperfect power control will account for more noise in the network

Soft and Hard CapacityCapacity Planning

▪ Hard Capacity: Hard limit imposed by actual channel elements

▪ Typ. 16 Kbps Channel elements. Also called “Resources” or “Cards”

▪ Soft Capacity: Variable, depending on Network loading

UL Pole Capacity

▪ Capacity is typically limited on the UL

▪ This is because, in the UL we don’t have Orthogonality to help us

Capacity Planning

( )iN

E

W

b +

≈

1

Capacity Pole UL

0

UL Pole Capacity Exercise- VoiceCapacity Planning

▪ If we assume a service with Eb/No = 6dB and i = 0.8

▪ Eb/No= 4 (linear) UL Pole Capacity= 533 kbps

▪ If you consider 12.2 kbps Voice bearers: ▫ 533/12.2 = 43.7 Voice Trunks

▪ Adding a typ. Voice activity factor (+overhead) of 58%

▪ New number of voice trunks is 533/(12.2x0.58) = 75.3

UL Pole Capacity Exercise- VoiceCapacity Planning

▪ A typical UMTS Cell can handle about 40E of Voice services

▪ With 75.3E being 100% capacity, 40E = 53% Loading

▪ Noise Rise= -10log (1-0.53) = 3.2dB

▪ Typically, 25% of this capacity will be allocated to Soft Handover

UL Pole Capacity Exercise- VTCapacity Planning

▪ If we assume a service with Eb/No = 3dB and i = 0.8

▪ Eb/No= 2 (linear) UL Pole Capacity= 1066 kbps

▪ If you consider 64 kbps VT bearers with 100% activity factors: ▫ 1066/64 = 16.6 Voice Trunks

▪ Comparing bitrates: 64kbps/7.1kbps = 9 (7.1= 12.2x0.58)

▪ Comparing trunks: 75.3/16.6 = 4.5

▪ Difference is due to different Eb/No’s 3dB (VT) vs 6dB (voice)

4.1 Multi-Services Capacity and Capacity Dimensioning

Capacity Planning

Multi-Service CapacityEb/No

▪ Voice= [email protected]

▪ VT= 3.8dB@64kbps

▪ 128PS= 2.8dB@128kbps

dB vs Linear

▪ 5.6dB= 3.6

▪ 3.8dB= 2.4

▪ 2.8dB= 1.9

Activity Factors

▪ 58%

▪ 100%

▪ 100%

Bitrate Ratios relative to voice

▪ (1x) 7.1 kbps

▪ (9x) 64 kbps

▪ (18x) 128 kbps

Capacity Planning

Campbell’s SpreadsheetCapacity Planning

6.10UL Noise Rise (Loading)

75.4%Loading of Cell

536Reference Pole Capacity (kbps)

0.8Factor for i

0.000.000.00192212.28Equivalent data rate (voice)

0.380.330.400.501Relative Ratio

1.511.321.582.003.98Eb/No ratio

1.81.2236Eb/No

0.00.00.064.07.1Average rate (kbps)

0.0%0.0%0.0%100.0%58.0%Activity factor

000Not ApplicableNot ApplicablePS Capture Data (Mbytes/hour)

Not ApplicableNot ApplicableNot Applicable330CS user per cell

384128646412.2Bearers (kbps)

PSPSPSCSCS

Traffic ExerciseCapacity Planning

▪ Manchester pop. = 2.2 Million

▪ Mobile penetration@80% = 1.76 Million

▪ For an operator with 25% market share = 440K Subs

▪ With an avg voice traffic of 35mE per users = 15,400 Erlangs

▪ Considering 30E per cell = 513 Cells or 171 Sites

▪ This with 52% loading and 2% GOS

Simple Capacity Dimensioning▪ Capacity calculation based

▪ Calculate maximum capacity per carrier

▪ Calculate maximum offered traffic per sector

▪ Calculate site area based on traffic density

▪ Calculate the maximum number of sites in an area

Calculate Carrier Capacity

Calculate Sector Offered Traffic

Calculate Maximum Site Area

Calculate Number of Sites in a Given

Area

Capacity Planning

Other Dimensioning Factors

▪ GSM/UMTS Interaction▫ Proportion a percentage of voice traffic to GSM▫ Don’t assume that UMTS carries all of the traffic

▪ Microcells▫ Offer capacity relief to macrocells▫ This allows macrocells to be larger, potentially with a lower loading

▪ Repeaters▫ Extend the coverage of macrocells at a lower cost than adding a new

Node-B

Capacity Planning

“2G” analysis

▪ Coverage thresholds can be set for various services and

coverage examined in a similar manner to that for GSM

systems

▪ Traffic captured by cells for GSM traffic can be

interpreted as cell loading for UMTS systems.

Capacity Planning

4.2 Analysis of DL Capacity

Capacity Planning

DL Pole CapacityCapacity Planning

( )iN

E

W

b +−

≈

α1

Capacity Pole DL

0

▫ The Downlink must be able to match uplink capacity

▫ If i=0.6 and Eb/No is 6 dB; pole capacity is 960kbps.

▫ At 50% loading UL capacity is 480 kbps (39 voice).

Further Analysis of the Downlink

▫ Minimum Rx power (25 dB processing gain, 3 dB Noise

figure) = -104 + 3 + 6 - 25 = -120 dBm

▫ If maximum Tx power is 21 dBm, then 141 dB link loss can

be tolerated. Can DL support this?

▫ For every user that’s “allowed” in the UL, the Cell will have to

provide enough power to support it on the DL

Capacity Planning

4.3 Traffic Planning

Capacity Planning

Traffic Density▪ Traffic Density is forecast in terms of a density in terms of Erlangs per

square kilometre.

▪ Different forecasts are given for different clutter categories.

▪ Knowing the clutter categories in the required service areas allows traffic to be simulated.

Traffic Density Weightings

Clutter Category 1: 10Clutter Category 2: 50Clutter Category 3: 30Clutter Category 4: 10

Capacity Planning

1

4 2

3

▪ It is important to realise that the weightings are in terms of terminal densities.

▪ Sometimes the clutter category with the highest weighting occupies a small percentage of the area.

▪ Notice that the actual traffic volume per category differs from the traffic density. Traffic density is the parameter entered in the simulation tool.

Density versus Numbers

3Area Weightings

Clutter Category 1: 28Clutter Category 2: 16Clutter Category 3: 28Clutter Category 4: 28

Weighting of Actual Traffic per Category

Clutter Category 1: 12.7Clutter Category 2: 36.4Clutter Category 3: 38.2Clutter Category 4: 12.7

1

2

3

Capacity Planning

4

4.4 Capacity Plots

Coverage vs. CapacityCapacity Planning

Coverage vs. Capacity

145.00

150.00

155.00

160.00

165.00

170.00

100 200 300 400 500 600 700 800

Throughput (kbps)

Max

imum

Pat

hlos

s (d

B)

Uplink

Dow nlink

Link Loss vs. CapacityCapacity Planning

0

200

400

600

800

1000

1200

120 130 140 150 160

Link Loss (dB)

Cap

acity

(kbi

t/s)

+37 dBm +40 dBm +43 dBm +46 dBm

Orthogonality vs. CapacityCapacity Planning

0

200

400

600

800

1000

1200

0 0.2 0.4 0.6 0.8 1

Orthogonality

Cap

acity

(kbi

t/s)

BTS Power: 37 dBm 40 dBm 43 dBm 46 dBm

Out of Cell Interf. vs. CapacityCapacity Planning

0200400600800

100012001400

0 0.4 0.8 1.2 1.6 2

Out of Cell Interference

Cap

acity

(kbi

t/s)

BTS Power: 37 dBm 40 dBm 43 dBm 46 dBm

Capacity Planning Summary▪ Capacity dependant on:

▫ Number of users

▫ Position of users relative to the cell

▫ Services demanded

▫ UE Power Control

▪ Multiple Services Traffic characteristic of UMTS

▪ Pole Capacity, UL Cell Loading and DL Cell Power

▪ Erlangs vs. Number of Terminals

Capacity Planning

5- UMTS-GSM Co-location Issues

Co-location main Issues▪ Have to live with existing GSM sites

▪ Have to live with existing antenna heights/azimuths

▪ GSM Interference: GSM1800, GSM1900, etc

▪ Different coverage extents

GSM Co-location

Interference IssuesGSM Co-location

▪ Interference can occur:

▫ between carriers

▫ between operators

▫ between systems

▪ Co-location of GSM and UMTS sites raises

special problems.

3rd Generation Spectrum Allocations

1800 20501900 1950 20001850 2100 2150 2200

ITU(WARC-92)

Europe

Japan

Korea

USA

1885 1980 20102025 2110 2170 2200

1920 1980 20102025 2110 2170 2200

1920 1980 2110 2170

2110 21701920 1980

1850 1910 1930 1990 2110 2200

MSS MSSIMT-2000

Land Mobile

IMT-2000

Land Mobile UL

IMT-2000

Land Mobile UL

IMT-2000

Land Mobile

IMT-2000

Land Mobile DL

IMT-2000

Land Mobile DL

UMTS

Paired UL

UMTS

Paired DL

UMTS

SAT

UMTS

SAT

UMTS

Unpaired

UMTS

Unpaired

IMT-2000

Land Mobile

PCS

UL

PCS

DLReserved

1900

DECTGSM 1800

1880

GSM Co-location

Intersystem Interference Issues▪ Wideband Noise - unwanted emissions from modulation process and

non-linearity of transmitter

▪ Spurious Emissions - Harmonic, Parasitic, Inter-modulation products

▪ Blocking - Transmitter carriers from another system

▪ Inter-modulation Products - Spurious emission, specifications consider this in particular

▫ Active: non-linearities of active components - can be filtered out by Cell Equipment

▫ Passive: non-linearities of passive components - cannot be filtered out by Cell Equipment

▪ Other EMC problems - feeders, antennas, transceivers and receivers

GSM Co-location

Isolation RequirementsGSM 900 GSM 1800 UMTS

Receiving band(UL)

890 – 915 MHz 1710 – 1785 MHz 1920 – 1980 MHz

Transmitting band(DL)

935 – 960 MHz 1805 – 1880 MHz 2110 – 2170 MHz

GSM 1800 TxGSM 1800 Tx

1805 MHz1805 MHz 1880 MHz1880 MHz

UMTS RxUMTS Rx

1920 MHz1920 MHz 1980 MHz1980 MHz

GSM 1800 RxGSM 1800 Rx

1710 MHz1710 MHz 1785 MHz1785 MHz

UMTS RxUMTS Rx

2110 MHz2110 MHz 2170 MHz2170 MHz

For example For example -- To prevent UMTS BTS blocking: with transmit power = 43 dBm To prevent UMTS BTS blocking: with transmit power = 43 dBm

Max level of interfering signal for blocking = Max level of interfering signal for blocking = --15 dBm in UMTS15 dBm in UMTS

Isolation required = 58 dBIsolation required = 58 dB

GSM Co-location

Typical Isolation Requirements

Isolation Requirements

SpecificationRequirements

GSM900/GSM1

800 toUMTS Rx

UMTS Tx toGSM 900

Rx

UMTS Tx toGSM 1800

Rx

UMTS Txto UMTS

Rx

Blockingisolation 58 dB 40 dB 48 dB 63 dB

Spuriousemissions/inter

-modulationproducts

39 dB 34 dB 34 dB 39 dB

GSM Co-location

Achieving Isolation Requirements

▪ Isolation can be provided in a variety of different ways.

▫ By antenna selection and positioning.

▫ By filtering out the interfering signal.

▫ By using diplexers and triplexers with shared feeder and multiband antennas.

UMTSUMTS

GSMGSM

FilterFilter

UMTSUMTS

GSMGSM

DiplexerDiplexer

UMTSUMTS

GSMGSM

GSM Co-location

6- Practical Examples

Small, isolated cell

▪ Traffic is spread across a small area with low path loss to the base

station. The cell is heavily loaded.

▪ Eb/No and Ec/Io failures are

associated with path loss.

▪ Noise Rise will be the only radio-

related cause of failure.

Practical Examples

Small, isolated cell

▪ Capacity improvements can be achieved by:

▪ Increasing Noise Rise limit.

▪ Reducing target Eb/No on the

uplink and the downlink.

▪ A Mast Head Amplifier will not be

of much use as uplink Eb/No is

not a significant cause of failures.

Practical Examples

Large, isolated cell

▪ As loading increases, meeting Eb/No targets will be a problem.

▪ Heavy loading will result in Cell Breathing.

▪ Users at a great distance from the base station will not be able to make a connection.

▪ Gaps will appear in network coverage.

Practical Examples

Sectored Sites

▪ Capacity will be affected by overlap of cell coverage areas.

▪ Cell overlap can be controlled by pointing of antennas.

▪ Combining mechanical and electrical tilt can control backlobe radiation.

Practical Examples

Pilot Pollution

▪ A mobile can be too well served.

▪ It may be impossible to decode a dominant pilot.

▪ Ec/Io and Eb/No failure due to co-channel interference.

▪ Scaling pilot power and controlling radiation patterns is vital.

Practical Examples

Soft Handover

▪ Soft handover regions must be controlled to ensure that capacity is

maximised.

▪ Handover margin can be adjusted.

▪ Pilot powers can be scaled.

▪ Effect on handover region can be monitored.

Practical Examples

Dimensioning and Simulating a Network

▪ We are able to approximately dimension a network with a simple spreadsheet.

▪ This is a simplified network not considering the effects of mapping data and uneven traffic distribution.

▪ However, it is possible to simulate such a simplified network so that a clear understanding of the working of the simulator can be established.

▪ The network can then be modified to incorporate practical features such as terrain features and traffic distribution.

Practical Examples

6.1 Simulation Examples

The Network and Height ProfilePractical Examples

▪ 3dB NR limit

▪ 20m antennas

▪ No MHA, no RX diversity

▪ 500 Terminals spread on Urban and Suburban areas

Voice- Reason for FailurePractical Examples

▪ Polygon area OK as far as Voice Service

▪ Some NR Limit reached failures (aqua pixels)

VT- Reason for FailurePractical Examples

▪ Polygon area shows UL Eb/No failures

▪ NR Limit reached failures (aqua pixels)

▪ Changing azimuths on site to the right of polygon is not an option due to existing traffic restrictions

VT- NR Limit increased to 6dBPractical Examples

▪ NR limit parameter changed from 3 dB to 6 dB on all cells

▪ NR Limit reached problem fixed

▪ UL Eb/No problem still there

Pilot Coverage for PolygonPractical Examples

▪ Looking for the causes of the failure, a Pilot Coverage plot is done

▪ It can be seen that Pilot level in Polygon area is very low (around -105 dB)

Height Profile for PolygonPractical Examples

▪ Looking for the causes poor coverage, a Height Profile is performed

▪ It can be seen that there is a significant obstruction preventing a good UL

Height increased to 40mPractical Examples

▪ Trying to fix the UL Eb/No failure, antenna height is increased from 20m to 40m

▪ This decreases the pathloss, however, the original problem is not solved

▪ No interference problems are created either

Adding MHA and RX DiversityPractical Examples

▪ Another option is to add an MHA and RX Diversity

▪ These additions prove the solution for most of the problem pixels inside the polygon

▪ Height is still 40m, due to obstructions and poor site location

End of course

UMTS Applied Radio Planning

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