UMTS RF Interface and Applied Planning

8/13/2019 UMTS RF Interface and Applied Planning

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UMTS Applied Radio Planning

Prepared By

M. Ahsan Raza

Copyright 2008 LCC Pakistan1

a s an


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Course Objectives

Understand the key planning parameters of the UTRAN

Produce UMTS Link Budgets for various services

Understand Capacity dimensioning in UMTS

Appreciate the Coverage/Capacity relationship in UMTS

va ua e - o- oca on ssues



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1- The UMTS Air Interface



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UMTSThe UMTS Air Interface

Universal Mobile Telecommunication System

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

The evolution from GSM-GPRS-EDGE

,



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The UMTS Air Interface

1.1- WCDMA, Processing Gain and Codes



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CDMA - Direct Sequence Spread Spectrum


Frame Period (we may still need

frames/timeslots for signaling)



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SPREAD SPECTRUM



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CDMA Spreading


Essentially Spreading involves changing the symbol rate on the air interface

P

Spreading DespreadingP

f

Channelf

Tx Bit Stream P

P

f P Rx Bit Stream

f Air Interface

Chip Streamf

codesCode Chip Stream Code Chip Stream



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Spreading and Despreading


1

-1

Code Chip Stream

XSpreading

Air Interface

Chip Stream

Code Chip Stream

esprea ng

Rx Bit Stream



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Spreading and Despreading with code Y


1

-1

Code Chip Stream

XSpreading

Air Interface

Chip Stream

Code Chip Stream Y

Rx Bit Stream



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Interference mitigation


Rx Signal (= Tx Signal + Noise)

f

P

P

Tx SignalP

fP

Channel

f f

P

f

Spreading Code

The gain due to Despreading of the signal over wideband

Wideband Noise/Interference

noise is the Processing Gain



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Processing Gain


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

ccbRREE =

cRG = We say the Processing Gain Gp is equal to: bR

Commonly the processing gain is referred to as the Spreading Factor



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Visualising the Processing Gain


W/Hz W/Hz W/Hz

Io

Before

Spreading

After

Spreading With Noise

f f f

W/Hz W/Hz dBW/HzEb

N Eb

Eb/NoAfter

Despreading

Post

Filtering

o

W/HzSignal

f f f

EbNo

Eb/Nob

No

Intra-cell NoiseInter-cell Noise

PostFiltering

Orthog > 0

f f



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PROCESSING GAIN



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Types of Codes


Channelisation Codes

Are used to separate channelsfrom a single cell or terminal S2

Scrambling Codes

Are used to se arate cells andterminals from each other ratherthan purely channels

S1

C1 C2 C3

Different base stations will usethe same spreading codes withseparation being provided by the

codes. C1 C2 C3



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USE OF CODESThe UMTS Air Interface



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Channelisation Codes


Channelisation codes are ortho onal and hence rovidechannel separation

Number of codes available is dependant on length of code



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Channelisation Code Generation


Used to separate transmissions from a single source

(from UE in uplink, from Node B in downlink) Uplink code lengths: 4 to 256

Downlink code lengths: 4 to 512

Code lengths are 2N, derived using the OVSF scheme enera e sprea ng



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OVSF codes


Orthogonal Variable Spreading Factor Codes can be defined bya code tree:

Cch,2,0 = (1,1)

ch,4,0 = , , ,

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

Cch,1,0 = (1)

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

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

SF = 1 SF = 2 SF = 4

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

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



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OVSF codes: Example 1




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OVSF codes: Example 2




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Scrambling Codes


The spread data symbols are then scrambled by multiplyingwith a complex scrambling sequence

Scrambling codes do not affect the chip rate

The scrambling code is specific for a cell and thus serves to

There are 512 Scrambling Codes in the DL which can be

allocated by Radio Planners



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MULTIPATH EFFECTSThe UMTS Air Interface



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MULTIPATH EFFECTS AND THE RAKE RECEIVER




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Power Control and Near/Far Effect


When a UE is near the NodeB it doesnt need much power toreach it

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

-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



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NEAR FAR EFFECTThe UMTS Air Interface



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Open Loop Power ControlThe UMTS Air Interface



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CLOSED LOOP POWER CONTROLThe UMTS Air Interface



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Soft and Softer Handover


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

When in Soft Handover, the RNC can combine the best signals ,

two cells on the same site. A Softer Handover gain also occurs.

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



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SOFT HANDOVER



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SOFTER HANDOVER



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RELOCATION DRIFT RNC



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HARD HANDOVER

Compressed Mode



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CELL BREATHING

Cell breathing refers to the effectiveexpansion and contraction of a given

number of mobile users within the cell.




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




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Interference and Noise Densities

From the point of view of a UE, every other UEs powerappears 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




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Ec/Io

Ec/Io is the Chip Energy we obtain in the presence of theInterference 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

a e an over ec s ons

Typical requirement -15 dB



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CPICH The Common Pilot Indication Channel (CPICH) is a common channel

broadcast from each and every cell within a WCDMA network. It carries noinformation and can be thought of as a beacon constantly transmitting theScrambling Code of the cell.

Defines cell boundaries and provides each UE with a lock signal todetermine the ownership cell.

Initial system acquisition and to aid the channel estimation for the dedicatedchannels

The CPICH is one of the downlink channels utilized by each sector or cell. If the mobile is unable to clearly receive one dominant CPICH, due tointerference or coverage problems, the result is likely to be dropped calls,

, .


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CPICH

The soft handoff algorithms for WCDMA are based on measurementsmade by the UE on the Primary Scrambling Code of the Common Pilot

anne .

Signal strength comparisons between base stations can be used todetermine when to o into soft handover between two cells.

If the UE cant see the CPICH the UE cant see the cell.

CPICH


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CPICH

From the Node B perspective the

to keep the initial cell boundaries

fixed.

Ec/IoPCPICH=33dBm

From the UE perspective the Pilot is perceivedas the ratio between the received energy perchip to total interference or Ec/Io


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CPICH Power

Increasing or decreasing the relative power allocated to this channel maymodify the CPICH coverage.

s common o a oca e - o a ava a e power o e

Node B Power Distribution per Sector


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CPICH Quality

Initial 3G network optimisation will be performed purely fromCPICH measurements. Three key related measurements for 3G

Ec - The Received Signal Level of a particular CPICH (dBm)

Io - The Total Received Power (dBm)

Ec/Io - The CPICH Quality (The ratio of the above two values)

Introduction


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IntroductionTotal Received Power Io

In a WCDMA network the User Equipment (UE) may receive signals frommany cells whether in handover or not

Io (RSSI) = The total sum of all of these signals + any background noise(dBm)

Ec1 Ec2

Introduction


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IntroductionReceived Power of a CPICH Ec

Using the properties of the WCDMA downlink scrambling codes the UE isable to extract the respective CPICH levels from the sites received.

Ec (RSCP) = The Received Power of a Particular CPICH (dBm)

E E

Th CPICH Q lit E /I


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The CPICH Quality Ec/Io

From the previous two measures we can calculate a signal quality for eachCPICH (Scrambling Code) received. The quality of the CPICH can bemeasured in terms of Ec/Io, which is a representation of the signal to noiseratio for spread spectrum signals.

Ec/Io = Ec -Io (dB)

Ec1=-95dBm Ec2=-90dBm

From the above three measurements we can calculate for each pilot the

Io=-80dBm

(Ec/Io)1 = -95 - -80 = -15dB

(Ec/Io)2 = -90 - -80 = -10dB

stronger.

/



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Eb/No

Eb/No is the Bit Energy we obtain after despreading in thepresence of the Noise generated by all other users and the

o se rom o e equ pmen

Typical requirement 1 to 10 dB

, , ,Mobile Speed, and Type of Receiver.


N i Ri



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Noise Rise

The effective noise floor of the receiver increases as thenumber 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

Two Users

Background NoiseOne User


Eff t f N i hb i C ll



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Effect of Neighbouring Cells

.

Typical ratio of power from other cells to power from


, , .

Th N i Ri E ti



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The Noise Rise Equation

jMjtotal LI

=

===

1

11

jbj

j

RE

L

+ =1

11

If we have M identical users:

Mj

j

jWN

ML

+

==

= 01 1jb RE

N

tota

WN

MP

==

0

1RiseNoise


jb RE

N i Ri d L di F t



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Noise Rise and Loading Factor

Capacity is linked to Eb/No value

Maximum Path Loss tolerated is linked to maximum NR

o se se oa ng ac or

1 dB 20%

6 dB 75%10 dB 90%

( )UL= 1log10RiseNoise 10


Loading Factor



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Loading Factor

ThroughputActual

RM :ratedatawithusersidenticalFor

CapacityPole

( )iNEW

b

+

=

1

FactorLoading

viEb + 1

RW=0


UL Pole Capacity



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UL Pole Capacity

usersofnumberlargeFor

( )iEb +

1

CapacityPole

0

0.53Eb/No3840000W === i

( )( )kbps853

5.013

3840000CapacityPole =

+

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


50% of 853 kbps = 426 kbps

DL Pole CapacityThe UMTS Air Interface


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DL Pole Capacity

The Downlink benefits from orthogonality between channelisation codes.

WCa acitPole( )i

N

Eb +

10

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


Active Set and Pilot Pollution



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Active Set and Pilot Pollution

The Cells with which the UE is communicating form the UEsActive Set

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

Any Pilot which is not a member of a UEs Active Set and

>- .Polluter

Pilot Pollution is a common WCDMA issue that needs to besorted immediately


Summary of Key Concepts



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Processing Gain

Ec/Io Eb/No

Noise Rise

Cell Loading Pole Capacity

Near/Far Effect

o an o er an over a n


Summary of Key FormulasThe UMTS Air Interface


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Summary of Key Formulas

Eb/No

( ) pcb GIE

dBN

E

+=

Pole Capacity

W W

( )iNEb +

1

0

( )iNEb +

1

0



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2- The UMTS Link Budget


UMTS Link Budget vs GSMs

The UMTS Link Budget


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UMTS Link Budget vs. GSM s

Interference Margin for Noise Rise

Target Eb/no

Processing Gain (dBs) in UMTS

=

ower on ro marg n

Handover Gains


Interference Margin



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Interference Margin

An admission control parameter. Same as Noise Rise Limit

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

NR= 3dB, Load Factor=50%

NR=6dB, Load Factor=75%


Target Eb/No



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Target Eb/No

UMTS Link Budgets are made for Bearers

A UMTS service ma use one or more Bearers with each

Bearer having a QoS Eb/No requirement

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

yp ca ps earer requ res an o o a ou


Processing Gain



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Processing Gain

Depends on the bitrate of the Bearer

Hel s with the re uired Ec/Io at the receiver

. ,

For a 128 kbps data Bearer, Gp= 15dB


Power Control (Fast Fading) Margin



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Power Control (Fast Fading) Margin

Its entered to allow for adequate Power Control to compensate

for Fast Fading

Its dependent on the Speed Profile of the Mobile

At higher speeds, its smaller as the network cannot effectively


Handover Gains



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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

paths


UL Link Budget



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UL Link Budget

Because UL power is lower than DL power coverage is

UL limited.

Initiall , most attention is aid to the UL bud et.


-120 dBm Receiver Sensitivity



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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 tar et 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



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Link Budget - voice



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Link Budget voice

Noise Floor -104 dBm

o se se m

Processing Gain 25 dB

Target Eb/No 5 dB

-

UE Tx Power +21 dBm

Maximum Link Loss 141 dB

Feeder loss 3 dB

Body loss 1 dB

Maximum ath loss 154 dB

Margins 24 dBTarget path loss 130 dB


UL Link Budget - VT



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UL Link Budget VT

UMTS is introduced to offer higher level services such as video

.

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



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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 kbps



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Allowable 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

( )( )Mbps3

6.05.0141.1

1084.3CapacityPoleDL

3

=+

= x

For 50% loading capacity = 1.5Mbps or 11- 128kbps channels

=


.

Conclusions



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Eb/No and capacity intimately linked.

Link budgets are affected by fast fading and interference margins.

Uplink and downlink affected differently by increased loading.

.

Asymmetric traffic requirements can be designed in.



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3- Coverage Planning


Coverage ObjectivesCoverage Planning


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Achieve Minimum Pilot Coverage on Service Area

Minimum Coverage dependant on:

ALP

Loading

KPIs

RSCP (Ec)

RSS (Io)

Ec/Io Pilot Pollution (Scrambling Code overlapping)


Factors affecting Coverage

Coverage Planning


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ALP is a function of:

Clutter Type

Shadow Fading Margin

erv ces:

The higher the bitrate the lower the coverage

Different Eb/No re uirements

Loading:

The higher the loading the lower the coverage

Loading factor tied to Noise Rise Limit


Coverage Planning


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.


Dimensioning Inputs

Coverage Planning


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SiteConfigurationService

GeographicDemographic


Simple Coverage

Coverage Planning


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Link Budget based

i.e. simple numerical calculationCreate Link Budget

Firstly a link budget is created Calculate Range

Max PL

The maximum path loss is used to calculate thecell range using a propagation model

Calculate Site Area

Max Range

The cell range is used to calculate the site area Max Area

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

Sites in a given Area


Shadow Fading and Building Penetration

Coverage Planning


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Building Penetration

Mean and standard deviation per environmentP(connect)

50% 75%

Shadow Fading

Typically calculated using Jakes

( )

+=

berf

baerfFu 1exp1

2 2

( )0 = xa

= log10

e

nbWhere: ;

x0 -

P(connect)

0

2x0-= Fade Margin

= Standard Deviation of Model

=

Point Location Probability

x0 -5.6

Area Location Probability


This assumes an isolated omni directional site

Environment Distribution

Coverage Planning


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prea s ee s on eawith topology or

morphology accurately,

distributed target areas

Interference and trafficcaptured by sites willvary

Margins for site Suburban Site Numbers?acquisition and overlap

are required Urban Area Site NumbersArea


Coverage Planning


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.


Pilot Power as an Indicator

Coverage Planning


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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 -Coverage Planning


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Pilot powers not necessarily equal

deployment of MHA at selected sites

will alter target pilot values.

Even if MHAs are universally,

feeder loss.

Generally, MHAs have a different

effect on UL to DL, therefore DL

measurement not a reliable indicator of

> -80 dBm

> -87 dBm .


Letting the tool do the work

Coverage Planning


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It is possible to define:

The UE: in articular 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

coverage ac eve

Voice coverage achievedeac ce o e e erm ne an

coverage to be calculated directly.


Pilot Strength PlotCoverage Planning


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Assessing Interference with aCoverage Planning


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a c na yser - c o Pilot Ec/Io indicates pilot

power as a ratio of total

wideband power (including

the pilot itself).

Not terribly scientific but

t correspon s rect y to

measurement reported by

the UE in drive tests.


Ec/Io PlotCoverage Planning


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Assessing Interference with a Static

Coverage Planning


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na yser - o

the pilot.

Effect of ortho onalit

on own-cell interference

is considered.

Pilot power not

considered as

interference.

Pilot SIR is always better

than Ec/Io.


Coverage Planning


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.


Limiting mutual interference

Coverage Planning


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Downtilt antennas.

side of buildings.



Coverage Planning


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6Elec 0Mech

0

6

6

0Elec 6Mech

66Elec -6Mech

-6

00

6

0

12

0

Controlling the backlobe can produce a small


but significant improvement in capacity.


Coverage Planning


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

FRE IntraN

=

(W)ceinterferencell-intratheisIntra

InterIntra

N

-Inter


Mast Head Amplifiers (TMAs)

Coverage Planning

Used to lower the Noise Figure of the receiver


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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).

Increase uplink capacity

Adds Insertion loss on DL (~ 1.3 dB)

AntAntBiasBias--TT

TMATMA

by passby pass


Uplink Receive Space Diversity

Coverage Planning

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


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

~ ,

improvement.

-

m apart.Receive

antenna 2

Receiveantenna 1


Uplink Receive Space Diversity

Coverage Planning


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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 estimationer ve rom e o c anne .

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

ery ow n v ua o w pro a y mean a very ow p o evewhich will lead to poor coherence and little gain - process becomes

self-defeating.


Coverage Planning


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.


Typical vendor valuesCoverage Planning

Pilot Power = 5-10% of Total Power (30-35 dBm)


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Pilot Power 5 10% of Total Power (30 35 dBm)

Control Channel Powers = 3-5 dB below Pilot (27-33 dBm)

CCPCHs

Other signalling Channels = 3-5 dB below Pilot (27-33 dBm)

, ,

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


Some additional constraintsCoverage Planning

GSM existing coverage


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GSM existing coverage

GSM legacy sites

Antenna limitations: height, azimuths, etc.

Copyright 2008 LCC Pakistan

98


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4- Capacity Planning


99

Capacity ObjectivesCapacity Planning

Manage effectively predicted Load on Service Area


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g y p

Capacity dependant on:

Number of users

os t on o users re at ve to t e ce

Services demanded

UE Power Control

KPIs

Cell UL Load Factor

Cell DL Power


100

Factors affecting Capacity

Capacity Planning

Number of Users: The more users the more noise


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Position of Users: The farther away, the more noise

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

UE Power Control: Imperfect power control will account for morenoise in the network


101

Soft and Hard Capacity

Capacity Planning

Hard Capacity: Hard limit imposed by actual channel elements


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p y p y

Typ. 16 Kbps Channel elements. Also called Resources or

Cards

Soft Capacity: Variable, depending on Network loading


102

UL Pole Capacity

Capacity Planning


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Capacity is typically limited on the UL

This is because, in the UL we dont have Orthogonality to help us

( )iEb +

1

CapacityPoleUL

0


103

UL Pole Capacity Exercise- VoiceCapacity Planning

If we assume a service with Eb/No = 6dB and i = 0 8


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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


104

UL Pole Capacity Exercise- VoiceCapacity Planning

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


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

Noise Rise= -10log (1-0.53) = 3.2dB

,


105

UL Pole Capacity Exercise- VTCapacity Planning

If we assume a service with Eb/No = 3dB and i = 0 8


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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/Nos 3dB (VT) vs 6dB (voice)


106

Capacity Planning


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4.1 Multi-Services Capacity andapac y mens on ng


107

Multi-Service CapacityCapacity Planning

Eb/No Activity Factors


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Voice= [email protected]

VT= 3.8dB@64kbps

58%

100% .

dB vs Linear Bitrate Ratios relative to voice

5.6dB= 3.6 (1x) 7.1 kbps

. .

2.8dB= 1.9

(18x) 128 kbps


108

Campbells SpreadsheetCapacity Planning

CS CS PS PS PS


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Bearers (kbps) 12.2 64 64 128 384

PS Capture Data (Mbytes/hour) Not Applicable Not Applicable 0 0 0

Activi ty factor 58.0% 100.0% 0.0% 0.0% 0.0%

Average rate (kbps) 7.1 64.0 0.0 0.0 0.0

Eb/No 6 3 2 1.2 1.8

Eb/No ratio 3.98 2.00 1.58 1.32 1.51

Relative Ratio 1 0.50 0.40 0.33 0.38

Equivalent data rate (voice) 212.28 192 0.00 0.00 0.00

Factor for i 0.8

Reference Pole Capacity (kbps) 536

Loading of Cell 75.4%

UL Noise Rise Loadin 6.10


109

Traffic ExerciseCapacity Planning

Manchester pop. = 2.2 Million


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Manchester pop. 2.2 Million

o e pene ra on = . on

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


110

Simple Capacity Dimensioning

Capacity Planning

Capacity calculation based Calculate CarrierCapacity


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Capacity

Calculate maximum capacityper carrier

Calculate SectorOffered Traffic

Calculate maximum offeredtraffic per sector

Calculate Maximum

Calculate site area based ontraffic density

Calculate Number of

Calculate the maximum number

Sites in a Given

Area


111

Other Dimensioning Factors

Capacity Planning

GSM/UMTS Interaction


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Dont 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

Node-B


112

2G analysis

Capacity Planning

Coverage thresholds can be set for various services and


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Coverage thresholds can be set for various services and

coverage examined in a similar manner to that for GSM

systems

ra c cap ure y ce s or ra c can e

interpreted as cell loading for UMTS systems.


113

Capacity Planning


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4.2 Analysis of DL Capacity


114

DL Pole CapacityCapacity Planning

WC itP lDL


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Ca acitPoleDL

( )i

N

Eb +

1

0

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

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


115

Further Analysis of the Downlink

Capacity Planning

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


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gure = - + + - = - m

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

be tolerated. Can DL support this?

provide enough power to support it on the DL


116

Capacity Planning


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.


117

Traffic Density

Capacity Planning

Traffic Density is forecast in terms of a density in terms of Erlangs persquare kilometre.


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.

Knowing the clutter categories in the required service areas allows traffic

to be simulated.

Traffic Density Weightings

Clutter Category 1: 10

1

2

u er a egory :Clutter Category 3: 30


3


118

Density versus Numbers

Capacity Planning

It is important to realise that the weightings are in terms of terminaldensities.

Sometimes the clutter category with the highest weighting occupies a small


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Sometimes the clutter category with the highest weighting occupies a smallpercentage of the area.

3

Area Weightings


Weighting of Actual Traffic

per Category1

24



.

Clutter Category 2: 36.4



Notice that the actual traffic volume per category differs from the traffic


ens ty. ra c ens ty s t e parameter entere n t e s mu at on too .


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.


Coverage vs. CapacityCapacity Planning

Coverage vs. Capac ity


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165.00

170.00

ss

(dB)

150.00

155.00

160.00

umP

athlo Uplink

Dow nlink

145.00

100 200 300 400 500 600 700 800Maxi


Link Loss vs. CapacityCapacity Planning

1200


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1200

800

1000

(k

bit/s)

200

400

Capacit

120 130 140 150 160

Link Loss (dB)

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


Orthogonality vs. CapacityCapacity Planning


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800

1000

1200

kbi

t/s)

200

400

600

apacity(

0

0 0.2 0.4 0.6 0.8 1

r ogona y

BTS Power: 37 dBm 40 dBm 43 dBm 46 dBm


Out of Cell Interf. vs. CapacityCapacity Planning

1400

)


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)

600

800

1000

ity

(kbit/s

0

200

400

Capa

0 0.4 0.8 1.2 1.6 2

Out of Cell Inter ference

BTS Power: 37 dBm 40 dBm 43 dBm 46 dBm


Capacity Planning SummaryCapacity Planning

Capacity dependant on: Number of users


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Position of users relative to the cell

Services demanded

Multi le Services Traffic characteristic of UMTS

Pole Capacity, UL Cell Loading and DL Cell Power

Erlangs vs. Number of Terminals



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- - -


Co-location main IssuesGSM Co-location

Have to live with existing GSM sites


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Have to live with existing antenna heights/azimuths

GSM Interference: GSM1800, GSM1900, etc


Interference Issues

GSM Co-location

Interference can occur:


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between carriers

between operators

between systems

Co-location of GSM and UMTS sites raises

.


3rd Generation Spectrum Allocations

GSM Co-location

ITU

WARC-92

1885 1980 20102025 2110 2170 2200

MSS MSS

IMT-2000

Land Mobile

IMT-2000IMT-2000

Land Mobile


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Europe1920 1980 20102025 2110 2170 2200UMTS

Paired UL

UMTS

Paired DL

UMTS

SAT

UMTS

SAT

UMTS

Unpaired

UMTS

Unpaired

1900

DECTGSM 1800

1880

Japan2110

2110 21701920 1980

IMT-2000

Land Mobile UL

IMT-2000

IMT-2000

Land Mobile DL

IMT-2000

USA1850 1910 1930 1990 2110 2200

Land Mobile UL Land Mobile DL

PCS

UL

PCS

DLReserved

1800 20501900 1950 20001850 2100 2150 2200


Intersystem Interference Issues

GSM Co-location

Wideband Noise - unwanted emissions from modulation process andnon-linearity of transmitter

S i E i i H i P i i I d l i d


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Spurious Emissions - Harmonic, Parasitic, Inter-modulation products

Blocking - Transmitter carriers from another system

Inter-modulation Products - Spurious emission, specifications considerthis in particular

c ve: non- near es o ac ve componen s - can e ere ou yCell Equipment

Passive: non-linearities of passive components - cannot be filtered

Other EMC problems - feeders, antennas, transceivers and receivers


Isolation Requirements

GSM Co-location

GSM 900 GSM 1800 UMTSReceiving band

(UL)

890 915 MHz 1710 1785 MHz 1920 1980 MHz

Transmitting band 935 960 MHz 1805 1880 MHz 2110 2170 MHz


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Transmitting band

(DL)

935 960 MHz 1805 1880 MHz 2110 2170 MHz

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

ax eve o nter er ng s gna or oc ng =ax eve o nter er ng s gna or oc ng = -- m nm n

Isolation required = 58 dBIsolation required = 58 dB

1805 MHz1805 MHz 1880 MHz1880 MHz

1920 MHz1920 MHz 1980 MHz1980 MHz1710 MHz1710 MHz 1785 MHz1785 MHz

2110 MHz2110 MHz 2170 MHz2170 MHz

GSM 1800 TxGSM 1800 Tx UMTS RxUMTS RxGSM 1800 RxGSM 1800 Rx UMTS RxUMTS Rx


Typical Isolation Requirements

GSM Co-location

Isolation Requirements

Specification


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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

emissions/inter-modulation

products

39 dB 34 dB 34 dB 39 dB


Achieving Isolation Requirements

GSM Co-location

Isolation can be provided in a variety ofGSMGSM

.


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UMTSUMTS

.

B filterin out the interferin si nal.FilterFilter

GSMGSM

By using diplexers and triplexers withUMTSUMTS

GSMGSM

s are ee er an mu an an ennas.DiplexerDiplexer



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-


Small, isolated cell

Practical Examples

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

base station The cell is heavily loaded


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base station. The cell is heavily loaded.

associated with path loss.

Noise Rise will be the only radio-

related cause of failure.


Small, isolated cell

Practical Examples

Capacity improvements can be achieved by:


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Increasing Noise Rise limit.

Reducing target Eb/No on the

A Mast Head Amplifier will not be

of much use as uplink Eb/No is

not a significant cause of failures.


Large, isolated cell

Practical Examples

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

Heavy loading will result in Cell Breathing.


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Heavy loading will result in Cell Breathing.

sers a a grea s ance rom e

base station will not be able to

make a connection.

Gaps will appear in network

.


Sectored Sites

Practical Examples

Capacity will be affected by overlap of cell coverage areas.


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Cell overlap can be controlled by

pointing of antennas.

Combining mechanical and

electrical tilt can control backloberadiation.


Pilot Pollution

Practical Examples

A mobile can be too well served.


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It may be impossible to decode a

.

Ec/Io and Eb/No failure due to co-

channel interference.

radiation patterns is vital.


Soft Handover

Practical Examples

Soft handover regions must be controlled to ensure that

capacity is maximised.


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p y

.

Pilot owers can be scaled.

Effect on handover region can be

monitored.


Dimensioning and Simulating a Network

Practical Examples

We are able to approximately dimension a network with a simple

s readsheet.


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This is a simplified network not considering the effects of mapping dataand uneven traffic distribution.

However, it is possible to simulate such a simplified network so that aclear 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.



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.


The Network and Height Profile

Practical Examples

3dB NR limit

20m antennas


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,

diversity

500 Terminalsspread on

Urban and


Voice- Reason for Failure

Practical Examples

Polygon area

OK as far as

Voice Service


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Some NR Limitreac e a ures

(aqua pixels)


VT- Reason for Failure

Practical Examples

Polygon area

shows UL Eb/No

failures


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NR Limitreac e a ures

(aqua pixels)

Changingazimuths on site

to the right of

polygon is not an

option due to

existing traffic


res r c ons

VT- NR Limit increased to 6dB

Practical Examples

NR limit

parameter

chan ed from 3

dB to 6 dB on all


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cells

NR Limit

reached problem

UL Eb/No

problem still

there


Pilot Coverage for Polygon

Practical Examples

Looking for the

causes of the

failure, a Pilot

Coverage plot is

d


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done

It can be seen

that Pilot level in

very low (around-105 dB)


Height Profile for Polygon

Practical Examples

Looking for the

causes poor

covera e, a

Height Profile is

f d


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performed

that there is a

significant

obstruction

preventing agood UL


Height increased to 40m

Practical Examples

Trying to fix the

UL Eb/No failure,

antenna hei ht is

increased from

20m to 40m


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20m to 40m

This decreases

the pathloss,

,

original problemis not solved

No interference

problems are


crea e e er

Adding MHA and RX Diversity

Practical Examples

Another option is

to add an MHA

and RX Diversit


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These additionsprove e

solution for most

of the problem

polygon

Height is still

40m, due to

obstructions and


poor s e oca on


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Final Summary

Processing Gain

Ec/Io


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Eb/No

Noise Rise

Cell Loading

Pole Capacity Near/Far Effect

o an o er an over a n


Summary of Key FormulasFinal Summary

Eb/No

( ) cb GE

dBE

+=


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( ) pGI

dB

N

+=

Pole Capacity

W W

( )iN

Eb +

1

0

( )iN

Eb +

1

0



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UMTS RF Interface and Applied Planning

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Transcript of UMTS RF Interface and Applied Planning