GSM Fundamentals by Dr. Hatem MOKHTARI

® Cirta Consulting LLC

GSM RF Design and Planning Fundamentals

Dr. Hatem MOKHTARICirta Consulting LLC


During the 1980s, in Europe, Many Systems were used without anyRegulation, Standards, or Compatibilities. Most of them were Analog. As a result :

* No Roaming between Countries

* Major Capacity Problems and Congestions

* Limited Market for each Technology

* Very high subscriber equipment cost...Further growth difficult !

In The USA and Canada DAMPS (Digital Advanced Mobile Phone Service) : Cheaper handsets, roaming, easy subscribing, etc

A. Introduction to Wireless Telephony


Modern Systems are :

* Digital : The signal is Digitized through A/D Converters, Modulated, and then sent via the Antenna

* High Capacity : They are able to simultaneously serve a large number of customers

* Encrypted : Due to the fact that they are digital, they have full protectionagainst fraud. Also, they are highly securised

* High Speech Quality : Due to Technology advance and electronicsimprovements

* Spectrum Efficient : They offer optimised frequency spectrum use

* Possibility to roam within the GSM Community Networks (provided a signedRoaming Agreement)



Role of the RF Design Engineer :Design the Network ArchitectureSelect type of AntennasAnalyze the Links : Downlink and UplinkPropose Solutions to Enhance the Capacity of a Base StationConsider Marketing Inputs and Propose Design accordinglyPerform Drive Test to ensure Quality of the LinkUse Radio Planning rules to install Antennas in different sitesUse Radio Planning tools to assess the Coverage using SimulationPerform RF Propagation Model Tunning using measurementsSelects the RF Infrastructure to fullfil the Link Budget requirementsCalculates Propagation, Site Clearance, Link Quality using different Hardware and Software Tools



A GSM subscriber (Mobile) Should be able to :Receive and Transmit within a given geographical areaRoam to other countries (If a Roaming Agreement exists)Have a continuous Quality of Service (QoS)

A Mobile Station should be able to :Change the Serving Base Station (BS) if the link is bad (or going to become bad) on the actual BS. This is the Handover (or Hand-off)Recognize which country, Network, or Base Station the user isattached toInform the actual Network about the Identity of the UserPrevent forthcoming Drop Calls, Quality Problems due to Interference, or Signal Level (shadowing by obstacles)



Notation in dBm, dBW, dBi, dBd, dB

P (dBm) = 10Log10(P mW/1mW)Example : 100 mW power results in 10Log10(100)=20 dBm

P dBW = 10Log10(P W/1W)Example : 15 W power results in 10Log10(15)= 11.76 dBW

Relation between dBW and dBm :dBm = dBW + 30Example : 100 mW = 20 dBm = -10 dBW

B. RF Fundamentals


If an internal resistor is to be considered:

•Voltage

•Power

•Voltage

•Power

E R

I

U

r

ER

I

U

B. RF Fundamentals : DC CIRCUITSRIU =

RUUIP

2

==

ErR

RU+

=

22)(E

RrRP

+=


e

r

i

u R

•Voltage• If • Then

•Power

•RMS Notion = Root Mean Square

Riu =tEte ωcos)( =

tUtrR

REte m ωω coscos)( ≡+

=

tRUtitutp m ω2

2

cos)()()( ==

∫=T

dttuT

U0

2 )(1

B. RF Fundamentals : AC CIRCUITS


Suppose we have a voltage :

With a period of

Compute the RMS Voltage for Um = 50 V

Is the RMS dependent of the frequency ?

B. RF Fundamentals : Exercise

tUtu m ωcos)( =

ωπ2

=T


222

111

**

jyxzjyxz

+=+=

)()(1()(

)()(

2121212122

22

22

21

2

1

2121212121

212121

xyyxyyxxyxz

zzzz

xyyxjyyxxzzyyjxxzz

−+−×==

++−=×±+±=±

==Θ

==Θ

−

−

2

2122

1

1111

)arg(

)arg(*

xytgz

xytgzIf

212

1

2121

)arg(

)arg(

Θ−Θ=

Θ+Θ=

zzzz

Given

Compute

21

21

21

zzzzzz

−+

2

1

zz

2

1

ΘΘ

( )( )

( )214

2

13

22

11

arg

arg

argarg

zzzz

zz

=Θ

=Θ

=Θ=Θ

31

21

2

1

jz

jz

+−=

+=

Exercise

Complex numbers B.RF Fundamentals


B.RF.Fundamentals

Exercise

Given

Given

Impedance

32

2

2

31

j

ej

−=Ζ

=Ζπ

( )

( )212121

2

1

2

1

2

1

212121

arg,)3

arg,)2

arg,)1

ΖΖΖΖΖΖ

ΖΖ

ΖΖ

ΖΖ

Ζ+ΖΖ+ΖΖ+Ζ

and

and

andCompute

Show thatΥ+Χ=Ζ j

ΧΥ

+Υ+Χ=Ζ −122loglog jtg

>~e U

( )12 −•=

=Ζ

•Ζ=

sradfjL

IU

πω

ωwhere

resistorpureaforR

inductoranforjL

capacitoraforCj

=Ζ

=Ζ

−=Ζ

ωω


Y

XReal Part

Z

θρ jejYXZ =+=

θρ

θρθρ

sincos

==

YX

B. RF Fundamentals : Complex numbersImaginary Part


ε

Zin

I

U Z

U=Z I U, Z and I are all Complex Numbers

B. RF Fundamentals : Impedance

Z : The Impedance of the Load and Zin internal to the Generator

ωjLZ =ωCjZ /−=

RZ = for a Resistorfor an Inductive Component

for a Capacitor

A

B

In Low Frequencies, all the power delivered to Z isabsorbed or dissipated into heat


Vertical PolarizationRefers to thedirection of theElectric Field

Horizontal Polarization wouldbe to configure thedipole horizontally

Horizontal Polarization Refersto the direction of the Electric Field

Er

Hr Π

rDipole

Antenna

Πr

is the Poynting Vector (Power)

ηHErr

r ×=Π

B. RF Fundamentals


ε

Zin

I

U Z

At RF domain, Energy flowsfrom the generator to the Load.It can be fully absorbed by Z, orPartly reflected and partly absorbed.

B. RF Fundamentals : High Frequency considerations

A

B

10011 2

×

+−

=VSWRVSWRρThe % of Reflected Energy is

VSWR : Voltage Standing Wave Ratio ( 1:1 is ideal )Acceptable VSWR = 1.5 : 1Impedance Match : Z* = Zin


EIRP or Equivalent Isotropic Radiated Power :The Power to supply to an antenna to obtain the same power in all directions at a distance d :

We always consider the main lobe direction where no losses exist

dBi : Refers to an Isotropic antenna and dBd to the Dipole :

dBi = dBd + 2.15 dBEIRP = ERP + 2.15 dB

Example : G = 16 dBi, so G = 13.85 dBd and if P = 33 dBm (2 W)Then PE = 16 + 33 = 49 dBm in the main Lobe

B. RF Fundamentals

),(),( ϕθϕθ rE LGPP −+=

GPPE +=


60

32.5

0

- 32,5

- 60dB

60

32.5

0

- 32,5

- 60dB

10 10

30 0

3

Horizontal Diagram Vertical Diagram

B. RF Fundamentals


- 1 . 0 5

- 0 . 6 0

- 0 . 1 5

0 . 3 0

0 . 7 5

- 6 0 . 0 0

- 4 0 . 0 0

- 2 0 . 0 0

0 . 0 0

2 0 . 0 0

0 . 0 0 - 2 0 . 0 0

- 2 0 . 0 0 - 0 . 0 0

- 4 0 . 0 0 - - 2 0 . 0 0

- 6 0 . 0 0 - - 4 0 . 0 0


B. RF Fundamentals

Directivity : Figure of Merit to quantify the ability of an antenna to concentrate the Energy in a particular Direction

Where Wmax is the Power Density at a distance d in the main lobe direction

Generally, we use the Gain instead :

Where PT is the supplied power to the antenna, commonly known as the output power (minus the cable and connector losses)

Given PT and G, we can compute the Power Density Wmax

densityMeanPowerDWD

@max=

2

max

4 dP

WGT

π

=


B. RF FundamentalsRelation Between W and E (The Electric Field) :

Besides :

Maximum Useful Power :

377120

222 EEEW ===πη

dGP

EdGPE TTTT 30

4120 2

2

=⇒=ππ

12024.

120

2222R

RGEGEAEP

===

πλ

πλ

πη


B. RF FundamentalsEffective Area of an Antenna (Reception) :

Received Power :W : Power Density (Per Unit Area)

Finally, the received power reads :

Free Space Loss Between Isotropic Antennas (GR=GT = 1) :

GAπ

λ4

2

=

WAP =

24 dGPW TT

π=

RTT

R GdGPP

πλ

π 44

2

2=

kmMHzT

R dLogfLogPPLogdBL 101010 202044.3210)( −−−==


B. RF FundamentalsPropagation Over a Plane Reflecting Surface (Flat Earth Model) :

Assuming d >> Ht and Hr, the Path Loss (Iinear) :

HtHr

TxRx

δjkdd eEEE −−=

d

2

2

=dHHGG

PP rt

RTT

R


B. RF FundamentalsReflection :

HtHr

TxRx

δjkdeEE −Γ=

d

Γ is the Complex Reflection CoefficientThe value of Γ depends upon frequency, Polarization and Electric Characteristicsof the reflecting surface


A B C

A

CB

P

Shadow region

B. RF Fundamentals


B. RF FundamentalsDiffraction :

HtHr

TxRx

δjkdeDEE −=

d

D is the Complex Diffraction CoefficientThe value of D depends upon frequency, Polarization, Geometry, and Angles of thestructure

h

D1D2


The Diffraction Loss is shown to be :

Where v, the Fresnel Parameter is given by :

B. RF Fundamentals

( )

( ) 4.24.21

1008.0

/225.020))1.038.0(1184.04.0(20

))95.0exp(5.0(2062.05.020

)( 2

><<

<<<<−

−−−−

−

=

vvvv

vLogvLog

vLogvLog

vL

21)21(2

DDDDhv

λ+

=


B. RF Fundamentals

Hb

Hp

Hm

Ho

A B

Compute L(v) for :Hb = 20 mHp = 5 mHo = 15 mHm = 1.5 mA = 1250 mB = 4.5 mFrequency = 900 MHz


Bullington Model :“equivalent” Knife - edge

T R

0102

D1 D2

d1 d2 d3

h1 h2

H

Ht Hr


Test : Bullington Diffraction Loss Model

Compute H, D1, D2, and then L(v) the DiffractionLoss given the following data :

Ht = 25 mHr = 1.5 md1=d2=d3=1000 mh1 = 30 m, h2 = 15 mFrequency = 1880 MHzCompare L(v) to the Free Space LossPlease Conclude


d1 x d2 x d3 x d4

T R

The Epstein – Petersen diffraction construction

01

02

03

Propagation over irregular terrain


d1 x d2 x d3 x d4

T R

The Deygout diffraction construction

01

02

03

Propagation over irregular terrain

Main edge


B. RF Fundamentals : Receiver Theory

ReceiverDemodulation& Selective

Filtering

BS / MS

Receiver Input

Receiver Output

To operate properly the receiver has to receivea minimum power : Sensitivity

The Sensitivity depends on the technology involved


Receiver Sensitivity :Is the minimum acceptable input signal level in dBm, at thereceiver‘s low noise amplifier, required by the system for reliablecommunication

Carrier to Noise Ratio CNR or C/N :For a given BER (Bit Error Rate) of about 10-3 for example, C/N isthe required minimum signal to noise ratio

Thermal/Environment Noise :Is a combination of

Antenna Noise (dBm)Receiver Noise Figure (NF) in dBTemperature and System Bandwidth




(S/N)in (S/N)out

ReceiverNF

NFNSNS

NFNSNS

NFNS

NS

outinin

outinin

outin

+

+=

+

=−

+

=

Nin : Thermal Noise,

NF : Noise Figure

outin N

SNFBTkLogS

++= )..(10 10

RECEIVER SENSITIVITY :



outin N

SNFBTkLogS

++= )..(10 10

k : Boltzmann Constant ( 1.38 * 10-23 J/°K)T : System Operating Temperature (°K)B : System Bandwidth (Hz)

T : 290 °K typical value

Exercise : Compute Sin (dBm) for a GSM signal of 200 kHz Bandwidth, with a receiver NF=6 dB and C/N = 9 dB


B. RF Fundamentals : Intermodulation

Non-LinearDevice

IM is a non-linear process that generates an output signalContaining frequency components not present in the inputsignal

...33

2210 ++++ xaxaxaax

Assuming x to be a two-carrier f1 and f2 sine wave :

)2cos()2cos()( 21 tfBtfAtx ππ +=



3210)( yyxaaty +++=

( ) ( )( ) ( )( )[ ] ( )( ) ( )( )[ ]2121222

122222

2 2cos2cos22cos22cos22

ffffABafBfAaBAay −++++++= ππππ

Spectral Characteristics of y2 Usingf1 = 1800 MHz and f2 = 1830 MHz, A=B=1, and a2 = 1

f1 f2

0

DC f2-f1 2f1 2f2

1800 MHz 1830 MHz

3600 MHz 3660 MHz

3630 MHz

f2+f1

Cellular Band

30 MHz



3210)( yyxaaty +++=

Spectral Characteristics of y3 Usingf1 = 1800 MHz and f2 = 1830 MHz, A=B=1, and a2 = 1

f1 f2

0

DC 2f2-f1

1800 MHz 1830 MHz

1860 MHz

Cellular Band

1770 MHz

2f1-f2

Six Different Frequencies are generated in IM3 :3f1, 3f2, 2f1-f2, 2f1+f2, 2f2-f1, 2f2+f1


B. RF Fundamentals : Fade Margin

R

• Due to shadowing and terrain effects the signal level measured on a circlearound the BS shows radom behaviour around the predicted value given by thePropagation Model

• This Random Signal level through the cell boundary has a Log-Normaldistribution

• Log-Normal variable is in fact a Gaussian Process when expressed in dB

( )

−−= 2

2

2exp

21)(

σπσmxxp

x : is the received levelm: Mean value of xσ : Standard Deviation of x


( )

−−= 2

2

2exp

21)(

σπσmxxp

B. RF Fundamentals

Theory shows that to ensure 90 % of Surface Reliability,One may push the received signal level requirement toHigher values than m (50%).

This leads to a notion called :

Fade Margin : the additional margin to fullfil y % of surfaceCovered.

PDF-Gaussian

0

0.01

0.02

0.03

0.04

0.05

0.06

-110

.00

-104

.00

-98.

00

-92.

00

-86.

00

-80.

00

-74.

00

-68.

00

-62.

00

-56.

00

-50.

00

PDF-Gaussian


Fade Margin

50% is the median value. To achieve higher %, one may adda Fade Margin to fullfil X% > 50%

The Probability that a Field Strength Exceeds a Threshold E0 is :

−

−=

=≥= ∫∞

21

21

)()(

0

0

0

0

0

σEEerfp

dEEpEEpp

mE

EE


Fade Margin

The Lognormal Margin is defined as :Mlog = Em – E0

Hata Model has a general form :

The Contour Probability can be written as :

)/(log10)( 100 RrErE m γ−=

+−=

Rrbaerfp E ln1

21

0


Fade MarginThe parameters a and b are :

The Area Coverage Probability over a Circle of Radius R is :

The contour probability depends only upon the radius r, which simplifiesthe computation and leads to :

2log10

210

0

σ

σeb

EEa m

=

−=

∫∫= θθπ

rdrdrpR

P E ),(102cov

( )

+

−

+

−+=b

aberfbabaerfP 1112exp1

21

2cov


Contour and Area Coverage Probability Versus the Fade Margin

0102030405060708090

100

0 1 2 3 4 5 6 7 8 9 10

Fade Margin (dB)

Prob

abili

ty (%

)

Cell Edge %Area %


BasefadeBldgBodymmup

upFadeBldgbodymmBase

RXMLLGPAPl

PlMLLGPARX

−−−−+=

−−−−+=

CCCB

CCCB

LGLG

−+−+

Ms AntennaGain Loss

ERP

Body Loss

In-Building CarPenetration Loss

Fade margin

Path Loss

CombinerCable &

ConnectorLosses

RYCCCL

AG

Gains and losses in uplink


PA

CombinerCable &

ConnectorLosses

PowerAmplifier

MBodyBldgDownFadeBCCCMobileB

MBodyBldgDownFadeBCCCBMobile

GLLPLMGLRXPA

GLLMMGLPARX

−++++−+=

+−−−−+−=

ERPFade margin

Path LossIn-Building CarPenetration Loss

Body Loss

MS AntennaGain Loss

CCCL

BG

RX

Gains and Losses in Down Link


Maximum Allowable Path Loss

Starting with the reverse link UL•Find the maximum Allowable Path Loss (MAPL)

- Start from MS maximum power- Subtract all the losses in due to, RF components- Subtract all the margins due to fading and interferencefor a given target loading

- Add all the gains in the path e.g. antenna and diversity gains- Subtract the receiver sensitivity of the base station for a given FER

- The result is MAPL

baseUp RXAllGainsAllLossesPLMAPL −+−=


Balance Equation:

•Write the balance equation and see which termsget cancelled•Find the Base station and EIRP that resultsin balanced paths.•Changing which parameter jeopardizes the path balance?- Antenna Gain- Antenna Height- PA output

UpDown

MBodyBldgMobileFadeBCCCBDown

CCCDivBBaseFadeBldgBodyMmUp

PLPL

GLLRXMGLPAPL

LGGRXMLLGPAPL

=

+−−−−+−=

−++−−−−+=


Cell Size / Count Estimation

• Objective- To determine the number of cells required to providecoverage for a given area

• Required Input:- Maximum Allowable Path Loss (MAPL)- Propagation Loss Model


MAPL

Path Loss

Range or Cell Radius

Distance from TX

From MAPL to Cell SizePropagation Loss Model


Cell Size Information With Hata Model

•Using Hata’s Empirical Formula

CFhaRhhfPL mbbc −−−+−+= )(log)log55.69.44(log82.13log16.2655.69 10101010

•Solve it backward to find cell radius estimate

b

mbc

hhahfCFMAPLR

10

101010 log55.69.44

)(log82.13log16.2655.69log−

++−−+=


BS Installation Requirements :A certain isolation has to be present between Tx and Rx antennasRadiation Patterns must not be distorted by obstacles or reflectionsnearby the antennas

Isolation :Between 2 antennas : Attenuation from the connector of oneantenna to the connector of the other antenna when bothantennas are in their installation positions

To avoid unwanted signals into the receiver Rx, the followingisolation values are required :

40 dB Between a Tx Antenna and a Rx Antenna20 dB Between 2 Tx Antennas

H. Guidelines for interference Minimisation


Isolation :

To obtain the Isolation values the antennas have to be placed at certain minimum distance from each other

The distance depends on : Antenna types, configuration

Omnidirectional antennas require greater horizontal distance thandirectional antennas

Vertical separation requires less distance than horizontal separation



a

k

Pre-condition : a > 1 mTx-Tx : 0.2 m minimumTx-Rx : 0.5 m minimum

As a General Rule :

Isolation :

For GSM 900, λ = 0.33 m

With A = 35 dB, k = 0.5 m

dBkLogAV

+=

λ104028

dBkLogAV 104047 +=

H. Guidelines for interference Minimisation : Vertical Separation


d

dBGGdLogAH )(2022 2110 +−

+=

λ

G1 : Gain of antenna 1 in dBdG2 : Gain of antenna 2 in dBd

dBGGdLogAH )(2031 2110 +−+=

General

@ 900 MHz

H. Guidelines for interference Minimisation : Horizontal Separation


3.0 m28.0 m10

2.5 m22.0 m9

1.0 m11.0 m6

1.0 m *5.5 m3

1.0 m *3.0 m0

Tx-Rx distance(20 dB)

Tx-Rx distance(40 dB)

Omni AntennaGain (dBd)

Could be less for Tx-Tx but 1.0 m is a conservative option toavoid shadowing effects

H. Guidelines for interference Minimisation : Horizontal Separation


d

k

α

H. Guidelines for interference Minimisation : Combined H/V Separation

( ) HHV AAAA +°°

−≈90

. α


h

D



5 10 15 20 25 30 35 40 45 distance(m)

4

3

2

1

Step function

First Fresnel zone

Antenna height



Mast

a2 m is recommended

The mast is allowedto swing 1° at a windvelocity of 30 m/s

1±



k



d



Forward direction

o90

oMax. 15


d

k

α



Ground level

H

Max

imum

div

ersi

ty

Axi

s

a

RxA RxB



hD



5 10 15 20 25 30 35 40 45 distance(m)

4

3

2

1

Step function

First Fresnel zone

Antenna height (m)



Wall

Top viewForward direction



Top view Forward direction

Maximum

Cell sector including safety margin °± 75

°15


Top view Forward direction

More than

Cell sector including safety margin °± 75

°15

Wall


Definition

Diversity is the statistical improvement of the received signal whenmore than one signal is used.

To improve the overall received signal level, due to multipathphenomenon, it is interesting to use more than one antenna and consider internally the best received signal.

Diversity in cellular is used only at the Base Station end, although it istheoretically possible for mobiles, it is quite cumbersome to have twoantennas moving with the subscriber !

H. Guidelines for interference Minimisation : Diversity


H. Guidelines for interference Minimisation : Diversity

MobileStation (MS)

Base Station(BS)

Antenna #1

Antenna #2The Receiver uses different combining techniques. The mostpopular is the Maximum CombiningRatio Technique

d


H. Guidelines for interference Minimisation : DiversityR

ecei

ved

sign

al

TimeSignal Level Received by Antenna 1 (RxA)Signal Level Received by Antenna 2 (RxB)Improvement due to Antenna Diversity

Typical Diversity Gains : 3.5 dB for Cross-Polarised antennas, 4.5 dB for SpaceDiversity. The maximum theoretical value is 6 dB.


H. Guidelines for interference Minimisation : Correlation vs distanceC

orre

latio

nFu

nctio

n

Normalized Distance10λ

0.7

40λ

d

Antenna #1 Antenna #2).(2

0 dkJα


Ground level

aRxA RxBa = distance betweenRx antennas

H = height of mastplus building(Effective antenna height)

H

H. Guidelines for interference Minimisation : Diversity Requirements

10Ha ≥


°90

a

Maximum diversityRxA RxB

Minimum diversity



Optimumdiversity

Coverage area RxB

RxA



Urban

Suburban

Rural

Market Boundaries•Usually a midsize market covers heterogeneous areas,e.g.

- Downtown,Urban or dense urban areas- Suburban, Light residential areas- Rural, open areas, farmland…


Radio Planning Methodology

Business Planning

Coverage Requirement & Demand Forecasts from

Marketing

Computer-BasedModelling

Design Nominal Cell Plan

Acquire Sites and Implement Cell Plan

Optimise Network

Define Design Rules and Parameters

Produce Frequency Plan

Set Long Term Plans and Performance Targets

Des

ign

Ite r

atio

n


Market Boundaries


( ) ( ) ( ) ( )[ ] ( )

( ) ( )[ ] ( )[ ]

( ) ( )[ ]

( )[ ]

( )[ ] ( )

( )[ ] ( ) 94,3533,1878,4

94,4033,1878,4

4,528/2

97,475,112,3

8,056,17,01,1

55,69,4482,1316,2655,69

2

2

2

2

−+−=

−+−=

−−=

−=

−−−=

−+−−+=

fLogfLogLL

fLogfLogLL

fLogLL

hhLogha

fLoghfLogha

dLoghLoghahLogfLogL

urqo

uro

usu

mmm

mm

bmbu

Hata RF Propagation Model for Urban Environments

For a Midium Size City

For a Big Size City and f > 400 MHz

For Suburban Environments

For Rural Environments

For Semi-Rural Environments


Hata Model is valid under certain conditions :

Frequencies between 150 and 1000 MHzBase Station Antenna Height between 30 an 200 mMobile Station Antenna Height between 1 and 20 mBS-MS Distance between 1 and 20 km

As a Result, it is suitable for GSM900 only and NOT GSM1800 or PCS1900 !!!

Hata RF Propagation Model for Urban Environments


[ ]

[ ] [ ]8,0)(56,17,0)(1,1)(

)()(55,69,44)()(82,13)(9,3333,46

−−−=

+−+−−+=

fLoghfLogha

CdLoghLoghahLogfLogL

mm

mbmbu

COST231-Hata RF Propagation Model for Urban Environments

dBCm 0=

dBCm 3=

For Medium Size Cities and Suburbs

For Big Metropolitan Centers

Validity : Frequencies between 1500 MHz and 2000 MHz


Table of Penetration Losses

In Building penetration (dB) 15 - 25In Car penetration (dB) 3 - 10Body Loss (dB) 2 - 5

For all receiving environments a loss associated with the effectof users body on propagation has to be included.

This effect is in the form of a few dB loss in both uplink and downlink directions.


Tower Mounted Amplifier : Effect on Coverage and Quality


BTS BTS

TMA

3 dB cable loss

4 dB Gainin the UL

Static Sensitivity=-110 dBm Static Sensitivity=-110 dBm

S(without TMA) = -110 + 3 = -107 dBm* S(with TMA) = -110 + 3-4 = -111 dBm*

* Body Loss and Lognormal Fading have to be added


Cell Range R computed using :MAPL=A+B*log(R)MAPL : Maximum Allowed Path LossMAPL = EIRP-Effective SensitivityExample :

Given EIRP=Pout+Gant-CableLosswith Pout=40 dBm; Gant=18 dBi; Cable Loss=3 dBEIRP=40+18-3=55 dBmMAPL =

• 55 - (-107+7+5) = 150 dB without TMA• 55 - (-111+7+5) = 154 dB with TMA

MAPL : The higher the bigger the cell radiuslog(R) = (MAPL-A)/B ⇒ R = 10^((MAPL-A)/B)

Overview on Linkbudget Impact (1/2)


Numerical Example :Assume we use a Rural Propagation Model PL = 135 + 30*log(R)

Cell Radius R=10^( (150-135)/30 )= 3.2 km without TMA10^( (154-135)/30 )= 4.3 km with TMA !


Path Loss (dB)

Distance (km)

135+30*lod(d)

MAPL=150 dB without TMA

MAPL=154 dB with TMA

3.2 km 4.3 km

4 dB due to TMA


Uplink Coverage

Downlink Coverage

TMA Improves Uplink vs Downlink: To balance the Linkbudgetthe BTS output power has to be raised by 4 dB ! (the TMA gain)

DirectionalAntenna

Due to linkbudget imbalance


Measurements and Propagation Model CalibrationThree Types of measurement equipment are commonly used :

1. Narrowband measurements (CW)a) Prior to starting the designb) For calibrating the prediction modelc) For verification of critical and borderline coverage areas

2. Test Mobile Measurementsa) Once the Network has been builtb) For analysis of System Parameters and Handover behaviorc) For Network Optimization

3. Reflection Measurements (channel sounder)a) As a research toolb) For analysis of Multipath Propagation and Delay Spreadc) Normally only necessary in mountainous regions


Measurements and Propagation Model CalibrationMeasurement requirement for Tool Calibration

- To measure out to the cell radius, requires typically 145 dB (MAPL)- To measure out to the point where interference is significant, requires typically another 20 dB (i.e. a total of 165 dB dynamic range)- The measuring equipment should handle this range easily, i.e. should have a dynamic range of the order of 175 dB- To achieve this dynamic range, narrowband CW measurements are necessary

Wideband Receivers and Test Mobiles (Based on a modified subscriber handset – measuring GSM RXLEV) are unsuitable for model calibration but may be used later for confirmation of coverage


Measurements and Propagation Model Calibration

Trigger Wheel

Antenna

Amplifier

Transmitter

Tx Antenna

Rx/Computer

Navigation

Rx Antenna

Storage

Trigger MSBTS


Measurements and Propagation Model CalibrationFor CW measurements it is important to record an averaged value of

instantaneous measurements

1. Rayleigh Fading makes instantaneous measurement unrepresentative

a) Aim to eliminate the Rayleigh fading, but not the shadow fadingb) Average over an interval which is less than the magnitude of streets and

buildings. Some refereneces speak about a distance of 40λ

2. Averaging interval should be greater than the Rayleigh Fading interval, but shorter than the building interval

a) 13 m outdoorsb) 6.5 m indoors

3. Separation of instantaneous measurements should be :a) More than 36 per interval to reduce averaging variation to less than 1 dBb) Corresponds to 0.36 m (1.1λ at 900 MHz)


Measurements and Propagation Model CalibrationSampling Rates

4.4492.00

3.40121.75

2.50161.50

1.74231.25

1.11361.00

0.63640.75

0.281440.50

ResultingSampling Interval(λ)

Number of averaged samplesin 13 m

RMS Error (dB)


Measurements and Propagation Model CalibrationGuidelines for CW Measurements

1. The Survey Route should include various road directions and street widths in built up areas

2. Special features relevant to propagation such as tunnels, bridges, etc. should be clearly marked in the case of calibration measurements

3. If possible, measurement antennas should be the same as the planned antenna in type and installation

4. Measurements must be conducted and documented accurately, especially regarding antenna installation and transmitter height

5. Only measure within 3 dB beamwidth (antenna aperture)The pattern outside the main beam may not correspond to the stored antenna

pattern, due to local obstructions, such as the mast and other antennas


Measurements and Propagation Model Calibration* To effectively calibrate a propagation model, many measurements

are needed :

1. About 10 different base stations in each city2. At least 75 km of survey route for each city3. At least 1000 km of route in total

* Measurements at each point are compared to the predictions at each point and the error statistics analyzed

Errors may be broken down by :

1. Clutter class2. LOS/NLOS3. Within a given range4. Outside a given range


Measurements and Propagation Model Calibration• Error Analysis Statistics

• The Error is commonly defined as the difference between the predicted value (Propagation Model) and the measured value. At a given distance of index i, the error is noted εi

• Root Mean Square Error and Mean Error are given by :

N

NRMS

N

ii

N

ii

∑

∑

=

=

=

−=

1

2

1

)(

εε

εε

The target is to ensure a mean error=0 and an RMS < 9 dB (The Lower the Better)


Non-uniform Propagation Types

• Each area has a different correction factor.• Also the coverage objectives are usually different for urban, suburban and rural areas.

• Therefore MAPL and the corresponding cell size has tobe calculated for each region and cell count is:• For each area: where R is the cell radius and A is the area of thecorresponding hexagon.

26.2 RA =

)()(

)()(

)()(

2

2

2

2

2

2

KmAKmRuralArea

KmAKmeaSuburbanAr

KmAKmUrbanAreaCellCount

RuralUrban Suburban

++=


Introduction

•Definition of Outdoor signal level design threshold to be used in prediction tool.

•Insure good quality communications.

•Threshold important because it is the basis for the design, and cell size and no. of cells depend on this.

•Aim: understand the different elements in the determinationof the threshold.


Introduction 2

• Receiver Sensitivity (from vendor or standard)

Use of Different Margins

• Outdoor coverage design threshold


Receiver sensitivity margin (1)

•Sensitivities defined in GSM Rec. 05.05Portable: -104 dBmHandheld: -102 dBmDCS1800: -100 dBm

•Sensitivity : Min required signal level at receiver to meetperformance requirements

•Sensitivities defined for mobiles in an urban environmenttraveling at 50 km/h (TU 50)

•These sensitivities with a C/I of 9dB correspond to errorrate of 10% or RxQual =6

•These values include a margin for Rayleigh Fading


Receiver sensitivity margin (2)

•Today many handsets used at walking pace or static

•At 50 km/h effect of fading is averaged but”static”mobiles will remain in fading “holes” longer.

•Measurements show that for a handheld moving at 3 km/h (TU3) then for an acceptable audio quality we need:- RxQual = 4 ( system without frequency hopping)- RxQual = 5 ( system with frequency hopping)

Quality margin must be introduced

® Cirta Consulting LLC 50 Km/h

5 dB

3 Km/h

Receiver sensitivity margin (3)• Measurements campaign by CNET to link C/N, C/I and

Rxqual• With no interference, without frequency hopping a

Rxqual = 4 is obtained with C = -97 dBm• Quality margin = 5 dB• (FT 3 dB, Cellnet 4 dB)


Prediction/Lognormal Margin (1)

• Propagation model predicts mean signal level

• Characteristics: Mean error (0) and standard deviation

• Shadow fading (obstacles) not taken into account

• Model this shadow fading by a probability following alognormal law

• Introduce Margin to guarantee a certain percentage of cell surface area is covered

( )σ



Standard Deviation ofPrediction model

Level of guaranteeRequired (probability)

Lognormal Margin

• To calculate the margin we use coverage probabilityat cell border which corresponds to the requiredcoverage probability over the surface of the cell.



•Typical values:- Urban environment (Typical distance exponent = 3.5 )- Standard Deviation of prediction model = 7 dB

Margin in dB Coverage probabilityon cell bordure %

CoverageProbabilityOver cell surface %

0 50 775 75 907 84 959 90 9712 95 99

- GSM Rec 3.30


Head Effect

•The human body creates loss for handheld mobile.•Loss due to distortion of antenna diagram•Some suggested values :•Recommendations GSM 03.30 = 3 dB.•Dr. Lee proposes 5 dB in worst case ( mobile on belt)•Most operators use 6 dB.•Motorola proposes 9 dB head effect, 15 dB at belt.

•Telemate suggested value is 5 dB.


Other Margins

• Hand – Over: Some Operators use a 2 dB margin to ensure a good HO to neighboring cell

• Material imperfections: we take a 1 dB margin to accountfor the tolerance in MS and BTS output power

• Interference Margin: Some vendors use an interferencemargin to overcome interference impairments


Example Calculation of Outdoor coverage threshold for 2W GSM handheld

Sensitivity ( GSM Rec. 5.50 )

Sensitivity margin

Lognormal margin ( for 90% area coverage probability)

Head Effect Margin

Outdoor Coverage Threshold

- 102 dBm

5 dB

7 dB

5 dB

- 85 dBm


Indoor Threshold (1)

• Different types of Indoor Threshold corresponding todifferent services

- Indoor Window: Near to window- Indoor: In room with windows- Indoor Deep : In corridor (loss through 2 walls)

• Penetration loss varies greatly. Depends on type ofmateriel, architecture (no. of windows…), floor withinbuilding etc.

• Mean penetration loss must be determined from extensive measurement campaigns


Indoor Threshold (2)

•To determine an Indoor threshold from the penetrationloss there are two methods:

- Use the distribution function of the measurements to findthe loss corresponding to 90 % of the samples

- Use the mean penetration loss and increase thelognormal margin to take into account the standarddeviation of the indoor measurements.


Use of margins

• Understand what goes into the determination of coveragethresholds.

• Make sure that all margins are included but only once!

• Translate the clients requirements for service quality intomargins

• Thresholds must be validated by the client.


TEST : Link Budgets

Balanced link budgets show Maximum Allowable Path Losses for thecoverage objectives shown below. Drive tests have shown the following propagation equations are valid. Determine the cell radius for each coverage objective.

Coverage objectives: Rural on-street MAPL = 147 dBSuburban in-car MAPL = 135 dBUrban in-building MAPL = 125 dB

Propagation equations:Rural: path loss = 110 + 32 log dSurburban: path loss = 115 + 37 log dUrban: path loss = 120 + 48 log d


The Cellular Concept

Urban Areas : High Interference AmountsC/(N+I)=C/I, The System is Interference-LimitedCoverage is not a problem (in General)Service Criterion : C > I

Rural Areas : Low Interference ProfileC/(N+I)=C/N, The System is Noise-LimitedInterference is not a problem (in General)Service Criteria : C > N


Frequency Planning aims at :Optimising the Allocated SpectrumGuaranteeing a seamless coverageEnsuring minimum interference

Main Difficulty of Frequency Planning is :Limited Number of TRXs (Available Channels)

The concept of Frequency Re-Use overcomes theSpectrum Limitations. Caution has to be made concerningthe risk of generating co-channel and adjacent channelinterference

The Cellular Concept


GSM SpectrumAllocated GSM1800 Band comprises two sub-bands :

1710 – 1785 MHz for Uplink (MS->BTS)1805 – 1880 MHz for Downlink (BTS->MS)Each Sub-band = 375 Channels of 200 kHz associated to a givencarrier95 MHz are necessary to ensure the isolation between Up and Down Links DuplexingEach Operator is allocated a DL/UL bandGSM uses TDMA (Time Division Multiple Access)

1 Physical Channel = 8 Logical Channels1 Logical Channel = TCH or Signalling Channel (SDCCH, FCCH, SCCH, AGCH, RACH, etc...)


Interference

Definition of the Signal to Noise Ratio irrespective to the co-or adjacent channels

C/I = Puseful/Pharmfull

Co-Channel InterferenceInterference Due to a Signal using the same Frequency :

C is the useful Signal, I1 and I2 are co-channel interferersusing the same frequency as CC, I1 and I2 are linear units (i.e. Watts or mW)

02

01 IIC

IC

channelco +=

−


InterferenceAdjacent Channel Interference are due to out-of-bandspurious transmissionGSM RF Mask is based upon the GMSK Modulation Scheme (GMSK = Gaussian Minimum Shift Keying)

NIIIC

IC

sulting ++++=

...210Re

GMSK RF Mask

0.5 dB

-30 dB

-60 dB

f f+200 kHz f+400 kHzf-200 kHzf-400 kHz


InterferenceInterference = Impossible to identify and extract the wantedand interfering signal (noise included)GSM Specifications require C/I to be higher than 9 dB

580.0000125-493rd

Adjacent

500.0000794-412nd

Adjacent

180.125-91st Adjacent

07.949Co-Channel

ProtectionC/IC/I (dB)Protection

RecommendationGSM


Traffic Theory : Erlang B

Poisson Input with mean of λ arrivals/sec.Mean Service Time = 1/µTraffic Intensity = A = λ. 1/µNumber of Serving Trunks (Channels) = SBlocked Calls Abandoned

∑=

== S

k

k

S

b

kASA

ASBP

0 !

!),(


Traffic Theory : Erlang B

Etc.48.759842.152734.745628.337521.029414.92238.21422.371ErlangNb TCHNb Carriers


Traffic Theory : Erlang CPoisson Input with mean of λ arrivals/sec.Negative Exponential Service Time with mean = 1/µTraffic Intensity = A = λ. 1/µNumber of Serving Trunks (Channels) = SBlocked Calls held until served

[ ]0),()(Pr >== DPASCDelayob τ

∑−

=

+−

−= 1

0 !.

!

.!),( s

i

iS

S

iA

ASS

SA

ASS

SA

ASC


Traffic Theory : Erlang C

Probability of Delay Greater than t :

Average Delay :

tsAD eASCtP µτ )1(),()( −−=>

µτ

SAASCE D )1(

),(][−

=


Traffic Theory : PoissonPoisson Input with mean of λ arrivals/sec.Negative Exponetial Service Time with Mean = 1/µTraffic Intensity = A = λ. 1/µNumber of Serving Trunks (Channels) = SBlocked Calls Held

∑∞

=

−==Sk

kA

b kAeASPP

!),(


Capacity PlanningAims of Capacity Planning

To allocated Sufficient Channels to support the expected traffic loadTo ensure future sites are planned and implemented in time to meetsubscriber growth (Business Plan)To provide Traffic Loading Figures on which the fixed network can bebased

Traffic UnitTraffic is measured in Erlang : Etot = Esub*Nsubs

Etot is the total TrafficEsub is the average traffic per subscriberNsub Number of Subscribers

Example : Esub = 25 mE* and Nsub = 100, then Etot = 2.5 Erlangs*25 mE = 1.5 minutes of occupied TCH per Hour


Capacity PlanningProcedure for Calculating Number of Required Channels

First Compute Busy Hour Traffic per Subscriber (Erlangs) :Average Daily Number of Call Attempts × Average Call LengthPlus Number times length of Incoming CallsTimes Proportion of Total Calls made in the Busy Hour

Then Calculate Total Traffic as Average Traffic Times Number of Subscribers

Finally Use Erlang B Tables to determine the number of Channelsrequired for a given Blocking Level

Example : For GSM, 2 % is the typical blocking rate used


Capacity PlanningTEST ON DIMENSIONING USING CAPACITY DEMANDS

Given a Dense Urban Area of about 35 km2 and a penetration rate estimatedto 9 % over a total population of 500.000 inhabitants

Assuming 4 TRX 3-sector BTSs will be used,

Each sector (using 4 TRXs) has a cell radius of 0.45 km

Each Subscriber will require a 25 mE traffic

Compute the total required Traffic (Erlang) within this dense urban area, along with the required number of 3-sectorial BTSs

What would be these numbers if the unit traffic increase to 40 mE ?


Tower Mounted Amplifier : Effect on Coverage and Quality


BTS BTS

TMA

3 dB cable loss

4 dB Gainin the UL

Static Sensitivity=-110 dBm Static Sensitivity=-110 dBm

S(without TMA) = -110 + 3 = -107 dBm* S(with TMA) = -110 + 3-4 = -111 dBm*

* Body Loss and Lognormal Fading have to be added


Cell Range R computed using :MAPL=A+B*log(R)MAPL : Maximum Allowed Path LossMAPL = EIRP-Effective SensitivityExample :

Given EIRP=Pout+Gant-CableLosswith Pout=40 dBm; Gant=18 dBi; Cable Loss=3 dBEIRP=40+18-3=55 dBmMAPL =

• 55 - (-107+7+5) = 150 dB without TMA• 55 - (-111+7+5) = 154 dB with TMA

MAPL : The higher the bigger the cell radiuslog(R) = (MAPL-A)/B ⇒ R = 10^((MAPL-A)/B)



Numerical Example :Assume we use a Rural Propagation Model PL = 135 + 30*log(R)

Cell Radius R=10^( (150-135)/30 )= 3.2 km without TMA10^( (154-135)/30 )= 4.3 km with TMA !


Path Loss (dB)

Distance (km)

135+30*lod(d)

MAPL=150 dB without TMA

MAPL=154 dB with TMA

3.2 km 4.3 km

4 dB due to TMA


Uplink Coverage

Downlink Coverage

TMA Improves Uplink vs Downlink: To balance the Linkbudgetthe BTS output power has to be raised by 4 dB ! (the TMA gain)

DirectionalAntenna

Due to linkbudget imbalance


RF Repeater : Problem Statement (1/2)

No Coverage Tunnel

High Penetration Lossadded to propagation loss

Base Station

In Car Coverage Threshold not reached


RF Repeater : Problem Statement (2/2)

Base StationMS

High Diffraction and Shadowing Loss : Hills, Blockings, etc.


RF Repeater : Design IssuesRepeater = Bidirectional Amplifier used to

* Provide Coverage to “shadowed” rural areas* Provide Coverage to Tunnels* Provide Coverage to Indoor Areas where Capacity is not an issue

Repeater comprises :* A High Gain Amplifier* A Duplex-filter for Up and Downlink Service* A Donor Antenna : From the Repeater to the Donor Site* A Re-Radiating Antenna : From the Repeater to the Area to be covered

Repeater Features :* High Amplifier Gain* High Isolation Between the Repeater Ends to avoid oscillation* High Channel or Band Selectivity


RF Repeater : Components

BPF

BPF

Donor Antenna (BTS)High Gain, Very Directional

Re-RadiatingAntenna (MS)Lower Gain, Wide Beamwidth

High Gain Amplifiersup to 85 dB

Band-Pass High Rejection Filters :Channel or Band Selective

To donor Cell

To poor area coverage


RF Repeater : Typical Antennae Mounting

R

To a valleywide bandwidthantenna

To donorcell

R

To donorcell

To Tunnel

Uni- or Bidirectional High Gain Antenna


RF Repeater : Design Tricks1. Donor Antenna should be :

a. Preferably in LOS with the Donor Cellb. High Gain and High Directionalc. Mounted in a location so that the RxLev > its static sensitivityd. Dip Fades have to be avoided : RF Measurements done prior to installation (Go or not Go)

2. To avoid interference between Donor and Re-Radiating antennas, an isolation is required : this should prevent the Repeater to oscillate.

3. Never have LOS between Re-Radiating antenna and Donor Cell

4. Depending on the application : Re-radiating antenna has to be chosen accordinglya. Tunnels : High gain (uni- or bidirectional)b. Valley or “shadow” : wide beamwidth and typical antenna gains


RF Repeater : Antennae Location

R

To donorcell NOT RECOMMENDED

R

To a valleywide bandwidthantenna R

To a valleywide bandwidthantenna

To donorcell

RECOMMENDED


RF Repeater : Powerbudget (1/3)

Allgon Indoor Repeater Technical Specs :Gain : 45 - 70 dBNoise Figure : 5 dBMaximum input power : +13 dBm

Assumptions :Donor BTS @ 4.5 km from the Repeater : Free Space and LOS assumed. BTS Donor Antenna EIRP : 48 dBmDonor Antenna to Repeater cable loss : 1.5 dBRe-radiating Antenna to Repeater cable loss : 0.5 dBDonor Antenna Gain : 18.5 dBiRe-radiating Antenna Gain : 14 dBi

Task : Balance the UL and DL, then compute the repeater cell radius


Received Power at the donor antenna connector :Pr(donor)=EIRP(donor BTS)-PL = -56.6 dBm

PL = 32.44+20*log10(4.5*900) = 104.6 dB (free space loss)EIRP(donor BTS) = 48 dBm

Input Power at the Repeater (Downlink) :Pin = Pr(donor) - Cable Loss(DL) + G(donor)

Pin = -56.6 -1.5 + 18 = -40 dBm

Repeater Output power (downlink) :Pout(min) = Pin + Gmin(Repeater) = -40 + 45 = 15 dBmPout(min) = 15 dBm > 13 dBm (need a 2 attenuation)

EIRP(Re-Radiating) = Pout - Cable(to antenna) + G(Re-Radiating)EIRP(Re-Radiating) = 13 - 0.5 + 14 = 26.5 dBm

Without a repeater the penetration loss of 15 dB leads to :Rxlev (indoor) = -56.6 - 15 = -71.6 dBm !!! @ the vicinity of the lossy wall



Received Power at the Re-radiating antenna connector :Pr(Re-Rad.)=EIRP(MS)-PL = 33 - 106.5 = - 73.5 dBm

PL = 120 + 45*log(0.5) = 106.5 dB (e.g. Okumura-Hata Model)EIRP(MS) = 33 dBm (no Power control considered)

Input Power at the Repeater (Uplink) :Pin = Pr(Re-Rad) - Cable Loss(UL) + G(Re-rad)

Pin = -73.5 - 0.5 + 14 = -60 dBm

Repeater Output power (Uplink) :Pout(min) = Pin + Gmin(Repeater) = -60 + 45 = -15 dBmPout(min) = -15 dBm < 13 dBm (OK)

EIRP(Donor) = Pout - Cable(to antenna) + G(Re-Radiating)EIRP(Donor) = -15 - 1.5 + 18 = 1.5 dBmUplink Power Amp. Of repeater must be raised to maximum 75 dBEIRP (donor) = 1.5 + 30 = 31.5 dBm



Hybrid Combiners : Possible Usage

-3 dB

TX1 TX2

To Antenna

Matched Load

-3 dB -3 dB

-3 dB

TX1 TX2 TX3 TX4

To Antenna

50 Ω 50 Ω

50 Ω


Hybrid Combiners : Features

Hybrid Combiners :4-Port Balanced Passive DevicesReciprocal : Tx/Rx

Disadvantage : High insertion loss : 3 to 3.3 dBNot suitable for large Number of Transmitters : High Losses

Advantage :Linear Device : Sufficient isolation between TransmittersCost-effective combining solution for small number of TransmittersBeing relatively Wide-band, permits Transmitter Frequency Hopping : Synthesized or Baseband


Slow Frequency Hopping

Radio Propagation Channel :Dynamic : Mobility and Scattering problemsFast Fading : Frequency Selective (dispersive)

Some frequencies are more or less affected by Multipath fast fading (Reighley Fading)Fast Moving mobiles less sensitive to Multipath : GSM Standard define TU3 and TU50 and a Sensitivity margin of 4 dB is considered.Effective Receive Sensitivity improved for Fast Mobiles

Slow Frequency Hopping (SFH) :Allows an effective “Frequency Diversity”SFH statistically improves the overall signal receive powerSFH “diversity” gain : between 3 and 6 dB (ref. W.Y. Lee)


Synthesized Frequency Hopping :The processor controlling the Tx retunes it to a new frequency on a per time-slot basis, according to a predetermined pattern or sequence

The Output from the Tx varies across a wide range of frequencies : Handled by the Hybrid combiner (wide-band device)

Baseband Frequency Hopping :The Digital baseband signal is applied to what is effectively a fast electronic switch, which is controlled by a processor in the Tx.The Switch is connected to a number of Txs, each being fixed-tuned to a different frequencyOn a per time-slot basis, baseband digital signal is switched between different transmittersCavity Filter Combiners or Hybrid Combiners can be used

Slow Frequency Hopping : Implementation


Synthesized and Baseband Frequency Hopping : Comparison

Synthesized FH :Offers a versatile solution for multiple channelsCost-effective : No Cavity Filter Combiners requiredFew Transmitters can be used for more channels hopped

Baseband FH :Low losses when Cavity Filter Combiners are usedHopping can only occur over the same number of frequencies as there are Transmitters


Slow Frequency Hopping : Implementation

Hybrid Combiner

TX1

TX2

TXProcessor

11001101110

0110110110

Tun

ning

Con

trol To Antenna

Varying Frequency

Varying FrequencyBaseband Data

Baseband Data

Synthesized Frequency Hopping

BasebandFrequency Hopping

TXProcessor

Baseband Data

11001101110

TX1

TX2

TX3

BPF

BPF

BPF

f1

f2

f3

To

An t

e nn a

ElectronicSwitch

Matching Stub

Cavity Filters


Receiver Multicoupler

RECEIVER MULTICOUPLER

RX1 RX2

RxAntenna

A

RxAntenna

B

AC/DC POWERSUPPLY

RX A RX A RX BRX B


DUPLEX FILTER

From TX To RX

Passes DLFrequencies only

Passes ULFrequencies only

DUPLEXFILTER

Common TX/RX Antenna


Typical Antenna Connection : X-POL Diversity

DuplexFilter

ReceiverMulticoupler

Tx Rx

Tx Rx

HybridCombiner

Matched Load

Bandpass Filter

Tx/Rx A Rx B

Cross-PolarizedAntenna Assembly

Rx B

Rx A

Rx A

Rx B Rx A

Rx B


Polarization Diversity SystemsUsing Separate Tx AntennaWithout Duplex Filter

d

RxARxBTx

BTS Equipment

Tx

2 Rx

2 Rx

2 Rx

Tx

Tx

Top View of 3-sector sitewith Vertical Polarization Diversity


Polarization Diversity Systems

Duplexer

Tx Rx A Rx B

VerticalTx/Rx Antenna

HorizontalRx Antena

Tx/Rx

Tx/RxTx/Rx


Polarization Diversity Systems

TxRx A Rx B

d1d2 d2

Horizontal separation d1 for diversity = 10λHorizontal Separation d2 for 30 dB Isolation = 2λ

Rx

Rx

Rx

Rx

Tx

Rx Tx

Tx

GSM Fundamentals by Dr. Hatem MOKHTARI

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Transcript of GSM Fundamentals by Dr. Hatem MOKHTARI