Repeaters in CDMA and UMTS cellular

7/16/2019 Repeaters in CDMA and UMTS cellular

1/86

PROPRIETARY1

Repeaters in CDMA and UMTS

Network Design Guidelines

Dr. Joseph [email protected]


2/86

PROPRIETARY2

Contents

Definitions and classification

Repeater interaction with the network

Network planning with repeaters

Radio Hole Rural area

Hot Spot

Multiple repeaters: Star, cascade

Backhaul and interference cancellation

Indoor Service Pico repeaters

Optimization with repeaters


3/86

PROPRIETARY3

Definitions

Repeater (3GPP): A device that receives, amplifies and

transmits the radiated or conducted RF carrier both in the

down-link direction (from the base station to the mobile

area) and in the up-link direction (from the mobile to the

base station).

Repeater is linked to the RF path and shares the BS resources

with the donor-serviced UEs.

Remote Sector is an access point that has its own resources

(bank of transceivers).


4/86

PROPRIETARY4

CDMA repeatersDL, UL

GRR

FR

GB

FB

BTS Repeater

Tr

n

TD

RC

RR

Tc

RC0

m

GRR

FR

GB

FB

BTS Repeater

Tr

n

TD

RC

RR

Tc

RC0

m

GRF

FRFBTS Repeater

TRF

n

m

TDF

RCF

RRF

TcF

RC0

PA

GRF

FRFBTS Repeater

TRF

n

m

TDF

RCF

RRF

TcF

RC0

PA

Up-Link Down-Link


5/86

PROPRIETARY5

Types of Repeaters

1. Embedded

2. Border extension

3. Remote

4. Cascaded

RR3

D3

D2

1

2

3

RR2

RR1

D1 RC

RR3

D3

D2

1

2

3

RR2

RR1

D1 RC


6/86

PROPRIETARY6

Repeater coverage - DL

Coverage extension repeater

Signal received in mobile [dBm] Cell boundary

Hole filler repeaterBoundary repeater

Coverage extender Other cell

PBT(0)

PBT(0)yE

PBT(0)yB

PBT(0)yH

Cell coverage

Co

verage extension repeater

Signal received in mobile [dBm] Cell boundary

Hole filler repeaterBoundary repeater

Coverage extender Other cell

PBT(0)

PBT(0)yE

PBT(0)yB

PBT(0)yH

Cell coverage

The transmission-gain (T) slope depends on the antenna height and tilt


7/86

PROPRIETARY7

Repeater Coverage - UL

Repeater embedded in a cell

Cell coverage

Pm[dB]

q

q/y

q/y

q

Repeater

coverage

Overlap

RC

RR

R0


8/86

PROPRIETARY8

Cascaded (multi-hop) repeaters

Repeaters are cascaded to increase coverage

1. Along roads

maximal area/ length

2. Within an area/ campus

mixed large/ small areas

3. Within buildings

limited area, complex coverage

Distribution (backhaul):

Star

Cascade


9/86

PROPRIETARY9

Repeater Interaction

Donor

antenna

Service

antenna

GF

GR

PF

PR RSSIR

RSSIF

DuplexDuplex

BTS

antenna

UE

antenna

yR=GRTDR

yF=GFTF

TDR

TUE R


10/86

PROPRIETARY10

Impact of repeater on donor cell - RL

Apparent repeater noise factor

Effective cell noise factor

Effective repeater noise factor

Total load m+n

C

R

FFyF

FF

Fy

F

FFyFFF

C

R

C

CECERCCE

11;

GRR

FR

GB

FB

BTSRepeater

Tr

n

TD

RC

RR

Tc

RC0

m

GRR

FR

GB

FB

BTSRepeater

Tr

n

TD

RC

RR

Tc

RC0

m

yFFFyFFF CRCRERE11


11/86

PROPRIETARY11

RL Impact of repeater on network

Loads the donor noise and reduces its coverage and/ or capacity

Overlap introduces diversity. Excess fingers introduce

interference.

No Rx diversityincreases UE_Tx and BS load, and reducescoverage

Change in Donor link gain causes change in coverage for both

repeater and donor

Imbalance DL-UL (excess offset) causes the P.C. open loop tobe noisy, and loss of capacity. Imbalance exceeding about

close loop range breaks the P.C. loop and drops RSUs


12/86

PROPRIETARY12

Sensitivity and Noise Rise

q [dB]

q [dB]

1

1;;

1

Re

0

Tbtb

BTS

m SNRN

nWRNEquired

WFN

rTrPq


13/86

PROPRIETARY13

Coverage-Capacity Trade-Off

The repeater coverage can be traded-off vs. Donor Capacity

Leaving donors coverage at nominal NR intact Donor Coverage

Maximizing the total capacity

User density in the area (coverage is linked to capacity)


14/86

PROPRIETARY14

Capacity-Coverage Trade-off

Noise rise =

ST set limit

ST[dB]

Capacity loss

Max allowable

slope

][110 dBFLOG

30%coverage loss

17.5% capacity

loss

But recovered

and more-

by repeaters

10101

;;1

1dBNRT

nN

N

nFS


15/86

PROPRIETARY15

Noise Rise vs Apparent Noise Figure

0

1

2

3

4

5

6

7

8

-25

-22

-19

-16

-13

-10

-7

-4

-1 2 5 8

Apparent Noise Figure [dB]

NoiseRise

[dB]

Noise Rise


16/86

PROPRIETARY16

Repeater coverage - UL

11

11

1

0

0

00

00

IC

y

FWFN

rTrP

IC

FWFN

rTrP

IC

WFN

rTrP

BTS

RRm

BTS

CCm

CBTS

CCm

4UrrT

UL link budget

Baseline donor

Donor loaded with

repeater

Repeater

But

212

21

0

2

0

21

0

2

0

11

1

1

1

1

1

Uy

R

R

F

Uy

R

R

FR

R

C

R

CC

R

CC

C

T is transmission gain (between Tx and Rx antennas)

U is antenna height & diversity parameter


17/86

PROPRIETARY17

Loss of Donors capacity and coverage

due to repeaters noise (no additional load)A Excess noise rise for fixed load limit (loss of coverage)B Loss of capacity for fixed noise rise limit

A B

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8

Apparent repeater noise figure

Re

lativerangeandcoverage

Range (normalized) Coverage( normalized)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

-10 -8 -6 -4 -2 0 2 4 6 8

Apparent repeater noise figure

Donorcapacityrelativeto

nomin

al(max.loadfactorvs.

nominal)


18/86

PROPRIETARY18

Repeater Noise RiseNRr,n fixed, N=40

0

5

10

15

20

25

30

35

40

45

50

1 4 7 10 13 16 19 22 25 28

Number of RSU

NRr[dB]

n=0;y=0 dB

n=0;y=-10 dB

n=0;y=-20 dB

n=5;y=0 dB

n=5;y=-10 dB

n=5;y=-20 dB

n=15;y=0 dB

n=15;y=-10 dB

n=15;y=-20 dB


19/86

PROPRIETARY19

Down (Forward) Link

Relays all donor transmission ( plus other interfering sources)

No automatic balancing UL/DLHas to be controlled for coverage (gain) and saturation

(AMLC)

Reduces RSU (repeater-served-users) per-user power

Increases PiCH/TCH ratio for RSU (TCH is power-controlled)

RFDFF GTy


20/86

PROPRIETARY20

Repeater specsPower (example)

Parameter Unit Assumed value

G dB 90 dB

Pout_DL_max dBm 30 dBm

Pout_UL_max dBm 12 dBm

NF dB 5 dB


21/86

PROPRIETARY21

Power UL vs Power DL

Why is Max power DL higher than UL?(up to 18 dB)

TDR is higher than TUER (not true for pico) Coupling to the donor is designed to be high (LOS, high-gain

antennas)

Coupling to the UE determines the coverage, and is low.

DL transmits all BS transmission, ULonly RSUs

Headroom for PC (typical to 9 dB) on DL. May be on ULtoo in Pico.

Repeaters in SHO carry up to 50% more DL power perlink.


22/86

PROPRIETARY22

SHO DL OverheadSHO Probability

(1, 2, 3 way) %

Average total DL

power [units]

UL noise rise

[dB]

67, 22, 11 4.37 1.7756, 25, 19 6.32 1.68

45, 27, 28 8.56 1.58

Ref: Laiho, A. Wacker, T. Novosad: Radio Network Planning and Optimization for UMTS, Wiley 2002

Repeaters in SHO carry up to 50% more DL power per link


23/86

PROPRIETARY23

Impact of Repeaters on the Network - DL

Net gain (yF) determines coverage

Excess gain causes oscillations/spurii

ALC reduces coverage, causes imbalance and reduces capacity

Amplifying other sources may lead to ALCInstability of the BS-Repeater (BSR) link (e.g. directive antenna

nodding, fiber loss change with temperature, etc.) changes

coverage

Overlap with donors coverage adds multiple fingers to the MSreceiver, introduces interference (reduces orthogonality) and

diversity (if there are enough fingers).


24/86

PROPRIETARY24

Coverage of repeaters

Embedded Border Remote

-10.00

-8.00

-6.00

-4.00

-2.00

0.00

2.00

4.00

6.00

8.00

10.00

0.02 0.

10.18

0.26

0.34

0.42 0.

50.58

0.66

0.74

0.82 0.

90.98

Distance from BTS (normalized)

Prs/Ps[dB]

-10.00

-8.00

-6.00

-4.00

-2.00

0.00

2.00

4.00

6.00

8.00

10.00

0.

46

0.

52

0.

58

0.

64

0.

7

0.

76

0.

82

0.

88

0.

94 1

1.

06

1.

12

1.

18

1.

24

1.

3


Prs/Ps[dB]

-15.00

-13.00

-11.00

-9.00

-7.00

-5.00

-3.00

-1.00

1.00

3.00

5.00

0.9

0.98

1.06

1.14

1.22 1.

31.38

1.46

1.54

1.62 1.

71.78

1.86

1.94


Prs/Ps[dB]

Cell border


25/86

PROPRIETARY25

Multipath, rake receiver

and search window

Ch l t


26/86

PROPRIETARY26

Channel response to an

ImpulseMultipath occurs in discrete

peaks (fingers)

The fingers follow a structured

path along UE motion.


27/86

PROPRIETARY27

Rake ReceiverThe rake receiver is a series of correlators searching in time-

delay for signal peaks with the right code (multipaths).

Each finger extends over one chip (0.26 ms).

The number of fingers in the receiver is limited.

The time delay from the first-arriving peak (delay spread)that is searched in UMTS is 20ms ( but is adjustable insome vendors systems).

Multipath fingers captured by the receiver are MRC-

combined (Maximal ratio combiningphase-adjusted andSNR-weighted) to create diversity gain.

Excess multipath adds only noise.


28/86

PROPRIETARY28

Repeater Delay and Multipath

(Fingers) Search WindowRSU excess delay

D=DR+ (dDR+dRUE-dDUE)/c

D


29/86

PROPRIETARY29

AGCAGC is not a required feature for CDMA repeaters. The fast

power control maintains the coverage, both DL and UL.

AGC is used with low-power repeaters, loosely coupled to

the BS (y


30/86

PROPRIETARY30

ALCALCAutomatic Level Controlis a guard measure against

amplifier saturation, signal distortion and generation ofspurious interference. It is used on the DL, and in somesystemson UL.

ALC reacts to amplifier saturation by reducing the gain whenthe amplifier reaches its limit, and maintaining a constanttransmission level. While in operationit biases the DL

power control and reduces coverage and functionality. Itretrieves the normal gain setting when the amplifieroverdrive is relaxed. Its operation is to be programmed by

the operator.ALC is a guard measure, not a normal mode of operation. Its

operation has to be limited and the respective problem (andassociated alarm) be addressed.


31/86

PROPRIETARY31

Network planning with repeaters

Major parameters:

Repeater location

Repeater UL/DL power, gain, dynamic range

(per channel, per location and purpose)

Height, beam-width, direction and tilt of

service antenna

Backhaul link


32/86

PROPRIETARY32

Coverage-capacity limits vs user density

5161 ; lR

0.45

0.55

0.65

0.75

0.85

0.95

1.05

1.15

1.25

1.35

1.45

1.55

0.05 0.

20.

35 0.5

0.65 0.

80.

95 1.1

1.25 1.

41.

55 1.7

1.85 2

2.15 2.

32.

45 2.6

2.75 2.

9

User area density (normalized)

Cellrange(normalized)

Coverage-

limited

Capacity-

limited

Density Log scale)

Radius R (Log scale)

Forward link power limit

Reverse link

(interference) limit

Available zone

Rr

a b

0.45

0.55

0.65

0.75

0.85

0.95

1.05

1.15

1.25

1.35

1.45

1.55

0.05 0.

20.

35 0.5

0.65 0.

80.

95 1.1

1.25 1.

41.

55 1.7

1.85 2

2.15 2.

32.

45 2.6

2.75 2.

9



Coverage-

limited

Capacity-

limited

0.45

0.55

0.65

0.75

0.85

0.95

1.05

1.15

1.25

1.35

1.45

1.55

0.05 0.

20.

35 0.5

0.65 0.

80.

95 1.1

1.25 1.

41.

55 1.7

1.85 2

2.15 2.

32.

45 2.6

2.75 2.

9



Coverage-

limited

Capacity-

limited

Density Log scale)

Radius R (Log scale)

Forward link power limit

Reverse link

(interference) limit

Available zone

Rr

a b

121 ; lRDL UL


33/86

PROPRIETARY33

Repeater parameters

42

C

R

C

R

C

R

C

R

t

t

H

H

g

g

G

GU

GR,C antenna gain

(note sectorization gain)

R,C repeater, cell

g diversity gain

H antenna height

t tilt parameter

Activity and interference Antennas and diversity

capacityPoleN

densityArea

N

Ns

R

C

C

RRC


34/86

PROPRIETARY34

Beam-tilt and foot-print

kHh

Tilted Beam

Reference

Reduced power

R

H

tilt

Rtilt

LOG(Rtilt)

Cell boundary:

Reference

With tilt

Stronger and

shorter coverage

LOG (R)

Power received at MS[dB]- R-2 propagation law

Tilt (BW) 0.4 0.6 0.8

Range R=1000m 72 46 28

With tilt (%) R=500m 74 50 32

R=200m 78 55 38


35/86

PROPRIETARY35

Directional donor/ repeater

If

the beamwidth of the donor

coverage is 1/n of a circle

the beamwidth of the repeatercoverage is 1/m of a circle

Then

smns

Un

mU

s

s

n1m1


36/86

PROPRIETARY36

Rural Area

(extension/ remote repeater)User density in the area is allowed to have two values, both in

the donor and in the repeater, accounting for denser inner

cores.

s1 ratio of donors inner core density to the rest

sR ratio of repeaters density to donors

sR1 ratio of repeaters inner core density to rest

R1 radius of donors inner core

RR1 radius of repeaters inner core


37/86

PROPRIETARY37

Rural AreaBase load=50%;s1=1;sr=0.5;sr1=1;r1=.3;rr1;=.1;F=0 dB

00.10.2

0.30.40.50.60.70.80.9

11.11.21.3

-30

-26

-22

-18

-14

-10

-6

-2 2

Donor coverage

Repeater coverage

Load

Coverage


38/86

PROPRIETARY38

Radio Hole in a Dense AreaThe objective is coverage of a well defined area with minimum

loss of capacity and coverage. The repeater coverage isembedded within the cells/ sectors coverage.

The cell base load is 70%

The radio hole covers 1% of the cells/ sectors area

Required density in the repeaters area sR=1

Antenna - U=.1 (U is a coverage-control parameter)

The working point is set to cover the required area.

y=-26dB Cov.=15% ; Donor cov.=98% ; Load=70%


39/86

PROPRIETARY39

Coverage of a radio hole

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

-30

-26

-22

-18

-14

-10

-6

-2 2 6

10

Net gain y

Lnearvalues

Coverage

Repeater fractional

coverage

Repeater coverage

repeater load

Total load

Normalized total load


40/86

PROPRIETARY40

Hot Spot

Hot spotthe density within the hot spot is high. The BS

power may not suffice, if the link to the hot spot is weak.

The working point is chosen so that the repeater coverage

exceeds the hot spot area, with a minimum effect on the

donors coverage.

Example presented: Hot Spot area 5%

Base Load s U HS cov. Fr [dB] y [dB] Load Cov.

0.3 10 0.10 0.07 0.00 -9.00 0.61 0.720


41/86

PROPRIETARY41

Hot Spot repeater

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

-30

-26

-22

-18

-14

-10

-6

-2 2 6

10

Net gain y

Lnearvalues

Coverage

Repeater fractional

coverage

Repeater coverage

repeater load

Total load

Normalized total load


42/86

PROPRIETARY42

Multiple Repeaters - Star/ Cascade

Star

Each repeater may be controlledindependently

The aggregate apparent noise factorcounts. Optimal settingsame net gainto each.

Cascade

The gain setting of each repeaterinfluence the rest of the chain. Thecoverage is successively smaller. Optimal

settingsame net gain (y) to all repeatersbut the first (preferablyy=1). Control thechain by the net gain of the first.

RC R1 R2 R3 R4

Total range

RC R1 R2 R3 R4

Total range


43/86

PROPRIETARY43

Coverage area vs. number of repeaters

Uniform density of users

4

664

0 ;;

nn

R

R

R

p

P

nRpRrdrrP

2

22

n

nR

RnRnRCoverage

Power limitation, DL

nCoveragen

Coverage

F

Fn

nR

R

n Fnn

1

2

1

;

1

1

1

2

1

2

1

212

Noise Rise limitation , UL

Coverage advantage to multiple repeaters for low-density

coverage, both UL and DL


44/86

PROPRIETARY44

Star Coverage

Uniform user density, very light load

1

1.2

1.4

1.6

1.8

2

2.2

2.4

2.6

-20

-18

-16

-14

-12

-10 -8 -6 -4 -2 0 2 4 6 8 10

net gain y[dB] per repeater

Totalcov

erage

n=1 n=2 n=3 n=4 n=5


45/86

PROPRIETARY45

STAR coverage5 repeaters

Coverage dependence on the load

uniform densityCoverage, n=5, U=1, s=1

1.000

1.200

1.400

1.600

1.800

2.000

2.200

2.400

-20

-18

-16

-14

-12

-10

-8

-6

-4

-2 0 2 4 6 8

10

y[dB]

Coverage

5%

30%

50%

60%

40%


46/86

PROPRIETARY46

Coverage, n=5, U=1, s=0.1

1.000

1.200

1.400

1.600

1.800

2.000

2.200

2.400

2.600

-20

-18

-16

-14

-12

-10

-8

-6

-4

-2 0 2 4 6 8

10

y[dB]

Coverage

5%

30%

50%

60%

40%

Coverage dependence on the loadRepeaters density s=0.1


47/86

PROPRIETARY47

Total length including donor

1.5

2

2.5

3

3.5

4

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5

y=repeater + link gain

to

tallength

1 repeater 2 3 4 5

Road Coverage with Cascaded RepeatersVery light load

Donor cell radius shrinkage

0.40

0.500.60

0.70

0.80

0.90

1.00

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.3 1.4 1.5

y=repeater +link gain

Don

orcellradius

5 4 3 2 1 repeater


48/86

PROPRIETARY48

Diversity GainSignal fading below threshold increases the

Bit Error Rate (BER)

Correlated fading: gain 3 dB

Threshold

Rx Diversity

MS

SDiversity gain is the rise of the average signal

level for the same BER (for the same fraction of

time below the threshold)

Uncorrelated fading: gain 7 dB

(at 1% FER)


49/86

PROPRIETARY49

Cumulative Distribution Function (CDF)

for Diversity Combining

Single Branch

Diversity Gain (dB)

Signal [dB]

CDF

10%

100%

Prob. Signal

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Repeaters in CDMA and UMTS cellular

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