Frequency Reuse Efficiency and Admission Control in Multirate

Systems

Wireless Technologies Laboratory (WITEK) Department of Communications

School of Electrical and Computer Engineering State University of Campinas - São Paulo - Brazil

Álvaro Augusto M. de Medeiros (UNICAMP/SP) Prof. Michel Daoud Yacoub (UNICAMP/SP)

César Kyn D’Ávila (CEDET/ SP)

ITS 2002, Natal - RN, September 9, 2002

Presentation Outline

Introduction Interference on Forward Link Relative Power and Admission Control Frequency Reuse Efficiency on CAC CAC Algorithm and an application

example Conclusion

Introduction

Frequency Reuse Efficiency Related to system capacity and coverage 3G Services Forward link limited Multirate services with different QoS requirements

OCk

kk IP

PF+

=

Interference on Forward Link

Cell j

rj

ri

ri

αδεjko

jT

kkSC rlPI

)(

)1( −=

∑≠=

=M

jii iko

iT

OC rlPI

1

)(

α

Same cell

Others cells

αα δδεjko

jT

kjko

jT

kkk rlP

rlPP

)()(

)1( +−=

Relative Power

Signal-to-interference ratio Relative power

( )SCOC

jkoj

Tk

kkt

b

IIrlP

RW

IE

+

=

αδ )(

kk

kkk

Lχεεδ

++

=

Relative Power

Jamming Margin

Lk parameter

α

∑≠=

=

M

jii i

jj

T

iT

k rr

PPL

1)(

)(

tB

kk IE

RW=χ

Depends on network topology, base stations’ transmission powers and propagation environment

Relative Power

Relative power

kk

kkk

Lχεεδ

++

=

Depending on the users’ location, a new subscriber may not have access to all services

Higher bit rates demand

a higher fraction of the forward link total power

Relative Power

Lk parameter in a four-tier network and PT

(i)/ PT (j)=1

0.0 0.2 0.4 0.6 0.8 1.00.0

0.2

0.4

0.6

0.8

1.0

α=4α=3

α=2

L k / L

k max

d/Rcell

α Lk (mean) Lk max

4 0.291 2.073 3 0.549 2.542 2 1.551 4.284

Relative Power

Lk parameter in a four-tier network and PT

(i)/ PT (j)=1

α=4

-1.0 -0.5 0.0 0.5 1.0-1.0

-0.5

0.0

0.5

1.0

Lk/Lk max

Y

X

00.100.250.500.751.0

Relative Power and CAC

Lk after user’s admission Relative power after user’s admission

α

∑≠= +

=+

M

jii ik

jk

tj

T

iT

k rr

PP

tL1 1

)(

)(

)()1(

1)()(

1)( )()()( ++ += t

jTkt

jTt

jT PPP δ

( )kkk tLtL δ−⋅=+ 1)()1(⇒

)()(

tLtL

kkk

kkk ++

+=

χεε

δ

Fk and CAC

Fk after user’s admission Jamming margin values

kkkkkk

kkkkk tLtL

tLFχχεε

χεε)()(

)(+++

++=

Service Rk (Eb/It)k χk Voice 8 kbps 7 dB 95.77

Video 144 kbps 7 dB 5.32

Packet Data 384 kbps 10 dB 1

Fk and CAC

Fk versus χk 4 tiers εk =0.5 α=4

0 20 40 60 80 1000.0

0.2

0.4

0.6

0.8

1.0α=4

Lk/Lk max=0,1; 0,2; ... 1,0

Reus

e effi

cienc

y (F k )

Jamming Margin (χk)

Fk and CAC

Fk versus χk 4 tiers εk =0.5 α=2

0 20 40 60 80 1000.0

0.2

0.4

0.6

0.8

1.0α=2

Lk/Lk max=0,1; 0,2; ... 1,0

Reus

e Effi

cienc

y (F k )

Jamming Margin (χk)

CAC using Lk and χk

Load Factor Subscriber’s contribution

∑=

=N

kk

1ρρ

−+=

k

kk

k

kk F

F1εχυρ

++

+=kkkk

kkk

k

kk L

Lχεε

χεχυρ

CAC using Lk and χk

ρk versus Lk / Lk max 4 tiers εk =0.5 α=4

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

υk= 0.2 →1

υk= 0.2 →1

υk= 0.2, 0.5, 1

ρ k

Lk / Lk max

384 kbps 144 kbps 8 kbps

Application example

Urban scenario (α=4), εk =0.5, ρmax=0.5, 4 tiers In this scenario, a packet data user has a

load factor contribution ρk=0.5 for Lk near zero. He must be confined within a maximum

distance dmax ≤ 0.3rcell

Application example

Before admission: Possible scenario after admission:

dmax/Rcell 0.2 0.4 0.6 0.8 0.9 Existing voice users 10 10 10 5 5

Possible combinations of new video users dmax/Rcell

S1 S2 S3 S4 S5 0.2 - 1 1 - 3 0.4 - - 1 3 - 0.6 - - 1 - - 0.8 - 1 - - - 0.9 1 - - - -

Total users 1 2 3 3 3

Conclusions

Frequency Reuse Efficiency must be calculated locally For higher bit rates or higher demands of

Eb/It , the required Fk has a considerable variation Fk is strongly dependent on the network

topology Which services and where within the cell they are

guaranteed

Conclusions

An admission control algorithm must consider the value of the reuse efficiency according to subscriber’s location and requested service. A CAC algorithm was proposed based on the

capacity equation. Finally, we presented an example of

admission control for WCDMA services using this algorithm.

Questions and Comments

Contact: alvaro@decom.fee.unicamp.br

WITEK – DECOM/FEEC/UNICAMP

Campinas - São Paulo - Brasil