cell edge performance of cellular mobile · pdf file · 2011-06-27cell edge...

Prof. Xiaohu You

National Mobile Comm. Research Lab., Southeast University

Shanghai Wireless Comm. Research Center

Cell Edge Performance of

Cellular Mobile Systems

� Introduction

� System Model

� Performance Metrics

� Single Cell Environment

� Multicell Environment

� Conclusion

�ational Mobile Communications Research Laboratory, Southeast University 2 / 31

� Introduction

� System Model




� Conclusion


� Future mobile communication systems should

provide high data rates and mass wireless access

services over a limited spectrum bandwidth

� Dramatic growth of wireless services: data, multimedia, broadband wireless Internet

� Radio spectrum becomes much more crowded than in the past

� Advanced transmission techniques improve the

spectrum efficiency

� Multiantenna techniques: Diversity, SDMA

� Multicarrier techniques: OFDM, GMC


东南大学移动通信国家重点实验室东南大学移动通信国家重点实验室东南大学移动通信国家重点实验室东南大学移动通信国家重点实验室（（（（�CRL@SEU）））） 2010年年年年9月月月月20日日日日第第第第5页页页页

Conceptual description:

― Limitations of conventional cellular architecture

― The cell-edge problem

Very low spectral efficiency and power efficiency at cell boundary !!!

r

� Spectrum efficiency near the cell edge is still poor

� Cell edge users suffer from large path loss� Inter-cell interference

� The cell edge problem received much interests from

both academic and industry researchers. Some

countermeasures are proposed

� Interference management� Cooperation：CoMP or DAS、network MIMO

� But the cell edge performance, by itself, was not well-

studied in the literatureMotivationMotivationMotivationMotivation


� Introduction

� System Model




� Conclusion


Cellular configuration --- Collocated Antenna System

Cell-6

Cell-5

Cell-1

Cell-7

Cell-4

Cell-2

Cell-3

0--3 2 3-2

0

-

-3

2

3

-2

(0, 0)

1 1( , )� �


Cell-6

Cell-5

Cell-1

Cell-7

Cell-4

Cell-2

Cell-3

0--3 2 3-2

0

-

-3

2

3

-2

( , )n n� �

1 1( , )� �

(km

)

Cellular configuration --- Distributed Antenna System


� Focus on the uplink

� In each cell, the base station is assumed to be

loaded with one user

� TDMA、FDMA

� The composite channel fading model

� Path loss : depends on the distance between the user and the antennas of BSs

� Large scale fading (shadowing) : log-normal distributed

� Small scale fading : Rayleigh, Rice


� Introduction

� System Model




� Conclusion


� Location-specific capacity

� The concept of “cell edge” is based on the location

� For a given channel matrix H

( , )n n� �

1 1( , )� �

(km

)

BPU

� Conditioned on the locations of the user and the RAU, take expectation over other random variables


BPU

� Metric 1 : The average capacity in the inscribed

circle of the hexagonal cell edge

(√3/ 2) (km)

(km

)

BPU


� Metric 2 : the worst case location-specific capacity in

the cell

Collocated antenna system Distributed antenna system

BPU


� Metric 3 : the outage area

(km)

Capacity >

Capacity =

Capacity <


� Introduction

� System Model




� Conclusion


� Large frequency reuse factor is used

� Inter-cell interference is negligible

� Large path loss causes performance degradation in the cell edge

Result : Location-specific capacity in single cell environment


Location-specific capacity with the cell

-D -D/2 0 D/2 D -D -D/2 0 D/2 D-D

-D/2

0

D/2

D

0

10

20

30Location-specific capacity in the single cell environment (normalized SNR 0 dB)

Lo

ca

tio

n-s

pe

cific

ca

pa

city

(2,10,1) CAS(2,2,5) DAS


The average capacity over the inscribed circle (Metric-1)

-10 -8 -6 -4 -2 0 2 4 6 8 102

4

6

8

10

12

14

16

18

20

Normalized SNR c*P/Dα (dB)

bits/tra

nsm

issio

n

The average capacity in the circle of radius 0.866D

DAS (2,2,5)

CAS (2,10,1)


The worst-case location-specific capacity (Metric-2)

-10 -8 -6 -4 -2 0 2 4 6 8 100

2

4

6

8

10

12

14

16The worst-case location-specific capacity in the single cell environment


bits/tra

nsm

issio

n

DAS (2,2,5)

CAS (2,10,1)


The contour map of the location-specific capacity

10

10

10

10

12

12

12

12

12

12

12

12

15

15

15

15

15

15

15

15

15

15

18

18

18

1818

18

18

18

18

18

21

21 21

21

21

21

21

21

21

21

30

30

30

30

30

Location (x-axis)

Location (

y-a

xis

)

DAS (2,2,5), normalized SNR 0 dB

-D -D/2 0 D/2 D-D

-D/2

0

D/2

DCAS (2,10,1), normalized SNR 0 dB

6.7

6.7

6.7

6.7

6.7

6.7

9

9

9

99

12

12

12

12

15

15

15

18

18

21

21 30

Location (x-axis)

Location (

y-a

xis

)

-D -D/2 0 D/2 D-D

-D/2

0

D/2

D


The outage area normalize by the area of the cell (Metric-3)

5 10 15 20 250

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Desired rate R

Th

e o

uta

ge

are

a n

orm

alize

d b

y th

e a

rea

of C

ell-1

Single cell environment

CAS, c*P/Dα = 0 dB

CAS, c*P/Dα = 5 dB

DAS, c*P/Dα = 0 dB

DAS, c*P/Dα = 5 dB


� Introduction

� System Model




� Conclusion


� The same radio spectrum is reused in all cells

� Severe inter-cell interference

� Large path loss

Result : Location-specific capacity in multicell environment


-D -D/2 0 D/2 D -D -D/2 0 D/2 D-D

-D/2

0

D/2

D

0

10

20

30Location-specific capacity in the multicell environment (normalized SNR 0 dB)

Lo

ca

tio

n-s

pe

cific

ca

pa

city

(2,10,1) CAS(2,2,5) DAS

Location-specific capacity with the cell


The average capacity over the inscribed circle (Metric-1)

-10 -8 -6 -4 -2 0 2 4 6 8 102

3

4

5

6

7

8

9

10

11

12The average capacity in the circle of radius 0.866D


bits/tra

nsm

issio

n

DAS (2,2,5)

CAS (2,10,1)


The worst-case location-specific capacity (Metric-2)

-10 -8 -6 -4 -2 0 2 4 6 8 101

2

3

4

5

6

7

8

9The worst-case location-specific capacity in the multicell environment


bits/tra

nsm

issio

n

DAS (2,2,5)

CAS (2,10,1)


The contour map of the location-specific capacity

Location (x-axis)

Location (

y-a

xis

)

DAS (2,2,5), normalized SNR 0 dB

7

7

77

9

9

9

9

9

9

9

9

12

12

12

12

12

12

12

12

12

12

16

16

16

16

16

16

16

16

16

16

21

21

21

21

21

3030

30

30

30

-D -D/2 0 D/2 D-D

-D/2

0

D/2

D

-D -D/2 0 D/2 D-D

-D/2

0

D/2

DCAS (2,10,1), normalized SNR 0 dB

4. 5

4.5

4.5

4.5

4.5

4.5

6.5

6.5

6.5

6.5

6.5

9

9

9

9

12

12

12

16

16 2

130

Location (x-axis)

Location (

y-a

xis

)


The outage area normalize by the area of the cell (Matric-3)

4 8 12 16 20 240

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1Multicell environment

Desired rate R

Th

e o

uta

ge

are

a n

orm

alize

d b

y th

e a

rea

of C

ell-1

CAS, c*P/Dα = 0 dB

CAS, c*P/Dα = 5 dB

DAS, c*P/Dα = 5 dB

DAS, c*P/Dα = 5 dB


� Introduction

� System Model




� Conclusions


� Cell edge effect of cellular systems was evaluated;

� An analytical framework was presented

� Collocated antenna system, Distributed antenna system;� Single cell environment, Multicell environment;

� Three metrics were proposed to quantify the cell

edge performance

� Analysis results were provided for typical system configurations;

� The theoretical results will serve as a baseline for

future work on cell edge problem and its

countermeasures.


THANKS


cell edge performance of cellular mobile · pdf file · 2011-06-27cell edge...

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