Pricing and Power Control in a Multicell Wireless Data Network

Po Yu ChenOctober, 2001

IEEE Journal on Select Areas in Communications

Prolog The data services in wireless

networks necessitate efficient and efficiency radio resource management

Power control is important in CDMA system

Outline Introduction Approach Simulation Result Conclusion and Discussion

Pricing and Power Control in a Multicell Wireless Data Network

Introduction

Introduction (1/2) Why using power control ?

To provide each signal with adequate quality without causing unnecessary interference to other signals

To minimize the battery drain in portable terminals

Introduction (2/2)

Paper Concept Extend reference [5] (single-cell

environment) to multi-cell environment Power control for data network under a

new light, powered by mathematics and concepts from microeconomics

Pricing scheme to improve utility with respect to both the transmit power and BS assignment

Key word Utility function: measure performance in

bits per joule (bits/joule) Nash equilibrium: no user has any incentive

to change its power level since no individual improvement in utilities is possible

Non-cooperative game: terminals operating independently to achieve best performance (a distributed power control algorithm )

Cooperative game: a centralized power control algorithm

Utility function & Nash equilibrium

將 Nash equilibrium 帶入所得之結果

Pricing and Power Control in a Multicell Wireless Data Network

Approach

Functions SIR

Utility function: 包含了 SIR和 power control的訊息

N

jkkkik

jijij

ph

ph

R

W

,1

2

Joulebits

p

f

M

RLPu

j

ja

jaj

j

)()(

hij: path gain

pj: power of user j

W: bandwidth

R: data rate

L/M: code rate , f(.):能成功被接收的機率

BS Assignment Based on MRSS (1/2) MRSS (Max. Received Signal Strength)

aj:被 assigned給 j的 BS hij:path gain dij:distance between terminal and BS

N j all for d h aiji

iji

j min arg max arg

BS Assignment Based on MRSS (2/2) 固定了 BS assignment的方法，所以只剩下 power control的變數

Multi-cell power control game (MCPG)

P-j: interference power vector, but not include pj

)()(max ,, jjjajjjPp

ppuppuj

jj

BS Assignment Based on MSIR (1/2) Generalize the MRSS ，將 BS assignm

ent也考慮進來。 方法：將有最大 SIR值的 BS assign給 t

erminal 所以在這裡 BS assignment也變成了一個變數

BS Assignment Based on MSIR (2/2) MCPG的 utility function (two dimension)

簡化問題，分成兩項討論：

先解決 BS assignment的問題（ MAX SIR ）再處理 power control的問題

Njallforppu jjjaap jjj

)(max ,,

)(maxmax)(max ,,,

jjjaap

jjjaap

ppuppuj

jjj

jj

Pricing (1/2) Define: every transmit power has pricing 加入 pricing後的結果： new utility function

ci:the pricing factor announced by BS

Alpha is a scalar, Ni is the number of the terminals assigned to BS

jajja pcpuj

)(,

ii Nc

Pricing (2/2) Pricing分為兩種：

--Global Pricing

--Local Pricing ci is based on the amount of traffic tha

t is offered in its service area

cconstsomeforiallforcci .

Power control game with Pricing

For MCPG-MRSS

For MCPG-MSIR

jajjjjaPp

pcppuj

jj

)(max ,

Njallforpcppu jajjjjaap jjj

)(max ,,

Best equal-SIR Good for MCPG (no pricing, the same SI

R) dependent on local information A centralized scheme,由 BS來計算 Term

inal的 SIR BS need to announce the best SIR The terminal needs to be applied an SIR

balancing algorithm

Pricing and Power Control in a Multicell Wireless Data Network

Simulation Result

System Model Multi-cell CDMA data system N=28 terminals K=4 base stations Frame size is fixed No forward error correction Simple path loss

4ij

ij d

Ch

Result (1/4)--utility Compare MCPG/MSIR and

MCPGP/MSIR(LP)

Result (2/4)--power in cell Compare MCPG/MSIR and

MCPGP/MSIR(LP)

Result (3/4)--utility Compare MCPG/MRSS and best

equal-SIR

Result (4/4)--power in cell Compare MCPG/MRSS and best

equal-SIR

Benefit of Local pricing (LP)1/2

congestion

Benefit of Local pricing (LP)2/2

Pricing and Power Control in a Multicell Wireless Data Network

Conclusion and Discussion

Conclusion 此篇利用microeconomics的 concept和mathematics來引導結果—證明加入pricing scheme有助於效能提升

傳 data和傳 Voice的方法不同，所以MRSS不能夠保證 data的 QoS ，因為 power最大並不代表 SIR就大。

Discussion 作者並沒有比較MRSS和MSIR ，所以我們就不知道 Best equal-SIR有沒有比MSIR好，因為這就是 Centralized和 Distributed power control的比較

Utility的可信度 缺乏其他參數的實驗數據，不知是否影響其的參數的 performance

個人覺得此實驗的model不夠完整，實際狀況應更為複雜