Pricing and Power Control in a Multicell Wireless Data Network

1. Pricing and Power Control in a Multicell Wireless Data Network Po Yu Chen October, 2001 IEEE Journal on Select Areas in Communications

2. Prolog • The data services in wireless networks necessitate efficient and efficiency radio resource management • Power control is important in CDMA system

3. Outline • Introduction • Approach • Simulation Result • Conclusion and Discussion

4. Pricing and Power Control in a Multicell Wireless Data Network Introduction

5. 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

6. 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

7. 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

8. Utility function & Nash equilibrium 將Nash equilibrium 帶入所得之結果

9. Pricing and Power Control in a Multicell Wireless Data Network Approach

10. Functions • SIR • Utility function:包含了SIR和power control的訊息 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

11. 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

12. 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

13. BS Assignment Based on MSIR (1/2) • Generalize the MRSS，將BS assignment也考慮進來。 • 方法：將有最大SIR值的BS assign給terminal • 所以在這裡BS assignment也變成了一個變數

14. 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

15. 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

16. Pricing (2/2) • Pricing分為兩種： --Global Pricing --Local Pricing ci is based on the amount of traffic that is offered in its service area

17. Power control game with Pricing • For MCPG-MRSS • For MCPG-MSIR

18. Best equal-SIR • Good for MCPG (no pricing, the same SIR) dependent on local information • A centralized scheme,由BS來計算Terminal的SIR • BS need to announce the best SIR • The terminal needs to be applied an SIR balancing algorithm

19. Pricing and Power Control in a Multicell Wireless Data Network Simulation Result

20. 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

21. Result (1/4)--utility • Compare MCPG/MSIR and MCPGP/MSIR(LP)

22. Result (2/4)--power in cell • Compare MCPG/MSIR and MCPGP/MSIR(LP)

23. Result (3/4)--utility • Compare MCPG/MRSS and best equal-SIR

24. Result (4/4)--power in cell • Compare MCPG/MRSS and best equal-SIR

25. Benefit of Local pricing (LP)1/2 congestion

26. Benefit of Local pricing (LP)2/2

27. Pricing and Power Control in a Multicell Wireless Data Network Conclusion and Discussion

28. 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。

29. 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