功率控制機制在TDMA/FDMA/CDMA行動通訊系統中依照控制之特性，可分成中央式和分散式兩種，要實現中央式功率控制機制，基地台必須掌握全部的鏈路增益資訊，才能解出使用者最佳的發射功率，但分散式功率控制的實現，基地台只需知道接收功率和信號干擾比等本地區域性資料。

首先，我們假設所有的鏈路資料已知的情況下，並假設所有的使用者要求相同的信號品質，分析了TDMA/FDMA/CDMA行動通訊系統中的使用者的最佳發射功率和能達到的最佳信號品質，並分析多媒體CDMA行動通訊系統中，具不同信號品質要求下之最佳解。

其次，我們探討各種分散式功率控制機制的收斂問題，在大刻度衰落為通道模型下，我們提出一個完全分散式功率控制演算法，來改進傳統方法無法快速收斂缺點，我們只須要利用基地台之區域量測資料，就可在公平之原則下達到不同之信號品質要求，並能保持發射功率在一合理之範圍。

第三，我們進一步考慮小刻度衰落之通道模型，我們發現在發射功率有限制之情況下發現，傳統的方法，都會處於高度的失誤機率，為了改善效能，我們提出了SOLPC演算法來降低失誤機率。

最後，以傳輸通道遭遇了嚴重的屏蔽和多路徑衰落時，所引起的SIR變動太大的問題為出發點，運用具有良有預測能力的灰色理論，來維持目標之品質，進而改善失誤機率。

Power control schemes for TDMA/FDMA/CDMA cellular mobile systems can be centralized or distributed depending on the nature of control. The base station has the full knowledge of link gains for the centralized control to decide the power adjustment of each individual mobile user, but has only the local information of the received power (different signal-to-interference, SIR, for example) for distributed mechanism.

Firstly, optimum solutions of TDMA/FDMA/CDMA cellular mobile systems based on the same required SIR threshold and optimum solution of multimedia CDMA cellular mobile system based on different SIR requirement are investigated for the centralized power control.

Secondly, we focus on the distributed power control based on the large-scale fading. The previous distributed power control schemes for TDMA/FDMA/CDMA cellular mobile systems are modified to be adaptive to the multimedia CDMA cellular mobile systems and a fully distributed uplink power control algorithm is proposed. The proposed power control scheme only needs the local measurements at the base station and can meet different SIR requirements of mobile users based on the fair principle. From the simulation results, the proposed schemes can not only converge fast but also keep the transmitted power in a reasonable range.

Thirdly, an SIR-based outer loop power control (SOLPC) algorithm is proposed for the multimedia CDMA systems. The proposed outer loop power control process only needs the local measurements at the base station and can provide SIR requirements of mobile users based on fair principle. From the simulation results, the proposed scheme can not only offer less outage probability, but also keep the transmitted power in a reasonable range.

Finally, the propagation channel of the mobile radio system exhibits severe signal shadowing and multipath fading which results in wide variation of SIR at the receiver. To tackle this problem, power control is used to maintain the desired link quality and thus achieve higher capacity. In order to mitigate the channel variation effect precisely, a new application of the grey theory to the power control strategy in the CDMA cellular mobile systems is introduced in this paper. This scheme aims to predict SIR affected by the channel variation at the receiver and issue appropriate control signal to the transmitter. The simulation results indicate that grey based scheme can offer less outage probability than the previous mechanisms.

[1] J. Zander, "Performance of Optimum Transmitter Power Control in Cellular Radio Systems," IEEE Trans. on Vehicular Technology, pp.57-62, Vol. 41, No. 1, Feb. 1992.
[2] S. A. Grandhi, R. Vijayan, D. J. Goodman, and J. Zander, "Centralized Power Control in Cellular Radio Systems," IEEE Trans. on Vehicular Technology, pp.466-468, Vol 42, No. 4, Nov. 1993.
[3] Q. Wu, "Performance of Optimum Transmitter Power Control in CDMA Cellular Mobile Systems,"} IEEE Trans. on Vehicular Technology, pp.571-575, Vol. 48, NO. 2,March 1999.
[4] J. Zander, "Distributed cochannel interference control in cellular radio systems,” IEEE Trans. on Vehicular Technology, Vol. 41, No. 3, August 1992.
[5] S. A. Grandhi, R. Vijayan, and D.J. Goodman, "Distributed Power Control in Cellular Radio Systems," IEEE Trans. on Commun., pp.226-228, Vol. 42, NO. 2/3/4, February/March/April 1994.
[6] C. Y. Lee and T. Park, "A Parametric Power Control with Fast Convergence in Cellular Radio Systems," IEEE Trans. on VT, pp.440-448, Vol. 47, NO. 2, May 1998.
[7] Q. Wu, "Optimum Transmitter Power Control in Cellular Systems with Heterogeneous SIR Thresholds," IEEE Trans. on Vehicular Technology, pp.1424-1429, Vol. 49, NO. 4, July 2000.
[8] S. L. Su, Y. C. Su and J. F. Huang, "Grey-based power control for DS-CDMA cellular mobile systems, " IEEE Transactions on Vehicular Technology, vol. 49, no. 6, pp.2081-2088, Nov. 2000.
[9] A. J. Viterbi, A. M. Viterbi, and E. Zehavi, "Other-Cell Interference in Cellular Power-Controled CDMA," IEEE Trans. on Commun., pp.1501-1504, Vol. 42, NO. 2/3/4, February/March/April 1994.
[10]W. C. Y. Lee, 'Overview of Cellular CDMA,' IEEE Trans. on Vehicular Technology. pp.291-302, Vol 40, May 1991.
[11] K. S. Gilhousen, 'On the Capacity of a cellular CDMA System,' IEEE Trans. on Vehicular Technology, pp.303-312, Vol 40, May 1991.
[12] S. Ariyavisitakul, 'Signal and Interference Statistics of a CDMA System with Feedback Power Control,' IEEE Trans. on communications, pp.1626-1634, Vol 41, Nov 1993.
[13] S. Ariyavisitakul, 'Signal and Interference Statistics of a CDMA System with Feedback Power Control Part 2,' IEEE Trans. on communications, pp.597- 605, Vol 42,Feb/Mar/Apr 1994.
[14] S. Ariyavisitakul, 'SIR-Based Power Control in a CDMA System,' IEEE GLOBECOMM, pp.868-873, 1992.
[15] C. J. Chang, J. H. Lee, and F. C. Ren, 'Design of Power Control Mechanisms with PCM Realization for the Uplink of a DS-CDMA Cellular Mobile Radio System,' IEEE Trans. on Vehicular Technology, pp.522-530, Vol. 45, NO. 3, AUGUST 1996.
[16] P. R. Chang, and B. C. Wang, 'Adaptive Fuzzy Power Control for CDMA Mobile Radio Systems,' IEEE Trans. on Vehicular Technology, pp.225-236, Vol. 45, NO. 2, MAY 1996.
[17] P. R. Chang, and B. C. Wang, 'Adaptive Fuzzy Power Control for a CDMA Mobile Radio Systems with Time Delay,' IEEE J. Select Areas Com- mun., Vol. 14, No. 9, pp 1818-1829, December 1996.
[18] J. Deng, 'Essential Topics on GREY SYSTEM Theory and Application,' China Ocean Press Beijing, 1988.
[19] A. J. Viterbi, A. M. Viterbi, and E. Zehavi, "Other-Cell Interference in Cellular Power-Controlled CDMA," IEEE Trans. on Commun., pp.1501-1504, Vol. 42, NO. 2/3/4, February/March/April 1994.
[20] B. Sklar, "Rayleigh Fading Channels in Mobile Digital Communication Systems Part I: Characterization,"” IEEE Comm. Mag., pp.90-100, July 1997.
[21] B. Sklar, "Rayleigh Fading Channels in Mobile Digital Communication Systems Part II: Mitigation," IEEE Comm. Mag., pp.90-100, July 1997.
[22] W. C. Y. Lee, “Mobile Cellular Telecommunications System, New York: McGraw-Hill, 1989.
[23] W. C. Jakes, Jr, Microwave Mobile Communications, A Wiley-Interscience Publication, 1989.
[24] X. Wang and X. Wu, 'Application of grey system models to rural economy analysis in China,' Uncertainty Modeling and Analysis, 1990. Proceedings., First International Symposium on IEEE Comput. Soc. Press.
[25] Golub, G. H. and C. F. V. Loan, Matrix Computions, 2nd ed. MD: Johns Hopkins University Press, 1989.