Distributed power control for rate-varying multimedia CDMA systems

Future wireless systems will support a variety of different services such as voice, data and video, with variable bit rate requirements. In this paper, we consider a multimedia code division multiple access (CDMA) system for which different rates are represented by varying the processing gain, and study the dynamic properties of distributed power control algorithms using the theory of stability for switched systems and M-matrices. Of particular interest is the stability issue under fluctuations in the desired rates for individual users. We demonstrate that the convergence of a distributed power algorithm can be jeopardized for some cases. Furthermore, we provide conditions to check for possible instabilities and study the degradation in system capacity when such instabilities need to be avoided.