WLC04-1: A Distributed BER-Based Power Control Algorithm for WCDMA Systems

Taking into consideration the dominance of the multiple access interference (MAI) in spread spectrum based CDMA systems, power control plays a vital role in reducing the system interference and helps in increasing the capacity of the system while maintaining the quality of the received signal. Closed loop power control is mainly used to mitigate the near-far effect in the uplink direction. In this paper, we propose a bit error rate (BER)-based first order distributed power control algorithm. Being distributed, the proposed algorithm has the flexibility of using the benefits of fast closed loop power control and thus can be used to update the transmit power of a single user at a time. Signal-to-interference ratio (SIR) based algorithms are in extensive use. But considering that the SIR is time variant, the BER would be a better quality of service (QoS) parameter because it can be easily measured using already known pilot bits. We analyze the convergence performance of the proposed algorithm and show that its convergence is always guaranteed. We demonstrate that a considerable improvement in the convergence speed along with the required average signal-to-noise ratio (SNR) is achieved as compared with other BER-based algorithms under comparison. We also show that the proposed algorithm performs well at different mobile speeds.