Performance evaluation of received power estimation for power control in CDMA systems

Transmitter power control is an effective scheme to improve the performance of cellular DS/CDMA systems. In the reverse link, time-multiplexed pilot symbols are used to assist the estimation of received signal power in order to improve the performance of power control. In this paper, two different approaches for received power estimation in power controlled CDMA systems are proposed and compared in terms of bit error rate (BER) by means of analytical and simulation studies. The first power estimator uses a simple sample average and the second power estimator uses a minimum mean square error (MMSE) filter approach. The MMSE approach requires knowledge of the Doppler spread and the signal-to-interference ratio (SIR). Comparison of the performance of the two power estimators is done with respect to deviations in the SIR and Doppler spread as used for the design of the MMSE filter, from their nominal values. Analysis results show that when the MMSE filter approach is used, BER can be further improved as compared to the simple sample average power estimator.