Adaptive SIR estimation in WCDMA systems

The near-far problem and multipath fading degrade the performance of the CDMA transceiver. The use of transmit power control (TPC) is widely applied to alleviate these effects. It is required to estimate signal-to-interference power ratio (SIR) of the received signal for the TPC. As the accuracy of the SIR increases, the transmit power can be reduced without degrading the bit error rate (BER) performance, increasing the system capacity. In this paper, we propose an improved SIR estimate scheme. The proposed scheme increases the SIR accuracy by considering not only present slot information but also previous slot information. The number of previous slots is adjusted in response to the channel condition. The performance of the proposed SIR estimator is verified by computer simulation.