Downlink throughput and fairness analysis in multi-rate CDMA systems

This paper presents an analytical model and a method for the evaluation of the downlink throughput and fairness performance in multi-rate CDMA systems. We propose and use a model that can show the impact of self-interference to the received E_b/N_t. The analytical method reflects the effect of lognormal shadowing, the best BS connection procedure, the bit rate granularity and the peak available bit rate limitation, and the limited number of spreading codes. A scheduling scheme for the fairness control is also developed and applied. The performance of packet channels for delay-tolerant service is evaluated in a 3GPP WCDMA system model. The system performance measures include asymptotic throughput, fairness performance factor, outage probability, and code shortage probability. From the analysis results, we can draw the downlink packet transmission control policy that can improve the system performance