Tradeoff analysis of throughput and fairness on CDMA packet downlinks with location-dependent QoS

This work presents the quantitative tradeoff relation between system throughput and fairness on multirate code-division multiple-access (CDMA) downlinks. We develop and use an analytical model and a method for performance evaluation. The proposed model and method reflect the effects of multiplexing scheme, a limited data-rate set, log-normal shadowing, the best base station selection, and self-interference. System performance measures include asymptotic throughput, fairness performance factors, and outage probability . The performance of packet channels for delay-tolerant service is evaluated based on 3GPP wide-band code-division multiple-access (WCDMA) system model. Using the method developed, various algorithms for time resource assignment are applied and the system performance measures are derived and compared. We have derived the tradeoff between asymptotic throughput and fairness performance factors caused by the location-dependent carrier-to-interference ratio. The results show that we can control the tradeoff by applying various time resource-assignment schemes. It is also shown that the tradeoff in the system with the limited data-rate set can be improved by setting the number of simultaneous users properly.