Handoff algorithms in dynamic spreading WCDMA system supporting multimedia traffic

The undergoing third-generation wireless network needs to support the integration of voice and multimedia data services with varying quality-of-service (QoS) requirements. It is critical that the least bit-error rate (BER) for voice traffic, World Wide Web (WWW) traffic, and streaming video traffic be guaranteed at all time. In this paper, we discussed the integration of soft handoff and dynamic spreading factor in wideband code-division multiple-access system in supporting multimedia traffic. The contribution of our work is twofold. First, the processing time of the handoff request is analyzed. We found that intensive mobile handoff might consume significant amount of access channel time and increase the delay of handoff. We, therefore, proposed a batch mechanism such that multiple handoff requests could be processed simultaneously. The average delay is reduced from 1.12 s to 800 ms at heavy handoff rate. Our second contribution is a new resource allocation algorithm, where the spreading factor and transmission power for the handoff mobiles are jointly considered to maximize the throughput. The BER requirements for the handoff mobiles and the target cell are maintained during the handoff process. The original problem is formulated into a nonlinear programming format. We proposed a procedure to simplify it into a linear constraint problem, which is solved by a revised simplex method. Numerical results show a 25% increase in throughput for WWW traffic and a 26% improvement for the video traffic.