Power control and adaptive resource allocation in DS-CDMA systems

With an increased request for wireless data services, methods for managing the scarce radio resources become needful. Especially for applications characterized by heterogeneous quality of service (QoS) requirements, radio resource allocation becomes an extensive task. Due to the necessity of sharing the radio spectrum, mutual interference will limit system capacity. Transmitter power control is a well-known method for upholding required signal quality and reducing the energy consumption. In this thesis, transmission schemes based on distributed power control are developed and analyzed for cellular DS-CDMA systems. The schemes are designed for providing various QoS, while assuring global stability and rapid convergence. First, we suggest an iterative power control algorithm which handles congested situations by autonomously removing radio connections. This algorithm is then extended with a greedy rate allocation procedure, with the purpose to maximize throughput in a multirate system, where users have a limited number of discrete transmission rates. For supporting downlink nonreal time services with a required average data rate, joint power control and scheduling is investigated. It is found that time division has merits in terms of increased capacity and multiuser diversity effects. For this, we suggest and evaluate power control and channel adaptive schedulers of different adaptation rate. Finally, a class of receivers, utilizing successive interference cancellation with soft feedback is investigated. We determine the optimal power control solution and characterize its user capacity region.