Distributed Power Control for Code Division Multiple Access Systems

Radio resources in wireless communication systems must be managed. This management is important since the variations in propagation channel are very fast. The complexity in the cellular system periodically contributes to different interference levels which ultimately resulting in the degradation of the system capacity. Transmitted power control is an efficient technique to mitigate the effect of interference, thereby solving the near-Far problem and preserving the battery life. Thus, an effective implementation of different power control algorithms in cellular radio communication systems can offer a significant improvement in the quality of service (QoS) to all the users. The choice of an appropriate power control algorithm is important to increase the overall efficiency of the system. A linear quadratic Gaussian (LQG) power control strategy is derived and compared with other approaches. Simulation results show that the uplink channel variations do not destroy the stability of these power control structures. However, delays in the closed-loop paths can severely affect the stability and performance of the resulting feedback schemes. It is also shown that the use of multiuser detection at the base station can bring significant improvements to the performance of power control.