Distributed power control algorithms in the uplink of wireless systems

In this paper, the problem of power control in wireless systems using a distributed approach is analyzed. The uplink of a direct-sequence code-division multiple-access communication (DS-CDMA) system is studied in this work. The power control strategies are derived using classical design approaches (PID and Dead-Beat). It is concluded that the uplink channel variations do not destroy the stability of the feedback structures. However, the delays in the closed-loop paths can severely affect the stability and performance of the resulting feedback schemes. As a result, the control laws have to be selected according with the expected transmision delays in order to maximize the resulting performance. Simulation results are presented to compare the control algorithms using a standard single-step power correction approach.