A two-loop power control scheme for a non-geostationary mobile satellite system

A novel two-loop power control strategy for a mobile satellite system is presented in this paper. The 'inner' fast-acting loop is a regulatory-type time-delay control system. It attempts to maintain received signal strength at a desired setpoint. The 'outer' slow-acting control loop adjusts the 'inner' loop setpoint in order to maintain received signal codeword error rate, WER, at an acceptable level, WER/sub des/. Computer simulations show that the twin-loop power control scheme is able to maintain received signal WER at or below the desired 2% in typical propagation scenarios. The mean transmit power cost required to maintain WER/sub des/ varies from one propagation scenario to another due to the different strengths in diffuse and specular multipath. The performance of the power control scheme is severely limited by the amount of time delay present in the control loop. Consequently, the transmit power costs required to maintain WER/spl les/WER/sub des/ increase with time delay.