Power control algorithm and architectures for fading communication channels

The present closed-loop power control algorithms in CDMA (code division multiple access) and UMTS (Universal Mobile Telephone System) ignore the round-trip delay incurred in the measurement of the received signal power. However, in contrast to terrestrial systems, such a condition is not satisfied in the case of satellite channels. The round-trip delay for the geostationary satellite, for example, may be in the range of 250 to 500 msec (including the terrestrial delay) for a single-hop or two-hop system respectively and is not negligible, compared to the inverse channel fading bandwidth of 1 to 10 sec and hence any algorithm based on the assumption of negligible delay will not have satisfactory performance. This paper describes an algorithm based on an adaptive nonlinear predictor, which explicitly takes into account the propagation delay. For the case of systems employing explicit or implicit diversity, the paper also proposes a new architecture for power control. The paper presents many simulation examples on the performance of the new power control architecture and algorithm showing that the residual loss due to fading is made relatively negligible, compared to the case of nonfading channels