Conservation of satellite transmitter energy with propagation and demand variations

This paper is concerned with the discussion and evaluation of strategies which may significantly reduce satellite average power requirements for data communication with propagation and demand fluctuations. Assumptions of signal- and message-processing capabilities beyond current practice are made. Also, an unconventional downlink modulation format which emphasizes transmitted energy usage roughly proportional to amount of data transmitted is assumed. A cost function is studied which weighs energy utilization and delay costs. During a period of poor communication conditions the bit rate per watt of transmitter power can be much less than when conditions are good. Thus, there is a conflict between delay costs and a desire to save energy by holding data while awaiting better channel conditions. Cost minimization conditions are derived for a simplified channel model. Assumption of an exponential delay cost function has some realistic features and leads to a compact mathematical result.