We consider power and server allocation in a multi-beam satellite downlink which transmits data to N different ground locations over N time-varying channels. Packets destined for each ground location are stored in separate queues, and the server rate for each queue i depends on the power p/sub i/(t) allocated to that server and the channel state c/sub i/(t) according to a concave rate-power curve /spl mu//sub i/(p/sub i/, c/sub i/). We establish the capacity region of all arrival rate vectors which admit a stabilizable system. For the case when channel states and arrivals are iid from timeslot to timeslot, we develop a particular power allocation policy which stabilizes the system whenever the rate vector lies within the capacity region. Such stability is guaranteed even if the channel model and the specific arrival rates are unknown. As a special case, this analysis verifies the stability of the "choose-the-K-largest-connected-queues" policy when channels can be in one of two states (ON or OFF) and K servers are allocated at every timestep (K<N). These results are extended to treat a joint problem of routing and power allocation, and a throughput maximizing algorithm for this joint problem is constructed. Finally, we address the issue of interchannel interference, and develop a modified policy when power vectors are constrained to feasible activation sets. Our analysis and problem formulation is also applicable to power control for wireless systems.
['Michael J. Neely', 'Eytan Modiano', 'Charles E. Rohrs']
Power and server allocation in a multi-beam satellite with time varying channels