Scheduling and Control of Multi-node Mobile Communications Systems with Randomly-varying Channels by Stability Methods

We consider a communications network consisting of many mobiles. There are random external data processes arriving at some of the mobiles, each destined for a unique destination or set of destinations. Each mobile can serve as a node in the possibly multi-hop (and not necessarily unique) path from source to destination. At each mobile the data is queued according to the source-destination pair.. Time is divided into small scheduling intervals. The capacity of the connecting channels are randomly varying. The system resources such as transmission power and/or time, bandwidth, and perhaps antennas, must be allocated to the various queues in a queue and channelstate dependent way to assure stability and good operation. Lost packets might or might not have to be retransmitted. At the beginning of the intervals, the channels are estimated via pilot signals and this information is used for the scheduling decisions, which are made at the beginning of the intervals. Stochastic stability methods are used to develop scheduling policies. The resulting controls are readily implementable and allow a range of tradeoffs between current rates and queue lengths, under very weak conditions. The basic methods are an extension of recent works for a system with one transmitter that communicates with many mobiles. The choice of Liapunov function allows a choice of the effective performance criteria. All essential factors are incorporated into a “mean rate” function, so that the results cover many different systems. Because of the non-Markovian nature of the problem, we use the perturbed Stochastic Liapunov function method, which is designed for such problems. Various extensions (such as the requirement of acknowledgments) are given, as well as a useful method for getting the a priori routes.