Scheduling for Fading Multiple Access Channels with Heterogeneous QoS Constraints

This paper addresses cross-layer resource allocation in quasi-static fading multiple access channels (MAC) with no channel state information at the transmitters (CSIT). Under the cross-layer approach without CSIT, the power and rate are determined based on an outage rate region as well as the current queue state information (QSI). For heterogeneous quality-of- service (QoS) requirements, an individual outage rate region results in better performance compared to the common outage rate region that is widely considered in the literature. This paper first reviews the recent notion of an individual outage rate region for the quasi-static fading MAC without CSIT. Individual outage rate regions are then used in two major types of scheduling policies: maximum weight matching scheduling (MWMS) and queue proportional scheduling (QPS). It is shown that MWMS and similar techniques based on weighted-sum-rate maximization require exponential complexity in the number of users because of the non-convex nature of the relevant optimization problems. By contrast, QPS can be very efficiently solved by using a successive feasibility check. Stochastic simulations show that compared to MWMS and the common outage rate region, significant throughput increase and delay reduction are possible by using the QPS scheduling policy with the individual outage rate region.