Cross-layer designs of multichannel reservation MAC under Rayleigh fading

We consider a reservation-based medium access control (MAC) scheme where users reserve data channels through a slotted-ALOHA procedure. The base station grants access to users in a Rayleigh fading environment using measurements at the physical layer and system information at the MAC layer. The paper has two contributions pertaining to simple reservation based medium access. First, we provide a Markov chain formulation to analyze the performance (throughput/channel utilization) of the multichannel slotted system. Second, a Neyman-Pearson like MAC design optimized for performance is presented. This design can serve as a benchmark in evaluating the performance of other designs based on conventional physical layer detectors such as maximum a posteriori probability, maximum likelihood, and uniformly most powerful detectors. Results show that utilizing system information in addition to the physical layer measurements indeed leads to a gain in performance. We discuss the issue of further improving the performance in fading by means of multiple measurements and also comment on the delay/channel-utilization trade-off for the optimal MAC design.