Performance Study of Hybrid MAC Using Soft Reservation for Wireless Networks

In wireless networks using hybrid MAC, nodes can reserve time periods inside scheduling cycles, and the time which is not reserved can be used by all the nodes through contention-based access. The hybrid MAC is attractive because it can provide satisfactory QoS by resource reservation and also achieve high channel utilization by multiplexing gain in the contention periods. However, we are still lacking a clear understanding of its performance and the optimization design scheme. In this paper, we propose an analysis framework for hybrid MAC using soft-reservation, where the unused reserved time can be released and accessed by the other nodes through contention. By the mean value analysis approach, the collision probability and average service time of one frame are obtained. The hybrid MAC based on the WiMedia ECMA-368 standard has been simulated to validate the analysis and compared to the conventional contention-based MAC and the hard-reservation hybrid MAC, which shows the soft reservation has much better performance and higher capacity when the network is relatively heavily loaded.