A probabilistic cross-layered call admission control for multi-hop ad hoc networks

We show in this papers how significant is the use of Call Admission Control (CAC) to improve performance of IEEE802.11 based multi-hop wireless networks. We propose a novel cross-layer framework jointly involving the PHY-MAC-NET layers. Then, we investigate the intricate interactions among PHY, MAC and Network layers implementing a simple probabilistic CAC. For instance, we incorporate carrier sense, transmit power, contention window, retransmissions retry limit, multi rates, routing, CAC rate and network topology. Then, we develop an analytical model that predicts the throughput of each connection as well as the stability of forwarding queues at intermediate nodes. Performance of such a system is also evaluated via simulation. We show that the performance measures of MAC layer are affected by the traffic intensity of flows to be forwarded (from NET layer). From now on, attempt rate and collision probability are dependent on the traffic flows, topology and routing. We have established that a good trade-off could be reached while fine-tuning the CAC rate and/or the forwarding probability. For better global performance and fairness issue, a selective-CAC scheme is also discussed.