MAC layer support for real-time traffic in a SAHN

In multi-hop ad-hoc wireless networks with shared medium and a contention based media access control (MAC) protocol, guaranteed quality of service (QoS) support for realtime traffic (e.g. voice, video, interactive applications etc.) is very challenging. Commercially available contention based MAC protocols, e.g. IEEE 802.11e, do not provide any mechanism to prevent a network from getting overloaded. Hence they fail to provide desired QoS (e.g. throughput, end-to-end delay, delivery ratio) for realtime traffic when the network is loaded beyond certain limits. In our previous work we have explained in details why trivial solutions are inadequate to support deterministic QoS for real-time traffic in multi-hop ad-hoc networks. We have also presented an analytical model to offer a distributed admission control and bandwidth reservation scheme by extending the features of the basic channel access mechanism of IEEE 802.11e and coordinating with the network layer. In this paper we have extended our analytical model to make it more effective than the initial one by considering neighboring nodes in bandwidth calculation. We refer to the improved IEEE 802.11e as SAHN-MAC. The proposed admission control mechanism of SAHN-MAC prevents any new data stream from initiating if the new stream saturates or is about to saturate any part of the network. The bandwidth reservation scheme is necessary for the admission control scheme to work properly. The proposed mechanisms have also been verified and evaluated via various simulations.