Cross-Layered MAC and Routing Algorithm for Real-Time Traffic over Wireless Multihop Networks

When the real-time traffic is transmitted under multi-hop network based on IEEE 802.11, there are many problems like the degradation of throughput, delay and higher frame drop by bottle-neck. We can classify the solution about these problems into three cases, i.e. modification of media access control (MAC) algorithm, definition and usage of required new packet, and use of multi-channel. One of modification of MAC algorithm, i.e., the method which both RTS and ACK are transmitted simultaneously is quite useful to reduce the delay in the real-time traffic. Also routing algorithm has to treat packets differently according to traffic types. The interaction between routing algorithm in network layer and MAC layer is required to differentiate QoS for different traffic type, which results in the cross-layer mechanism. In this paper, proposed cross-layer algorithm, named as differentiated data-driven cut-through medium access (DDCMA), integrates the modified MAC algorithm and modified ad-hoc routing algorithm with cross-layer interaction to provide the efficiently differentiated QoS between real-time and non-real-time traffics. DDCMA is based on existing DCMA in MAC layer and enhanced DSR for network routing and targets for differentiated QoS between real/non-real-time traffics. The performance validation has done extensively using GloMoSim, well-known multihop network simulator.