Cross Layer Rate Constraints For Qos Routing In Multi-rate Wireless Ad Hoc Networks

With the development of multimedia applications and wireless devices, there is a great vision that wireless ad hoc networks carry diverse multimedia traffic such as videos and voices. Real time multi-media traffics require high QoS(quality of service) provided by the network. However, it is a great challenge to meet their requirements because of the channel fadings (attenuation, interference and multi-path fadings) in the wireless ad hoc networks. Therefore, the bandwitdth-constraint based QoS routing is a hot topic recently.Based on the NABE constraint with two-hop interference model, we presented a cross-layer rate constraint for QoS flows in multi-rate wireless ad hoc networks, and a distributed algorithm CRCA based on measurement. In CRCA, according to the strength of interference, nodes adjust their MAC data rate in order to reduce collisions and improve spatial reuse. Nodes exchange their sending probablility, and analyze intra/inter-flow interference caused by newly arrived QoS flows. After that, they figure out the channel busyness ratios and adapt MAC data rates to determine the admission/rejection of the QoS traffic. We extended DSR to support QoS based on CRCA.CRCA and the QoS routing protocol are implemented in NS-2. Simulation results in various scenarios show that CRCA predict the available bandwidth accurately. CRCA based routing protocol can meet the traffic QoS requirement. The test-bed experiments verify the accuracy of CRCA, and that rate adaption improves spatial reuse.