Available bandwidth estimation and admission control for QoS routing in wireless mesh networks

This article presents an integrated admission control and routing mechanism for multi-rate wireless mesh networks. Admission control depends on precise estimates of available bandwidth at involved nodes and the bandwidth consumption required by a new flow. Estimating these parameters in wireless networks is challenging due to the shared and open nature of the wireless channel. Existing available bandwidth estimation techniques do not accurately consider interference from neighboring nodes and flow bandwidth requirement estimates or act overly conservative, restricting opportunities for parallel transmission due to spatial reuse. We propose the DCSPT method for available bandwidth estimation, based on dual carrier sensing with parallel transmission awareness. We also introduce a packet probing-based available bandwidth estimation method, suitable for legacy device implementations, and verify it experimentally. These techniques are integrated in an admission control mechanism designed for a hop-by-hop routing protocol (LUNAR), enabling alternate route identification when shortest paths are congested. Our protocol uses temporal accounting to enable bandwidth estimation across links using different bit-rates. Simulation results demonstrate that our admission control mechanism can effectively control the traffic load while considering parallel transmission opportunities, leading to cumulative system throughput improvements up to 80% compared to more conservative approaches. We further show that additional gains in system throughput come without significant cost in terms of packet delivery ratio or end-to-end delay and discuss our implementation experience on the ORBIT wireless research testbed.