SNR-Based Link Quality Estimation

The ability to accurately estimate wireless link quality is critical to the performance of routing protocols and rate adaptation algorithms in wireless mesh networks. Current link quality estimation methods utilize the packet delivery ratio (PDR) measurement of periodic broadcast probes sent at the lowest transmission rate. However, the estimated link quality does not readily translate to the performance of unicast data traffic at higher transmission rates. In this paper, we propose the use of a measurement-based signal-to-noise ratio (SNR) model to estimate wireless link quality in terms of its PDR performance. Using broadcast traffic measurements at the lowest transmission rate, we construct an "SNR profile'' that characterizes the relationship between the PDR metric and the SNR values computed at a node. We show how we can use the SNR profile to predict the PDR performance at different transmission rates. More importantly, we argue that the frame delivery ratio (FDR) at the MAC layer is a better link quality metric compared to PDR, and show that our proposed approach can use an SNR profile generated with broadcast traffic, to accurately estimate the FDR performance of unicast data traffic at different transmission rates. This then allows us to also accurately estimate the maximum achievable throughput of the wireless link at those rates.