Understanding Channel and Interface Heterogeneity in Multi-channel Multi-radio Wireless Mesh Networks

Multi-channel multi-radio architectures have been widely studied for 802.11-based wireless mesh networks to address the capacity problem due to wireless interference. They all utilize channel assignment algorithms that assume all channels and radio interfaces to be homogeneous. However, in practice, different channels exhibit different link qualities depending on the propagation environment for the same link. Different interfaces on the same node also exhibit link quality variations due to hardware differences and required antenna separations. We present a detailed measurement study of these variations using two mesh network testbeds in two different frequency bands --- 802.11g in 2.4GHz band and 802.11a in 5GHz band. We show that the variations are significant and `non-trivial' in the sense that the same channel does not perform well for all links in a network, or the same interface does not perform well for all interfaces it is paired up with for each link. We also show that using the channel-specific link quality information in a candidate channel assignment algorithm improves its performance more than 3 times on average.