| We consider parallel use of multiple channels in a multi-radio, multi-hop 802.11 wireless network, with the goal of maximizing the total multi-hop throughput. We first quantify several fundamental forms of radio interference that cause performance degradation when the number of hops increases and that prevent total throughput from scaling up with number of radio interfaces at each node. We then evaluate three different methods of parallel channel use: Ad-Hoc, Frequency-Division Multiplexing (FDM), and Time-Division Multiplexing (TDM). We measure their performance on a linearly connected multi-hop network of dual-radio nodes. Although theoretically these three methods should have comparable performance, their actual measured performances are quite different. We find that TDM has the best performance, followed by Ad-Hoc and then FDM. The performance differences are due to these methods' capabilities of combating interference. We conclude that interference, especially adjacent channel interference, has significant effect on the achievable performance of a multi-radio, multi-hop network and hence should be carefully taken into account in the design and deployment of such a network. |