WSN07-1: Adjacent Channel Interference in Dual-radio 802.11a Nodes and Its Impact on Multi-hop Networking

We evaluate the performance impact of adjacent channel interference (ACI) in multi-hop wireless networks based on dual-radio 802.11a nodes. Although these nodes use chipsets that satisfy the transmit-mask requirements set by the IEEE 802.11 standard, the multi-hop performance is still significantly affected by ACI. That is, a node's transmitter can interfere with its own receiver on a different channel; as a result, multi-hop throughput is severely degraded. This degradation is especially pronounced for 802.11a. We use a spectrum analyzer with a signal combiner to quantify ACI under various conditions and propose solutions to mitigate the effect of such interference on multi-hop forwarding. Field experiments with multi-hop relay have validated these findings as well as the effectiveness of our solutions.