A distributed, adaptive protocol for handling interference in wireless communications

The recent advent of wireless applications at the 2.4GHz level (e.g. wireless LAN, Bluetooth headsets, wireless mice and keyboards, remote controls, cordless phones, microwave ovens etc) creates a significant potential for widespread interference. Yet the most popular wireless protocols (e.g. Wi-Fi (802.11) and Zigbee (802.15)) currently lack the ability to switch in a coordinated manner to a different frequency once the channel currently in use becomes jammed. For example, Zigbee specifies a collision-avoidance algorithm (similar to 802.11b). Each device listens to the channel before transmitting to minimize the frequency of collisions between Zigbee devices. Zigbee does not change channels during heavy interference; instead, it relies upon its low duty cycle and collision-avoidance algorithms to minimize data loss caused by collisions. Hence, if Zigbee uses a channel that overlaps a heavily-used Wi-Fi channel, significant retransmission effort will be undertaken. In this paper we propose a simple channel hopping protocol to make wireless networks resilient to interference. In an exploration phase, each radio keeps track of how many neighbors are currently using each available channel. This phase continues until the empirical frequency of total number of neighbors in a given channel exceeds a given threshold. We present the results from a simulation test-bed and a physical implementation with SunSPOTs.