Throughput Optimal Switching in Multichannel WLANs

We observe that in a multichannel wireless system, an opportunistic channel/spectrum access scheme that solely focuses on channel quality sensing measured by received SNR may induce users to use channels that, while providing better signals, are more congested. Ultimately the notion of channel quality should include both the signal quality and the level of congestion, and a good multichannel access scheme should take both into account in deciding which channel to use and when. Motivated by this, we focus on the congestion aspect and examine what type of dynamic channel switching schemes may result in the best system throughput performance. Specifically, we derive the stability region of a multiuser multichannel WLAN system and determine the throughput optimal channel switching scheme within a certain class of schemes. We also empirically examine the impact of considering congestion in addition to signal quality in making channel selection decisions.