Achievable throughput in duty-cycled wireless networks

Capacity studies for wireless networks typically focus on scheduling of transmissions but rarely on scheduling of radio sleep-wakeup. We show that in a multi-hop network setting the duty-cycling of radios results in a per-node throughput capacity of Θ(W ψ√log n/√n) as opposed to Θ(W ψ/√ n log n) where ψ is the fraction of time each node radio is active. Likewise, in a single-hop clique network the duty-cycling of radios results in a per-node throughput capacity of Θ (Wψ), as opposed to Θ(Wψ/n). These capacity gains of Θ(log n) and Θ(n) respectively result from spreading interference over time. They emphasizes the importance of efficient co-scheduling of transmissions and sleep-wakeup, which is normally a function of the Medium Access Control (MAC) layer. We also examine how well canonical classes of duty-cycled MAC protocols achieve throughput capacity. In particular, we abstract four schedulers, each of which represents several well-used MAC schedulers, namely sender-centric synchronous (e.g. S-MAC, T-MAC, SCP-MAC), receiver-centric synchronous (e.g. O-MAC), sender-centric asynchronous (e.g. B-MAC, X-MAC, BoX-MAC), and receiver-centric asynchronous (e.g. RI-MAC). We compare the achievable throughput of these schedulers analytically; extensive experiments are then performed to corroborate our MAC analysis. The findings strongly suggest that out of the four classes receiver-centric synchronous scheme yields the smallest gap between existing MACs and the optimal scheduler.