Distributed and Energy Efficient Scheduling for IEEE802.11s Wireless EDCA Networks

Abstract

We consider scheduling over IEEE802.11s wireless mesh networks running the standard Hybrid Wireless Mesh Protocol (HWMP) which forms a tree rooted at the mesh gateway. We propose Time-Split, a very simple and distributed scheduling algorithm compatible with the conventional EDCA mode of access. Time-Split is equipped with a simple mechanism to remove off-path interference without knowledge of the interference graph. Furthermore, Time-Split limits time-line fragmentation by creating contiguous inactivity periods within a beacon interval that can be used for deep power saving. We compare the performance of Time-Split with a greedy scheduler which performs optimally over the tree formed by HWMP for traffic routed to/from the gateway. We show that Time-Split can achieve more than 90 % optimal throughput at a packet delivery ratio of almost 100 %. More importantly, we propose split-depth as a means to strike a balance between interference elimination and spectrum sharing. In addition, we introduce a multi-channel version of Time-Split improving connection acceptance ratio by about 15 % using a single radio interface. Furthermore, due to its contiguous deep sleep intervals, Time-Split can potentially provide up to 25 and 50 % energy savings compared to conventional EDCA with sleep capability and a greedy sleep scheduler, respectively.