BQPS: A Broadcast Mechanism for Asynchronous Quorum-based Power Saving Protocols in Ad-Hoc Networks

Quorum-based power saving (QPS) protocols allow “asynchronous” wireless hosts, operating in a multi-hop ad-hoc network, to tune to the low power mode conceived in IEEE 802.11 MAC standard. QPS schemes guarantee that the wake-up schedule for every two neighboring hosts would ultimately overlap within a bounded latency so as to be able to accomplish their reciprocal “unicast” communications. A major drawback in quorum-based rendezvous schemes, however, lies in the absence of an efficient mechanism for enabling the simultaneous re-activation of all PS neighbors to receive “broadcast” messages. In this paper, a novel asynchronous wake-up scheduling mechanism is proposed, which specifically tackles the broadcast transmission problem in QPS systems. We introduce a special control packet at the MAC layer through which a sending host notifies its neighbors of forthcoming broadcast traffic, allowing the receivers to estimate the approximate re-activation time for ensuring the successful delivery of the messages. We will investigate, analytically, the optimum frequency with which to emit notifications so that the energy overhead induced is minimized in both single-hop broadcasting as well as network-wide flooding scenarios. Evaluation results derived from our simulation experiments reveal that the proposed mechanism can effectively improve the performance of an asynchronous QPS system in terms of both throughput as well as energy saving ratio; for instance, when operating with a wake-up ratio of 16%, network throughput will be enhanced by at least 60% in comparison with the existing schemes.