Power Saving Mechanisms for Ad hoc networks Based on Handshaking Information Tapping

This paper presents an optimization of the functional properties of IEEE 802.11 PSM to improve its energy conservation without changing or requiring additional control or management frames. PSM relies on a handshaking procedure to announce data traffic before its transmission. This announcement traffic puts a heavy constraint on the sizes of both the ATIM window and the beacon interval and consequently on the network throughput, delay and power saving. All Stations are required to stay awake during the entire ATIM window, and hence they can infer from the already exchanged handshaking frames whether other stations in their vicinities have decided to stay active during the rest of the beacon internal. As such, many announcements could be avoided. First, we present the Neighborhood Aware Power Saving Mechanism (NA-PSM) that reduces the announcement period and hence provides much throughput and power saving than PSM, yet reduces the mean sojourn time of data frames. Second, we present a further refinement of NA-PSM based on the fact that a station having no more traffic to send or receive can power down its tranceiver even though it has already issued an ATIM frame or an ATIM-ACK frame. We show using extensive simulations that the proposed mechanisms outperform clearly PSM in terms of throughput, delay and power saving.