Performance evaluation of power save protocols using carrier sensing in multihop ad hoc networks

Extending system lifetime by effectively managing power on participating nodes is critical in wireless ad hoc networks. Recent work has shown that, by appropriately powering off nodes, energy may be significantly saved. The IEEE 802.11 protocol specifies a simple power save mechanism (PSM) to conserve energy. Data frames are advertised during a fixed period of time, known as an ATIM window, at epochs known as beacon intervals. However, the announcement traffic puts a heavy constraint on the size of both the ATIM period and the beacon interval and consequently on throughput, end to end delay and power saving. In this paper, we address this problem by proposing the use of carrier sensing during the ATIM window to reduce the number of exchanged announcement frames. Carrier sensing is used as an energy efficient method to let nodes know if their neighbors are Awake. We propose two new protocols (the BTA-PSM and the UTA-PSM), derived from the PSM. These protocols try to enhance PSM´s performances by inferring from the already advertised future behaviors of the neighboring nodes of a given mobile station. Simulation results testified to the superiority of BTA-PSM and UTA-PSM over PSM and the Dynamic Carrier Sense PSM (DCS-PSM) in ensuring greater power saving, higher throughput and lower delay.