Optimal fully adaptive power management protocols for IEEE 802.11 ad hoc wireless LANs

In an IEEE 802.11 ad hoc wireless LAN, the listen interval (LI) of a power-saving (PS) station should be fixed at one even there is no data traffic or its remaining battery power is low. However, if the value of LI is allowed more than two (in units of beacon interval), 802.11 power management may completely fail. In this paper, we propose a novel power management protocol, named OFPM, which not only equips a PS station with dynamic LI adjustment ability, but also conquers the following problems: (i) the possibly forever loss of ATIM frames, (ii) the waste of futile ATIM frames, and (iii) neighbor maintenance problem. Above all, OFPM has the following attractive features. (i) Given the maximum value of LI, L_max, the number of tunable LIs is L_max. (ii) For all LIs, the number of awake beacon intervals in an LI is minimal. (iii) The time complexity of OFPM neighbor maintenance is constant. (iv) By using our newly designed factor-hereditary quorum space technique, OFPM ensures that two PS neighbors can discover each other in finite time regardless of their offset and their individual LIs. (v) A closed-loop LI adjustment scheme is proposed such that a PS station can adaptively adjust its LI according to flow timeliness requirements. Via analyses and simulations, we show that OFPM significantly outperforms AQEC, the most energy-conserving protocol to date, in terms of adaptiveness, futile ATIM-frame ratio, and energy throughput.