An Adaptive “Sleep” Algorithm for Efficient Power Management in WLANs Mahasweta Sarkar and Rene L Cruz CAL(IT)2 Student Spectrum October 25th, 2004 The System Model • The Problem • Sleeping increases delay • Sleeping decreases power consumption • Hence, the obvious question is: • What is the optimal “sleep duration” for a given delay constraint, that maximizes power saving ? Another Service Order Besides RR Nodes are served as and when they wake up. At every slot, sleep durations are arranged in ascending order. Service policy is the same Calculate NextSleepDuration similarly, except definition of waking up “early” changes. Tx Buffer • Timedivided into equal unit • length slots • Bernoulli Packet Arrival at the • beginning of a slot with rate = p • Deterministic service rate • [1 packet/slot] • Cut-through service policy • Perfect channel condition • Downlink traffic only • Pa >> Ps Rx1 Rx2 Rx3 Sleep Psa Awake RR scheme -At time t=0 At time t=Sa..Calculate Next Sleep Duration Ps Pa A Psa 1 Calculate Da –(CD)a = a which can take the following values: a =0, a >0, a <0 AP 2 B 3 C Allocate random sleep durations to each node (say…Sa, Sb, Sc ) Buffers are empty • At time t=Sa…..Service Policy • Gated Time limited Service Policy • Occasionally Exhaustive Policy • What if B doesn’t wake up? • What if C wakes up?