Adaptive contention access suspension in IEEE 802.15.3 MAC

In IEEE 802.15.3 MAC, CSMA/CA is used in contention periods (CPs) to send commands. The brief occurrences of CPs cause bursty channel access, thus conventional models based on Poisson arrivals and saturation assumptions are no longer applicable. In this paper, we model CP access in each superframe as a contention resolution problem by applying a frame aggregation strategy for efficient frame transmissions in CPs. Insight gained from this problem formulation motivates us to propose a novel Adaptive CP Suspend (ACS) scheme that is easily implemented using a CP Counter (CPC) at the piconet controller (PNC). The CPC counts down in each idle slot and resets with the appropriate contention windows size after each collision. When the CPC reaches zero, which implies the completion of the contention resolution process, the PNC can safely suspend the remaining CP and devices (DEVs) can go into SLEEP mode to save power. Simulation results show that ACS effectively adapts to changes in channel traffic, substantially shortening the effective region in a CP in which all active DEVs continue to sense the channel, and significantly reducing the system energy cost by allowing DEVs to turn off their radios during the suspended parts of the CPs.