Delay Guaranteed Media Access Control for Wireless Home Automation Networks

In this paper, we propose UA-MAC, a user adaptive MAC protocol for Wireless Home Automation Network (WHAN) to take tradeoff between energy consumption and user tolerable end to end delay. At first, a relationship between collision rate and number of users is given based on the probability theory and random process. Then, a user adaptive distributed algorithm by adjustment of active window is presented, which can adjust according to the number of users and collision rate. Moreover, a hybrid media access protocol combining with contention-base (Aloha-like) and contention-free (TDMA-like) method is adopted. When there is little collision, the active window is set to a small period and a pure ALOHA protocol is used for saving the energy. When collision rate is increased, active window will be enlarged and contention free transmission is employed to guarantee tolerable end to end delay. The simulation results show that the rate of collision can be controlled, though the number of users is increased, and end to end delay can be guaranteed less than three beacon intervals even in the worst case, which is hard to be realized in existing protocols.