Delay Analysis of IEEE 802.15.4 Slotted CSMA/CA Considering Deference Mechanisms

Slotted CSMA/CA is employed in the beacon enabled IEEE 802.15.4 to resolve collisions in the contention access period with a low energy cost. To address the problem of excessive contentions at the beginning of each superframe, IEEE 802.15.4/2006 assigns each uncompleted transmission an additional random backoff delay before accessing the channel in the next superframe, by using deference mechanisms. Previous simulation studies have shown that deference mechanisms bring a significant impact on the delay performance of slotted CSMA/CA. In this paper, we develop an analytical model to predict the actual delay performance, and verify our evaluation by using simulation results.