Traffic adaptive active period control with adaptive backoff window for cluster-based IEEE 802.15.4 wireless sensor networks

This paper proposes an adaptive 2-level active period control method with adaptive backoff window based on traffic load in each cluster for cluster-based wireless sensor networks (WSNs) employing IEEE 802.15.4 medium access control (MAC) protocol under temporal and geographical non-uniform traffic distribution. The proposed method consists of three elements: cluster level active period control, network level active period control, and adaptive backoff window control. In the cluster level control, cluster heads autonomously control their active period length in the superframe defined by a personal area network (PAN) coordinator. The PAN coordinator manages the superframe structure for the whole network in the network level control. In the adaptive backoff window control, the backoff window size is determined according to the length of current active period. The results evaluated by computer simulation show that the proposed method can improve the energy efficiency for the cluster-based WSNs with geographical non-uniform traffic distribution in addition to the improvement of the transmission performance.