An Efficient TDMA Scheme with Dynamic Slot Assignment in Clustered Wireless Sensor Networks

In this paper, we present an efficient MAC layer scheme using Dynamic Slot Assignment (DSA) in TDMA-based MAC protocols for cluster-based wireless sensor networks. The DSA scheme is presented to analyze the energy efficiency and channel utilization in a bursty traffic environment under low traffic conditions with a large number of sensor nodes in a single cluster. The DSA scheme will allow the network to adapt to the changing traffic load. Based on the network activity, the connection is established between the cluster-head node and those sensor nodes which have data to send, and a TDMA slot is assigned to each of them dynamically. We present the complete system model and model the data traffic by a correlated stochastic process (i.e. Markov chain) for a network where the second and subsequent connection arrival rate is dependent on the first arrival rate. We numerically compare our DSA with a traditionally proposed static TDMA model, the BMA model, and a variant of the BMA model (EA-TDMA), and prove substantial improvement in the energy consumption and channel utilization in low activity sensor networks. Results show that the efficiency of the MAC protocol can be increased significantly using the presented model.