TDMA scheduling for data gathering in wireless sensor networks

We consider wireless sensor networks where a number of unconstrained nodes (Access Points) with unlimited power source can be deployed together with constrained and limited energy sensor nodes. The presence of unconstrained nodes promotes the use of centralized TDMA scheduling mechanisms that can potentially reduce the delay and save power by eliminating collisions. In this paper we propose two scheduling schemes: Interleaved and Non-interleaved scheduling, that allocate time slots to nodes in a spatial way to enable the follow of data from sensors to the Access Point (Sink). We investigate the performance of these schemes in terms of energy and latency. Through simulation we show that interleaved scheduling reduces average end-to-end delay by a factor of 5.25 for a 60 nodes network and by 3.07 for a 400 nodes network compared to non-interleaved scheduling. In addition, interleaved scheduling consumes on average less energy (42.6 mJ) per packet than non-interleaved which consumes about 138 mJ when network size is 400 nodes.