A Slot Sharing TDMA Scheme for Reliable and Efficient Collision Resolution in WSNs

Abstract

With the advent of Internet of Things (IoT), an increasing number of devices may spontaneously communicate to exchange information. This puts emphasis on wireless sensor networks (WSNs) and, in particular, on intelligent medium access control (MAC) protocols, as there is a need to guarantee a certain quality of service (QoS) on timely data/packet delivery. Most existing approaches, however, are either of random nature, making it impossible to guarantee any bounded delay, or do not scale well for a higher number of nodes. As a result, we propose slot sharing TDMAs², a deterministic contention resolution scheme in form of generating TDMA cycles with shared slots at the event of collisions. Every TDMA slot is assigned to a range of IDs, in which the corresponding nodes can transmit. By further dividing these slots in case of collisions, we implement an interval tree search enabling for fast collision resolution in logŝ-complexity, where ŝ is the number of slots in each cycle. Since our scheme is activated upon collisions, it incurs in zero overhead during normal operation and is able to quickly react to changing traffic load such as bursty traffic. We perform a large set of detailed simulations on OMNeT++ showing that our technique offers a fast collision resolution and is able to handle a large number of nodes in the network.