Collision avoidance and service differentiation at the MAC layer of WSN designed for multi-purpose applications

Wireless Sensor Networks are increasingly used for multi-purpose applications. In these networks we need to differentiate services or resources in order to provide a good performances to the prioritized data. Since the MAC layer is the responsible of managing the access to the shared medium, we need to handle the QoS at this layer in order to give more chance to nodes having high priority to get access to the medium before others. The lack of energy resources was behind the idea of alternating the transceiver between two modes; sleep and active modes. Though, this scheme is very efficient in terms of energy consumption, it causes high latency that degrades the QoS of real-time messages. In this paper we present a new policy that handles the energy constraint and the QoS of WSN designed for multipurpose applications. Our protocol intends to control the medium access of nodes according to the priority of their messages and reduce collision by using different random contention windows. Our results prove that our algorithm enhances quality of service in terms of prioritized message latency, as well as in other performance criteria.