An overhearing based routing scheme for Wireless Sensor Networks

Congestion control in Wireless Sensor Networks (WSN) has always been a major challenge as contention for medium and limited storage space in nodes lead to loss of packets through collisions and buffer overflows. The congestion problem is tougher for multi-hop mesh networks, required when the deployment area is large compared to the communication range of individual nodes and the network is Ad-Hoc in nature. The objective is to design a routing scheme that minimizes congestion in such type of networks without increasing communication overheads. Often these networks use medium access control protocols like Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) that require sensor nodes to listen to the medium using an overhearing technique. This paper proposes an energy efficient routing scheme for multi-hop WSNs having mesh topologies. Here, a sensor node takes advantage of overhearing to predict the onset of congestion in the neighbouring nodes by estimating their respective buffer occupancies (number of messages queued in the buffer). This information is utilized directly in routing. The advantage of this approach is a significant reduction in congestion in the medium leading to reduction in number of packets being dropped and consequently minimization of average transmission delay. Also there is no additional communication overhead to implement the scheme. Software simulation demonstrates its effectiveness.