Hybrid Algorithm to Control Congestion in Wireless Sensor Networks

The Congestion in wireless sensor networks occurs when packets arrive at a fully loaded buffer of a sensor node. Due to lack of space in the buffer, packets are dropped. It also leads to packet delay, retransmission of packets, reduced QoS and throughput. A hybrid of rate control and resource control algorithms can be used to control congestion considering the priority of the packets. Congestion is detected when the service time is greater than the interarrival time of packets. The inter-arrival time can be increased by a certain factor computed as congestion degree, thus reducing the rate of sending packets. The congestion degree which is the ratio of service time to inter-arrival time can be sent to the sources. The sources can then adjust the rate of sending packets accordingly to control congestion in the upstream nodes. At the time of congestion, high priority packets are sent using multiple paths after increasing the time between generations of packets thus decreasing the rate of sending packets. Low priority packets are sent using a single path after decreasing the packet sending rate thus increasing the time between sending consecutive packets. The method also serves as a hybrid of congestion control and congestion avoidance.