Congestion is an essential problem in Wireless Sensor Networks (WSNs). It not only wastes the scarce energy due to a large number of retransmissions and packet drops, but also hampers the event detection reliability. Thus, to meet the Quality of Service (QoS) requirements for network applications, a reliable and fair transport protocol is mandatory. For some applications however, such as in wireless multimedia sensor networks, having a 100% packet delivery ratio is not necessary. In this paper, we present PCC-PRG, a Priority Based Congestion Control and Partial Reliability Guaranty protocol for wireless multimedia sensor networks. The proposed PCC-PRG protocol can be used for partial order services in WMSNs. PCC-PRG uses the maximum queue length of intermediate nodes to detect and notify congestion in the network. PCC-PRG protocol uses a rate control mechanism to adjust the transmission rate of each traffic flow based on the congestion degree in the network and also the flow priority. All transmitted packets are classified into two different priority groups: high and low. Only lost high priority packets are retransmitted. To use a node’s energy efficiently, we use a hop-by-hop NACK-based reliability guaranty model. Simulation results confirm the superiority of the proposed model.

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