A new CoAP congestion control scheme considering strong and weak RTT for IoUT

Inter-networking of sensor nodes underwater results in the formulation of the Internet of Underwater Things (IoUT). Due to the harsh and dynamic underwater environment, the communicating wireless acoustic sensor nodes form low power and lossy network. Network congestion and packet loss due to link error is one of the fundamental problems faced by these networks. IETF standard application protocol for the Internet of things (IoT) is Constrained Application Protocol (CoAP) designed to counter such challenges. The existing congestion control algorithms for CoAP have known shortcomings while maintaining a satisfactory performance level when the link error is high. In this paper we propose, SWR-CC scheme in which the sensor nodes monitor the congestion in real-time and adjusts the congestion window size accordingly. The size of the congestion window is adjusted based on the congestion ratio and loss ratio information of the confirmable message. The simulation analysis showed that the proposed algorithm outperforms the congestion control mechanism introduced in CoAP.