A new CoAP congestion control scheme using message loss feedback for IoUT

Internet of Underwater Things (IoUT) 1 is a network of networks mostly comprising of Underwater Wireless Sensor Networks (UWSNs) of underwater objects. These sensing nodes provide various services such as disaster prevention and management, tactical surveillance and environmental monitoring. Due to the underwater environmental constraints, these sensor nodes mostly communicate using an acoustic channel which inherits long propagation delay and network congestions. Congestion control schemes of existing protocols such as TCP require transmission of Ack messages for congestion detection which consumes unnecessary bandwidth. In this paper, we propose a reliable lightweight congestion control method for CoAP while using Ack message only in a necessary situation to reduce the use of Ack message. The proposed method adjusts the transmission rate based on the network successful packet delivery ratio of current time. Simulation results showed that our proposed scheme promises enhanced performance that can achieve higher throughput when compared with the congestion control mechanism of default CoAP standard.