RCOAP: A Rate Control Scheme for Reliable Bursty Data Transfer in IoT Networks

The Internet Engineering Task Force (IETF) standardized the Constrained Application Protocol (CoAP) for Internet of Things (IoT) devices to meet the demands of IoT applications. Due to the constrained IoT environment, CoAP was designed based on UDP as a lightweight protocol with simple congestion control, which leverages the basic binary exponential backoff. However, the basic congestion control of CoAP is unable to effectively perform reliable bursty data transfer in IoT networks. Recent studies have indicated that CoAP and its modifications still suffer from critical performance problems regarding congestion control, throughput, and delay. The current congestion control of the CoAP does not support bursty data transfer. In contrast to the current schemes that focus on a loss-based mechanism and a retransmission time-out (RTO) calculation, we propose a new rate control scheme, RCOAP, for reliable bursty data transfer in IoT networks. RCOAP uses the concept of regulating the transmission rate of CoAP sources. The key features of RCOAP are 1) estimating the initial sending rate by probing the bottleneck bandwidth, 2) adjusting the sending rate according to the dynamic network condition, and 3) distinguishing between losses due to congestion and losses due to wireless errors for the purpose of maintaining high throughput. Simulation results indicate that RCOAP is suitable for bursty data transfer. RCOAP shows a throughput increase of approximately 135% compared to the basic CoAP, CoCoA, and CoCoA+ under the same conditions while maintaining a low delay, loss rate, and a low number of retransmission attempts.