Congestion Control in CoAP Protocol: A Case study of Observing Resource with Block-Wise Transfer

doi: 10.14456/mijet.2023.11


  • Thavrak Chan Khon Kaen University, Thailand
  • Chanwit Suwannapong Nakhon Phanom University, Thailand
  • Chatchai Khunboa Khon Kaen University, Thailand


Block-Wise Transfer, CoAP, Congestion Control, Group Communication, IoT, Observe Resource


The Constraint Application Protocol (CoAP) is a restricted protocol used for communication in the Internet of Things (IoT). It allows limited resource devices to connect to the Internet, exchange request/response messages, and block-wise transfer for large data transfers. CoAP also includes an observed mode, which allows a client to monitor resources on servers and receive notification messages via unicast when the state of the resource is changed. However, the default congestion control algorithm used by CoAP, called Binary Exponential Back-Off (BEB), is insufficient for group communication resource observation with block-wise transfer and can lead to significant congestion, resulting in a buffer overflow, data loss, and connection drop. To address this problem, we conducted a study to evaluate the effectiveness of two alternative algorithms for congestion control in CoAP: Fibonacci Pre-Increase Back-off (FPB) and Half Binary Exponential Backoff (HBEB) algorithms. We tested these algorithms using a Cooja simulation and compared their performance to the default BEB algorithm. Our results showed that HBEB outperformed both BEB and FPB in terms of throughput and packet loss ratio (PLR), where BEB provides the best in term of end-to-end delay.

Author Biographies

Thavrak Chan, Khon Kaen University, Thailand

Department of Computer Engineering, Faculty of Engineering, Khon Kaen University, Thailand

Chanwit Suwannapong, Nakhon Phanom University, Thailand

Division of Computer Engineering, Faculty of Engineering, Nakhon Phanom University, Thailand

Chatchai Khunboa, Khon Kaen University, Thailand

Department of Computer Engineering, Faculty of Engineering, Khon Kaen University, Thailand


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How to Cite

Chan, T., Suwannapong, C., & Khunboa, C. (2023). Congestion Control in CoAP Protocol: A Case study of Observing Resource with Block-Wise Transfer: doi: 10.14456/mijet.2023.11. Engineering Access, 9(1), 86–92. Retrieved from



Research Papers