IEEE 802.15.6 CSMA/CA access method for WBANs: Performance evaluation and new backoff counter selection procedure

Wireless body area networks (WBANs) are supposed to be an effective proposition to revolutionize the present and the future of health care services. They provide a proactive diagnosis for many deadly diseases, as well as remote and real-time monitoring. On the other hand, they impose several challenges to the medium access control (MAC) protocols design, regarding the energy-efficiency, quality-of-service, priority, scalability, reliability, and security. The standardization of the IEEE 802.15.6 provides new MAC specifications for WBANs, that take these issues into account. In the case of the narrowband frequency (402 to 405 MHz) dedicated to medical applications, the WBAN employs the carrier sense multiple access with collision avoidance (CSMA/CA) access method: the main contention-based access method of the IEEE 802.15.6 MAC protocol that supports the unpredictable data traffic. This access method suffers from the loss of its performance with the increase of the network density. Consequently, evaluating and improving it is important, especially with the sensitivity of the medical data it deals with. In this paper, we evaluate the performance of the IEEE 802.15.6 CSMA/CA access method, through an illustrative case-study, using the statistical model-checking (SMC) toolset UPPAAL-SMC. Then, based on the results of this evaluation regarding the negative impact of the converged contention window (CW) intervals, we propose new ones and a new backoff counter (BC) selection procedure. Relevant metrics we use are energy-efficiency, throughput, and delay. Finally, we validate the performance of our proposition, in comparison to the old one, on the same case-study and toolset. Our access method manages to decrease the number of collisions and to increase the number of packets successfully transmitted.