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.

无线体域网（WBAN）被认为是彻底改变医疗保健服务现在和未来的有效命题。它们为许多致命疾病提供了主动诊断，并提供了远程和实时监控。另一方面，它们在能效，服务质量，优先级，可伸缩性，可靠性和安全性方面对媒体访问控制（MAC）协议设计提出了一些挑战。IEEE 802.15.6的标准化为WBAN提供了新的MAC规范，并将这些问题考虑在内。在专用于医疗应用的窄带频率（402至405 MHz）的情况下，WBAN采用带冲突避免的载波侦听多路访问（CSMA / CA）访问方法：IEEE 802.15的基于竞争的主要访问方法。6 MAC协议，支持不可预测的数据流量。随着网络密度的增加，这种访问方法遭受性能损失。因此，评估和改进它很重要，尤其是要处理的医学数据具有敏感性。在本文中，我们使用统计模型检查（SMC）工具集UPPAAL-SMC，通过示例性案例研究，评估了IEEE 802.15.6 CSMA / CA访问方法的性能。然后，根据有关融合竞争窗口的负面影响的评估结果（我们使用统计模型检查（SMC）工具集UPPAAL-SMC，通过示例性案例研究，评估了IEEE 802.15.6 CSMA / CA访问方法的性能。然后，根据有关融合竞争窗口的负面影响的评估结果（我们使用统计模型检查（SMC）工具集UPPAAL-SMC，通过示例性案例研究评估了IEEE 802.15.6 CSMA / CA访问方法的性能。然后，根据有关融合竞争窗口的负面影响的评估结果（$C\mathrm{w\; ^}$）间隔，我们建议新的间隔和新的退避计数器（$乙C$）选择程序。我们使用的相关指标是能效，吞吐量和延迟。最后，在相同的案例研究和工具集上，与旧的相比，我们验证了我们的命题的性能。我们的访问方法设法减少冲突数并增加成功传输的数据包数。