Khan Pervez, Ullah Niamat, Ali Farman, Ullah Sana, Hong Youn-Sik, Lee Ki-Young, Kim Hoon
Department of Electronics Engineering, Incheon National University, Incheon 406-772, Korea.
Department of Computer Science, Govt. Postgraduate Jahanzeb College, Saidu Sharif, Swat 19130, Khyber Pakhtunkhwa, Pakistan.
Sensors (Basel). 2017 Mar 2;17(3):492. doi: 10.3390/s17030492.
The Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) procedure of IEEE 802.15.6 Medium Access Control (MAC) protocols for the Wireless Body Area Network (WBAN) use an Alternative Binary Exponential Backoff (ABEB) procedure. The backoff algorithm plays an important role to avoid collision in wireless networks. The Binary Exponential Backoff (BEB) algorithm used in different standards does not obtain the optimum performance due to enormous Contention Window (CW) gaps induced from packet collisions. Therefore, The IEEE 802.15.6 CSMA/CA has developed the ABEB procedure to avoid the large CW gaps upon each collision. However, the ABEB algorithm may lead to a high collision rate (as the CW size is incremented on every alternative collision) and poor utilization of the channel due to the gap between the subsequent CW. To minimize the gap between subsequent CW sizes, we adopted the Prioritized Fibonacci Backoff (PFB) procedure. This procedure leads to a smooth and gradual increase in the CW size, after each collision, which eventually decreases the waiting time, and the contending node can access the channel promptly with little delay; while ABEB leads to irregular and fluctuated CW values, which eventually increase collision and waiting time before a re-transmission attempt. We analytically approach this problem by employing a Markov chain to design the PFB scheme for the CSMA/CA procedure of the IEEE 80.15.6 standard. The performance of the PFB algorithm is compared against the ABEB function of WBAN CSMA/CA. The results show that the PFB procedure adopted for IEEE 802.15.6 CSMA/CA outperforms the ABEB procedure.
用于无线体域网（WBAN）的IEEE 802.15.6媒体访问控制（MAC）协议中的载波侦听多路访问冲突避免（CSMA/CA）过程采用了替代二进制指数退避（ABEB）过程。退避算法在避免无线网络冲突方面起着重要作用。不同标准中使用的二进制指数退避（BEB）算法由于数据包冲突导致的巨大竞争窗口（CW）间隙而无法获得最佳性能。因此，IEEE 802.15.6 CSMA/CA开发了ABEB过程，以避免每次冲突时出现大的CW间隙。然而，ABEB算法可能导致高冲突率（因为CW大小在每次交替冲突时都会增加），并且由于后续CW之间的间隙而导致信道利用率低下。为了最小化后续CW大小之间的间隙，我们采用了优先斐波那契退避（PFB）过程。该过程导致每次冲突后CW大小平滑且逐渐增加，最终减少等待时间，并且竞争节点可以几乎没有延迟地迅速访问信道；而ABEB导致CW值不规则且波动，最终增加冲突和重传尝试前的等待时间。我们通过采用马尔可夫链来为IEEE 80.15.6标准的CSMA/CA过程设计PFB方案，从而对这个问题进行分析。将PFB算法的性能与WBAN CSMA/CA的ABEB函数进行了比较。结果表明，IEEE 802.15.6 CSMA/CA采用的PFB过程优于ABEB过程。
