Miśkowicz Marek
Department of Measurement and Electronics, AGH University of Science and Technology, 30-059 Kraków, Poland.
Sensors (Basel). 2021 Oct 27;21(21):7135. doi: 10.3390/s21217135.
This paper is focused on the analysis of unfairness of random media access in Local Operating Networks (LON), which is one of the commercial platforms of the Industrial Internet of Things (IIoT). The unfairness in accessing the LON channel is introduced by a collision avoidance mechanism in the predictive -persistent CSMA protocol adopted at the media access control layer. The study on the bandwidth share in predictive -persistent CSMA calls for the analysis of multiple memoryless backoff. In this paper, it is shown that the channel access in LON systems is unfair in the short term for medium traffic load conditions, and in the long term for heavy loaded networks. Furthermore, it is explained that the average bandwidth allocated to a particular node is determined implicitly by the load scenario, while an actual node bandwidth fluctuates in time according to stochastic dynamics of the predictive -persistent CSMA. Next, it is formally proven that the average bandwidth available to a node is a linear function of its backoff state and does not depend on backoff states of the other stations. Finally, it is demonstrated that possibly unfair bandwidth share in LON networks determined implicitly by load scenario is stable because, with lowering a fraction of actual network bandwidth accessible by a given station, the probability to decrease it in the future also drops.
本文聚焦于对本地操作网络（LON）中随机媒体接入不公平性的分析，本地操作网络是工业物联网（IIoT）的商业平台之一。媒体接入控制层采用的预测持续CSMA协议中的冲突避免机制导致了在LON信道接入中的不公平性。对预测持续CSMA中带宽共享的研究需要对多个无记忆退避进行分析。本文表明，对于中等流量负载条件，LON系统中的信道接入在短期内是不公平的；对于重负载网络，在长期内是不公平的。此外，还解释了分配给特定节点的平均带宽由负载场景隐含确定，而实际节点带宽根据预测持续CSMA的随机动态随时间波动。接下来，正式证明了节点可用的平均带宽是其退避状态的线性函数，且不依赖于其他站点的退避状态。最后，证明了由负载场景隐含确定的LON网络中可能不公平的带宽共享是稳定的，因为随着给定站点可访问的实际网络带宽比例降低，其未来降低的概率也会下降。
