具有能量收集能力的IEEE 802.15.7的能量自适应MAC协议研究

发布时间：2018-05-09 22:17

本文选题：IEEE + 802.15.7　；参考：《吉林大学》2017年硕士论文

【摘要】：近年来,可见光通信技术VLC(visible light communication)以兼顾照明和通信的双重优势成为无线通信领域的研究热点。IEEE 802.15.7协议为短距离无线光通信提供了一个全球标准,该协议可以应用于区域照明、标识牌、路灯、车载系统、交通信号灯等领域,具有很广阔的应用前景。可见光通信中的终端设备通常是使用电池供电,设备的能量受限,从而影响使用寿命。本文研究的场景是将可见光终端设备用于智能家居,终端设备镶嵌在墙壁,这将会使得更换电池变得不可操作,而能量收集技术(EH)是针对能量受限网络的一种有效的解决办法。本文主要考虑收集室内随处可见且稳定的可见光能量,并建立可见光能量收集模型,考虑了终端设备与协调器之间的距离、终端处的接收角以及不同位置的遮挡概率对能量收集产生的影响。由于可见光具有衰减快、直线传播的特性,能量收集技术的引入会给IEEE 802.15.7可见光通信协议带来新的挑战。本文将具体研究能量收集技术与可见光通信结合后产生的问题并给出解决方案,为实际网络中的性能评估和优化提供一定的依据。本文首先研究了室内可见光能量收集模型。针对室内可见光场景,文章通过理论和仿真给出了室内LED灯的合理布局。在考虑了终端设备和协调器之间的距离、终端处的接收角后,给出了室内可见光能量收集模型。由于本文主要考虑的场景是设备部署在墙壁上,所以通过仿真给出了四周墙壁的能量分布图。文中还考虑了可见光的易遮挡特性,给出了一个考虑移动物体高度分布的室内可见光遮挡模型。然后,本文研究了具有能量收集能力的室内可见光通信的MAC协议(EH-MAC)。由于能量收集速率随着距离、接收角和遮挡概率的不同而变化,所以设备间就会存在吞吐量不公平性。在之前提出的可见光能量收集模型和可见光遮挡概率模型的基础上,我们给出了能量自适应竞争算法(EAC)来改善这个不公平性难题。使用该算法,设备能根据能量接收速率自适应调整竞争窗口,能量收集速率低的设备获得较小的竞争窗口来提高它的传输机会,而能量收集速率高的设备将获得较大的竞争窗口,降低了它的传输机会。通过实验仿真,改进的MAC协议提高了能量收集速率低的设备的吞吐量,降低了能量收集速率高的设备的吞吐量,从而使得设备获得较高的公平性。最后,本文使用二维离散时间马尔科夫链对EH-MAC/EAC的退避过程进行建模。不同能量收集速率的设备会选择两种不同的退避策略,文章对这两种退避策略分别进行Markov chain建模,并且在建模过程中考虑了可见光的易遮挡特性。通过理论分析给出了改进后的EH-MAC/EAC的吞吐量和公平性,实验仿真和理论分析基本吻合。
[Abstract]:In recent years, the visible light communication technology (VLC(visible light) has become a research hotspot in wireless communication field with the dual advantages of both lighting and communication. IEEE 802.15.7 protocol provides a global standard for short-range wireless optical communication, and this protocol can be applied to regional lighting. Signboards, street lamps, vehicular systems, traffic lights and other fields, has a very broad application prospects. The terminal equipment in visible light communication is usually powered by battery, and the energy of the equipment is limited, which affects the service life. The scene studied in this paper is that the visible light terminal device is used in the smart home, and the terminal device is embedded in the wall, which will make the battery replacement become inoperable. The energy collection technology (EH) is an effective solution for the energy limited network. In this paper, we mainly consider collecting the visible light energy which is everywhere and stable in the room, and establish the visible light energy collection model, considering the distance between the terminal equipment and the coordinator. The influence of the receiving angle at the terminal and the occlusion probability at different positions on the energy collection. Because visible light has the characteristics of fast attenuation and straight line propagation, the introduction of energy collection technology will bring new challenges to IEEE 802.15.7 visible light communication protocol. In this paper, the problems caused by the combination of energy collection technology and visible light communication are studied and the solutions are given, which provide some basis for the performance evaluation and optimization of the actual network. In this paper, the energy collection model of indoor visible light is studied. Aiming at the scene of indoor visible light, the reasonable layout of indoor LED lamp is given through theory and simulation. After considering the distance between the terminal equipment and the coordinator and the receiving angle of the terminal, an indoor visible light energy collection model is presented. Because the main scenario of this paper is that the equipment is deployed on the wall, the energy distribution diagram of the surrounding wall is given by simulation. In this paper, an indoor visible light occlusion model considering the height distribution of moving objects is presented. Then, the MAC protocol of indoor visible light communication with energy collection capability is studied. Because the rate of energy collection varies with distance, reception angle and occlusion probability, there is unfairness in throughput between devices. Based on the visible light energy collection model and the visible light occlusion probability model, we present an energy adaptive competition algorithm (EAC) to improve the unfairness problem. Using this algorithm, the device can adjust the competition window adaptively according to the energy receiving rate, and the device with low energy collection rate can obtain smaller competition window to improve its transmission opportunity. And the equipment with high energy collection rate will obtain a large competition window, which reduces its transmission opportunity. Through the experimental simulation, the improved MAC protocol can improve the throughput of the equipment with low energy collection rate and reduce the throughput of the equipment with high energy collection rate, thus making the device obtain higher fairness. Finally, the two-dimensional discrete-time Markov chain is used to model the Backoff process of EH-MAC/EAC. Two different Backoff strategies are chosen for devices with different energy collection rates. In this paper, Markov chain is used to model the two Backoff strategies, and the obfuscation characteristics of visible light are taken into account in the modeling process. The throughput and fairness of the improved EH-MAC/EAC are given through theoretical analysis, and the experimental results are in good agreement with the theoretical analysis.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.1

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