基于能量采集的无线体域网MAC协议研究

发布时间：2018-07-15 13:47

【摘要】：无线体域网是一种以人体为中心的低功耗无线传感器网络,它在很多领域都有应用,比如军事、医疗、运动和娱乐等。因为对无线体域网节点隐蔽性和便携性的要求,节点有限的电池容量使得能量问题成为无线体域网一直面临的重要挑战。近年来,一种新兴的为无线体域网节点供电技术——能量采集,成为无线体域网能量问题的有效解决方案。传统的由电池供电的节点会因为电池耗尽而进入永久的睡眠状态,而基于能量采集的节点则只会短暂进入睡眠状态,能量充足后又会进入工作状态。因此基于能量采集的无线体域网的核心问题是如何利用采集到的能量提高网络的数据传输效率。本文研究了基于能量采集技术的无线体域网中媒体访问控制层(Medium Access Control,MAC)协议问题,分别提出了分布式MAC协议策略和集中式MAC协议策略,目标是提高基于能量采集技术的无线体域网的数据传输效率,其中分别考虑的因素是时隙分配策略的决策速度和最优化程度。 1.在分布式MAC协议策略中,我们从子节点的角度考察WBAN数据传输过程,以子节点为主对信道接入方式进行分布式的决策。我们结合子节点的缓存区数据包数量和可用能量数,构造了无限MDP决策模型,通过使收益函数代表子节点的数据包传输量并对子节点非竞争性时隙的使用进行控制,我们求解出MDP模型最优策略。以MDP最优策略为根据,子节点可以实现根据自身数据包数量和可用能量数进行进行动态的信道接入。仿真表明我们这种分布式的动态MAC协议策略获得了比传统的时隙CSMA/CA更高的数据包传输量,减少了节点缓存区的数据包溢出。 2.在集中式MAC协议策略中,我们将整个WBAN中所有子节点的数据包状态和能量状态结合成联合的系统状态,以此构建无限MDP决策模型,决策结果即为每一个子节点的信道接入方式。通过根据数据包传输量设计收益函数,我们使用近似求解算法求解出最优时隙分配策略,以获得最大化的WBAN网络数据包传输量。仿真结果表明,集中式的MAC协议策略获得了比分布式MAC协议策略和时隙CSMA/CA更高的数据传输量和数据传输率。分布式MAC协议中子节点根据自身状态对信道接入方式进行决策,因为数据包和能量状态空间小,子节点可以快速地根据实时状态获得最佳信道接入方式。但是因为缺少其他WBAN节点的状态和行为信息,节点得到的只是局部最优的策略结果。而集中式MAC协议把所有节点的状态结合成联合的系统状态,以此对每个节点的信道接入方式进行决策,因为是基于整个系统的状态信息做的决策,所以集中式MAC协议可以得到全局最优的决策结果。但是,因为集中式MAC协议的状态空间很大,集中式MAC协议进行信道接入决策需要的时间相对于分布式MAC协议很大。
[Abstract]:Wireless body-area network is a low-power wireless sensor network centered on human body. It has many applications in many fields, such as military, medical, sports and entertainment. Due to the requirement of concealment and portability of wireless body-area networks, the limited battery capacity of nodes makes the energy problem an important challenge for wireless body area networks. In recent years, energy acquisition, a new power supply technology for wireless body area network nodes, has become an effective solution to the energy problem of wireless body area networks. The traditional battery-powered nodes will enter the permanent sleep state because of the battery depletion, while the energy-based nodes will only enter the sleep state for a short time, and then the energy will be sufficient and then into the working state. Therefore, the core problem of wireless body-area network based on energy acquisition is how to use the collected energy to improve the data transmission efficiency of the network. In this paper, the medium Access Control (MAC) protocol in wireless body area network based on energy acquisition technology is studied, and the distributed and centralized MAC protocols are proposed, respectively. The aim is to improve the data transmission efficiency of wireless bulk area network based on energy acquisition technology, in which the factors considered are the decision speed and optimization degree of slot allocation strategy. 1. In the distributed MAC protocol strategy, we investigate the WBAN data transmission process from the point of view of the sub-nodes, and make the distributed decision on the channel access mode based on the sub-nodes. We construct an infinite MDP decision model by combining the number of packets in the buffer area and the number of available energy of the sub-nodes, and control the use of the non-competitive time slots of the sub-nodes by making the income function represent the number of packets transmitted by the sub-nodes. We solve the optimal strategy of MDP model. Based on the MDP optimal strategy, the sub-nodes can realize dynamic channel access based on the number of packets and the number of available energy. Simulation results show that our distributed dynamic MAC protocol achieves higher packet traffic than the traditional slot CSMA / CA protocol and reduces the packet overflow in the node buffer. 2. In the centralized MAC protocol strategy, we combine the data packet state and energy state of all sub-nodes in the whole WBAN into a joint system state, and construct an infinite MDP decision-making model. The decision result is the channel access mode of each sub-node. By designing the income function according to the packet traffic, we use approximate solution algorithm to solve the optimal slot allocation strategy to obtain the maximum packet traffic in WBAN network. Simulation results show that the centralized MAC protocol achieves higher data transmission and data transmission rate than the distributed MAC protocol and slot CSMA / CA. In the distributed MAC protocol, the neutron nodes decide the channel access mode according to their own state. Because the data packet and energy state space is small, the sub-nodes can quickly obtain the best channel access mode according to the real-time state. However, due to the lack of state and behavior information of other WBAN nodes, only local optimal policy results are obtained. The centralized MAC protocol combines the states of all nodes into a joint system state to make decisions on the channel access mode of each node, because it is based on the state information of the whole system. So the centralized MAC protocol can get the global optimal decision result. However, because of the large state space of the centralized MAC protocol, the time required for the centralized MAC protocol to make channel access decision is much larger than that for the distributed MAC protocol.
【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN915.04

【共引文献】