认知无线电网络中动态合作中继选择算法的研究

发布时间：2018-06-08 02:27

本文选题：认知无线电 + 合作中继技术　；参考：《北京交通大学》2016年硕士论文

【摘要】：在无线通信终端日益普及的今天,频谱资源已经成为了一种宝贵的稀缺资源。然而目前大部分的频谱都是固定分配给用户,但是用户对频谱的使用在时间和空间上都具有多样性,这样就造成了频谱资源的严重浪费,频谱资源利用率较低。认知无线电网络技术由于其可以感知网络中的空闲频段并动态调整通信参数来利用空闲频谱而得到了广泛的关注,被认为是一种提高频谱资源利用率的有效途径。然而,在认知无线电网络中,双方的通信也会受到阴影、衰落等因素的影响,而不能满足通信质量。合作中继技术具有空间分集增益,可以有效地对抗衰落,提高通信质量。中继选择算法是合作中继的关键技术,它主要帮助用户高效的选择合适的中继节点。而无线网络中的大部分用户是处于不断移动的状态,将理论研究与实际的移动模型相结合十分具有现实意义。所以本文主要研究的是认知无线电网络中针对移动用户的合作中继选择算法。本文主要有两个创新点：一是将合作中继选择算法建立在用户处于移动状态的基础上,更接近于现实的网络场景,这是以往的研究工作所忽视却对于算法的实际实施十分必要的；二是将优化停止理论应用在了动态中继选择算法上,使得中继选择过程中不需要遍历所有的中继节点,从而大大减小了中继选择的时间和损耗,提高了中继选择的效率。本文首先介绍了合作中继选择算法的国内外研究现状,并重点强调了本文研究内容的背景意义和必要性。然后介绍了认知无线电的基本原理、移动社交网的常用模型、合作中继技术的基本原理及本文引入算法的基本原理。为了解决网络中用户移动性的问题,我们引入了约束马尔科夫决策过程模型,将主用户的位置移动和缓存器状态作为主用户的两个状态,将丢包率和中继传输损耗作为约束条件,并用线性规划进行求解,中继选择算法达到了系统通信质量和损耗之间的动态平衡。然而这种算法具有两个局限性,首先它并没有考虑SU的移动性,而且它对中继的选择的需要以遍历所有候选中继为基础,这降低了中继选择效率。所以,为了使移动模型更加接近现实情况,并解决遍历所有中继节点所导致的中继选择效率低的问题,我们将移动模型进一步复杂化,创新性地将用户的移动性建模转化为次级用户可作中继节点的概率,并引入了经济学领域的优化停止理论,提出了基于优化停止理论的动态中继选择算法,从而在保证通信质量的同时提高了中继选择效率。最后,我们通过实验仿真验证,本文提出的两种中继选择算法都达到了预期的效果并在用户移动的网络环境中具有良好的性能表现。
[Abstract]:With the increasing popularity of wireless communication terminals, spectrum resources have become a valuable scarce resource. However, most of the spectrum is allocated to users at present, but the users have diversity in time and space, which results in a serious waste of spectrum resources and low utilization of spectrum resources. Cognitive radio network (CRN) technology has been widely concerned because it can perceive the idle frequency band and dynamically adjust the communication parameters to use the idle spectrum. It is considered to be an effective way to improve the utilization of spectrum resources. However, in cognitive radio networks, the communication between the two sides will also be affected by the shadow, fading and other factors, and can not meet the quality of the communication. Cooperative relay technology has spatial diversity gain, which can effectively combat fading and improve communication quality. Relay selection algorithm is the key technology of cooperative relay. It mainly helps users to select appropriate relay nodes efficiently. However, most of the users in wireless networks are in the state of continuous movement, so it is of great practical significance to combine the theoretical research with the actual mobile model. Therefore, this paper mainly studies cooperative relay selection algorithm for mobile users in cognitive radio networks. There are two main innovations in this paper: first, the cooperative relay selection algorithm is based on the user in the mobile state, more close to the reality of the network scene, This is ignored by the previous research work but it is very necessary for the practical implementation of the algorithm. Secondly, the optimal stop theory is applied to the dynamic relay selection algorithm, so that the relay selection process does not need to traverse all relay nodes. Thus, the time and loss of relay selection are greatly reduced, and the efficiency of relay selection is improved. This paper first introduces the research status of cooperative relay selection algorithm at home and abroad, and emphasizes the background significance and necessity of the research content in this paper. Then it introduces the basic principle of cognitive radio, the common models of mobile social network, the basic principle of cooperative relay technology and the basic principle of the algorithm introduced in this paper. In order to solve the problem of user mobility in the network, we introduce a constrained Markov decision process model, which takes the position movement of the primary user and the buffer state as the two states of the primary user. The packet loss rate and relay transmission loss are taken as the constraint conditions and solved by linear programming. The relay selection algorithm achieves the dynamic balance between the communication quality and the loss. However, this algorithm has two limitations. Firstly, it does not consider the mobility of Su, and its need for relay selection is based on traversing all candidate relays, which reduces the efficiency of relay selection. Therefore, in order to make the mobile model closer to reality and solve the problem of inefficient relay selection caused by traversing all relay nodes, we further complicate the mobile model. In this paper, the mobility modeling of users is transformed into the probability of secondary users as relay nodes, and the optimal stopping theory in economics is introduced, and a dynamic relay selection algorithm based on optimal stopping theory is proposed. Thus, the relay selection efficiency is improved while the communication quality is guaranteed. Finally, through the experimental simulation, the two relay selection algorithms proposed in this paper have achieved the desired results and have good performance in the mobile network environment.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN925

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