【作者】 武文斌；

【导师】 张源；

【作者基本信息】 东南大学 ， 电子与通信工程， 2015， 硕士

【摘要】 在过去几十年里,移动通信技术经历了飞速的发展,但随着无线应用对速率的要求越来越高,而无线资源极为有限,因此为提升蜂窝通信系统的频谱效率,学术界提出了Device-to-Device(D2D)通信的概念,并将其应用在蜂窝网络中。D2D通信是一种在系统控制下,允许终端之间通过复用小区资源直接进行通信的技术。它不仅能增加蜂窝通信系统的频谱效率,还能有效降低蜂窝小区基站负载和无线终端的发射功率。为了在蜂窝通信系统中支持D2D通信,就要在多方面引入相应的使能机制,本文研究的无线资源分配方法就是其中之一。本文研究的场景是基于频分双工(FDD, Frequency Division Duplexing)的蜂窝系统,采用D2D通信专用模式,即将频谱资源分成两部分,一部分分配给D2D通信,另一部分分配给蜂窝用户,以避免D2D通信与蜂窝用户间的干扰。基于上述场景,本文主要研究基于干扰图的D2D通信资源分配方法,并详细介绍了构建蜂窝小区D2D通信干扰图的方法。首先,本文提出了一种蜂窝网络下基于干扰图的D2D通信资源分配方法,该方法分为三步：1)通过引入分数频率复用(FFR, Fractional Frequency Reuse),采用小区间干扰协调算法,将多小区无线资源分配问题转化为单小区无线资源分配；2)对单小区里的多个D2D通信对进行按照可用无线资源数进行频域分组,且每组用户只能使用对应的资源,在分组过程中尽量保证每个分组内的负载和干扰均衡；3)采用时域调度算法,对每个分组内的D2D通信对进行时域调度,以保证频谱效率最高。本文针对提出的方法进行了仿真分析,仿真结果表明,该方法能够有效提升频谱效率。文中针对蜂窝网络下基于干扰图的D2D通信资源分配方法提出了D2D通信干扰图构建协议.该协议是一个包含广播和ACK (Acknowledgement)多次迭代过程的协议。通过判断D2D通信是否收到另一对D2D通信的广播信号或ACK信号,来确定它们之间是否存在干扰关系。由于在接收广播信号或ACK信号过程中可能存在冲突,所以广播和ACK过程需要迭代进行,直到构建出小区D2D通信完整干扰图。该协议的时延和复杂度均比较低,且能够准确构建出蜂窝网络下完整的D2D通信干扰图。为验证蜂窝网络下基于干扰图的D2D通信资源分配方法和构建小区D2D通信干扰图协议的正确性和可行性,本文对上述两部分内容进行了详细的理论分析和仿真实验。结果表明,理论分析的结果与仿真实验的结果基本吻合,因而本文所提出的蜂窝网络下基于干扰图的D2D通信资源分配方法能够有效提升系统频谱效率。更多还原

【Abstract】 The last decades have seen a great development in mobile communications. However, the demands for transmission rates by wireless applications are growing rapidly with the extremely limited wireless resource. In order to improve the spectrum efficiency in cellular networks, the concept of Device-to-Device (D2D) communications is proposed. The basic idea of D2D communications is terminal devices can communicate directly with each other by reusing cellular resources, while terminal devices in D2D connections remain con-trolled by the system. D2D communications can improve the spectrum efficiency and decrease transmitting power of terminal devices as well as loads of the base station in the cellular communication networks. To enable D2D communications in cellular communication networks, we propose a wireless resource allocation in this paper.We employ frequency division duplexing (FDD) in cellular communication networks and focus on a dedicated scenario for D2D communications. In this scenario, we divide wireless resource into two parts, one for D2D communication and the other for conventional users. In such dedicated scenario, the interference between D2D communications and cellular users can be avoided. For the communication scenario mentioned above, we study the conflict-graph-based resource allocation method for D2D communications in cellular networks first. And the method to construct the conflict graph is illustrated.The proposed conflict-graph-based resource allocation method for D2D communications consists three steps:1) Transform the problem of wireless resource allocation problem in multi-cell system into a single-cell system by fractional frequency reuse (FFR) scenario with the inter-cell interference coordination algorithm.2) Divide D2D communications in each cell into several groups, and each group can only use the corresponding resource. During the procedure of grouping, we have to ensure the balance of loads and interference as much as possible.3) With the proposed slot scheduling algorithm, we schedule D2D communications in every group on the time domain to improve the spectrum efficiency. Simulation results show that the proposed resource allocation method can effectively improve the spectrum efficiency.In order to enable the proposed resource allocation method, we propose a new protocol to construct the conflict graph for D2D communications. It is an iterative process with broadcasting and acknowledgement (ACK). D2D users check if they can receive the broadcasting signal and ACK signal from others. If it can be received successfully, interference exists between the pair of users upon the same frequency resource assigned. There may be some conflicts in receiving broadcasting signals and ACK signals, thus we need to construct the conflict graph for D2D communications in a iterative way until it appears no conflicts. This protocol has an lower complexity and latency, and it can accurately construct an effective conflict graph for D2D communication in cellular networks.To verify the feasibility of proposed conflict-graph-based resource allocation method and the conflict graph constructing protocol, theoretical analysis and simulation experiments are shown in this paper. It can be indicated that the theoretical results match well with the simulation results. Furthermore, the proposed conflict-graph-based resource allocation method for D2D communications can improve spectrum efficiency effectively in cellular networks.更多还原