【作者】 赵汀；

【导师】 孙礼；

【作者基本信息】 北京邮电大学 ， 通信与信息系统， 2010， 硕士

【摘要】 协同通信是一种虚拟多天线技术,是空间分集概念的升华。这种技术利用通信网中其它用户的天线作为中继,实现“虚拟天线”的空间传输分集,从而提高系统性能。随着汽车配置电子化水平的不断提高,装备有无线通信工具的车辆可以提供安全警报服务、交通拥塞的探测及应用到一些商业领域。在实际的车载运动环境中,每个车辆都可以看成一个移动终端,每个车辆在和基站进行通信的同时,也帮助其他车辆发送信息,形成了车载协同通信系统。功率分配方案对系统性能有重要影响,它的目的是为了减少用户设备能量的消耗和其他用户的干扰,所以如何进行功率分配是车载协同通信系统的研究重点。本论文着重对车载协同通信系统中,在放大转发模式下的功率分配算法进行了研究。首先,从理论上数学推导了功率分配算法公式,提出了一种针对车载系统的改进的功率分配方案,最后通过大量仿真,证明了数学推导的正确性,并且得到一些重要结论。本论文的主要工作如下：1.对车载协同通信系统的基本原理深入研究,分别对协同系统的转发原则,协同伙伴的选择原则,接收端的合并原则进行对比分析,并且做出总结。建立单中继系统的数学模型,用来辅助功率分配算法的推导。2.本文首先推导了在放大转发协同通用模型中,在中继信道模型中的瞬时信道状态信息下,接收端分别采用最大比合并方式,等增益合并方式,加强信噪比合并方式时的单中继系统信道容量或接收端的信噪比,并在发射机与中继器的功率之和为定值的限制之下,在信道容量或信噪比最大化的准则下给出了相应的最佳功率分配方案。在此基础上,提出一种针对车载通信的改进最佳功率分配方案,即基于业务优先级划分的控制策略：给两路分集信号设定不同的优先级,根据实际情况进行优先级取值,在接收端加以叠加,以适应不同的车载环境。3.在曼哈顿移动模型和高斯—马尔可夫移动模型的基础上,提出了一种新的车载通信移动模型。这种模型加入了对实际移动情形和移动方式的考虑。并且针对此模型,对车载协同通信系统的物理层进行仿真。验证了第三章中最佳功率分配方案推导的正确性。更多还原

【Abstract】 Cooperative communication technology is a virtual antenna technology, which is the distillation of the concept of multiple-input multiple-output (MIMO) technology. This technology uses antennas of other users as relays in wireless networks to achieve space diversity and full diversity gain. As the technology of the vehicles continues to improve, vehicles equipped with wireless communication devices are poised to deliver vital services in the form of safety alerts, traffic congestion probing and on-road commercial applications. In vehicular communication system, a car is viewed as a mobile node which can not only communicate with base station but also help other nodes to communicate. This is the vehicular cooperative communication system.Power distribution is an important element in vehicular cooperative communication system, which directly affects the quality of the whole system performance. Its purpose is to reduce the energy loss and interference of the users. This paper focuses on the power allocation algorithms in amplify-and-forward cooperative communication system. Firstly, a mathematical derivation of the power allocation algorithms in vehicular communication is described theoretically. Then a large number of simulations prove the correctness of the mathematical derivation, reaching some important conclusions as well. The main contributions of this paper are as follows:1. Research on the basic principles of cooperative communication in vehicle communication system and analyzes the key techniques such as forwarding principle, partner selection principle, and receiver combing principle. A mathematical model of single relay system is also constructed for the derivation of power allocation algorithms. 2. First, it derives formulas of channel capacity and received signal-to-ratio (SNR) in single relay system based on instantaneous channel state information when the receiver adopts Maximum Ratio Combining, Equal Gain Combining, Fixed Ratio Combining and Enhanced SNR Combining respectively. With a limit power sum of transmitter and repeater, it presents optimal power allocation schemes based on maximum channel capacity principle and maximum SNR principle respectively. On the basis of theoretical research and mathematical derivation, a improved power allocation algorithm about vehicular communication system is given:set different priorities to two signals which are superimposed at the receiving part in order to adapt to different vehicle environments.3. On the basis of Manhattan mobility model and Gauss-Markov mobility model, vehicular mobility model is proposed which is capable of describing car movement in environment where city block places exist. On the basis of theoretical research and vehicular mobility, a lot of simulations have been done, and simulation results prove the correctness of the mathematical derivation of optimal power algorithm scheme.更多还原