【作者】 陈伍；

【导师】 方旭明；

【作者基本信息】 西南交通大学 ， 通信与信息系统， 2010， 硕士

【摘要】 随着我国新一轮大规模基础建设的兴起,以高速铁路为代表的高速移动环境下无线宽带业务需求也随之不断的增长,高速移动环境下的通信系统引起了人们越来越多的关注。在高速移动环境下,无线通信具有频率偏移较大、信道条件变化较快等特点,现有的无线资源分配方式,已不能完全满足高速移动用户的需求。当用户高速移动时,其信道质量变化较快,短时间内可能经历深度衰落,若此时仍采用和低速移动用户相同的资源分配方式,将导致一段时间内高速移动用户误码性能的急剧恶化。因此,需要在充分考虑高速、低速移动用户信道变化的特点的基础上结合其服务质量(Quality of Service, QoS)需求进行资源分配。本文主要研究OFDMA-MIMO系统中在保证用户QOS需求的前提下充分利用用户的无线信道变化特性,合理的分配无线资源,优化系统性能。本文在首先介绍了高速移动环境和相关技术背景及原理,并简单分析了快速变化的信道条件对自适应调制编码技术的影响。其次,介绍了正交振幅调制(Quadrature Amplitude Modulation, QAM)技术的相关原理,并分析了QAM信号星座图的最小欧氏距离与误码率以及QAM信号能量间的关系。然后分析给出了高速、低速移动用户的信号预处理方式。同时,结合高速、低速移动用户的信号预处理方式,详细介绍了高速、低速移动用户资源分配的依据——满足用户误码要求的最小欧氏距离门限值的计算方式,并据此提出了一种以贪婪算法为基础的区分用户移动速度的无线资源分配算法。最后,介绍了OFDMA-MIMO系统相关仿真参数,搭建了系统仿真平台,并结合了二维时频资源分配特性对所提算法进行了仿真分析与评价。仿真分析表明,该算法不仅能够很好的满足低速用户的QoS需求,并能在保证高速移动用户的QoS需求的情况下,为高速、低速移动用户合理的分配无线资源,优化了系统性能。更多还原

【Abstract】 With the coming of the new round of large-scale infrastructure investment, we demand for wireless broadband services in the high-speed mobile environment which is represented by the continuous development of high-speed railway. Wireless communication system in the high-speed mobile environment has attracted more and more attention. Due to the constraints of larger frequency offset, fast channel variation and other factors, the existed wireless resources allocation schemes cannot satisfy the QoS requirements of users when they move fast.When a user moves fast, he/she may experience deep fading in a short time because of the fast channel variation, which will result in the sharp deterioration of BER performance. Therefore, resources allocation needs to consider the QoS requirements of users while the characteristics of the high-speed mobility are taken into account. This thesis focuses on how to allocate radio resource reasonably, in order to optimize system performance on the basis of ensuring the QoS requirements.We firstly introduce the characteristics of high-speed mobile environment and the related technical background. On this basis, the impact to AMC technology due to the fast channel variation is analyzed. Then we introduce the theory of QAM technology, and discusse the relationship between the minimum Euclidean distance of the QAM signal constellation and the BER as well as the energy of the QAM signal. Futhermore, we give the signal preprocessing method of high-speed user and low-speed user. Based on this, we detail the principles of resource allocation for high-speed and low-speed users, which calculates the threshold of minimum Euclidean distance that satisfies the requirements of user BER. After that, based on greedy algorithm, a resources allocation algorithm which distinguishes high-speed and low-speed users is proposed. Finally, we introduce the related simulation parameters of OFDMA-MIMO system and build up system simulation platform. Combined with the characteristic of the two-dimensional time-frequency, we give the simulation and evaluation results. The simulation results show that this algorithm can not only meet the QoS requirements of low-speed users, but also ensure the QoS demand of high-speed users through allocating radio resource reasonably which aims to optimize system performance.更多还原