【作者】 杨娇瑜；

【导师】 朱刚；

【作者基本信息】 北京交通大学 ， 通信与信息系统， 2007， 硕士

【摘要】 本文首先研究了无线通信信道小尺度衰落特性,并对多径衰落信道进行仿真。小尺度衰落包括多径效应和多普勒频移等问题。多径效应造成的码间干扰会极大地降低通信系统的性能,而自适应均衡是时变无线移动信道中对抗码间干扰的一项重要技术。在研究自适应均衡的原理、结构和算法的基础上,本文深入研究了最大似然序列估计(MLSE)。在无线信道中应用MLSE存在两个问题,即存在较大的判决延迟和较高的计算复杂度。判决延迟在高速移动无线信道中影响尤为严重。本文研究分析了减少MLSE判决延迟和计算复杂度的多种改进方法,并将逐幸存处理算法(PSP)和基于簇的序列估计(CBSE)算法作为研究的重点。在保证性能的前提下,PSP算法减少了判决延迟,而CBSE算法大大减少计算复杂度。本文详细介绍了这两种算法的基本原理和实现方法。针对在无线时变信道中具体应用该算法时存在的问题,尤其是在高速移动且快速时变环境中应用时出现的问题,提出了改进方法,并结合仿真,分析比较其性能,最后给出详细的计算复杂度比较。图38幅,表10个,参考文献39篇。更多还原

【Abstract】 First of all, this paper does a lot of research on the characteristics of mobile wireless channel, especially on the small-scale fading. Simulation of multipath fading channel is also presented. Multipath effect and Doppler shift are two troublesome problems in mobile wireless channel. Inter symbol interference (ISI) caused by multipath effect is a major factor to degrade the performance of modern digital communication systems. Adaptive equalization is an important technique to combat the ISI in time varying mobile wireless channel. This paper focuses on Maximum Likelihood Sequence Estimate (MLSE), based on the widely study of basic principle, structure and algorithms of adaptive equalization.When MLSE is put into real practice, decision delay and computational complexity are two problems to be solved. The decision delay is terribly serious in high speed mobile wireless channel. Many improvement methods of MLSE are discussed. This paper mainly concerns two of them, i.e., PSP and CBSE. Per-Survivor-Processing (PSP) is an effective way to solve the problem of decision delay. Cluster Based Sequence Estimation (CBSE) is an effective solution to reduce the computational complexity of classic MLSE.When those schemes are used in the mobile wireless communication system, especially in the high speed mobile environment, some problems come out and solutions to them are proposed in this paper. Analysis of performance and complexity are also presented, combined with simulation.更多还原