时变信道下的OFDM载波间干扰抑制技术研究

发布时间：2018-04-11 21:18

本文选题：正交频分复用 + 载波间干扰　；参考：《哈尔滨工程大学》2014年硕士论文

【摘要】：正交频分复用(OFDM)技术已经成为高速水声通信中的重要研究课题之一。载波间的正交性一方面为OFDM带来了很多优势,例如频谱利用率高、抗多径能力强,便于实现等,另一方面也使得OFDM系统对信道的时变性十分敏感。水声信道的随机时变,节点的相对运动等因素都容易破坏载波间的正交性而引起载波间干扰,使通信系统的性能恶化。常见的线性均衡方法往往假设信道在一个OFDM符号周期内是不变的,不适应于快速时变的水声信道。因而,时变信道下的信道估计与均衡技术、载波间干扰抑制技术等已经成为了水声通信领域的研究热点。本文主要研究了水声时变信道下的载波间干扰抑制技术,所做的工作主要有:1.总结了载波间干扰抑制技术的研究现状,分析了 OFDM系统在水声通信应用中的优缺点以及水声信道的特性,并对水声时变信道进行了建模。2.深入研究了 OFDM系统中的载波间干扰抑制问题,介绍了水声通信中ICI的主要成因并推导其数学模型,通过理论分析和计算机仿真探究了 ICI对水声通信系统性能的影响。重点针对信道时变引起的ICI进行了深入探讨,并对现有的多普勒估计及补偿技术进行了研究。3.研究了基于时变信道估计的并行迭代ICI消除算法,讨论了分段近似线性信道模型的理论基础及具体应用。通过仿真和外场试验分析对比了并行迭代ICI消除算法,与线性均衡器,例如LS,DFT,MMSE等在水声时变信道下的性能。4.结合判决二次均衡算法以及基于差分编码的ICI自消除算法对上述并行迭代ICI消除算法进行了改进,分析了其原理及实现方法,并通过计算机仿真进行验证。
[Abstract]:Orthogonal Frequency Division Multiplexing (OFDM) technology has become one of the most important research topics in high speed underwater acoustic communication.On the one hand, the orthogonality between carriers brings many advantages to OFDM, such as high spectral efficiency, strong anti-multipath ability, easy to implement, etc. On the other hand, it also makes the OFDM system very sensitive to channel time variability.The random time-varying of underwater acoustic channel and the relative motion of nodes are all easy to destroy the orthogonality between carriers and cause inter-carrier interference and worsen the performance of communication system.Common linear equalization methods often assume that the channel is invariant in a OFDM symbol period and is not suitable for fast time-varying underwater acoustic channels.Therefore, channel estimation and equalization in time-varying channels, intercarrier interference suppression and so on have become the research hotspot in underwater acoustic communication field.In this paper, the intercarrier interference (ICI) suppression technique in underwater acoustic time-varying channels is studied, and the main work done is as follows: 1.The research status of intercarrier interference suppression technology is summarized. The advantages and disadvantages of OFDM system in underwater acoustic communication and the characteristics of underwater acoustic channel are analyzed.In this paper, the intercarrier interference suppression problem in OFDM system is deeply studied, the main cause of formation of ICI in underwater acoustic communication is introduced and its mathematical model is deduced. The influence of ICI on the performance of underwater acoustic communication system is explored by theoretical analysis and computer simulation.The ICI caused by time-varying channel is discussed in detail, and the existing Doppler estimation and compensation techniques are studied.The parallel iterative ICI cancellation algorithm based on time-varying channel estimation is studied. The theoretical basis and practical application of piecewise approximate linear channel model are discussed.The parallel iterative ICI cancellation algorithm is compared with that of linear equalizer such as LSS-DFT MMSE in underwater acoustic time-varying channels by simulation and field experiments.Combined with the decision quadratic equalization algorithm and the ICI self-cancellation algorithm based on differential coding, the parallel iterative ICI cancellation algorithm is improved. The principle and implementation method are analyzed and verified by computer simulation.
【学位授予单位】：哈尔滨工程大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.3

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