非合作通信下OFDM系统的盲均衡方法研究

发布时间：2018-06-25 14:26

本文选题：非合作通信 + 正交频分复用　；参考：《西安电子科技大学》2014年硕士论文

【摘要】：军事电子侦察,军事对抗是未来信息战的基础,然而无线信道的多径衰落、信号干扰等因素导致信号产生了严重的码间串扰。为了检测和恢复有用信号,针对这种特殊环境的非合作通信系统,研究人员尝试通过信号检测技术、调制识别、盲均衡等技术来降低码间干扰,抵抗信道的影响,取得了较好的效果。盲均衡是一种新兴的自适应均衡技术,它仅需要接收序列本身的统计信息来均衡信道特性,能够很好地应用于非合作通信。正交频分复用(OFDM)技术是典型的多载波调制方式之一,不仅能够抵抗多径带来的干扰,而且还可以有效地提高系统的带宽利用率。论文基于OFDM多载波系统模型,在多径衰落的信道条件下,研究了非合作通信中OFDM的盲均衡技术,在此基础上,采用数据复用以及变步长迭代处理了非合作接收中短数据的问题,分析了改进后算法性能。论文主要工作如下：1.基于OFDM多载波调制,建立了基于Bussgang性质的盲均衡模型,给出了MCMA算法、MMM A算法和DD算法的均衡表达式。进而得到MMMA-DD多模均衡算法的切换准则和算法框图。比较了MMMA_DD和MCMA算法均衡后的星座图,误符号率曲线,均方误差,剩余码间干扰；研究了不同信噪比、不同多径信道条件下MMMA_DD多模算法的性能。研究表明,MMMA_DD算法比MCMA算法性能更优异。并且MMMA_DD算法在不同信噪比,不同多径信道条件下都有良好的均衡效果。2.在非合作通信中,针对短数据难以收敛的问题,选择分段数据复用技术；为了进一步加快收敛速度,提高均衡性能,提出了基于剩余符号间干扰(ISI)的变步长迭代技术。在短数据输入的条件下,验证了复用技术对MMMA_DD的算法均衡性能的改善。研究了在变步长条件下,MMMA_DD算法的收敛性能。仿真结果表明,复用技术和变步长技术可以使MMMA_DD算法获得很好的均衡效果。本论文研究成果为非合作通信系统多载波调制的均衡提供一定的理论参考。
[Abstract]:Military electronic reconnaissance and military confrontation are the basis of future information warfare. However, the multipath fading of wireless channel and signal interference cause serious inter-symbol crosstalk. In order to detect and recover useful signals, researchers try to reduce inter-symbol interference (ISI) and resist the influence of channel by signal detection, modulation recognition, blind equalization and so on. Good results have been achieved. Blind equalization is a new adaptive equalization technique. It only needs the statistical information of the received sequence to equalize the channel characteristics. It can be applied to non-cooperative communication. Orthogonal Frequency Division Multiplexing (OFDM) is one of the typical multicarrier modulation schemes, which can not only resist the interference caused by multipath, but also improve the bandwidth efficiency of the system. Based on the OFDM multicarrier system model, the blind equalization technology of OFDM in non-cooperative communication is studied under the condition of multipath fading channel. On this basis, data multiplexing and variable step size iteration are used to deal with the problem of non-cooperative receiving medium and short data. The performance of the improved algorithm is analyzed. The main work of this paper is as follows: 1. The blind equalization model based on Bussgang property is established based on OFDM multicarrier modulation, and the equalization expressions of MCMA algorithm and DD algorithm are given. Then the switching criterion and block diagram of MMMA-DD multimode equalization algorithm are obtained. The constellation diagram, symbol error rate curve, mean square error and residual inter-symbol interference (ISI) of MMMADD and MCMA algorithms are compared, and the performance of MMMASP multimode algorithm with different signal-to-noise ratio and multipath channel is studied. The results show that MMMADD algorithm has better performance than MCMA algorithm. Moreover, MMMA _ s _ DD algorithm has good equalization effect under different SNR and multi-path channels. In non-cooperative communication, the piecewise data multiplexing technique is chosen to solve the problem that short data is difficult to converge. In order to further accelerate the convergence speed and improve the equalization performance, a variable step size iterative technique based on residual Intersymbol interference (ISI) is proposed. Under the condition of short data input, the performance of MMMADD algorithm is improved by multiplexing technology. The convergence performance of MMMADD algorithm with variable step size is studied. The simulation results show that the multiplexing technique and variable step size technique can make MMMADD algorithm achieve a good equalization effect. This paper provides a theoretical reference for multi-carrier modulation equalization in non-cooperative communication systems.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.53

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