【作者】 周雷；

【导师】 李建东；

【作者基本信息】 西安电子科技大学 ， 通信与信息系统， 2006， 博士

【摘要】 近年来,随着经济、社会和科技的发展以及人们生活水平的提高,人们对通信方式尤其是无线通信的要求也越来越高。随时随地、高速率、高质量的无线数据传输已经成为4G发展的方向。目前,紧张的无线频谱资源已经使频谱利用率成为无线通信系统面临的重要问题。多载波调制技术能有效地解决上述问题并以其高效的频谱利用率和良好的抗多径衰落性能成为4G的核心传输技术之一。正是在这一背景下,本文主要针对基于小波包的新型多载波调制技术及信道估计和均衡技术进行了深入的研究。本文研究工作的主要内容与成果如下:1.提出了基于最优导频信号辅助调制的离散小波包调制(DWPM)系统。我们利用基于LMS(Least Mean Square)算法的最优导频信号辅助调制消除信道干扰的同时,提出了一种新的传输帧结构与之相匹配,然后通过欧式距离检测出解调后的码元,最后推导出基于QPSK调制的离散小波包调制(DWPM)设计方案的误比特率公式,仿真结果表明:在瑞利衰落信道下,DWPM系统的性能要比传统的OFDM系统的性能要好,OPSAM-DWPM系统的性能要比普通的PSAM-DWPM系统的性能要好,最优导频信号辅助调制(OPSAM)的性能要比DQPSK的性能要好并且最优导频信号辅助调制(OPSAM)在一定信噪比范围内没有误码下限。2.提出了一种基于导频信号和最大似然信道估计算法的离散小波包调制(DWPM)系统。我们通过对导频信号结构的特殊设计,来获得信道状态信息,并利用最大似然估计(Maximum Likelihood Estimation)算法估计出最优的信道状态信息,最后,利用基于迫零(Zero Forcing,ZF)算法的H~矩阵消除由多径衰落信道引起的码间干扰(Inter-Symbol Interference, ISI)。通过仿真分析了该系统在多径衰落信道下的性能。仿真结果表明,在多径衰落信道环境中,而且没有信道编码的情况下,带有(QPSK、16QAM、64QAM)调制的DWPM系统的性能要比传统的OFDM系统的性能要好。3.提出了一种自适应分数间隔均衡器(Fractionally -Spaced Equalizers, FSE)的新型离散小波包(DWPM)调制系统。该系统主要是利用LMS算法的分数间隔均衡器来抑制多径衰落信道引起的码间干扰(ISI)并且利用离散小波包调制来并行传输数据。在多径衰落信道和高斯噪声情况下,推导出基于M-ary QAM调制的DWPM设计方案的误码率公式。仿真结果表明在多径衰落信道和高更多还原

【Abstract】 Recently, the requirement for wireless communication is more and more, with the development of economy, society, technology, and the improvement of people’s standard of living. Wireless data transmission whenever and wherever with high speed, high quality is the direction of the development of the fourth generation wireless communication technique. The efficiency of frequency spectrum is very important for wireless communication system because of the lack of frequency spectrum resource. Multicarrier modulation can availably solve the above-mentioned problem. For its high efficiency of frequency spectrum and effectively eliminating the inter-symbol interference (ISI) resulted from the multipath fading channel, multicarrier modulation becomes one of the important technologies of the fourth generation wireless communication.In the above-mentioned background, multicarrier modulation based on wavelet packet, channel estimation and equalization technologies are studied in this dissertation. The major achievements and results are outlined as follows:1. Discrete Wavelet Packet Modulation (DWPM) System based on ML (Maximum Likelihood) algorithm and Optimum Pilot Symbol Assisted Modulation (OPSAM) is studied for Rayleigh Fading Channels. The channel interference is suppressed by OPSAM based on LMS (Least Mean Square) algorithm and the demodulated symbols are detected by ML detecting algorithm and novel transmission frame structure is proposed. Finally, an expression for the probability of error for a DWPM scheme on QPSK is derived in the presence of flat fading channel and Gaussian noise. It is demonstrated by simulation results that in the flat fading channels and Guassian noise, the performance of the proposed scheme is better than that of the traditional the OFDM scheme; the proposed scheme can provide greater immunity to flat fading channels and Guassian noise than both the DQPSK DWPM scheme and the normal-PSAM (Pilot Symbol Assisted Modulation) DWPM scheme; the performance of the OPSAM is better than that of the DQPSK modulation and the error floor of the OPSAM is inexistent within SNR limits.2. Novel DWPM (Discrete Wavelet Packet Modulation) system with blind channel更多还原