【作者】 李国松；

【导师】 周正欧；

【作者基本信息】 电子科技大学 ， 信号与信息处理， 2005， 博士

【摘要】 随着社会进步和发展,无线宽带数字通信系统引起了广大研究人员的浓厚兴趣。在这一系统中,无线信道时延扩展引起的符号间干扰是限制传输性能和信息速率的主要因素之一;而在消除符号间干扰和均衡由无线信道时延扩展引起的频率选择性衰落方面,正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)技术具有明显优势。因此,将OFDM技术应用到无线宽带数字通信系统的研究在最近几年得到了广泛关注。在无线OFDM系统中,接收端通过信道估计获得对信道状态信息的估计;该估计值是接收端均衡由无线信道引起的频率选择性衰落和进行空时解码的必需条件。本论文对无线OFDM系统中的信道估计方面的问题进行了一定研究,获得了以下成果: (1)针对LS信道估计算法时域结果的构成特点和无线信道冲激响应在时域为有限冲激响应的特点,提出对LS信道估计算法的时域结果进行能量检测,实行逆向搜索以获得信道有效阶数估计值的算法,并给出了判决准则以及判决门限。理论分析和计算机仿真表明此算法能够得到很好的无线信道有效阶数估计结果。 (2)介绍了移动视频广播传输系统SMCC-plus的一个重要创新点:无循环前缀和频域导频的OFDM系统;基于该OFDM系统信号时域构成的特点,提出一种实现SMCC-plus系统信道估计和跟踪的算法。通过理论分析和计算机仿真表明,SMCC-plus系统使用本算法能够对相邻两个符号之间的信道特性变化较小的信道进行估计和跟踪。 (3)针对固定波形时间保护间隔OFDM系统接收端OFDM信息符号和信道冲击响应之间不具有循环卷积特性的系统特点,本文提出一种简单有效的信号处理算法对该系统接收端OFDM信息符号和信道冲击响应之间的循环卷积特性进行恢复。理论分析和计算机仿真表明,该算法能够恢复接收端此循环卷积特性;在时延扩展和AWGN信道条件下,系统误符号性能受到的影响微弱。更多还原

【Abstract】 Along with development and improvement of society, many researchers pay much attention to developing system of wireless broadband digital communication. In wireless broadband digital communication, Inter-Symbol Interference (ISI) caused by time disperse of radio channel is one of main factors that limit bandwidth of communicated information and system performance of communication. In receiver, Orthogonal Frequency Division Multiplexing (OFDM) system can easily cancel ISI and equalize frequency-selective fadings that are both caused by time disperse of radio channel. For this, the research aiming to apply OFDM to system of wireless broadband digital communication had received more and more attention in recent years. In system of wireless broadband digital communication based on OFDM, receiver must acquire Channel Status Information (CSI) to equalize frequency-selective fading and implement decoding of Space-Time Code (STC). This paper did some investigations on channel estimation of wireless OFDM system, and achieved the following result and innovation:(1) This paper pays much attention to the character of LS algorithm’s result in time-domain. At the same time, we take the character of wireless Channel Impulse Response (CIR) in time-domain into account. Then we propose to detect energy of CIR’s tap in LS algorithm’s result in time-domain and search the effective order of wireless channel conversely. And we gave out decision criteria and decision threshold. By theoretical analyses and computer simulation, it is indicated that this algorithm shows good performance in estimating effective order of radio channel.(2) A new kind of OFDM system is introduced without time-domain Cyclic Prefix (CP) and frequency-domain Pilot tones in mobile video broadcasting system, SMCC-plus, which is key innovation of SMCC-plus. Based on the time-domain signal structure of this OFDM system, an algorithm is proposed, by which SMCC-plus carries out channel estimation and tracking CSI. By theoretical analysis and computer simulation, it is更多还原