【作者】 宋立军；

【导师】 李少谦； 唐友喜；

【作者基本信息】 电子科技大学 ， 通信与信息系统， 2005， 博士

【摘要】 由于信道的时变特性、用户的快速移动等原因,在某些无线应用环境中,对信道的精确估计十分困难,在这种情况下,差分检测成为了很有吸引力的一种方案,差分检测技术可以克服相干检测中载波相位难以恢复的缺点,同时简化了接收机设计。当前,多载波无线通信技术得到了广泛的研究,本论文从差分检测的实现方式出发,研究了差分检测方案在三种多载波通信系统:正交频分复用系统、多载波频域扩频系统以及二维扩频通信系统中的应用。 本文首先介绍了多载波通信系统的特点以及差分检测技术的研究现状,总结了需要进一步解决的问题。 本文的第二部分针对正交频分复用系统中的差分检测方式进行了研究。对于差分检测正交频分复用系统,无论采用频域差分检测还是时域差分检测,需要考虑信道不同的衰落条件。时域差分检测的性能已有文献进行了分析,而频域差分检测的性能分析还十分不完善,因此本文在不同的衰落信道条件下,分析了频域差分检测正交频分复用系统的性能,并与时域差分检测正交频分复用系统的性能进行了比较,同时,分析了符号间干扰对频域差分检测正交频分复用系统的影响,研究了多字符差分检测在频域差分检测正交频分复用系统中的应用。 码片级差分检测方法是在直接序列扩频系统中被提出的,与一般的基于数据符号进行差分检测不同,码片级差分检测在扩频码片上进行差分检测,并使直接序列扩频系统具有抵抗信道时间选择性衰落的能力。本文第三部分提出了多载波频域扩频码片级差分检测的方法,并从理论上分析了多载波频域扩频码片级差分检测的误码率性能,讨论了信道参数对多载波频域扩频码片级差分检测性能的影响,得到了多载波频域扩频系统具有抵抗信道频率选择性衰落能力的结论,同时,本文提出了一种多符号频域扩频码片级差分检测方法,该方法的目的是为了减少载波间干扰对码片级差分检测的影响,从而进一步改善了多载波频域扩频码片级差分检测在时间选择性较强的信道中的性能。 二维扩频通信是近年来提出的新的扩频通信方式,由于二维扩频系统从时域和频域分别对数据进行扩展频谱,因此它同时具有时域扩频和频率扩频通信系统的特点。本文最后针对二维扩频通信系统,提出了一种导引辅助的相干解调方法和一种时频码片级差分检测方法,并从理论上分析了这两种方法的误码率性能,同时对两种方法的性能进行了对比,分析结果表明时频码片级差分检测同时具有抵抗信道时间和频率选择性衰落的能力。更多还原

【Abstract】 Because of the time variation of channel, getting the exact channel estimation and good synchronization is difficult for the receiver, the differential detection enables the receiver to detect the data symbols without knowledge of the reference phase, so it can be applied into these environments. Multi-carrier wireless communications have been obtained extensive research in these years. This thesis will respectively research the performances of differential detection on the three multi-carrier wireless communications systems: Orthogonal frequency division multiplexing (OFDM) system, multi-carrier frequency domain spread spectrum (MC-FDSS) system and Two-Dimension Spread Spectrum (2D-SS) system.We firstly introduced the characteristics of multi-carrier wireless communications and the research background of differential detection, and summarized the questions needed to be further researched.Research on the performance of differential detection in OFDM system will be introduced in the second part of this thesis. For OFDM system, the differential detection can be carried out either in time domain or in frequency. There are more results of research on the performance of time domain differential detection (TDDD) OFDM system than that of frequency domain differential detection (FDDD) OFDM system, so the further research on the FDDD is a necessary part of differential detection OFDM system. In this thesis, the performance of FDDD in different fading channels was firstly analyzed, and then we compare the results with the performance of TDDD, further more, the effect of intersymbol interference on the performance of FDDD was analyzed, at last, we obtained the results of the research on the performance of multiple-symbol differential detection FDDD system.Chip-level differential detection (CLDD) was proposed in the direct sequence spread spectrum (DS-SS) system, in which the differential encoding/detection is implemented on chips rather than on data symbols, and it had been found to make the DS-SS system resistant to the time-selective fading. In the third part of this thesis, The CLDD was proposed in MC-FDSS system, and the bit error rate (BER) performance of CLDD in MC-FDSS was analyzed, and the results of research indicated that CLDD made the MC-FDSS system resistant to the frequency-selective fading. At last, we更多还原