基于OFDM的空时分组码的研究与性能仿真

发布时间：2018-04-14 23:34

本文选题：空时分组码 + OFDM技术　；参考：《东北大学》2014年硕士论文

【摘要】：空时编码技术是实现宽带无线数据通信的一种极有潜力的技术,它将信道编码、调制、发送和接收分集有机结合,能够有效地提高衰落信道环境下通信系统的抗噪声性能。空时分组码(Space Time Block Coding, STBC)以其结构简单、易于实现且性能较好的特点,成为了人们研究的热点。但是目前对空时分组码的研究大多是在平坦衰落信道下进行的,本文利用正交频分复用(Orthogonal Frequency Division Multiplexing, OFDM)技术有效对抗多径衰落的特点,详细分析了频率选择性衰落信道下的基于OFDM的空时分组码技术STBC-OFDM的系统结构和编译码方法。本文首先紧紧围绕空时编码技术,阐述了空时分组编码技术的基本思想和原理,给出了准静态平坦衰落信道下空时码的设计准则,对空时分组码的编译码原理、特点进行了全面的分析。深入研究了传统的准正交空时分组码的编译码方法,并针对其不能实现满分集增益的缺点,将准正交空时编码技术与星座旋转和矩阵旋转相结合,提出了一种改进的可以实现全速率满分集的空时分组编译码方案。论文还对OFDM的基本原理和循环前缀进行仔细探讨,通过对数据块进行添加循环前缀和去循环前缀操作,以及IFFT和FFT变换,可以将频率选择性衰落信道转变为平坦衰落信道。本文分析了空时编码技术与正交频分复用技术相结合的理论基础,给出了基于OFDM的空时分组编码系统的系统结构,研究和分析了STBC-OFDM系统的编译码原理,并提出了一种带有预编码模块的系统的设计方法。最后,对于平坦衰落信道下的空时编码系统和频率选择性衰落信道下的基于OFDM的空时编码系统,在不同的编码方式、不同的调制方式、不同的译码算法下进行了性能仿真。仿真结果表明,平坦衰落信道下改进的编码方案,能够保证数据以全速率传输,同时可以获得满分集增益,其性能比传统的准正交编码方案优越。频率选择性衰落信道下,基于OFDM的空时编码系统在加入预编码模块之后,可以以较低的译码复杂度利用最大似然译码算法进行译码,其误码率与QOSTBC-OFDM系统相比在不同的调制方式有不同程度的降低。
[Abstract]:Space-Time coding (STC) is a promising technique for wideband wireless data communication. It combines channel coding, modulation, transmission and reception diversity, and can effectively improve the anti-noise performance of communication systems in fading channels.Space Time Block coding (STBC) has become a hot topic for its simple structure, easy implementation and good performance.However, most of the researches on space-time block codes are carried out in flat fading channels. In this paper, orthogonal Frequency Division Multiplexing (OFDM) is used to effectively combat multipath fading.The system structure and encoding and decoding methods of space-time block code (STBC-OFDM) technology based on OFDM in frequency-selective fading channel are analyzed in detail.In this paper, the basic idea and principle of space-time block coding are expounded, and the design criteria of space-time codes in quasi-static flat fading channels are given. The encoding and decoding principle of space-time block codes is discussed.The characteristics are analyzed comprehensively.In this paper, the traditional encoding and decoding methods of quasi-orthogonal space-time block codes are deeply studied, and the quasi-orthogonal space-time coding technique is combined with the rotation of constellation and matrix rotation, aiming at the disadvantage that it can not realize the gain of full division set.An improved space-time block encoding and decoding scheme with full rate full division set is proposed.The basic principle and cyclic prefix of OFDM are also discussed in detail. By adding cyclic prefix and removing cyclic prefix to data block and transforming IFFT and FFT, frequency selective fading channel can be transformed into flat fading channel.In this paper, the theoretical basis of combining space-time coding technology with orthogonal frequency division multiplexing technology is analyzed, the system structure of space-time block coding system based on OFDM is given, and the encoding and decoding principle of STBC-OFDM system is studied and analyzed.A design method of the system with precoding module is presented.Finally, the performance of space-time coding system based on OFDM in flat fading channel and frequency selective fading channel is simulated in different coding mode, different modulation mode and different decoding algorithm.The simulation results show that the improved coding scheme in flat fading channel can guarantee the data transmission at full rate and obtain full diversity gain, and its performance is superior to the traditional quasi-orthogonal coding scheme.In frequency-selective fading channel, the space-time coding system based on OFDM can be decoded by maximum likelihood decoding algorithm with low decoding complexity after adding precoding module.Compared with the QOSTBC-OFDM system, the bit error rate (BER) is reduced in different modulation modes.
【学位授予单位】：东北大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.53

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