OFDM调制系统峰均比抑制算法及FPGA实现

发布时间：2018-06-05 19:54

本文选题：正交频分复用 + 非线性失真　；参考：《西安电子科技大学》2014年硕士论文

【摘要】：正交频分复用技术(Orthogonal Frequency Division Multiplexing,OFDM)是一类将高速数据流划分成低速数据流同时采用多个子载波并行传输数据的技术。该技术利用多个彼此之间相互正交的子载波传输信息,与传统的单载波调制技术相比其在频谱效率方面有了很大程度的改善。由于同时还具有很好的抗多径衰落能力以及较强的抗符号间干扰(Inter Symbol Interference,ISI)能力,该技术已成为新一代移动通信的热点研究技术。作为OFDM系统的主要问题之一,峰值均值功率比(Peak-to-Average Power Ratio,PAPR)过高的现象阻碍了OFDM技术的发展。因为每个OFDM符号由多个子载波上传输的的信号相互叠加而成,当多个子载波上的信号相位相同或相似时,叠加后就会产生峰值功率较大的OFDM信号。把这种动态范围很大的信号送入非线性器件时,将会使带内失真和带外干扰都增加,严重影响OFDM系统的性能。针对高峰均比的问题,本文详细研究了四种非常具有代表性的OFDM峰均比抑制算法:限幅法、压缩扩展变换法、选择映射法和部分传输序列法。首先着手于限幅法,指出传统的限幅算法有峰值再增长的缺陷,进而研究限幅滤波算法和改进之后的迭代限幅滤波算法,在对算法的原理分析和对其性能的Matlab仿真分析的基础上,指出迭代限幅滤波算法抑制峰均比效果明显,但是误码率性能一般;然后分析了压缩扩展变换法,在研究其基本原理的基础上选择μ率压扩算法进行了Matlab仿真,结果表明此算法虽然实现简单,但是带外干扰问题比较严重,导致误码率增大;针对前两种方法会导致系统误码性能下降的缺点,本文还着重分析了选择映射法和部分传输序列法的基本原理,并通过对各个算法性能的Matlab仿真分析指出两种算法都会增加系统的复杂度。最后,在算法性能和实现复杂度的综合考虑之下,本文采用了迭代限幅滤波算法进行方案设计,并在FPGA上进行实现。
[Abstract]:Orthogonal Frequency Division Multiplexing (OFDM) is a kind of technology which divides high speed data stream into low speed data stream and uses multiple subcarriers to transmit data in parallel. This technique utilizes several orthogonal sub-carriers to transmit information, which greatly improves the spectral efficiency compared with the traditional single-carrier modulation technique. Due to its good anti-multipath fading ability and strong inter-symbol interference (ISI) capability, this technology has become a hot research technology in the new generation of mobile communication. As one of the main problems in OFDM systems, the high peak-to-average power ratio (PAPR) hinders the development of OFDM technology. Because each OFDM symbol is superposed by the signals transmitted on multiple sub-carriers, when the phase of the signals on multiple sub-carriers is the same or similar, the OFDM signals with high peak power will be produced after superposition. The in-band distortion and out-of-band interference will be increased when the signal with a large dynamic range is fed into the nonlinear device, which will seriously affect the performance of OFDM system. Aiming at the problem of peak-to-average ratio (PAPR), four kinds of PAPR suppression algorithms for OFDM are studied in detail: limiting method, compression expansion transform method, selective mapping method and partial transmission sequence method. Firstly, the limitation method is introduced, and the limitation algorithm is pointed out, and then the amplitude limiting filtering algorithm and the improved iterative limiting filtering algorithm are studied. Based on the analysis of the principle of the algorithm and the Matlab simulation analysis of its performance, it is pointed out that the peak to average ratio (APR) of the iterative limiting filtering algorithm is obvious, but the performance of the bit error rate (BER) is general, and then the compression expansion transform method is analyzed. On the basis of studying its basic principle, the simulation results show that the algorithm is simple, but the problem of out-of-band interference is serious, which leads to the increase of bit error rate (BER). In view of the shortcoming that the first two methods will lead to the deterioration of the system error performance, the basic principles of the selective mapping method and the partial transmission sequence method are also analyzed in this paper. The Matlab simulation results show that both algorithms can increase the complexity of the system. Finally, under the consideration of the performance and complexity of the algorithm, this paper uses the iterative limiting filter algorithm to design the scheme, and implements it on FPGA.
【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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