基于TR-OFDM通信系统中的ULDS抑制研究
发布时间：2019-06-21 08:47
【摘要】：在正交频分复用(OFDM,Orthogonal Frequency-division Multiplexing)通信中,加入循环前缀(CP,Cyclic Prefix)是为了确保其子载波在符号周期内的彼此正交,以及多径引起的符号间干扰(ISI,Intersymbol Interference)减小。在普通通信环境下,信道的最大时延扩展(MDS,Maximum Delay Spread)长度小于CP时长,则能够有效的减小ISI,通信性能可得以保证。然而,对于极端复杂的多径环境,诸如航天舱、地下隧道、潜艇舱等混响腔环境,MDS将远大于常规的CP时长,以致传输的信号波形重叠并且相互影响。如果CP的时长不变,则其抑制的ISI能力将失效、系统性能显著恶化。如果将CP的时长变大,则OFDM通信的频谱资源利用率将大大降低,而且其性能也将下降。本文基于时间反演(TR,Time Reversal)的时空聚焦机制,研究OFDM通信系统中超长时延扩展(ULDS,Ultra-long Delay Spread)抑制的方法。本文重点研究ULDS信道以及有效的均衡方式。论文的主要工作如下:首先,对OFDM通信中由于多径引起的符号间干扰的抑制方法做了调研分析,说明了本论文研究的必要性。介绍了TR广泛的应用领域。TR技术的空时聚焦特性以及抑制信道时延扩展的能力,使其对ULDS信道下OFDM系统性能的研究具有重要的意义。其次,对复杂环境中多输入多输出(MIMO,Multi-input Multiple Output)信道相关性以及TR与MIMO技术结合的通信性能进行研究。另外,研究了ULDS信道主瓣与最大旁瓣之比(MSR,Main to Maximum Side-lobe Ratio),分析了在ULDS信道下TR-OFDM的通信性能。得到了在特定的MSR情况下具有良好的通信性能的结论。对前置TR和后置TR在复杂的通信环境以及简单的通信环境中进行仿真研究,得出在ULDS信道下前置TR稍微优于后置TR的结论。最后,对排序连续干扰消除(OSIC,Ordered Successive Interference Cancellation)方法进行理论分析。在此基础上,本文提出TR与OSIC结合的检测方法,并且对比不同排序检测的性能。另外,本文提出TR与最小二乘(RLS,Recursive Least Squares)结合的均衡技术。通过Matlab仿真分析,得出TR-RLS均衡技术对ULDS的抑制具有一定的作用。总结了本论文的工作内容,对下一步研究指出方向。
[Abstract]:In orthogonal Frequency Division Multiplexing (OFDM,Orthogonal Frequency-division Multiplexing) communication, cyclic prefix (CP,Cyclic Prefix) is added to ensure that its subcarriers are orthogonal to each other in the symbol period, and the inter-symbol interference (ISI,Intersymbol Interference) caused by multi-path is reduced. In the ordinary communication environment, the maximum delay spread of the channel (the MDS,Maximum Delay Spread) length is less than the CP time length) can effectively reduce the ISI, communication performance can be guaranteed. However, for extremely complex multi-path environments, such as space capsule, underground tunnel, submarine cabin and other reverberation cavity environment, MDS will be much longer than the conventional CP, so that the transmitted signal waveforms overlap and affect each other. If the length of CP is constant, the ability of ISI suppression will fail and the performance of the system will deteriorate significantly. If the time length of CP is increased, the spectrum resource efficiency of OFDM communication will be greatly reduced, and its performance will also be degraded. In this paper, based on the temporal and spatial focusing mechanism of time inversion (TR,Time Reversal), the method of super long delay spread (ULDS,Ultra-long Delay Spread) suppression in OFDM communication systems is studied. In this paper, the ULDS channel and effective equalization methods are studied. The main work of this paper is as follows: firstly, the suppression methods of inter-symbol interference caused by multi-path in OFDM communication are investigated and analyzed, and the necessity of this paper is explained. This paper introduces the wide application field of TR. The space-time focusing characteristics of tr technology and the ability to suppress channel delay spread make it important to study the performance of OFDM system in ULDS channel. Secondly, the multi-input multiple-output (MIMO,Multi-input Multiple Output) channel correlation and the communication performance of the combination of TR and MIMO technology in complex environment are studied. In addition, the ratio of main lobe to maximum sidelobe in ULDS channel (MSR,Main to Maximum Side-lobe Ratio),) is studied. The communication performance of TR-OFDM in ULDS channel is analyzed. It is concluded that the communication performance is good in the case of specific MSR. The pre-TR and post-TR are simulated in complex communication environment and simple communication environment, and it is concluded that the pre-TR is slightly better than the post-TR in ULDS channel. Finally, the sequential interference cancellation (OSIC,Ordered Successive Interference Cancellation) method is analyzed theoretically. On this basis, this paper proposes a combination of TR and OSIC detection method, and compares the performance of different sort detection. In addition, an equilibrium technique combining TR with least squares (RLS,Recursive Least Squares) is proposed in this paper. Through Matlab simulation analysis, it is concluded that TR-RLS equilibrium technology plays a certain role in ULDS suppression. The work content of this paper is summarized, and the direction of the next research is pointed out.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.53
本文编号：2503946
[Abstract]:In orthogonal Frequency Division Multiplexing (OFDM,Orthogonal Frequency-division Multiplexing) communication, cyclic prefix (CP,Cyclic Prefix) is added to ensure that its subcarriers are orthogonal to each other in the symbol period, and the inter-symbol interference (ISI,Intersymbol Interference) caused by multi-path is reduced. In the ordinary communication environment, the maximum delay spread of the channel (the MDS,Maximum Delay Spread) length is less than the CP time length) can effectively reduce the ISI, communication performance can be guaranteed. However, for extremely complex multi-path environments, such as space capsule, underground tunnel, submarine cabin and other reverberation cavity environment, MDS will be much longer than the conventional CP, so that the transmitted signal waveforms overlap and affect each other. If the length of CP is constant, the ability of ISI suppression will fail and the performance of the system will deteriorate significantly. If the time length of CP is increased, the spectrum resource efficiency of OFDM communication will be greatly reduced, and its performance will also be degraded. In this paper, based on the temporal and spatial focusing mechanism of time inversion (TR,Time Reversal), the method of super long delay spread (ULDS,Ultra-long Delay Spread) suppression in OFDM communication systems is studied. In this paper, the ULDS channel and effective equalization methods are studied. The main work of this paper is as follows: firstly, the suppression methods of inter-symbol interference caused by multi-path in OFDM communication are investigated and analyzed, and the necessity of this paper is explained. This paper introduces the wide application field of TR. The space-time focusing characteristics of tr technology and the ability to suppress channel delay spread make it important to study the performance of OFDM system in ULDS channel. Secondly, the multi-input multiple-output (MIMO,Multi-input Multiple Output) channel correlation and the communication performance of the combination of TR and MIMO technology in complex environment are studied. In addition, the ratio of main lobe to maximum sidelobe in ULDS channel (MSR,Main to Maximum Side-lobe Ratio),) is studied. The communication performance of TR-OFDM in ULDS channel is analyzed. It is concluded that the communication performance is good in the case of specific MSR. The pre-TR and post-TR are simulated in complex communication environment and simple communication environment, and it is concluded that the pre-TR is slightly better than the post-TR in ULDS channel. Finally, the sequential interference cancellation (OSIC,Ordered Successive Interference Cancellation) method is analyzed theoretically. On this basis, this paper proposes a combination of TR and OSIC detection method, and compares the performance of different sort detection. In addition, an equilibrium technique combining TR with least squares (RLS,Recursive Least Squares) is proposed in this paper. Through Matlab simulation analysis, it is concluded that TR-RLS equilibrium technology plays a certain role in ULDS suppression. The work content of this paper is summarized, and the direction of the next research is pointed out.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.53
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