直接序列扩频系统中多用户检测技术的研究
发布时间：2018-07-20 18:41
【摘要】：近年来，3G移动通信产业发展迅速，CDMA技术作为3G核心技术有着容量大、保密性好、频谱利用率较高的优势。然而，CDMA系统作为一种直接序列扩频系统，由于用户的随机接入和扩频码互相关的非零性，各用户信号之间会产生多址干扰，导致系统性能的恶化，限制了系统的容量。多址干扰不同于一般噪声，它携带着扩频码相关信息，在一定程度上具有可预测性，多用户检测技术运用了这一特点，一定程度上降低甚至消除了多址干扰。本文围绕直接序列扩频系统中的多用户检测技术展开相关研究。 首先，本文针对直接序列扩频系统建立了同步、异步多用户检测模型，并分析了检测性能测度和多用户检测经典算法基本原理、特点。 其次，具体分析了现有干扰消除检测器和它们的优缺点，引入基于用户可靠性的改进的串行干扰消除（RB-SIC）检测器，并将其应用到CDMA检测中。该算法利用用户可靠性确立干扰信号消除的优先级，同时用MMSE检测替代原有的匹配滤波检测。仿真结果表明改进算法在瑞利衰落信道下有更优的性能，，并在系统用户数较多、甚至用户数K高于扩频码长N时仍保有较好的检测性能。 最后，深入研究了子空间盲多用户检测相关理论和算法，然后基于改进的FAPI算法和修正MMSE检测模型，提出了高性能的基于AFAPI的修正盲MMSE算法（AFAPI-ModifiedMMSE）和低复杂度的基于SFAPI的修正盲MMSE算法（SFAPI-ModifiedMMSE）且分析了相应的复杂度。仿真结果显示这两种算法在子空间跟踪误差、检测器输出信干噪比、检测器的平均误码率三项指标上均体现出较优的性能。
[Abstract]:In recent years, 3G mobile communication industry has developed rapidly. As the core technology of 3G, CDMA technology has the advantages of large capacity, good confidentiality and high spectrum efficiency. However, as a kind of direct sequence spread spectrum system, because of the random access of users and the non-zero of spread spectrum code cross-correlation, multiple access interference (mai) will occur among the user signals, which leads to the deterioration of system performance and limits the capacity of the system. Multiple access interference (mai) is different from general noise. It carries spread spectrum code related information and is predictable to a certain extent. Multi-user detection technology uses this feature to reduce or even eliminate multiple access interference to a certain extent. This paper focuses on the multi-user detection technology in direct sequence spread spectrum system. Firstly, the synchronous and asynchronous multiuser detection models are established for direct sequence spread spectrum system, and the basic principles and characteristics of the detection performance measure and the classical multiuser detection algorithm are analyzed. Secondly, the existing interference cancellation detectors and their advantages and disadvantages are analyzed, and an improved serial interference cancellation (RB-SIC) detector based on user reliability is introduced and applied to CDMA detection. The algorithm uses user reliability to determine the priority of interference cancellation and replaces the original matched filter detection with MMSE detection. The simulation results show that the improved algorithm has better performance in Rayleigh fading channels, and has better detection performance even when the number of users K is higher than the spread spectrum code length N. Finally, the related theories and algorithms of subspace blind multiuser detection are deeply studied, and then based on the improved FAPI algorithm and the modified MMSE detection model, High performance modified Blind MMSE algorithm based on AFAPI (AFAPI-Modified MMSE) and low complexity modified Blind MMSE algorithm based on SFAPI (SFAPI-Modified MMSE) are proposed and the corresponding complexity is analyzed. Simulation results show that the two algorithms have better performance on three indexes: subspace tracking error, detector output signal-to-noise ratio and average bit error rate of detector.
【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】：TN914.42
本文编号：2134412
[Abstract]:In recent years, 3G mobile communication industry has developed rapidly. As the core technology of 3G, CDMA technology has the advantages of large capacity, good confidentiality and high spectrum efficiency. However, as a kind of direct sequence spread spectrum system, because of the random access of users and the non-zero of spread spectrum code cross-correlation, multiple access interference (mai) will occur among the user signals, which leads to the deterioration of system performance and limits the capacity of the system. Multiple access interference (mai) is different from general noise. It carries spread spectrum code related information and is predictable to a certain extent. Multi-user detection technology uses this feature to reduce or even eliminate multiple access interference to a certain extent. This paper focuses on the multi-user detection technology in direct sequence spread spectrum system. Firstly, the synchronous and asynchronous multiuser detection models are established for direct sequence spread spectrum system, and the basic principles and characteristics of the detection performance measure and the classical multiuser detection algorithm are analyzed. Secondly, the existing interference cancellation detectors and their advantages and disadvantages are analyzed, and an improved serial interference cancellation (RB-SIC) detector based on user reliability is introduced and applied to CDMA detection. The algorithm uses user reliability to determine the priority of interference cancellation and replaces the original matched filter detection with MMSE detection. The simulation results show that the improved algorithm has better performance in Rayleigh fading channels, and has better detection performance even when the number of users K is higher than the spread spectrum code length N. Finally, the related theories and algorithms of subspace blind multiuser detection are deeply studied, and then based on the improved FAPI algorithm and the modified MMSE detection model, High performance modified Blind MMSE algorithm based on AFAPI (AFAPI-Modified MMSE) and low complexity modified Blind MMSE algorithm based on SFAPI (SFAPI-Modified MMSE) are proposed and the corresponding complexity is analyzed. Simulation results show that the two algorithms have better performance on three indexes: subspace tracking error, detector output signal-to-noise ratio and average bit error rate of detector.
【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】：TN914.42
【参考文献】
相关期刊论文 前2条
1 李辉;王珏;于红梅;;逼近幂迭代子空间跟踪算法在多用户系统中的应用研究[J];电子学报;2007年12期
2 李辉;于红梅;郭莉;;一种改进的子空间盲多用户检测系统[J];西北工业大学学报;2008年01期
相关博士学位论文 前1条
1 张东红;CDMA多用户检测器线性统一模型与非线性改进算法研究[D];西安电子科技大学;2010年
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