【摘要】：近年來(lái)，3G移動(dòng)通信產(chǎn)業(yè)發(fā)展迅速，CDMA技術(shù)作為3G核心技術(shù)有著容量大、保密性好、頻譜利用率較高的優(yōu)勢(shì)。然而，CDMA系統(tǒng)作為一種直接序列擴(kuò)頻系統(tǒng)，由于用戶的隨機(jī)接入和擴(kuò)頻碼互相關(guān)的非零性，各用戶信號(hào)之間會(huì)產(chǎn)生多址干擾，導(dǎo)致系統(tǒng)性能的惡化，限制了系統(tǒng)的容量。多址干擾不同于一般噪聲，它攜帶著擴(kuò)頻碼相關(guān)信息，在一定程度上具有可預(yù)測(cè)性，多用戶檢測(cè)技術(shù)運(yùn)用了這一特點(diǎn)，一定程度上降低甚至消除了多址干擾。本文圍繞直接序列擴(kuò)頻系統(tǒng)中的多用戶檢測(cè)技術(shù)展開(kāi)相關(guān)研究。 首先，本文針對(duì)直接序列擴(kuò)頻系統(tǒng)建立了同步、異步多用戶檢測(cè)模型，并分析了檢測(cè)性能測(cè)度和多用戶檢測(cè)經(jīng)典算法基本原理、特點(diǎn)。 其次，具體分析了現(xiàn)有干擾消除檢測(cè)器和它們的優(yōu)缺點(diǎn)，引入基于用戶可靠性的改進(jìn)的串行干擾消除（RB-SIC）檢測(cè)器，并將其應(yīng)用到CDMA檢測(cè)中。該算法利用用戶可靠性確立干擾信號(hào)消除的優(yōu)先級(jí)，同時(shí)用MMSE檢測(cè)替代原有的匹配濾波檢測(cè)。仿真結(jié)果表明改進(jìn)算法在瑞利衰落信道下有更優(yōu)的性能，，并在系統(tǒng)用戶數(shù)較多、甚至用戶數(shù)K高于擴(kuò)頻碼長(zhǎng)N時(shí)仍保有較好的檢測(cè)性能。 最后，深入研究了子空間盲多用戶檢測(cè)相關(guān)理論和算法，然后基于改進(jìn)的FAPI算法和修正MMSE檢測(cè)模型，提出了高性能的基于AFAPI的修正盲MMSE算法（AFAPI-ModifiedMMSE）和低復(fù)雜度的基于SFAPI的修正盲MMSE算法（SFAPI-ModifiedMMSE）且分析了相應(yīng)的復(fù)雜度。仿真結(jié)果顯示這兩種算法在子空間跟蹤誤差、檢測(cè)器輸出信干噪比、檢測(cè)器的平均誤碼率三項(xiàng)指標(biāo)上均體現(xiàn)出較優(yōu)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.
【學(xué)位授予單位】：西安電子科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TN914.42

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