【摘要】：單載波頻域均衡(SC-FDE)技術(shù),不僅具有較強(qiáng)的對抗頻率選擇性衰落信道的特性,同時具有較低的峰均比、良好的誤碼率性能、對載波頻偏和相位噪聲敏感性小等優(yōu)勢,是寬帶無線通信系統(tǒng)中的重要組成技術(shù)。在SC-FDE系統(tǒng)中,因為空間無線信道的復(fù)雜性,接收端必須采取相應(yīng)的措施消除信道帶來的影響。所以,對信道特性的估計與均衡算法在整個傳輸系統(tǒng)中起著決定性作用。除此之外,由于系統(tǒng)接收機(jī)的模擬前端通常采用正交下變頻,這樣不可避免的存在同相與正交(IQ)支路幅度和相位的不平衡問題,非常小的IQ不平衡都會影響信道估計的精度。因此,對同相與正交支路之間不平衡因子的估計與補(bǔ)償算法也很重要。本文圍繞單載波頻域均衡技術(shù)展開研究,重點研究單載波頻域均衡的信道估計與均衡算法,主要完成以下研究工作:(1)對傳統(tǒng)的信道估計與均衡算法進(jìn)行詳細(xì)的理論分析,并對最小均方誤差(MMSE)均衡算法中噪聲方差估計方案展開研究,引入Boumard在OFDM系統(tǒng)中噪聲方差估計方法的思路,將該方法運(yùn)用到SC-FDE系統(tǒng)中,得到很好的噪聲方差估計性能。(2)針對傳統(tǒng)的信道估計與均衡算法的缺陷,提出一種基于特殊訓(xùn)練序列的信道估計與均衡改進(jìn)算法,詳細(xì)地闡述整個算法的各個實現(xiàn)步驟。由于該算法采取與數(shù)據(jù)幀等長的Chu序列作為訓(xùn)練序列進(jìn)行信道估計,從而提高信道估計的精度。并在迫零(ZF)均衡算法基礎(chǔ)上,再進(jìn)行一次反傅里葉變換和傅里葉變換,這些操作都可以借助FFT模塊實現(xiàn),復(fù)雜度不是很高,但其性能卻在ZF均衡算法基礎(chǔ)上有很大提高。(3)針對同相與正交支路之間不平衡因子的估計與補(bǔ)償算法進(jìn)行研究,對傳統(tǒng)的時域IQ不平衡估計與補(bǔ)償算法進(jìn)行詳細(xì)的分析,由于該算法忽略了IQ不平衡因子與信道估計之間的相互影響,在多徑衰落信道環(huán)境中,性能較差。因此,本文針對時域方法的不足提出一種頻域IQ不平衡與信道聯(lián)合估計的方案,該方案由于考慮了信道估計與IQ不平衡的相互影響,所以無論是在任何信道下,對IQ不平衡都有一定的補(bǔ)償作用。(4)通過結(jié)合Matlab仿真結(jié)果,驗證各種方案理論分析的正確性。
[Abstract]:Single carrier frequency domain equalization (SC-FDE) technology not only has strong characteristics of frequency selective fading channel, but also has the advantages of low peak-to-average ratio, good bit error rate performance and low sensitivity to carrier frequency offset and phase noise. Wideband wireless communication system is an important component technology. In SC-FDE systems, due to the complexity of the space wireless channel, the receiver must take appropriate measures to eliminate the influence of the channel. Therefore, the estimation and equalization algorithm of channel characteristics plays a decisive role in the whole transmission system. In addition, because the analog front end of system receiver usually uses quadrature downconversion, it is inevitable that the amplitude and phase of the phase and amplitude of the in phase and quadrature (IQ) branch are unbalanced. The very small IQ imbalance will affect the accuracy of channel estimation. Therefore, it is also important to estimate and compensate the imbalance factor between the same phase and the orthogonal branch. This paper focuses on single-carrier frequency-domain equalization technology, focusing on single-carrier frequency-domain equalization channel estimation and equalization algorithm. The main work is as follows: (1) the traditional channel estimation and equalization algorithm is analyzed in detail. The minimum mean square error (MMSE) equalization scheme is studied. The Boumard method of noise variance estimation in OFDM system is introduced and applied to SC-FDE system. Good performance of noise variance estimation is obtained. (2) aiming at the shortcomings of the traditional channel estimation and equalization algorithm, an improved channel estimation and equalization algorithm based on special training sequence is proposed, and the implementation steps of the whole algorithm are described in detail. The algorithm uses Chu sequence with the same length as the data frame as the training sequence to estimate the channel, thus improving the accuracy of the channel estimation. Based on the zero-forcing (ZF) equalization algorithm, the inverse Fourier transform and Fourier transform are carried out again. These operations can be implemented with FFT module, and the complexity is not very high. However, its performance is greatly improved on the basis of ZF equalization algorithm. (3) the estimation and compensation algorithm of imbalance factor between in-phase and orthogonal branches is studied, and the traditional time-domain IQ imbalance estimation and compensation algorithm is analyzed in detail. Because the algorithm ignores the interaction between IQ imbalance factor and channel estimation, the performance of the algorithm is poor in multipath fading channel. Therefore, this paper proposes a scheme of frequency domain IQ imbalance and joint channel estimation, which takes into account the interaction between channel estimation and IQ imbalance, so it can be used in any channel. It can compensate the IQ imbalance to some extent. (4) by combining the Matlab simulation results, the correctness of the theoretical analysis of various schemes is verified.
【學(xué)位授予單位】：西安電子科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TN929.53

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