【摘要】：隨著無線通信技術(shù)的迅猛發(fā)展,無線頻譜資源變得越來越緊缺。然而占據(jù)了甚高頻和特高頻(VHF/UHF)頻段大量資源的廣播電視等授權(quán)用戶卻沒能夠有效地利用該段頻譜,隨之出現(xiàn)了很多電視頻段白色空間(TVWS)。為了充分利用TVWS,電氣和電子工程師協(xié)會(IEEE)于2011年提出了無線區(qū)域網(wǎng)(WRAN)。WRAN系統(tǒng)旨在不干擾授權(quán)用戶的前提下,利用TVWS為農(nóng)村、偏遠地區(qū)等低人口密度區(qū)域提供無線寬帶接入。WRAN系統(tǒng)的物理層采用了正交頻分復(fù)用(OFDM)調(diào)制技術(shù)。而在采用相干解調(diào)的OFDM接收機中,信道估計的精度直接關(guān)系到整個系統(tǒng)的性能,有著重要的研究意義。論文主要對WRAN系統(tǒng)的信道估計方法展開了研究。論文的研究工作主要包括以下幾個方面:1.建立了WRAN系統(tǒng)基于VS2010的C語言仿真平臺。并通過將該系統(tǒng)仿真平臺在加性高斯白噪聲(AWGN)信道下的誤碼性能和理論誤碼公式對比,初步驗證了仿真平臺的正確性。2.利用WRAN系統(tǒng)每一幀中插入的前導(dǎo)序列,研究了基于前導(dǎo)序列的信道估計方法。在對基于前導(dǎo)序列信道估計方法的研究中,其首要目標是根據(jù)高密度訓(xùn)練序列,提高初始信道估計的精度。為此,重點研究了頻域低復(fù)雜度的多項式插值方法以及時域CIR檢測方法,并針對最大長度多徑時延法存在濾除噪聲不足的缺點,提出了一種改進的基于雙滑動窗信道沖擊響應(yīng)(CIR)檢測方法,該方法可以檢測出小功率CIR分量,提高信道估計的精度。3.利用WRAN系統(tǒng)每一幀數(shù)據(jù)OFDM符號中插入的導(dǎo)頻序列,研究了基于導(dǎo)頻序列的信道估計方法。在對基于導(dǎo)頻序列信道估計方法的研究中,重點研究了實系數(shù)FIR濾波插值的方法,并在分析了實系數(shù)FIR內(nèi)插在對抗長時延SFN信道存在不足的基礎(chǔ)上,提出了一種改進的自適應(yīng)復(fù)插值信道估計方法。該方法將實系數(shù)內(nèi)插通過相位旋轉(zhuǎn)轉(zhuǎn)化為復(fù)系數(shù)內(nèi)插,大大提升了WRAN系統(tǒng)對抗多徑時延的能力,并且通過自適應(yīng)的方法,可以靈活地匹配信道的真實最大多徑時延,提高信道估計的性能。
[Abstract]:With the rapid development of wireless communication technology, wireless spectrum resources become increasingly scarce. However, authorized users such as radio and television, who occupied a lot of resources in the very high frequency and ultra-high frequency (VHF/UHF) bands, were unable to make effective use of the spectrum, and a lot of white space (TVWS). Appeared in the television frequency bands. In order to make full use of the (IEEE) of TVWS, Electrical and Electronic Engineers in 2011, the wireless area network (WRAN). WRAN system was proposed to use TVWS for rural areas without interfering with authorized users. Low population density areas such as remote areas provide wireless broadband access. The physical layer of WRAN system is based on orthogonal Frequency Division Multiplexing (OFDM) modulation technology. In the OFDM receiver with coherent demodulation, the accuracy of channel estimation is directly related to the performance of the whole system. In this paper, the channel estimation method of WRAN system is studied. The research work includes the following aspects: 1. The C language simulation platform of WRAN system based on VS2010 is established. The correctness of the simulation platform is preliminarily verified by comparing the error performance of the system simulation platform in the additive Gao Si white noise (AWGN) channel with the theoretical error code formula. 2. The channel estimation method based on the preamble sequence is studied by using the preamble sequence inserted in each frame of the WRAN system. In the research of channel estimation method based on preamble sequence, its primary goal is to improve the accuracy of initial channel estimation based on high-density training sequence. Therefore, the low complexity polynomial interpolation method in frequency domain and the CIR detection method in time domain are studied, and the shortcomings of the maximum length multipath delay method in filtering noise are discussed. An improved (CIR) detection method based on double-sliding window channel impulse response is proposed. This method can detect low-power CIR components and improve the accuracy of channel estimation. The channel estimation method based on pilot sequence is studied by using pilot sequence inserted in each frame of data OFDM symbol in WRAN system. In the research of channel estimation method based on pilot sequence, the method of real coefficient FIR filter interpolation is studied emphatically, and the deficiency of real coefficient FIR interpolation in counteracting long delay SFN channel is analyzed. An improved adaptive complex interpolation channel estimation method is proposed. In this method, the real coefficient interpolation is transformed into complex coefficient interpolation by phase rotation, which greatly improves the ability of WRAN system to resist multipath delay, and the adaptive method can flexibly match the real maximum multipath delay of the channel. Improve the performance of channel estimation.
【學位授予單位】：電子科技大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TN911.2

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