本文選題：正交頻分復(fù)用 + 信道估計(jì)�。� 參考：《北京交通大學(xué)》2014年碩士論文

【摘要】：隨著移動(dòng)通信技術(shù)的不斷發(fā)展,目前LTE系統(tǒng)已經(jīng)在全球范圍內(nèi)開始商用。其采用了正交分頻復(fù)用(OFDM)技術(shù),可以通過快速傅里葉變換(FFT)將高速數(shù)據(jù)流調(diào)制到相互正交的N路子載波上。這樣,OFDM技術(shù)將頻率選擇性衰落信道轉(zhuǎn)化為若干個(gè)頻率非選擇性衰落信道,能有效地抵抗多徑引起的符號間干擾(ISI)和多徑衰落。在接收端,通常采用相干檢測的方法來獲得頻域數(shù)據(jù)符號。為了能夠恢復(fù)出傳輸信號,我們必須要正確地估計(jì)出無線信道對傳輸信號的影響,這就要求事先有效的估計(jì)出信道參數(shù)。因此,在移動(dòng)通信系統(tǒng)中,信道估計(jì)是接收機(jī)設(shè)計(jì)的重要組成部分。 本文首先分析了目前存在的各種信道估計(jì)方法,它們通常假設(shè)信道參數(shù)在一個(gè)OFDM符號內(nèi)是恒定不變的。基于LTE系統(tǒng)的信道估計(jì)算法屬于導(dǎo)頻輔助估計(jì),主要有兩個(gè)步驟：首先對含有參考信號的OFDM符號進(jìn)行統(tǒng)計(jì)估計(jì),這里主要采用最小二乘(LS)算法和最小均方誤差(MMSE)算法。降秩LMMSE算法、SVD算法、變換域降噪算法等信道估計(jì)算法大多是對上述兩種基本方法優(yōu)化改進(jìn)而來。隨后,數(shù)據(jù)載波處的信道響應(yīng)可以通過內(nèi)插技術(shù)得到,主要包括常值插值,一階線性插值,二階多項(xiàng)式插值,三次樣條插值等等。本文還給出了這些信道估計(jì)算法基于TD-LTE標(biāo)準(zhǔn)的仿真分析。 之后,本文研究了在高速移動(dòng)場景中的信道估計(jì)方法。當(dāng)終端高速移動(dòng)時(shí),會造成多普勒效應(yīng),并導(dǎo)致信道發(fā)生時(shí)間選擇性衰落。因此,信道在一個(gè)OFDM符號內(nèi)呈現(xiàn)出較為明顯的變化,這時(shí)子載波間干擾(ICI)就會影響傳統(tǒng)的信道估計(jì)方法,使估計(jì)性能明顯下降。本文提出通過冪級數(shù)基的形式來建模無線信道變化的方法,將時(shí)變的信道估計(jì)轉(zhuǎn)變成有限參數(shù)變量在冪級數(shù)基上的投影,這大大減少了估計(jì)信道參數(shù)的個(gè)數(shù)。理論分析及基于TD-LTE Release8的仿真結(jié)果表明,該方法能有效地跟蹤和估計(jì)時(shí)變的信道參數(shù),具有良好性能。
[Abstract]:With the development of mobile communication technology, LTE system has been used in the world. The orthogonal Frequency Division Multiplexing (OFDM) technique is used to modulate the high-speed data stream to the orthogonal N-channel subcarriers by means of fast Fourier transform (FFT). In this way, OFDM can transform frequency selective fading channels into several frequency non-selective fading channels, which can effectively resist inter-symbol interference (ISI) and multipath fading caused by multipath. At the receiving end, coherent detection is usually used to obtain frequency domain data symbols. In order to recover the transmitted signal, we must correctly estimate the influence of the wireless channel on the transmitted signal, which requires the effective estimation of the channel parameters in advance. Therefore, in mobile communication systems, channel estimation is an important part of receiver design. In this paper, we first analyze the existing channel estimation methods, which usually assume that the channel parameters are constant in an OFDM symbol. The channel estimation algorithm based on LTE system belongs to pilot aided estimation. There are two main steps: firstly, the OFDM symbol with reference signal is estimated statistically, and the least square (LS) algorithm and the minimum mean square error (MMSE) algorithm are mainly used in this algorithm. Most of the channel estimation algorithms such as reduced rank LMMSE algorithm SVD algorithm and transform domain noise reduction algorithm are improved from the above two basic methods. Subsequently, the channel response at the data carrier can be obtained by interpolation techniques, including constant interpolation, first-order linear interpolation, second-order polynomial interpolation, cubic spline interpolation and so on. This paper also presents the simulation analysis of these channel estimation algorithms based on TD-LTE standard. Then, the channel estimation method in high-speed mobile scene is studied. When the terminal moves at high speed, it causes Doppler effect and time selective fading. Therefore, the channel changes obviously in an OFDM symbol. In this case, the inter-carrier interference (ICI) will affect the traditional channel estimation methods, and the estimation performance will be significantly reduced. In this paper, a method of modeling wireless channel variation by power series basis is proposed. The time-varying channel estimation is transformed into the projection of finite parameter variables on the power series basis, which greatly reduces the number of estimated channel parameters. Theoretical analysis and simulation results based on TD-LTE release 8 show that the proposed method can effectively track and estimate time-varying channel parameters and has good performance.
【學(xué)位授予單位】：北京交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TN929.5

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相關(guān)期刊論文 前1條

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