發(fā)布時(shí)間：2018-06-11 12:56

  本文選題：多輸入多輸出 + 正交頻分復(fù)用　； 參考：《解放軍信息工程大學(xué)》2014年碩士論文

【摘要】：多輸入多輸出(Multiple-Input Multiple-Output,MIMO)技術(shù)充分利用空間資源,能夠?yàn)橄到y(tǒng)提供空間分集增益與空間復(fù)用增益,抵抗信道衰落,提高信道容量與頻帶利用率。此外,正交頻分復(fù)用(Orthogonal Frequency Division Multiplexing,OFDM)技術(shù)作為一種高頻帶利用率的多載波調(diào)制技術(shù),能夠?qū)㈩l率選擇性衰落信道轉(zhuǎn)化為平坦衰落信道,克服多徑傳播對(duì)系統(tǒng)帶來(lái)的不利影響。結(jié)合兩者優(yōu)勢(shì)的MIMO-OFDM技術(shù)作為4G核心物理層的首選傳輸技術(shù),受到了廣泛地關(guān)注。同時(shí),在MIMO-OFDM系統(tǒng)中,信道估計(jì)能夠?yàn)榻邮斩说南喔蓹z測(cè)提供重要的信道參數(shù),對(duì)構(gòu)建均衡器、校正畸變信號(hào)以及恢復(fù)發(fā)送序列具有至關(guān)重要的作用,直接影響著系統(tǒng)性能的好壞。因此,信道估計(jì)成為了MIMO-OFDM系統(tǒng)的研究熱點(diǎn)。本文基于多輸入多輸出信道模型,以信道估計(jì)作為課題的研究方向,出于對(duì)高頻譜效率以及高系統(tǒng)容量的追求,重點(diǎn)對(duì)盲信道估計(jì)技術(shù)進(jìn)行了研究,主要工作與創(chuàng)新點(diǎn)歸納如下:1、在研究傳統(tǒng)噪聲子空間算法的基礎(chǔ)上,對(duì)算法進(jìn)行改進(jìn),提出了一種適用于MIMO-OFDM系統(tǒng)的子空間盲信道估計(jì)算法。該算法通過(guò)采用塊矩陣方案減少了求解自相關(guān)矩陣所需的樣本數(shù),有效地降低了自相關(guān)矩陣與噪聲子空間的擾動(dòng),提高了算法的收斂速度與估計(jì)精度。2、針對(duì)確定性子空間算法對(duì)信道階數(shù)過(guò)估計(jì)比較敏感的缺點(diǎn),本文基于頻域?yàn)V波方法與子空間方法相結(jié)合,提出了一種具有階數(shù)誤差魯棒的子空間算法。該算法利用頻域子空間算法對(duì)信道進(jìn)行估計(jì),通過(guò)頻域?yàn)V波算法進(jìn)行降噪處理,提高估計(jì)精度。接著,為了進(jìn)一步評(píng)價(jià)信道估計(jì)器的性能,推導(dǎo)了算法的最小約束克拉美羅界。理論分析與仿真結(jié)果表明,該算法對(duì)信道階數(shù)的過(guò)估計(jì)具有很強(qiáng)的魯棒性。3、針對(duì)MIMO-OFDM系統(tǒng)中頻偏與信道聯(lián)合估計(jì)問(wèn)題進(jìn)行了研究,綜合考慮頻偏估計(jì)與信道估計(jì)這兩方面的因素,克服其單獨(dú)估計(jì)無(wú)法使系統(tǒng)性能達(dá)到最優(yōu)這一缺陷,提出了一種新的適用于MIMO-OFDM系統(tǒng)的半盲載波與信道聯(lián)合估計(jì)算法。該算法通過(guò)將子空間方法與時(shí)域重復(fù)數(shù)據(jù)段的方法相結(jié)合,完成了MIMO-OFDM系統(tǒng)的載波同步與信道估計(jì),并分析了載波頻偏對(duì)系統(tǒng)性能的影響。實(shí)驗(yàn)仿真結(jié)果表明,所提算法具有較寬的頻偏估計(jì)范圍,在頻率選擇性衰落信道下能夠取得優(yōu)于其它同類算法的良好估計(jì)性能。
[Abstract]:Multiple-Input Multiple-OutputMimo (MIMO) technology can provide spatial diversity gain and spatial multiplexing gain, resist channel fading, and improve channel capacity and frequency band efficiency by making full use of space resources. In addition, orthogonal Frequency Division Multiplexing OFDM (OFDM) technology, as a high-frequency band efficient multicarrier modulation technique, can transform the frequency-selective fading channel into a flat fading channel to overcome the adverse effects of multipath propagation on the system. MIMO-OFDM, which combines the advantages of both, as the preferred transmission technology of 4G core physical layer, has received extensive attention. At the same time, in MIMO-OFDM systems, channel estimation can provide important channel parameters for coherent detection at the receiver, which plays an important role in constructing equalizer, correcting distorted signals and restoring transmission sequences. It directly affects the performance of the system. Therefore, channel estimation has become a hotspot in MIMO-OFDM systems. In this paper, based on the multi-input and multi-output channel model, the blind channel estimation technology is studied for the pursuit of high spectral efficiency and high system capacity. The main work and innovations are summarized as follows: 1. On the basis of studying the traditional noise subspace algorithm, this paper proposes a subspace blind channel estimation algorithm for MIMO-OFDM systems. The algorithm reduces the number of samples needed to solve the autocorrelation matrix by adopting the block matrix scheme, and effectively reduces the disturbance of the autocorrelation matrix and the noise subspace. The convergence speed and estimation accuracy of the algorithm are improved. Aiming at the shortcoming that the subspace algorithm is sensitive to the channel order overestimation, this paper combines the frequency domain filtering method with the subspace method. A robust subspace algorithm with order error is proposed. The frequency domain subspace algorithm is used to estimate the channel and the frequency domain filtering algorithm is used to reduce the noise to improve the estimation accuracy. Then, in order to further evaluate the performance of channel estimators, the minimum constrained Crameiro bound is derived. The theoretical analysis and simulation results show that the algorithm is robust to the over-estimation of channel order. The problem of joint estimation of intermediate frequency offset and channel in MIMO-OFDM system is studied. The two factors of frequency offset estimation and channel estimation are considered synthetically. To overcome the shortcoming that the system performance can not be optimized by single estimation, a new semi-blind joint carrier and channel estimation algorithm for MIMO-OFDM systems is proposed. By combining subspace method with time domain repeat data segment method, the carrier synchronization and channel estimation of MIMO-OFDM system are completed, and the influence of carrier frequency offset on system performance is analyzed. Experimental results show that the proposed algorithm has a wide range of frequency offset estimation and can achieve better estimation performance than other similar algorithms in frequency-selective fading channels.
【學(xué)位授予單位】：解放軍信息工程大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TN919.3

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本文編號(hào)：2005323