本文選題：OFDM + 信道估計��； 參考：《吉林大學(xué)》2014年碩士論文

【摘要】：如今通信技術(shù)正發(fā)生著日新月異的變化，為人類社會的發(fā)展做出了巨大的貢獻。然而，人們對通信質(zhì)量的要求也在日益提高。因此，如何不斷的提高通信系統(tǒng)的性能一直是眾多研究者面臨的課題。本論文選擇通信系統(tǒng)中的OFDM（正交頻分復(fù)用）系統(tǒng)，深入研究了其無線信道、基本原理和信道估計算法等技術(shù)，并基于傳統(tǒng)的DFT信道估計算法，提出一種改進方法。改進算法可以進一步消除噪聲的影響，具有很好的使用價值。 OFDM技術(shù)是一種多載波傳輸方案，并且具有廣泛發(fā)展前景。MIMO-OFDM（多輸入多輸出正交頻分復(fù)用）是應(yīng)用于下一代蜂窩通信（3GPP-LTE，移動WiMAX，IMT-Advanced）、無線局域網(wǎng)（IEEE802.11a，IEEE802.11n）、無線局域網(wǎng)絡(luò)（MB-OFDM）和廣播（DAB數(shù)字音頻廣播，DVB數(shù)字視頻廣播，，DMB數(shù)字多媒體廣播）的一種關(guān)鍵技術(shù)。信道估計技術(shù)作為正交頻分復(fù)用技術(shù)的一項關(guān)鍵技術(shù)，在無線移動通信系統(tǒng)中成為一個新的研究熱點。在OFDM系統(tǒng)中，發(fā)射機將信息比特序列調(diào)制成PSK/QAM符號，然后對相應(yīng)的符號執(zhí)行IFFT將其變換成時域信號，最后通過一個（無線）信道將它們發(fā)射出去。接收的信號通常因受到信道特性的影響而失真。為了恢復(fù)發(fā)送的比特信息，在接收機必須對信道的影響進行估計和補償。 本文首先介紹了無線信道建模的基本概念，并對無線信道的衰落現(xiàn)象進行了建模。介紹了衰落信道的分類：大尺度衰落和小尺度衰落。并分別對大尺度和小尺度衰落的各種模型分別進行了建模和仿真。然后，文章又介紹了OFDM通信系統(tǒng)的基本原理和OFDM信號的產(chǎn)生和其基本特征。分析了可以抵抗系統(tǒng)多徑效應(yīng)的機制的插入保護間隔(GI)與循環(huán)前綴(CP)技術(shù)以及具體實現(xiàn)插入循環(huán)前綴的方法。又分析了系統(tǒng)中的各項關(guān)鍵技術(shù)，并對各項技術(shù)建立數(shù)學(xué)模型。最后，本文介紹了被廣泛應(yīng)用于信道估計的兩種技術(shù)：最小二乘LS和最小均方差MMSE技術(shù)。然后研究了能夠提高LS或MMSE信道估計性能的基于DFT的信道估計技術(shù)。并提出一種改進的基于DFT的信道估計方法，最后對該改進算法進行仿真研究，通過仿真實驗比較證明了該算法的優(yōu)越性，具有很好的使用價值。
[Abstract]:Nowadays, communication technology is changing with each passing day, and has made great contribution to the development of human society. However, people's demand for communication quality is also increasing. Therefore, how to continuously improve the performance of communication systems has been a topic facing many researchers. In this paper, OFDM (orthogonal Frequency Division Multiplexing) system is selected for communication system. The wireless channel, basic principle and channel estimation algorithm are studied in detail. Based on the traditional DFT channel estimation algorithm, an improved method is proposed. The improved algorithm can further eliminate the influence of noise and has a good use value. OFDM technology is a multi-carrier transmission scheme. MIMO-OFDM (multiple input and multiple output orthogonal Frequency Division Multiplexing) is widely used in the next generation cellular communications (3GPP-LTEN, mobile WiMAXPIMT-Advanced WLAN, IEEE802.11aEIEEE802.11nPU, WLAN / MB-OFDM) and DVB DVB digital video broadcasting (DMB). A key technology of digital multimedia broadcasting. As a key technology of orthogonal frequency division multiplexing (OFDM), channel estimation has become a new research hotspot in wireless mobile communication systems. In OFDM system, the transmitter modulates the sequence of bits into PSK / QAM symbols, then performs Ifft on the corresponding symbols to transform them into time-domain signals, and then transmits them over a (wireless) channel. The received signal is usually distorted by channel characteristics. In order to recover the transmitted bit information, the channel influence must be estimated and compensated in the receiver. Firstly, the basic concept of wireless channel modeling is introduced, and the fading phenomenon of wireless channel is modeled. This paper introduces the classification of fading channels: large scale fading and small scale fading. The models of large scale fading and small scale fading are modeled and simulated respectively. Then, the paper introduces the basic principle of OFDM communication system, the generation of OFDM signal and its basic characteristics. The techniques of insertion protection interval (Gi) and cyclic prefix (CPP) which can resist the multipath effect of the system and the method of inserting cyclic prefix are analyzed. The key technologies of the system are analyzed, and the mathematical model of each technology is established. Finally, this paper introduces two techniques widely used in channel estimation: least square LS and minimum mean square error (MMSE). Then the DFT-based channel estimation technology which can improve the performance of LS or MMSE channel estimation is studied. An improved channel estimation method based on DFT is proposed. Finally, the simulation of the improved algorithm is carried out. The simulation results show that the algorithm is superior and has good practical value.
【學(xué)位授予單位】：吉林大學(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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本文編號：2001064