發(fā)布時(shí)間：2018-03-09 17:08

  本文選題：OFDM　切入點(diǎn)：信道估計(jì)　出處：《電子科技大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

【摘要】：正交頻分復(fù)用(OFDM)技術(shù)具有良好的抗多徑衰落能力和高頻譜利用率,所以在通信領(lǐng)域得到了廣泛的應(yīng)用。信道估計(jì)與均衡是OFDM系統(tǒng)的關(guān)鍵技術(shù)之一,關(guān)系到整個(gè)OFDM系統(tǒng)性能的優(yōu)劣。同時(shí)未來的無線通信技術(shù)發(fā)展的主要趨勢是更高的用戶傳輸速率和更高的用戶移動(dòng)速度。為此,本文重點(diǎn)研究了基于QAM調(diào)制的慢時(shí)變信道和快時(shí)變信道下的OFDM信道估計(jì)與均衡算法。主要工作表現(xiàn)在以下三個(gè)方面:首先,研究OFDM系統(tǒng)慢時(shí)變信道下的信道估計(jì)與均衡算法。針對(duì)慢時(shí)變信道,研究了經(jīng)典的基于導(dǎo)頻的信道估計(jì)算法。首先介紹了常用的導(dǎo)頻結(jié)構(gòu);然后詳細(xì)敘述了導(dǎo)頻位置的信道估計(jì)算法和非導(dǎo)頻位置的信道估計(jì)算法;最后對(duì)所介紹的算法通過仿真進(jìn)行了詳細(xì)分析和性能驗(yàn)證,以便根據(jù)項(xiàng)目的要求選擇合適的算法。對(duì)于均衡介紹了適用于OFDM系統(tǒng)的迫零均衡,判決反饋迫零均衡和改進(jìn)的判決反饋迫零均衡。其次,研究OFDM系統(tǒng)快時(shí)變信道下的信道估計(jì)與均衡算法。當(dāng)信道的多普勒頻移較大時(shí),系統(tǒng)會(huì)出現(xiàn)嚴(yán)重的子載波干擾現(xiàn)象,針對(duì)慢時(shí)變信道提出的算法已經(jīng)不再適用,故針對(duì)快時(shí)變信道研究相應(yīng)的信道估計(jì)算法。為了更好地實(shí)時(shí)跟蹤快時(shí)變信道,研究了基于基擴(kuò)展的信道估計(jì)算法,用一組有限的基函數(shù)加權(quán)求和的方式來擬合時(shí)變信道。本文介紹了不同的基函數(shù)類型;根據(jù)分析時(shí)變信道的特點(diǎn),給出了分簇狀梳狀導(dǎo)頻結(jié)構(gòu);并針對(duì)各種基函數(shù)類型和導(dǎo)頻結(jié)構(gòu)進(jìn)行了大量的仿真。為了應(yīng)對(duì)ICI現(xiàn)象,并恢復(fù)解調(diào)出發(fā)送的數(shù)據(jù),介紹了一種針對(duì)基擴(kuò)展模型的時(shí)變信道下塊判決反饋均衡算法。最后,基于資源使用量和系統(tǒng)速率兩方面的考慮,針對(duì)基于導(dǎo)頻的信道估計(jì)與均衡中的部分算法和數(shù)字正余弦信號(hào)發(fā)生器進(jìn)行硬件方案設(shè)計(jì),并在FPGA硬件平臺(tái)上進(jìn)行了實(shí)現(xiàn),通過仿真結(jié)果和綜合報(bào)表分析給出了各算法的性能效果和資源使用量,以便在工程項(xiàng)目中根據(jù)項(xiàng)目要求選擇合適的算法。
[Abstract]:OFDM (orthogonal Frequency Division Multiplexing) technology has been widely used in the field of communication because of its good anti-multipath fading ability and high spectral efficiency. Channel estimation and equalization is one of the key technologies in OFDM system. At the same time, the main trend of the future wireless communication technology development is higher user transmission rate and higher user mobile speed. This paper focuses on the OFDM channel estimation and equalization algorithm based on QAM modulation in slow time-varying channel and fast time-varying channel. The main work is as follows: first, This paper studies the channel estimation and equalization algorithm for slow time-varying channel in OFDM system. For the slow time-varying channel, the classical pilot-based channel estimation algorithm is studied. Firstly, the common pilot structure is introduced. Then the channel estimation algorithm of pilot position and the channel estimation algorithm of non-pilot position are described in detail. In order to select the appropriate algorithm according to the requirements of the project. For the equilibrium, we introduce the zero-forcing equalization, the decision feedback zero-forcing equalization and the improved decision feedback zero-forcing equalization for the OFDM system. Secondly, The channel estimation and equalization algorithm for fast time-varying channel in OFDM system is studied. When the Doppler frequency shift of the channel is large, there will be serious subcarrier interference in the system, and the algorithm proposed for slow time-varying channel is no longer applicable. Therefore, the corresponding channel estimation algorithm is studied for fast time-varying channel. In order to better track the fast time-varying channel in real time, a channel estimation algorithm based on base expansion is studied. A set of finite basis function weighted summation is used to fit time-varying channels. Different types of basis functions are introduced, and a cluster-like comb pilot structure is given according to the characteristics of time-varying channels. In order to deal with the ICI phenomenon and recover the transmitted data, a block decision feedback equalization algorithm for time-varying channel based on the extended basis model is introduced. Based on the consideration of resource usage and system rate, the hardware scheme of channel estimation and equalization based on pilot and digital sine cosine signal generator is designed and implemented on FPGA hardware platform. The performance effect and resource usage of each algorithm are given through simulation results and comprehensive report analysis, in order to select the appropriate algorithm according to the project requirements in engineering projects.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TN929.53

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