OFDM系統(tǒng)的信道估計(jì)研究與實(shí)現(xiàn)
發(fā)布時(shí)間：2018-07-31 17:14
【摘要】：無線通信技術(shù)作為最有朝氣的科研領(lǐng)域之一,它打破了存在物理方面的限制和制約的有線通信的桎梏,使得各用戶可以任意的在無線電波能夠輻射到的地區(qū)進(jìn)行通信,極大的開拓了通信的時(shí)間尺度和空間尺度。隨著越來越大的數(shù)據(jù)量和越來越快的傳輸速率的需求,作為一種關(guān)鍵技術(shù),通信系統(tǒng)對信道估計(jì)也有著更加嚴(yán)苛的要求。本文的主要內(nèi)容是研究不同導(dǎo)頻圖案以及不同信道估計(jì)算法的性能,并選取一種低復(fù)雜度的算法完成基于FPGA的實(shí)現(xiàn)。本文首先闡述了無線通信系統(tǒng)中信道估計(jì)理論的研究背景與研究意義,并對信道估計(jì)的國內(nèi)外研究現(xiàn)狀進(jìn)行了簡單分析。由于信道估計(jì)的本質(zhì)是對信道響應(yīng)的求解,所以本文就大尺度衰落和小尺度衰落兩種無線信道衰落特征進(jìn)行簡要介紹,并對兩種常用的適用于頻選信道的Jakes模型和可以對時(shí)頻雙選性衰落信道精確近似的復(fù)指數(shù)基擴(kuò)展模型進(jìn)行數(shù)學(xué)建模分析。本論文研究并借助計(jì)算機(jī)進(jìn)行仿真分析的信道估計(jì)算法包括LS、DFT消噪和MMSE算法。研究中還對塊狀、梳狀和菱形三種導(dǎo)頻圖案進(jìn)行分析,研究在不同速度下各個(gè)導(dǎo)頻圖案信道估計(jì)的性能變化。本文研究的另一個(gè)重點(diǎn)是在FPGA中對相關(guān)的信道估計(jì)算法進(jìn)行實(shí)現(xiàn)。由于LS信道估計(jì)算法和線性插值的性能較好,且復(fù)雜度很低,所以在進(jìn)行FPGA實(shí)現(xiàn)時(shí)采用這種算法。相較于大多數(shù)的基于FPGA+DSP架構(gòu)的基帶設(shè)計(jì),把信道估計(jì)算法的實(shí)現(xiàn)從DSP中搬移到FPGA中實(shí)現(xiàn)可以降低二者的數(shù)據(jù)通信帶來的效率問題和設(shè)計(jì)難度問題。本論文中基于FPGA的設(shè)計(jì)有著估計(jì)方案可變的優(yōu)勢,即可以通過用戶定義來完成塊狀、梳狀、菱形導(dǎo)頻圖案的切換,也可以實(shí)現(xiàn)不同時(shí)域間隔和頻域間隔的設(shè)置,以滿足不同應(yīng)用場景的需求。論文主要圍繞OFDM系統(tǒng)的基本框架進(jìn)行闡述。第一章簡要描述了無線通信中信道估計(jì)理論的研究背景與研究意義,并對信道估計(jì)的國內(nèi)外研究現(xiàn)狀進(jìn)行了簡單分析,隨后還對本文所做工作和論文章節(jié)安排進(jìn)行簡單梳理。第二章探究了無線信道的特征和常用的無線信道模型,主要就大尺度衰落和小尺度衰落兩種無線信道衰落特征進(jìn)行簡要介紹,并對兩種常用的Jakes模型和復(fù)指數(shù)基擴(kuò)展模型進(jìn)行數(shù)學(xué)建模分析。第三章首先分析了 OFDM的基本原理,然后從導(dǎo)頻圖案著手展開詳細(xì)的研究,對比分析了不同的導(dǎo)頻圖案適用于何種信道。研究發(fā)現(xiàn),梳狀導(dǎo)頻最適用于高速移動(dòng)的環(huán)境,但是菱形導(dǎo)頻在保證與梳狀導(dǎo)頻性能接近的前提下,需要的導(dǎo)頻資源更少,提高了頻譜利用率。此外還研究了菱形導(dǎo)頻圖案中導(dǎo)頻間隔對信道估計(jì)性能的影響。第四章對第三章的結(jié)果做總結(jié)分析,選出較容易實(shí)現(xiàn)的LS信道估計(jì)算法在FPGA中進(jìn)行實(shí)現(xiàn)。在設(shè)計(jì)方案中首先給出了系統(tǒng)頂層文件和時(shí)序規(guī)劃的設(shè)計(jì)思想,并對各個(gè)模塊的設(shè)計(jì)原理以及波形仿真等方面進(jìn)行論述。設(shè)計(jì)中采用可變參數(shù)的設(shè)計(jì)思路,例如所要移除的CP長度、導(dǎo)頻的初始位置、導(dǎo)頻個(gè)數(shù)、導(dǎo)頻的時(shí)頻域間隔等均可以由用戶定義,具有很好的移植性。
[Abstract]:As one of the most active research fields, wireless communication technology has broken the shackles of wired communication, which is restricted and restricted by physics, so that users can communicate freely in areas where radio waves can be radiated, greatly expanding the time scale and space scale of communication. With the increasing amount of data As a key technology, as a key technology, the communication system has more stringent requirements for channel estimation. The main content of this paper is to study the performance of different pilot patterns and different channel estimation algorithms, and to select a low complexity algorithm to complete the implementation based on FPGA. The research background and significance of channel estimation theory in line communication system are discussed, and the research status of channel estimation at home and abroad is briefly analyzed. Since the essence of channel estimation is to solve the channel response, this paper briefly introduces two kinds of wireless channel fading characteristics of large scale fading and small scale fading, and two kinds of frequent. The Jakes model applied to the frequency selective channel and the complex exponential base extension model which can accurately approximate the time-frequency doubly selective fading channel are modeled and analyzed. The channel estimation algorithms of this paper and the computer simulation analysis include the LS, the DFT denoising and the MMSE algorithm. In the study, three pilots of block, comb and diamond are also used in the study. The pattern is analyzed and the performance changes of the channel estimation for each pilot pattern at different speeds are studied. Another focus of this paper is to implement the related channel estimation algorithms in FPGA. Because of the better performance and low complexity of the LS channel estimation algorithm and linear interpolation, this algorithm is used in the implementation of the FPGA. Compared with most of the Baseband Design Based on FPGA+DSP architecture, the implementation of the implementation of channel estimation algorithm from DSP to FPGA can reduce the efficiency and design difficulty of the data communication of two persons. In this paper, the design based on FPGA has the advantage of variable estimation, that is, the block can be completed by user definition. In order to meet the needs of different application scenes, the paper mainly focuses on the basic framework of the OFDM system. The first chapter briefly describes the research background and research significance of the channel estimation theory in wireless communication and the channel estimation. In the second chapter, the characteristics of wireless channel and the common wireless channel model are explored, and the characteristics of two wireless channel fading of large scale fading and small scale fading are briefly introduced, and two kinds of commonly used Jake are introduced. The mathematical modeling and analysis of S model and complex exponential base extension model are carried out. The basic principle of OFDM is analyzed in the third chapter. Then the detailed study is carried out from pilot pattern, and the different pilot patterns are compared and analyzed. The research shows that the comb pilot is most suitable for the high-speed moving environment, but the diamond guide frequency is guaranteed. On the premise of approaching the comb pilot performance, the required pilot resources are less and the spectrum utilization is improved. In addition, the influence of pilot interval on channel estimation performance in rhombus pilot pattern is also studied. The fourth chapter summarizes and analyzes the results of the third chapter, and selects the LS channel estimation algorithm which is easier to implement in the design of the FPGA. The design idea of the top layer file and time sequence planning of the system is given first, and the design principle of each module and the waveform simulation are discussed. The design ideas of variable parameters, such as the length of the CP to be removed, the initial position of the pilot, the number of pilot, the interval of the time-frequency domain of the pilot and so on, can be used by the user. Definition, with good portability.
【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TN929.53
本文編號：2156285
[Abstract]:As one of the most active research fields, wireless communication technology has broken the shackles of wired communication, which is restricted and restricted by physics, so that users can communicate freely in areas where radio waves can be radiated, greatly expanding the time scale and space scale of communication. With the increasing amount of data As a key technology, as a key technology, the communication system has more stringent requirements for channel estimation. The main content of this paper is to study the performance of different pilot patterns and different channel estimation algorithms, and to select a low complexity algorithm to complete the implementation based on FPGA. The research background and significance of channel estimation theory in line communication system are discussed, and the research status of channel estimation at home and abroad is briefly analyzed. Since the essence of channel estimation is to solve the channel response, this paper briefly introduces two kinds of wireless channel fading characteristics of large scale fading and small scale fading, and two kinds of frequent. The Jakes model applied to the frequency selective channel and the complex exponential base extension model which can accurately approximate the time-frequency doubly selective fading channel are modeled and analyzed. The channel estimation algorithms of this paper and the computer simulation analysis include the LS, the DFT denoising and the MMSE algorithm. In the study, three pilots of block, comb and diamond are also used in the study. The pattern is analyzed and the performance changes of the channel estimation for each pilot pattern at different speeds are studied. Another focus of this paper is to implement the related channel estimation algorithms in FPGA. Because of the better performance and low complexity of the LS channel estimation algorithm and linear interpolation, this algorithm is used in the implementation of the FPGA. Compared with most of the Baseband Design Based on FPGA+DSP architecture, the implementation of the implementation of channel estimation algorithm from DSP to FPGA can reduce the efficiency and design difficulty of the data communication of two persons. In this paper, the design based on FPGA has the advantage of variable estimation, that is, the block can be completed by user definition. In order to meet the needs of different application scenes, the paper mainly focuses on the basic framework of the OFDM system. The first chapter briefly describes the research background and research significance of the channel estimation theory in wireless communication and the channel estimation. In the second chapter, the characteristics of wireless channel and the common wireless channel model are explored, and the characteristics of two wireless channel fading of large scale fading and small scale fading are briefly introduced, and two kinds of commonly used Jake are introduced. The mathematical modeling and analysis of S model and complex exponential base extension model are carried out. The basic principle of OFDM is analyzed in the third chapter. Then the detailed study is carried out from pilot pattern, and the different pilot patterns are compared and analyzed. The research shows that the comb pilot is most suitable for the high-speed moving environment, but the diamond guide frequency is guaranteed. On the premise of approaching the comb pilot performance, the required pilot resources are less and the spectrum utilization is improved. In addition, the influence of pilot interval on channel estimation performance in rhombus pilot pattern is also studied. The fourth chapter summarizes and analyzes the results of the third chapter, and selects the LS channel estimation algorithm which is easier to implement in the design of the FPGA. The design idea of the top layer file and time sequence planning of the system is given first, and the design principle of each module and the waveform simulation are discussed. The design ideas of variable parameters, such as the length of the CP to be removed, the initial position of the pilot, the number of pilot, the interval of the time-frequency domain of the pilot and so on, can be used by the user. Definition, with good portability.
【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TN929.53
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