本文選題：基帶 + OFDM��； 參考：《東南大學(xué)》2017年碩士論文

【摘要】：隨著移動通訊技術(shù)的全面普及與飛速發(fā)展,正交頻分復(fù)用(OFDM,Orthogonal Frequency Division Multiplexing)技術(shù)作為一種多載波調(diào)制的高速傳輸方式,以其高效的頻譜利用率,穩(wěn)定的抗多徑能力等優(yōu)點,使之成為當(dāng)前應(yīng)用于第四代移動通信系統(tǒng)中的核心技術(shù),并且在針對LTE芯片測試等方面也具有一定的應(yīng)用價值。然而OFDM系統(tǒng)對符號同步的同步偏差具有很高的要求。因此符號同步的精確與否,對于OFDM系統(tǒng)性能的提升具有非常重要的作用。本文針對基于訓(xùn)練序列的OFDM符號同步算法進(jìn)行研究與改進(jìn),綜合了 SchmidlCox算法與Park算法在訓(xùn)練序列上的一致性以及它們在性能上的互補(bǔ)關(guān)系,對OFDM符號同步方法提出了改進(jìn)方法,該方法的整個同步環(huán)節(jié)由粗同步估計和精同步估計兩個階段構(gòu)成。首先運用SchmidlCox的算法進(jìn)行一個粗略的同步估計。然后以粗略同步估計的位置來確定精同步估計階段的估計窗口,最后以Park算法的方式進(jìn)行精符號同步估計得到最終確定的符號定時的位置。Matlab的仿真結(jié)果表明改進(jìn)算法的同步均方誤差(MSE,Mean Square Error)在高信噪比和低信噪比情況下相對于現(xiàn)有算法均保持在較低水平。關(guān)于OFDM符號同步算法的硬件實測從功能和性能指標(biāo)兩個方面展開,結(jié)果表明,基于FPGA平臺實現(xiàn)的改進(jìn)算法能夠?qū)崿F(xiàn)對OFDM基帶信號進(jìn)行符號同步的功能,并可以繪制出相應(yīng)的星座圖。在誤差矢量幅度(EVM,Error Vector Magnitude)指標(biāo)上,通過將OFDM系統(tǒng)中FFT模塊的輸出數(shù)據(jù)導(dǎo)入至Matlab中計算,EVM的計算結(jié)果在5%以下。在MSE指標(biāo)上,通過在Matlab中對同步誤差值進(jìn)行統(tǒng)計與計算,MSE在SNR小于8dB時計算結(jié)果在105以下,MSE在SNR大于8dB時計算結(jié)果在10以下,且均優(yōu)于現(xiàn)有算法。本文的OFDM符號同步估計方法在功能和性能上均滿足了設(shè)計要求和指標(biāo),可實現(xiàn)OFDM基帶系統(tǒng)中對信號的符號同步,其研究成果對于應(yīng)用OFDM技術(shù)的通信系統(tǒng)具有一定的工程實用價值。
[Abstract]:With the popularization and rapid development of mobile communication technology, orthogonal Frequency Division Multiplexing) (orthogonal Frequency Division Multiplexing) technology, as a high speed transmission mode of multi-carrier modulation, has the advantages of efficient spectrum efficiency and stable anti-multipath capability. It has become the core technology applied in the fourth generation mobile communication system, and also has certain application value in the field of LTE chip test and so on. However, the synchronization deviation of symbol synchronization in OFDM system is very high. Therefore, the accuracy of symbol synchronization plays a very important role in improving the performance of OFDM system. In this paper, the algorithm of OFDM symbol synchronization based on training sequence is studied and improved. The consistency of SchmidlCox algorithm and Park algorithm in training sequence and their complementary relationship in performance are synthesized, and the improved method of OFDM symbol synchronization is proposed. The whole synchronization of this method consists of rough synchronization estimation and precision synchronization estimation. First, a rough synchronization estimation is made by using SchmidlCox algorithm. Then the estimation window of the precise synchronization estimation stage is determined by the rough synchronization estimation position. Finally, the position of the final symbol timing is estimated by using Park algorithm. The simulation results of Matlab show that the improved algorithm has high SNR and low SNR relative to MSE mean Square error in the case of high signal-to-noise ratio (SNR) and low signal-to-noise ratio (SNR). The existing algorithms are kept at a lower level. The hardware measurement of OFDM symbol synchronization algorithm is carried out from two aspects: function and performance index. The result shows that the improved algorithm based on FPGA platform can realize symbol synchronization of OFDM baseband signal. And can draw the corresponding constellation map. On the index of error vector amplitude, the output data of FFT module in OFDM system are imported into Matlab. The result of calculation is less than 5%. In terms of MSE index, the synchronous error value in Matlab is counted and calculated. When SNR is less than 8dB, the calculated result is less than 10 when SNR is larger than 8dB, and it is better than existing algorithms. The OFDM symbol synchronization estimation method in this paper meets the design requirements and specifications in function and performance. It can realize the symbol synchronization of signals in the OFDM baseband system. The research results have certain engineering practical value for the communication system using OFDM technology.
【學(xué)位授予單位】：東南大學(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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