【導讀】用率，優(yōu)良的抗窄帶干擾和多徑衰落能力而被視為下一代無線通信的核心技術。最后在此基礎上，驗證了一種改進的內(nèi)插算法。

　　

【正文】 系統(tǒng)參數(shù)如表 所示。兩者均采用 LS+線性內(nèi)插，改進的算法中添加了低通濾波器。 蘭州理工大學畢業(yè) 論文 23 圖 加低通濾波器 從圖 可以看出在相同的誤碼率條件下，改進的內(nèi)插算法可以優(yōu)于原有的線性內(nèi)插算法約 3dB， 這是因為在線性內(nèi)插后增加了一級低通濾波器，該濾波器消除了一部分噪聲分量，使系統(tǒng)的性能得到提高， 這與理論分析的結果一致從而驗證了理論分析的 。 0 5 10 15 20 25 30 35 40102101100S N R ( d B )BER不同插值計算比較 無信道估計線性插值線性插值 + 低通濾波器蘭州理工大學畢業(yè) 論文 24 結論 本文通過數(shù)值仿真對基于導頻的 OFDM 系統(tǒng)信道估計中的幾種插值算法進行了對比分析，得出了以下結論： （ 1）線性插值算法僅對具有大致斜面特性的函數(shù)有效，不能用于本文所討論的OFDM 系統(tǒng)的信道估計或類似的系統(tǒng)。 （ 2） 一階線性內(nèi)插 ，二階內(nèi)插和三次樣條內(nèi)插算法的性能依次增加，其復雜度也依次變大。 （ 3）通過在線性內(nèi)插的基礎上提出了一種改變內(nèi)插算法，改進的算法由于在線性內(nèi)插后增加了一級低通濾波器，濾除了一部分噪聲，從而提高了系統(tǒng)性能，通過仿真驗證，可以看出改進的內(nèi)插算法優(yōu)于本來的線性內(nèi)插算法。 蘭州理工大學畢業(yè) 論文 25 參考文獻 ［ 1］彭鈴 .OFDM 系統(tǒng)中基于導頻的信道估計及其 MATLAB 仿真［ J］ .井岡山學院學報（自然科學）， 2020， 29（ 2） ［ 2］劉軍峰，馬海武 .基于導頻符號的信道估計算法研究［ J］ .通信技術， 2020， 41（ 01） ［ 3］李冬霞，王高虎，劉海濤 .基于導頻的 OFDM 信道估計算法性能分析［ J］ .中國民航大學學報， 2020， 25（ 5） ［ 4］ 楊小牛，樓才義，徐建良著 . 軟件無線電原理與應用 . 北京：電子工業(yè)出版社， 2020 ［ 5］劉鈞雷，葉芳，朱琦 .OFDM 系統(tǒng)中基于導頻的信道估計［ J］ .重慶郵電學院學報， 2020，16（ 4） ［ 6］ 陳邦媛，射頻通信電路 . 北京：科學出版社， 2020 ［ 7］ 佟學儉，羅濤 . OFDM 移動通信技術原理與應用 . 北京：人民郵電出版社， 2020 ［ 8］沈若聘，李健 .基于梳狀導頻的 OFDM 信道估計算法［ J］ .電力系統(tǒng)通信， 2020， 29（ 187） ［ 9］韓丹夫，吳慶標 .數(shù)值計算方法［ M］ .杭州：浙江大學出版社， 2020 ［ 10］萬永革 .數(shù)字信號處理 的 MATLAB 實現(xiàn)［ M］ .北京：科學出版社， 2020 ［ 11］Ｃ leve ［美］著，喻文健譯 .MATLAB 數(shù)值計算［ M］ .北京：機械工業(yè)出版社，2020 ［ 12］ 曹志剛，錢亞生 . 現(xiàn)代通信原理 . 北京：清華大學出版社， 1998 ［ 13］蔣濤 .OFDM 系統(tǒng)中的信道估計技術［ J］ .四川師范大學學報（自然科學版）， 2020，30（ 1） ［ 14］葉晟 .基于導頻的 OFDM 系統(tǒng)信道估計［ J］ .中山大學研究生學刊（自然科學、醫(yī)學版）， 2020， 28（ 2） [15] Heiskala J, Terry J. OFDM Wireless LANs: A theoretical and practical guide .Pearson Education, Inc. 2020 [16] T. W. Parks, and J. H. McClellan. Chebyshe approximation for nonrecursive digital filters with linear phase .IEEE Trans. On Circuit , CT19。 189~194 [17] H Holma , A Toskala. WCDMA for UMTS: Radio Acess For Third Generation Moble Communications. Wiley. 2020 蘭州理工大學畢業(yè) 論文 26 附錄 A 英文文獻 Time and Frequency Synchronisation in 4G OFDM Systems Due to its many advantages, orthogonal frequency division multiplexing (OFDM) was adopted for the European standards of terrestrial stationary and handheld video broadcasting systems (DVBT, DVBH) as well as wireless work standards and . It was also chosen as one of the transmission techniques for 3GPP LongTerm Evolution system and WINNER Radio Interface Concept [1], which has recently been proposed for 4G systems. However, the OFDM transmission is sensitive to receiver synchronisation imperfections. The symbol timing synchronisation error may cause interblock interference (IBI) and the frequency synchronisation error is one of the sources of intercarrier interference (ICI). Thus, synchronisation is a crucial issue in an OFDM receiver design. It depends on the form of the OFDM transmission (whether it is continuous or has a bursty nature). synchronisation algorithms specific for packet or bursty transmission have to be applied. Synchronisation is not fully obtained after the acquisition mode since the sampling frequency offset still remains unpensated. The inaccuracy of the sampling clock frequency causes slow drift of the FFT window giving rise to ICI and subcarrier phase rotation. Both signal distortions, but not their sources, may be removed by a frequencydomain channel equaliser. However, the time shift of the FFT window builds up, and eventually the FFT window shifts beyond the orthogonality window of the OFDM symbol giving rise to IBI. Therefore, the sampling clock synchronisation, performed by a resampling algorithm, should also be implemented in the OFDM receiver. A number of time and frequency synchronisation algorithms in the OFDMbased systems have already been proposed. The less plex but less accurate algorithms are based on the correlation of identical parts of the OFDM symbol. The correlation between the cyclic prefix and the corresponding end of the OFDM symbol, or between two identical halves of the synchronisation symbol, is applied in [3, 4], 蘭州理工大學畢業(yè) 論文 27 respectively. The use of pseudonoise sequence correlation properties was proposed in [5, 6]. Both solutions offer very accurate time and frequency offset estimates。 however, the main disadvantage of both of them is their plexity. In this paper, fast and accurate timing and frequency synchronisation algorithms are proposed. The synchronisation is a twostage process. First, coarse timing and fractional frequency offset synchronisation are performed. After detecting the transmitted signal, the carrier frequency and sampling frequency offsets are tracked during the tracking mode by a lowplex algorithm, which is immune to symbol timing offset estimation errors. The algorithm is designed for OFDM systems with a small pilot overhead, and it applies channel estimates already puted by the channel estimation block It supports high data rate services and at the same time provides low cost per bit transmission. It concentrates on integrating all the existing technologies so that user can easily roam from one service provider area to another. So this increases the roaming capability. The expected data rate is 20Mbps in high mobility (vehicle traveling 200 km/h) and 1Gbps in low mobility (speed 3 km/h). Of course achieving this data rate requires careful selection of multi carrier modulation scheme. Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies arenot made or distributed for profit or mercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, or republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. In multi carrier approach the original data stream is divided into N number of parallel streams. Then each stream is modulated with different carrier frequency and sent across