本文選題：正交頻分復(fù)用 + 高鐵信道模型��； 參考：《電子科技大學(xué)》2014年碩士論文

【摘要】：高鐵環(huán)境下,無(wú)線信道的快時(shí)變性使OFDM技術(shù)面臨子載波間干擾;為了節(jié)省帶寬或者適應(yīng)不同的多徑環(huán)境,OFDM系統(tǒng)的循環(huán)前綴有可能不夠充分,這種循環(huán)前綴不足的情況會(huì)為OFDM系統(tǒng)帶來(lái)符號(hào)間干擾。為了盡可能地消除子載波間干擾和符號(hào)間干擾,實(shí)現(xiàn)數(shù)據(jù)準(zhǔn)確傳輸,本文主要研究高鐵環(huán)境下OFDM系統(tǒng)信道估計(jì)和信號(hào)檢測(cè)。本文第二章主要研究基于基擴(kuò)展模型的高鐵信道模型。首先研究高鐵環(huán)境下典型信道模型以及基擴(kuò)展模型的概念及其分類(lèi),重點(diǎn)研究了廣受關(guān)注的復(fù)指數(shù)基擴(kuò)展模型,針對(duì)其所存在的高頻部分采樣誤差,利用改進(jìn)復(fù)指數(shù)基擴(kuò)展模型使采樣點(diǎn)都落在多普勒擴(kuò)展譜內(nèi)部,最高采樣頻率等于最大多普勒頻移;其次,研究并提出改進(jìn)復(fù)指數(shù)基擴(kuò)展模型的基維數(shù)和基函數(shù)的優(yōu)化設(shè)計(jì)方法,理論分析和仿真證明,基維數(shù)主要取決于信道最大多普勒頻移和信噪比,在導(dǎo)頻數(shù)目固定的條件下,基維數(shù)越高,建模誤差越小,但參數(shù)估計(jì)的準(zhǔn)確度也會(huì)降低,需要在二者之間進(jìn)行折中,基函數(shù)則會(huì)在基維數(shù)確定后,影響對(duì)多普勒擴(kuò)展譜描述的準(zhǔn)確性。本文第三章研究時(shí)變信道下OFDM系統(tǒng)梳狀導(dǎo)頻的優(yōu)化設(shè)計(jì)方法。首先研究基于線性最小均方誤差準(zhǔn)則的最優(yōu)的簇型梳狀結(jié)構(gòu)導(dǎo)頻設(shè)計(jì),基于OFDM系統(tǒng)信道時(shí)域矩陣和頻域矩陣的等效轉(zhuǎn)換關(guān)系,建立信道頻域矩陣的離散Karhuen-Loeve基擴(kuò)展模型等效模型,并分析接收端采用基于線性最小均方誤差估計(jì)準(zhǔn)則的估計(jì)方程和性能指標(biāo),討論在導(dǎo)頻功率一定的條件下,均方誤差最優(yōu)的梳狀導(dǎo)頻設(shè)計(jì)需滿足的條件。研究了基于頻域Kronecker函數(shù)的簇型梳狀導(dǎo)頻結(jié)構(gòu)(每簇中中間有一個(gè)非零導(dǎo)頻,其它兩邊都是零導(dǎo)頻構(gòu)成的保護(hù)間隔)的改進(jìn),增加每簇中非零導(dǎo)頻數(shù)目的個(gè)數(shù)以增加所攜帶的信息量,雖然其子載波間干擾有所提升,但信道估計(jì)性能反而能得到提高;針對(duì)傳統(tǒng)的要求簇與簇之間導(dǎo)頻數(shù)據(jù)相同,并且每簇中導(dǎo)頻數(shù)據(jù)為零相關(guān)區(qū)序列的導(dǎo)頻結(jié)構(gòu),分析驗(yàn)證可以在每簇導(dǎo)頻數(shù)據(jù)前通過(guò)偽隨機(jī)序列加擾的方法,來(lái)降低該結(jié)構(gòu)的峰均比。本文第四章研究快變信道下基于梳狀導(dǎo)頻的OFDM系統(tǒng)信道估計(jì)與信號(hào)檢測(cè)算法。首先提出梳狀導(dǎo)頻結(jié)構(gòu)下基于多個(gè)OFDM符號(hào)信道估計(jì)的算法,該算法將多個(gè)OFDM符號(hào)作為一組進(jìn)行信道估計(jì),在該段持續(xù)時(shí)間內(nèi)基擴(kuò)展模型只進(jìn)行一次基維數(shù)向上取整的近似,總的估計(jì)量減少,此時(shí)利用相同的導(dǎo)頻觀測(cè)量進(jìn)行信道估計(jì),帶來(lái)實(shí)際估計(jì)性能的提高;接下來(lái),針對(duì)多徑時(shí)延較大的環(huán)境,提出時(shí)變信道中循環(huán)前綴不足條件下,基于基擴(kuò)展模型的OFDM系統(tǒng)信道估計(jì)和信號(hào)檢測(cè)技術(shù),理論推導(dǎo)出基擴(kuò)展模型下符號(hào)間干擾消除和循環(huán)卷積重構(gòu)技術(shù),數(shù)字仿真結(jié)果證明,本文算法能取得較好的系統(tǒng)性能。綜上,本文從高鐵信道模型、發(fā)端導(dǎo)頻設(shè)計(jì)以及接收端信道估計(jì)和信號(hào)檢測(cè)的角度,討論基擴(kuò)展模型的運(yùn)用,具有理論研究和實(shí)際應(yīng)用價(jià)值。
[Abstract]:In the high speed environment, the fast time variability of the wireless channel makes the OFDM technology face intercarrier interference. In order to save bandwidth or adapt to different multipath environments, the cyclic prefix of the OFDM system may not be sufficient. The insufficiency of this kind of cyclic prefix will bring the intercarrier interference to the OFDM system. In order to eliminate the inter carrier interference and symbol as much as possible This paper mainly studies the channel estimation and signal detection of OFDM system in the high speed rail environment. In this paper, the second chapter mainly studies the model of the high speed iron channel based on the base extended model. The complex exponential base expansion model, aiming at its high frequency partial sampling error, uses the improved complex exponential base extension model to make the sampling points fall inside the Doppler spread spectrum, and the highest sampling frequency is equal to the maximum Doppler frequency shift. Secondly, the optimization design method for improving the base dimension and basic function of the complex exponential base expansion model is proposed. The theoretical analysis and simulation prove that the base dimension mainly depends on the maximum Doppler shift and the signal to noise ratio of the channel. Under the condition of the fixed number of pilots, the higher the base dimension, the smaller the modeling error, but the accuracy of the parameter estimation will be reduced. It is necessary to compromise between the two, and the base function will affect the Doppler expansion spectrum after the base dimension is determined. The third chapter studies the optimal design method of comb like pilot of OFDM system in time-varying channel. Firstly, the optimal pilot design of cluster comb structure based on linear minimum mean square error criterion is studied. Based on the equivalent transfer relationship between the time domain matrix and the frequency domain matrix of the OFDM system, the discrete Karhu of the frequency domain matrix of the channel is established. The equivalent model of en-Loeve based extended model is used, and the estimation equation and performance index based on the linear minimum mean square error estimation criterion are analyzed. Under the condition of certain pilot power, the conditions for the design of comb like pilot with the best mean square error are discussed. The cluster comb pilot structure based on the frequency domain Kronecker function is studied. In the middle of the cluster, there is a non zero pilot in the middle, and the other sides are the protection interval of zero pilot. The number of non zero pilot frequencies in each cluster is increased to increase the amount of information carried. Although the inter carrier interference is improved, the channel estimation performance can be raised, and the pilot data between clusters and clusters is required. In the fourth chapter, the fourth chapter studies the channel estimation and signal detection algorithm based on comb pilot in the fast changing channel. The algorithm is based on multiple OFDM symbol channel estimation. The algorithm uses multiple OFDM symbols as a group to estimate the channel. In the duration of the interval, the base extension model only performs an approximation of the base dimension of one base dimension. The total estimation is reduced. At this time, the same channel estimation is used to estimate the channel, which brings the actual estimation. In order to improve the performance, next, the OFDM system channel estimation and signal detection technology based on the base extended model are proposed for the environment of large multipath delay, and the technology of channel estimation and signal detection based on the base extended model is proposed. The algorithm of inter symbol interference cancellation and cyclic convolution reconstruction under the base extended model is derived. The results of digital simulation prove the algorithm of this paper. In conclusion, this paper discusses the application of the base expansion model from the angle of the high speed iron channel model, the design of the originator pilot and the channel estimation and signal detection of the receiver, which has theoretical research and practical application value.

【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(lèi)號(hào)】：TN929.53

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