Research On Channel Estimation And Channel Equalization Technology Under Internet Of Vehicles Channels

With the rapid development of communication,Internet of Vehicles（Io Vs）based intelligent transportation has received extensive attention in recent years.At present,there are two main categories technology of Io Vs:Dedicated Short-Range Communication（DSRC）technology and the cellular mobile communication assisted LTE-V2X.Specifically,Orthogonal Frequency Division Multiple（OFDM）and Single Carrier Frequency Division Multiple Access（SC-FDMA）technology are adopted by DSRC and LTE-V2X,respectively.Moreover,SC-FDMA has the advantage of lower peak-to-average ratio compared to OFDM.Due to frequency domain equalization is utilized by single-carrier block transmission,the outstanding signal processing capability is obtained at the receiver.Therefore,LTE-V2X draws considerable interests from academia and industry.In LTE-V2X channel,it is a great challenge to the design of the receiver because the high-speed movement of the transceiver and the high carrier frequency band.To overcome the time-frequency dual-selection feature brought by the wireless channel of LTE-V2X,accurate channel estimation and effective equalization technology are essential.This thesis aim to investigative channel estimation and equalization technology in LTE-V2X.The specific research contents include:1.Aiming at the low accuracy of traditional channel estimation algorithms in fast time-varying channels,a basis extension model（BEM）based channel estimation algorithm is introduced in this thesis.However,while improving the estimation accuracy,this algorithm also brings about the problem of computational complexity.In order to solve the above complexity problem,a low-complexity BEM channel estimation algorithm is researched by this thesis.Specifically,a direct relationship between the base coefficients and the channel frequency domain response is derived,which can directly obtain the channel frequency domain response through the base coefficients.The complexity of the whole estimation algorithm is reduced from o（N ³）to o（N）,due to the part of converting the base coefficients into Toeplitz matrices and fitting the time-domain channel with the base coefficients in the traditional BEM algorithm is omitted.The correctness of the theoretical derivation is verified by simulation,and it is proved that the BER performance of the traditional BEM algorithm and the improved low-complexity BEM algorithm is better than that of the traditional channel estimation algorithm.Moreover,the BER performance of improved low-complexity BEM algorithm only loses 0.5～0.6d B when the bit error rate performance reaches10^-4 compared with the traditional BEM algorithm.2.To further improve the reliability of LTE-V2X,nonlinear equalization of SC-FDMA systems is researched.The traditional linear frequency domain equalizer has the disadvantages of amplifying noise and unable to completely eliminate the Inter Symbol Interference（ISI）.Therefore,a nonlinear based equalizer with high robustness is designed in this thesis.Moreover,the traditional nonlinear equalization algorithm has high complexity due to time-domain feedback and only eliminate the ISI caused by the forward symbol.Hence,two Iterative Block Decision Feedback Equalizers（IB-DFE）are designed in the SC-FDMA system with both feedforward and feedback filters working in the frequency domain,and the theoretical analysis is carried out respectively.In addition,the validity of the theoretical analysis is verified by simulation,and it is concluded that the bit error rate performance of IB-DFE is better than that of the two traditional nonlinear equalizers.Therefore,the designed low-complexity BEM algorithm and IB-DFE equalizer are combined in the fast time-varying Io V to obtain a channel estimation equalization system with high reliability,which is verified by simulation.