Research In Synchronization And Channel Estimation For OFDM In IOV System

Internet of Vehicles(IOV)is a system that connects vehicles to roadside facilities,pedestrians,networks and so on.It has has a promising future in improving traffic jams and Intelligent vehicle control.The key technology of data transmission in the IOV is wireless communication technology.While the physical layer in the wireless communication protocol that defines and regulates wireless communication technology plays a key role.It has great influence on the stability,real-time and effectiveness of the networking system.This paper focused on the problem of synchronization and channel estimation in the OFDM technology,which is used in physical layer transmission.Firstly,several typical algorithms based on training symbols for symbol timing synchronization and carrier frequency synchronization in OFDM were introduced,including Schmidl&Cox(SC)algorithm,Minn's two improved algorithms and Park algorithm,and the advantages and disadvantages of these three algorithms were compared from theoretical derivation and experimental simulation.Secondly,for the problems of symbol timing measurement function curve in SC,Minn and Park algorithms,including "platform effect",the peak value of curve being not sharp enough,"side peak" interference,this paperproposed an improved time frequency synchronization scheme based on CAZAC sequence.The new training symbols proposed in this scheme effectively solves the problem of "platform effect" and the peak value of curve being not sharp due to its own structural characteristics and the ideal autocorrelation and cross-correlation characteristics of CAZAC sequence.And through the PN weighting of new training symbols,the "side peak" interference problem is further effectively solved.Then,based on the new training symbols,the definition and Simulation of the symbol timing synchronization algorithm and the carrier frequency offset estimation algorithm were completed.The simulation results showed that the timing curve of the new training symbols can generate a sharp spike type at the correct timing estimation point,and there is no "side peak" effect,which effectively improves the accuracy of symbol timing estimation.Finally,aiming at some typical application scenarios of IOV,three key processes of pilot aided channel estimation technology were studied,including three key processes of selecting pilot structure,channel estimation at pilot location and channel estimation at data location.The simulation results showed that trellis pilot structure can perform effective channel estimation work at both high and low Rician channels with low pilot occupancy.By using the LS estimation algorithm and DFT noise reduction technique for the channel estimation at the pilot location,a highly accurate CSI estimation value can be obtained under low computational complexity conditions.An accurate CSI estimate can be obtained by using a simple linear interpolation algorithm for channel estimation at the data location.