Research On Mm Wave Channel Estimation And CRAN In The High-speed Mobile Scenario

Millimeter wave(mmWave)communications are drawing great attention in building future 5G cellular networks,which can meet exploding demand for high-speed mobile data.By exploiting the large bandwidth available mmWave frequencies,it has potential to offer high communication data up to a few Gbps.To compensate the significant path loss incurred by signals over mmWave frequency,large array should be established on mRRH and mTAT to provide sufficient beamforming gains,posing a challenge in channel estmation in the highspeed train(HST)systems.Therefore,the paper studies the channel estimation for HST wireless communications and analyses the performance of the proposed CRAN architecture.The main contributions of this paper are summarized as follows:Firstly,Consider the mmWave MIMO channel model for HST system,analyze the timevarying characteristics in high-speed mobile scenarios which takes form of the phase deflection in the channel model.We first estimate the channel model based on traditional LS algorithm and MMSE channel estimation method.After that,a channel estimation method based on phase deflection is proposed to analyze the bit error rate of the received channel after phase deflection processing.Secondly,HST mmWave channels tend to have only a light-of-sight(LOS)or few significant non-LOS paths,which appear to has the property of sparsity.Channel estimation can be carried out by leveraging compressed sensing(CS)theories.The first step is to design reasonable measurement matrix for HST mmWave channel estimation and then vectorize the HST mmWave channel model having sparse nature.Utilize the classical CS algorithms to reconstruct the virtual channel model after vectorization and compute the NMSE.After that,optimize the exist CS algorithms to improve the success rate of reconstruction,which boosts the MSE performance of channel estimation.At last,consider the mmWave HST wireless communication system,the idea of CRAN will be introduced to the HST network.A classical Dual-Hop structure is adopted and the opinion of cooperative between smart antenna and dual-Hop architecture is utilized.A train access terminal(mTAT)is placed on the top of a fast-running train,and a mmWave Remote Radio Head(mRRH)is placed near the track axis.Smart antennas are placed on the top of the mTAT.The Doppler frequency shift,outage probability and ergodic capacity of the system are analyzed.The simulation results show that the proposed millimeter wave CRAN system has excellent system performance.