Channel Estimation Of Millimeter Wave Massive MIMO Sparse Systems

With the rapid growth of business requirements such as high-speed,low-latency,highreliability and massive connections,5G wireless communications are facing exponentially increasing data transmission pressure.Due to the rich spectrum resources,the millimeter-wave multiple-input multiple-output(MIMO)system has attracted widespread attention.The base station uses an array of a large number of antennas to compensate for the serious path loss in the millimeter wave band to achieve a high array gain,which can significantly improve the throughput and transmission rate of the system.In order to obtain accurate channel state information,this paper conducts research work on millimeter wave massive MIMO channel estimation.The detailed work is included as follows.Considering that the channel is sparse in the time domain and the angular domain,compressed sensing(CS)technology can be used for channel estimation.This paper focuses on the compressive sensing greedy reconstruction algorithm.According to the known and unknown sparseness,it compares a variety of greedy reconstruction algorithms in detail,focusing on the optimization of atoms and the method of updating residuals.On this basis,a variety of greedy reconstruction algorithms are applied to the coherent channel estimation of millimeter-wave massive MIMO systems.The simulation results show that the channel estimation algorithm based on generalized orthogonal matching pursuit has lower mean squared error than other algorithms under the condition of high signal-to-noise ratio.Random phase offset caused by large carrier frequency offset(CFO)and system hardware defects will destroy the received pilot signal in different time periods.In consideration of random phase offset,this paper first studies a non-coherent channel estimation algorithm that uses only signal strength information for compressive phase retrieval(CPR).This paper uses the partial coherence in hybrid mm Wave systems,i.e.,the pilots sent from different radio frequency chains share the same phase distortion in the same time frame,while the phase distortions are different across different time frames.Using the partial coherence,the on-grid partial coherence CPR(PC-CPR)channel estimation algorithm is studied.On this basis,a modified PC-CPR(MPC-CPR)channel estimation algorithm is proposed.Simulation results show that the performance of MPC-CPR algorithm is better than that of PC-CPR algorithm under the conditions of high signal-to-noise ratio,different measured values and different number of radio frequency links.