| In millimeter-wave massive MIMO Telematics systems,the high-speed movement of vehicles leads to Doppler shifts,rapid channel changes and difficult estimation of channel state information,thus presenting a huge challenge for Telematics communications.Beamforming techniques for millimeter-wave large-scale MIMO systems aim to transmit high-gain signal beams in specific directions and reduce the effects of multipath fading.In this paper,we combine tensor methods and ultrasonic assistance to investigate the channel estimation and beamforming design issues for millimeter-wave massive MIMO Telematics systems as follows.Firstly,an ultrasonic-assisted millimeter-wave massive MIMO vehicular networking fast-layered alternating iterative tensor channel estimation algorithm is proposed to meet the high speed and stability requirements of V2 X communication transmission.After the high-dimensional complex millimeter-wave received signal is represented by a tensor,the proposed subspace dimensionality reduction tensor decomposition model is used for dimensionality reduction,followed by the proposed fast-layered alternating iterative tensor algorithm for the decomposed tensor,which performs channel estimation through the joint iteration of elements in the tensor space.The proposed ultrasonic-assisted DOA tracking method based on quantized grid and dictionary matrix adaptive iterative update is subsequently used to perform beam direction update after position change when the vehicle moves.The effectiveness and accuracy of the proposed algorithm for V2 X vehicular network channel estimation is verified by comparing the simulation results with some other algorithms.Secondly,a tensor-based ultrasonic and RIS-assisted millimeter-wave large-scale MIMO vehicular network beamforming design scheme is proposed considering the limitations of conventional beamforming methods in high-mobility environment communication.The scheme is based on the joint iterative optimization idea to jointly design the BS beamforming matrix,RIS phase shift matrix and user vehicle combination matrix to satisfy the maximum spectral efficiency to design the optimal beamforming.For the design of the RIS phase shift matrix,an ultrasonic-assisted subspace self-organized iterative RIS phase shift matrix design algorithm for V2 X communication scenarios is proposed.The DOA of the vehicle’s ultrasonic signal is tracked and used to design the initial RIS phase shift matrix,and subsequent RIS phase shift matrix updates are performed by the proposed subspace self-organizing iterative algorithm.The BS beamforming matrix design is performed by SVD and water injection power allocation methods.The combined matrix design of the user vehicle is derived using the tensor method.Simulation results show a significant improvement in the spectral efficiency of the proposed joint beamforming method compared with other methods.Finally,two scenarios are built for the practical testing of the above two algorithms.The performance of the relevant evaluation metrics is obtained by hardware and software settings and control variables.The test results show the practical value of the proposed channel estimation and joint beamforming algorithms applied to the two set scenarios,with excellent performance in data throughput and packet acceptance rate. |
