A Research Of Low Complexity Millimeter Wave Large-Scale MIMO Beamforming

With the development of communication technology and industrial application,the demand for large capacity and high speed of communication in contemporary life is more and more prominent.millimeter wave frequency band has rich spectrum resources and can meet the requirements of speed and delay in future communication,such as multimedia and Internet of Things,so it is regarded as a very important physical layer technology in 5G.However,due to the strong fading of millimeter-wave channels,the advantages of large bandwidth can only be demonstrated by the beamforming structure.Based on hybrid beamforming structure compared to the full digital beamforming system,system structure is more simple.However,even the system with hybrid beamforming structure still needs expensive devices such as radio frequency links and phase shifter network in millimeter wave band,which still makes the whole millimeter wave system difficult to be applied in scenarios with low cost.As technology evolves,there is an increasing need for high data rates and large-scale connectivity,such as providing connectivity to a large number of cameras.Low complexity and low cost millimeter-wave communication system is still widely concerned in the application of millimeter-wave system.This paper takes the low-complexity millimeter-wave beamforming system as the research content,and takes the realization of the low-complexity,low-cost millimeter-wave beamforming system as the research starting point,and proposes the WBM system and the multi-node WBM system.The proposed millimeter-wave communication system has a simple structure and can be applied in some low-cost and high-bandwidth scenarios.In addition,this paper proposes a hybrid access protocol based on grant-free and grant-based access for multi-node access,which can meet the requirements of low delay and robustness.In order to ensure that the data can be correctly decoded in the case of multi-node access,this paper proposes an iterative pilot elimination algorithm,which can better estimate the pilot sequence used in node access and the latency of received data arrival.Compared with the traditional hybrid beamforming system,the WBM system pro-posed in this paper has the following innovations:1 The characteristic of WBM system is the transmission of bit information through the propagation attenuation difference of the signal beam,rather than carried by the original signal beam.This change gives IoT nodes the advantages of high energy efficiency and low cost millimeter-wave hardware and software implementations while maintaining high data transmission capabilities at millimeter-wave frequen-cies.It can be deployed without phase shifter arrays and complex signal processing,such as precoding,or even channel estimation.2 The basic idea of WBM is based on the recently proposed OTAM approach,but with several significant improvements.By forming multiple beams at the central access point,WBM can achieve multi-user access through spatial division multiplexing,which significantly improves spectral efficiency compared to OTAM.In addition,by aligning multiple beams between IoT nodes and central access points,WBM provides robust transmission sessions.3 The channel estimation of WBM is mainly realized by pilot detection and beam energy estimation.An iterative pilot cancellation beam estimation algorithm is proposed to estimate the transmit pilot signal.First,the pilot signal and delay of transmission are determined by using the correlation characteristics.Then,we use Bayesian Gauss-Markov theorem to estimate the pilot energy.In addition,we iter-atively subtracted the pilot signal with the highest energy to reduce the interference to the remaining pilot signals and improve the robustness of the beam estimation.In summary,the WBM system proposed in this paper not only has extremely low hardware cost and energy consumption,but also can support multi-node access and com-munication.The system architecture can be used in low-complexity demanded communi-cation scenarios without the deployment of phase shifter arrays and complex signal pro-cessing,such as precoding or even channel estimation.Through the idea of beam seg-mentation,the spectral efficiency is improved more effectively.In addition,an algorithm is designed which can be used to reduce the interference from other nodes and maintain a certain communication performance advantage.