Research Of Beamforming Technique For Massive MIMO In CRAHNs Network

In recent years,the CRAHNs network has been widely studied because of its high reliability of communication,but it has limits on the transmission power of the signal and can not effectively solve multipath fading.Massive MIMO technology performs excellently in enhancing the spectrum and energy efficiency.Therefore,this paper combines Massive MIMO technology with CRAHNs network and studies the beamforming technology in this system to improve the communication performance and reduce the energy consumption.(1)Broadband beamforming technology.The signal reception model and criterions of narrowband beamforming are extended to broadband,and the processing method and mathematical expression of broadband beamforming are given.In view of the shortcomings of conventional beamforming applied to the side lobe of sensor antenna array,the paper proposes broadband sidelobe constrained beamforming algorithm,and the simulation results verify the performance of the algorithm.(2)Beamforming techniques in OFDM system to solve multipath fading.The paper combines beamforming techniques with OFDM systems to confront or use multipath fading.The paper introduces two implementations of beamforming in OFDM systems,and studies the conventional LMS-OFDM algorithm.A new algorithm of MCMV-OFDM is proposed to solve the shortcomings of LMS-OFDM algorithm,namely,the weak anti-jamming performance.The simulation results show that the algorithm can reduce the bit error rate more effectively.(3)Beamforming technology in Multi-user MIMO system to eliminate the co-channel interference(CCI).The mathematical model of MU-MIMO system is given,and the conventional beamforming scheme which eliminates CCI at the transmitter is studied.The algorithm has limits on the number of transmitting antennas.In order to overcome this shortcoming,a new method of beamforming based on maximum signal to leakage ratio is proposed.The algorithm can eliminate the interference between multiple users and does not have requirement on the number of transmit antennas.The superiority of the proposed algorithm is verified by simulation.