Research On Low Power Consumption Beamforming In MmWave MIMO Systems

Millimeter wave(mmWave)MIMO communication has a promising prospect due to its merit of rich spectrum resource and multigigabit-per-second data rate.In order to solve the problem of high path loss in mmWave MIMO communication systems,the beamforming is usually used to obtain the array gain to overcome the path loss.However,for the mmWave MIMO communication systems,the full digital beamforming requires a large number of RF links and the complexity and cost of signal processing undoubtedly bring great challenges to the actual systems.Therefore,hybrid beamforming technology emerges at the right moment.The beamforming is divided into the digital domain and the analog domain in the hybrid beamforming,which greatly reduces the number of the required RF links and the complexity of implementation.Aiming at the millimeter-wave MIMO communication system,this paper focuses on the low-power hybrid beamforming from the perspective of different beamforming architectures.The main work is summarized as follows: Firstly,the characteristics of the Switches and Inverters-based architecture are analyzed,and the problem model under the structure is reconstructed.Aiming at the problem that the architecture can only provide limited phase control and the complexity of the cross entropy(CE)-based hybrid beamforming algorithm is high,combining with Gibbs sampling idea in markov chain monte carlo(MCMC)method,the Gibbs sampling-based hybrid beamforming algorithm is proposed.Starting from the initial samples,the elements on each coordinate are updated position by position in the algorithm,then the beamforming matrix can be obtained by finite iterations.Simulation results show that the proposed algorithm can achieve reasonable spectral efficiency and lower algorithm complexity.Secondly,combined with the phase modulation array(PMA)in the phased array,a PMA-based hybrid beamforming architecture is proposed.By introducing time degrees of freedom,low-power RF switches and delay lines are used to replace the analog phase shifter to realize the beam control in the analog part.The characteristics of this architecture are studied then the advantages of low power consumption,high precision phase control and equivalent amplitude control are proved by theoretical analysis.According to its characteristic of breaking the constant modulus constraint of the phase shifter,the problem model under this structure is reconstructed.First,due to the phase-amplitude control in the analog part,the phase extraction ZF(PZF)beamforming algorithm is improved.In addition,combined with the idea of the particle swarm optimization(PSO)algorithm,the PSO-based hybrid beamforming algorithm is proposed.The intermediate variables of the anolog beamforming matrix are regarded as particles,and the anolog beamforming matrix is obtained by updating the velocity and position of the particles in the particle swarm to optimize the required phase and time.Simulation results show that the proposed scheme has lower power consumption,higher energy efficiency(EE)and approximately optimal spectrum efficiency(SE)compared with the traditional hybrid beamforming schemes.