Low Complexity Multi-Resolution Beamforming Codebook Design In Millimeter Wave Communication

The Fifth Generation(5G)of mobile communication is considered as an effective solution to provide Gbps data rate for the next generation communication.The existing microwave frequency band is gradually saturated,so the Millimeter Wave(mm-wave)frequency band from 28 GHz to 300 GHz is regarded as a new spectrum providing a high data rate for the 5G n etwork.However.the propagation characteristics of mm-wave signals are different from those of traditional microwave signals.The free space path loss and environment attenuation have a serious impact on mm-waves.On the other hand,the small wavelength characteristic of the mm-wave signal allows large-scale antenna array to achieve large beamforming gain.Therefore,it is very important to use Multiple-Input Multiple-Output(MIMO)technology to overcome the transmission loss of mm-waves.The design of dominant beamforming and combining vectors between transmitter and receiver requires Channel State Information(CSI),which is hard before beamforming due to large antennas and low Signal to Noise Ratio(SNR)in mm-wave.By sounding narrow beams of high gain in all the spatial domain,the channel can be search ed.However,in this case,the problem of using high-resolution narrow beams to estimate the channel becomes challenging,and the training overhead increases to sound the narrow beam in all spatial directions.Generally speaking,the beam alignment program in the millimeter wave system has been studied extensively,and attention has been focused on the exhaustive and iterative search procedures to align the beams and achieve CSI.However,these methods have high complexity and high channel training cost.In this wok,the beamforming technology based on a multi-resolution codebook in 5G mobile communication is studied and analyzed in detail.By designing multi-resolution codebook sequences,an effective beam alignment and channel estimation method are proposed,which can minimize the training cost and maximize the beamforming gain.The codebook is composed of a multi-stage sequence,which is used to find out the main ch annel between th e Base Station(BS)and the Mobile Station(MS)in the minimum training time,so as to make full use of the channel coherent time for data transmission.This work adaptively selects a subset of the beamforming vectors from the multistage beamforming sequences to provide an improved average data rate within the constraint period.In addition,the multi-resolution codebook is constructed by using the Phase-Shifting Discrete Fourier Transform(PS-DFT)vector to obtain the constant main lobe directional gain beam pattern with maximum received signal power.The simulation results show that the low complexity and multi-resolution codebook designed in this paper can greatly reduce the complexity of channel estimation.