Research On IRS Aided Multi-User Broadcast Communication System

In the era of big data,a variety of new services emerge endlessly and data traffic explodes,which brings great challenges to mobile communication technology.The research of the sixth generation mobile communication system is also in full swing.Intelligent Reflection Surface(IRS)can generate reflected beams and dynamically adjust the channel environment.With the characteristics of low cost,low power consumption and easy deployment,IRS which is considered as one of the key technologies of 6G communication system is suitable for assisting millimeter wave and terahertz communication to solve the problem of channel fading.IRS gain is closely related to IRS phase design,so how to adjust IRS phase is the focus of current IRS research.In this paper,IRS technology is introduced into the traditional broadcast communication system,and the communication performance between the Access Point(AP)and the user is deeply studied through reasonable distribution of transmitting power,beam vector and adjustment of IRS phase vector.The main work is as follows:1)The rate problem of IRS aided single antenna broadcast communication system is studied.The system consists of one AP and multiple users,each equipped with a single antenna,and an IRS to improve communication link quality.By allocating the transmitted power of each user reasonably at the AP end and optimizing the phase at the IRS,the system weight and rate maximization are expected to be achieved under the condition of satisfying the power constraints and phase constraints.2)The energy efficiency of IRS aided multi-antenna broadcast communication system is studied.The system consists of one AP and multiple users with a single antenna for the user,multiple antennas for the AP,and an IRS to improve communication link quality.It is expected to achieve the maximum energy efficiency of the system under the condition of satisfying power constraints and phase constraints by reasonably distributing the transmitted beam of each user at the AP end and optimizing the phase at the IRS.Since the objective function is non-convex and the form is more complex,an alternate optimization algorithm framework is proposed: SCA algorithm is used to optimize IRS phase,and the beam transmitted at AP is optimized based on typical beamforming techniques(zero forced beamforming and minimum mean square error beamforming).In this paper,several IRS deployment schemes are simulated.The results show that the alternate optimization algorithm proposed in this paper can reduce the computational complexity while bringing better energy efficiency of the communication system,which reflects the important role of IRS in improving the energy efficiency of the communication system and the necessity of optimizing the IRS phase.