Research On The Spectrum Sharing Of MIMO Radar And MU-MIMO Communications

In recent years,with the explosive growth of connected devices,the demand for extra frequency spectrum is on the rise.Given the scarcity of the spectrum,the future wireless systems will have to explore the possibility for cohabiting with other electronic equipments in the same frequency band.As an emerging research topic,the communication-radar spectrum sharing(CRSS)not only presents the advantage for enabling the coexistence of the two systems,but also provides a new way for designing novel dual-functional systems that can simultaneously communicate with the users and detect radar targets.Focusing on the two aspects of CRSS,i.e.,1)radar and communication coexistence and 2)dual-functional radar-communication system design,this thesis makes breakthroughs on interfering channel estimation,constructive interference precoding,dual-functional radar-communication beamforming and dual-functional waveform design.For clarity,the contribution of this thesis is summarized as follows:1.Interfering channel estimation for radar-communication coexistence.By assuming that the MIMO radar is operating at the "search-and-track" mode,we design several hypothesis testing approches to decide the status of radar based on the known/partially known information at the base station(BS),with which we can estimate the interfering channel.For completeness,we consider both the fading and the Line-of-Sight(Lo S)scenarios,and derive the theoretical performance of the proposed methods by use of statistical theory.2.BS precoding design for radar-communication coexistence.Firstly,we propose precoding design approaches to reduce the multi-user interference(MUI)as well as the interference from BS to radar.Based on this,we improve the performance of the precoders by applying the emerging concept of constructive interference(CI),and propose an efficient gradient projection algorithm to solve the corresponding optimization problem.By considering the practical constraints,we further propose the robust precoding designs under imperfect CSI.Finally,we analyze the impact that the BS's interference impose on the detection and estimation performance of the radar.3.Beamforming for dual-functional MIMO radar-communication system.We consider two operational options for the antenna array deployment,i.e.,separated and shared deployments,and solve the corresponding beamforming optimizations with the Semidefinite Relaxation algorithms.To accelerate the process for obtaining the beamformer,we simplify the shared beamforming designs as weighted optimizations,which are further solved by lowcomplexity manifold algorithms under both total and per-antenna power constraints.4.Waveform design for dual-functional MIMO radar-communication system.First,we consider dual-functional waveform designs that can strictly achieve the given radar beampatterns while minimizing the communication MUI energy.Based on these waveforms,we further propose a weighted optimization to enable a flexible tradeoff between radar and communication performance.It is worth highlighting that all the three waveform design approaches mentioned above can yield globally optimal solutions with low computational costs.Finally,we address the problem of constant-envelope waveform design under given referenced radar waveform constraint,and obtain the globally optimal solution by use of the branch-and-bound algorithm.