Spectrum Sharing Joint Design Of MIMO Radar And MIMO Communication System

Radar-Communications system is a kind of new integrated system with both functions of radars and communication devices,in the other way,for simultaneously performing both data transmission and radar sensing in the same frequency band,in terms of both spectrum efficiency and cost-effectiveness with broadly application foreground.However,at present the Radar-Communications systems have some problems,such as poor detection performance,low information transmission rate,and unable to eliminate mutual interferences between different integrated systems and different communication users.The thesis studies the above problems and proposes a joint beampattern design method for Radar-Communication systems,which eliminates the interference between radar and communication users and the mutual interference between different communication users.Then,the OFDM subcarrier allocation technique is applied on Radar-Communication system,in order to eliminate interferences between different Radar-Communications systems,and the performance of the algorithm is verified through theoretical simulations.The specific work is as follows:In the first place,the basic theory of Radar-Communications system is presented,including the basic theory MIMO radar system and MIMO communication system,the channel capacity of MIMO communication systems,the data modulation and demodulation,guard interval and target detection theory of the OFDM signals.Based on these,the mathematical model of MIMO-OFDM Radar-Communication system is established.Secondly,the joint beampattern design of Radar-Communication system is carried out.Using the existing beampattern and precoding design methods are able to eliminate the interference between MIMO radar and communication users,but,incapable of eliminating the mutual interference between communication users.For the sake of solving above problems,a new algorithm is proposed,the new algorithm takes the beampattern of the Radar-Communications system and SINR of each communication user as the optimization objective of the radar subsystem and the communication subsystem respectively.According to the optimization objective and the mathematical model of the system,three coupling optimization problems are proposed.Then,the suboptimal radar communication covariance matrix,communication precoding and communication user’s receiving beam are obtained while the three coupling optimization problems are solved by using alternative optimization method.Simulation results show that the proposed algorithm has fast convergence speed and it will provide higher mainbeam gain.In the last part of this paper,in view of the coexistence of multiple MIMO-OFDM Radar-Communication systems,it is proposed to allocate OFDM subcarriers to different Radar-Communication systems.It is verified by analyzing radar signals and communication signals,by using the orthogonality of the subcarriers,the mutual interference among Radar-Communication systems,the interference between radar and communication users,and the mutual interference between communication users can be eliminated.Then,for radar subsystem,the OFDM target detection theory is extended to MIMO-OFDM system,and multi-target sensing can be realized.For the communication subsystem,in order to improve data transmission rate,two subcarrier reallocation scheme is presented,one can maximize the total channel capacity of the system,the other one ensures the fairness of allocation,taking into account the channel capacity of each user.The Simulations verifies that the MIMO-OFDM Radar-Communication system could execute multi-target detection,and subcarrier allocation scheme is effective.