Research On Technologies Of Hybrid Beamforming For Radar And Communication Integration Systems At Mm Wave Band

The abundant spectrum resources of millimeter wave(mm Wave)band and its super capacity to the future wireless mobile communication system,as well as the super-high resolution and precision of radar perception,make the mm Wave radar and communication(Rad Com)integration technology become one of the key technologies for the development of future mobile communic ation system,smart city and intelligent transportation system(ITS).For mm Wave Rad Com integrated system,large-scale antenna array and hybrid b eamforming(HBF)technology make it the basic technology of Rad Com integration performance.If fully digital beamforming(DBF)scheme is adopted in mm Wave Rad Com integration system,the beam gain can hardly make up for the propagation loss of mm Wave.If the mm Wave Rad Com integration system adopts the analog beamforming(ABF)technology,although it can make full us e of the gain of large-scale antenna array,it is difficult for the ABF to realize multiple data stream transmission,and the signal processing is limited.Therefore,the development of HBF which combines DBF with ABF has become a very competitive technical solution.In mm Wave Rad Com integration system,the design method of HBF is different from different technical indexes,such as spectral efficiency,transmit beam mode and signal mean square error(MSE).Considering different criteria,the design of HBF is expressed as different optimization objectives,an d the optimization objectives are non-convex affected by constraints.In order to solve the non-convex optimization problem,effective algorithms are proposed.The performance of the proposed algorithms is verified in simulation part in terms of performance of communication,performance of radar sensing and performance of Rad Com tradeoff.The specific work is as follows:(1)In this paper,a HBF design based on the optimal approximation criterion for the Rad Com system is proposed,which formulates a non-convex trade-off optimization problem between communication and radar.Specifically,for communication,the optimal DBF of mm Wave MIMO system is used as the target for HBF approach,and the optimal radar beamforming obtained by convex optimization is used as the target for HBF approach.To solve the non-convex optimization problem,a feasible solution of HBF is found via using the orthogonal matching pursuit(OMP)method.To overcome the limitation of OMP algorithm and improve the performance,an improved Riemannian manifold optimization(IRMO)algorithm is proposed.(2)In terms of purpose of improving the reliability of communication transmission and the accuracy of radar sensing,a HBF method based on minimum mean square error(MMSE)criterion is propo sed,and a non-convex trade-off optimization problem between communication and radar is formed.For communication,the optimization goal is minimizing the MSE between the received signal after decoding and the transmitted signal before precoding.For radar,the optimization goal is to minimize the MSE of the power distribution between the beampattern realized by HBF and the ideal radar beampattern.A scale factor is introduced to relax the constraints of this multi-variable non-convex optimization problem,which can thus be decoupled into the subproblems of corresponding variables.After solving the non-convex subproblem based on Riemannian manifold optimization,an alternative minimization algorithm is proposed to obtain the effective solution of the multi-variable.Finally,an alternative minimization algorithm based on intelligent search(i.e.,adaptive particle swarm optimization,APSO)is proposed to achieve low computational complexity.Simulation results verify the effectiveness of the proposed algorithms from spectrum efficiency,MSE,BER,beam pattern and other dimensions.In the design of HBF based on the optimal approximation criterion,the IRMO algorithm achieves better performance than the OMP algorithm,and the performance of communication and radar approaches the optimal benchmark closely.At the same time,it can also achieve the trade-off between communication and radar.In the design of HBF based on the MMSE criterion,on the one hand,the alterna ting minimization algorithm based on IRMO achieves the performance closest to that of all digital MMSE algorithm;on the other hand,the alternating minimization algorithm based on APSO also realizes the functions of communication and radar with low computational complexity.