Research On Integrated Sensing And Communication Based On OTFS

In recent years,the integrated sensing and communication(ISAC)technology plays an increasingly important role in military and civil fields.Compared with implementing communication and radar sensing technology respectively,ISAC can make full use of spectrum resources,reduce mutual interference and save equipment costs.Besides,in emerging area such as Internet of Vehicles and unmanned aerial vehicles network,ISAC is very necessary,however,Doppler shifts caused by high mobility will cause interference to orthogonal frequency division multiplexing(OFDM),resulting in poor system performance.Therefore,how to improve ISAC system performance under high mobility scenarios is of great significance today.As a new waveform technology,Orthogonal time frequency space(OTFS)converts a doubly dispersive channel into an almost non-fading channel in the delay-Doppler domain.OTFS has strong robustness to Doppler shifts and can effectively resist the negative effects caused by fast time-varying channel.Based on these advantages,this thesis studies the joint design method of integrated sensing and communication based on OTFS.The main contributions of the thesis can be summarized as follows:First,the beamforming design of ISAC based on OTFS is studied.The joint communication and sensing system based on OTFS,which has one user and one target,is modeled and analyzed.Furthermore,the power and sensing echo signal to interference plus noise ratio(SINR)are constrained to maximize the communication achievable rate by optimizing the beamforming vector.Then the low complexity algorithm based on Dinkelbach and bisection method is proposed by solving the optimization problem.Simulation results show that the proposed algorithm can effectively reduce the solution complexity,and OTFS can effectively improve the IS AC system performance in high mobility scenarios.Second,the joint beamforming design and power allocation method of ISAC based on OTFS-nonorthogonal multiple access(NOMA)is studied.In consideration of the speed difference between target and multiuser,this thesis proposes the joint communication and sensing model based on OTFS-NOMA to improve the spectral efficiency.The minimum achievable rate of multiuser is maximized under the constraints of power,sensing echo SINR and target achievable rate.Then this thesis proposes a two-step algorithm based on semidefinite relaxation(SDR)to solve this joint design problem,which is divided into beamforming sub-problem and power allocation sub-problem respectively,and the corresponding beamforming and power allocation method is obtained.Simulation results show that the proposed beamforming and cross-domain power allocation method has better performance by comparison,the proposed OTFSNOMA method has better system performance than OFDM-OMA method.