Transmit Waveform And Receive Filter Design In ISAC Systems

With the continuous development of communication system hardware and software,its processing capability is also increasing,and we have higher and higher requirements for communication systems to perform not only communication tasks,but also other tasks such as environment sensing.Many scholars have been working on integrated sensing and communication systems.However,the realization of this system faces an important challenge: there is an urgent need to design a transmitting waveform that achieves the dual functions of target sensing and information transfer,while ensuring the reliability and effectiveness of both,and the need to exclude many interference factors,such as multi-user interference and obstacle occlusion.To address this issue,this paper investigates the multi-target detection of integrated sensing and communication systems,jointly optimizes the transmit waveform and receive filter,proposes a problem model to optimize the radar performance,and solves the problem using alternating optimization and convex optimization methods.Also,this paper considers the case of obstacle occlusion in this system and introduces an active intelligent reflective surface to enable the base station to sense the target effectively even without a direct path between the base station and the detected target.Specifically,the main research elements of this paper are as follows:(1)A joint optimization algorithm of transmit waveform and receive filter for integrated sensing and communication system for multi-target detection.The algorithm focuses on the joint optimization of the transmit waveform and receive filter to allow the transmit signal to detect multiple targets and optimize the detection performance while satisfying the communication performance requirements and power constraints.In order to solve this nonconvex problem,an optimization algorithm combining alternating optimization algorithm,Dinkelbach transform and semi-positive definite relaxation method is proposed in this paper.The simulation results show that this algorithm has better radar performance than the multi-target detection method without considering the joint optimization of transmit waveform and receive filter,which illustrates the superiority and advancement of this algorithm.(2)Joint optimization scheme of transmit waveform and receive filter for integrated sensing and communication system in the case of multiple detection targets obscured by obstacles.The scheme considers the case where multiple detection targets are obscured by obstacles and cannot be detected directly,and introduces an active intelligent reflective surface through which the detection signals are refracted and amplified to complete the detection of the targets.In this paper,an algorithm is proposed to jointly optimize the transmit waveform,the receive filter and the reflectance matrix of the smart reflective surface to maximize the radar receive signal-to-noise ratio while satisfying the communication performance requirements and power constraints.To solve this nonconvex problem,an optimization algorithm is proposed in this paper by combining the alternating optimization algorithm,the majorization-minimization,and the Dinkelbach transform.Simulation results show that this scheme can still detect the target well in the presence of obstacle occlusion,and the radar performance is better compared with the method without considering the receive filter optimization,which proves the feasibility and effectiveness of this scheme.