Waveform Optimization For Radar-embedded Communications

Wireless devices have developed rapidly and the number of users is increasing dramatically,which bring many challenges to the future military communication system.Therefore,the Radar-Embedded Communication(REC)arises against this background.As a new but potential technology,REC can at the same time implement both spectrum sharing and covert communication.The key is to hide the communication signal in the radar stopband and cover the signal by the radar echo.This paper focuses on the waveform design strategy of REC,the main contributions are as follows:(1)Considering that the design freedom,calculation complexity and response delay have an effect on the REC waveform,the performance evaluation index of REC system is further improved.Meanwhile,the traditional REC waveform design strategy is more comprehensively analyzed,and the previous conclusion is modified.Besides,the strategy that it can first filter and then match is proposed on the basis of the existing receiver.The simulation results have shown that the communication reliability of REC system is significantly improved.(2)To solve the non-orthogonal problem of traditional REC waveform,the Orthogonal Weighted-Combining(OWC)strategy and the Orthogonal Dominant Projection(ODP)strategy are proposed.And the OWC strategy can be divided into the Constrained WeightedCombining(CWC)strategy and the Improved Weighted-Combining(IWC)strategy.Five aspects,such as communication reliability and Low Probability of Intercept(LPI),have been analyzed and simulated.The results have shown that three improved strategies are better than the traditional ones.And either of the three strategies has its own advantages and is suitable for different application circumstances.(3)For the limitation of traditional eigen-decomposition framework,an REC waveform design strategy based on Singular Value Decomposition(SVD)is proposed.This strategy uses SVD to study the radar signal directly,and the designed SVD waveform is much more similar to the radar waveform.At the same time,it can ensure the communication reliability of SVD waveform by orthogonal design.Theoretical analysis and simulation results have shown that SVD waveform is the best in the four aspects,such as Low Probability of Detection(LPD)and LPI performance.Besides,a method to calculate the similarity between SVD waveform and radar waveform is put forward,which can make LPD metric quantify,and the similarity can be adjusted flexibly to weigh the reliability and concealment.