This paper focuses on the waveform design for a radar-embedded communication (REC) system which can achieve covert communication while improving the spectrum utilization. In order to solve the problem that the conventional embedded communication waveforms are not orthogonal, this paper proposes the orthogonal weighted-combining (OWC) strategy and the orthogonal dominant-projection (ODP) strategy. Furthermore, the OWC strategy can be broken into two strategies: constrained weighted-combining (CWC) strategy and improved weighted-combining (IWC) strategy. Theoretical analysis and simulation results have shown that these three strategies can dramatically improve communication reliability. Moreover, the performance of the strategies mentioned above has been assessed by the low probability of intercept (LPI) metric. Comparing to the traditional strategies, the IWC strategy shows better LPI performance while the CWC strategy and ODP strategy remain unchanged. Additionally, the ODP strategy can also reduce computational complexity and response delay, which is rather important in the REC system. Any of the three strategies can be selected in accordance with the needs of the application scenario.
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