Symbiotic Security: Achieving Concurrent Secure Transmissions for Symbiotic Backscatter Systems

This paper proposes a physical-layer-security-based symbiotic backscatter non-orthogonal multiple access (NOMA) system, where a backscatter device (BD) modulates its message over a primary NOMA signal. In particular, the symbiotic transmissions of confidential messages are considered with the aim to preserve different degrees of the secrecy constraints on User 2’s decoding capability by adaptively adjusting the BD’s reflection coefficient. Additionally, we introduce a metric in the coexistence secrecy outage probability and develop the corresponding theoretical framework at high transmit signal-to-noise ratio. Unlike a conventional backscatter-NOMA system, the proposed symbiotic system significantly restrains the internal eavesdropper from deciphering the classified confidential signal.