Symbiotic Backscatter System: OMA Backscatter versus NOMA Backscatter

In this paper, we make a comparative study of symbiotic backscatter system with orthogonal multiple access (OMA) backscatter signaling and the non-OMA (NOMA) backscatter signaling, where the backscatter device (BD) conducts the backscatter modulation. To characterize the system achievable performance, we derive the closed-form expression of the coexistence outage probability (COP) and the sum throughput efficiency (TE) for the considered system, respectively. It is analytically shown that the COP of the proposed system with OMA/NOMA backscatter signalings obeys the scaling law of $\frac{{\ln \left( {{P_s}} \right)}}{{{P_s}}}$, where P<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">s</inf> is the total transmit power. More importantly, our theoretical and simulation results show that the sum TE performance of the proposed system with NOMA backscatter signaling is significantly superior to the counterpart with OMA backscatter signaling.