Outage analysis for multi‐BD symbiotic radio system

Abstract Symbiotic radio (SR) is a new spectrum sharing paradigm that allows backscatter device (BD) to transmit information over the ambient radio frequency signal, where the BD is parasitic in the primary transmission, and the secondary system (i.e. backscatter system) shares not only the same spectrum but also the same receiver with the primary system. Here, a multi‐BD SR system with a primary transmitter (PT), a cooperative receiver (CR) and two backscatter devices (BDs), that is, BD1 and BD2 is studied. The accurate expressions for the outage probability of both primary system and secondary system are derived. Simulation results verify the correctness of this theoretical analysis. Additionally, the effect of the distance parameters (i.e. the distance of the backscatter links) on the outage probability of BD1 and BD2 when the backscatter coefficients are fixed is investigated. Simulation results indicate that the desired outage performance can be obtained by adjusting the distance parameters. Finally, the performance of the multi‐BD SR system is compared with the SR system containing only one BD, and the results show that the multi‐BD SR system can enable the backscatter system to achieve better rate performance, which highlights the importance of applying multi‐BD to the SR system.