Symbiotic Backscatter System over Cascaded Fading Channels

Cascaded fading plays a vital role in backscatter communications but its effect on the transmission robustness of symbiotic backscatter system has not been well understood yet. In this paper, we investigate this effect under three symbiotic mechanisms, namely commensal, parasitic and competitive schemes. Our analysis indicates that: 1) For the commensal scheme, cascaded backscatter fading incurs an inferior outage performance of the backscatter system in comparison with the counterpart over single-hop backscatter fading; 2) For the parasitic scheme, cascaded backscatter fading leads to a superior outage performance of the primary system in comparison with the counterpart over single-hop backscatter fading; 3) For the backscatter system, regardless of single-hop or cascaded backscatter fading, the exact outage probability of the parasitic scheme overlaps with the asymptotic of the commensal scheme; 4) For the competitive scheme, as the decoding threshold of the primary system approaches zero, the asymptotic outage performance of the primary system in cascaded and single-hop backscatter fading tend to be the same; and 5) Unlike single-hop backscatter fading, as the decoding threshold of backscatter signal approaches zero, the outage probability of the competitive and parasitic schemes for the backscatter system in cascaded backscatter fading approaches that of the competitive scheme for the primary system.