Enabling Full Mutualism for Symbiotic Radio with Massive Backscatter Devices

TL;DR

This paper explores how deploying a large number of backscatter devices in symbiotic radio can significantly enhance both primary and secondary communication links, enabling full mutualism and improved spectrum efficiency.

Contribution

It introduces a massive backscatter device approach for symbiotic radio, deriving achievable rates and demonstrating mutualism benefits with large BD numbers.

Findings

Achievable rates increase with the number of BDs.

Full mutualism is achievable with massive BD deployment.

Closed-form expressions for rates are derived in the asymptotic regime.

Abstract

Symbiotic radio is a promising technology to achieve spectrum- and energy-efficient wireless communications, where the secondary backscatter device (BD) leverages not only the spectrum but also the power of the primary signals for its own information transmission. In return, the primary communication link can be enhanced by the additional multipaths created by the BD. This is known as the mutualism relationship of symbiotic radio. However, as the backscattering link is much weaker than the direct link due to double attenuations, the improvement of the primary link brought by one single BD is extremely limited. To address this issue and enable full mutualism of symbiotic radio, in this paper, we study symbiotic radio with massive number of BDs. For symbiotic radio multiple access channel (MAC) with successive interference cancellation (SIC), we first derive the achievable rate of both the primary and secondary communications, based on which a receive beamforming optimization problem is formulated and solved. Furthermore, considering the asymptotic regime of massive number of BDs, closed-form expressions are derived for the primary and the secondary communication rates, both of which are shown to be increasing functions of the number of BDs. This thus demonstrates that the mutualism relationship of symbiotic radio can be fully exploited with massive BD access.