Range maximization by optimizing tag-to-tag cooperative backscatter communication

Backscatter communication (BackCom) is a wireless technology that transmits information wirelessly by modulating the reflection of an incident signal, offering the advantages of low power consumption and low cost. This paper introduces a novel cooperative timing protocol in a two-tag BackCom network, where a single reader communicates with two passive backscatter tags using a cooperative scheme. These tags encode their information by modulating the backscattered signal and then transmitting it back to the reader. In the considered tag-to-tag cooperative scheme, the tag closer to the reader assists the farther tag in relaying its information, effectively mitigating the doubly near-far problem commonly experienced in BackCom systems. The primary objective is to maximize the transmission range of the farther tag by jointly optimizing the proposed time allocation scheme and reflection coefficients while meeting the spectral efficiency and energy threshold constraints for the quality of service and sustainability requirements. This article formulates a non-convex optimization problem and proposes a solution methodology that efficiently approximates the optimized solution with low complexity. Numerical simulations are presented to analyze the effects of varying energy and spectral efficiency requirements on the maximized transmission range. The results demonstrate that the proposed tag-to-tag cooperative BackCom framework provides a significant performance improvement, with an average range gain of over 30% compared to the non-cooperative scheme.