Enabling Dual-Band Wi-Fi Backscatter

This paper presents dual-band Wi-Fi backscatter (DBscatter), which is the first system supporting 2.4 GHz and 5 GHz Wi-Fi backscatter simultaneously in a single tag. Our key insight is that most existing Wi-Fi devices communicate in the clean 5 GHz band. The 5 GHz band provides more chances for “free riding” with less interference, while the 2.4 GHz band presents better NLoS performance. DBscatter combines the strengths of the existing 2.4 GHz band with the unexplored 5 GHz backscatter in a unified design, developing a robust and high-throughput ambient Wi-Fi backscatter system. We make the following technical contributions: (1) We design a dual-band RF frontend to support dual-band Wi-Fi signals. (2) We propose a tag data demodulation algorithm, which merges the common phase error in multi-antenna received signals, improving the tag transmission reliability while reducing the number of required receivers. (3) We build a prototype of DBscatter system using COTS FPGAs and SDRs. Compared to TiScatter and FreeRider, DBscatter boosts Wi-Fi backscatter throughput by 3.74X and 7.35X, and energy efficiency by 1.78X and 1.38X respectively.