R²Scatter: Long-Range Rapid LTE Backscatter Communication Using Tunnel Diodes

An LTE backscatter system allows a tag to detect and backscatter LTE signals where the tag data is modulated to the backscatter receiver. The existing LTE backscatter communication suffers from lower throughput and shorter communication range, hindering its application. In this paper, we introduce R2Scatter, the first higher-throughput LTE backscatter system with longer backscatter communication range of 18m. Our key innovations include: 1) A sample-level anchor position modu-lation (APM) scheme that improves the throughput. Unlike the previous systems using classical modulation schemes to convey tag data, we pick one of half-symbol signals from each LTE symbol and shift it to the backscatter channel, referred to as the anchor symbol, and utilize the anchor symbol position to signify more bits of the tag data. 2) A stronger RF front-end hardware design of the backscatter tag with 188μ W power consumption. Our design that uses a tunnel diode provides 18.8dB backscatter gain, enabling the tag to detect and synchronize with an LTE excitation signal under -60dBm. We build the prototype of the tag and conduct comprehensive experiments. Our results demonstrate that R2Scatter provides 2.7× higher throughput, 11.25× longer synchronization distance, and 6.4 × longer backscatter distance than the state-of-the-art LTE backscatter system CABLTE.