Ambient Backscatter Communication in LTE Uplink Using Sounding Reference Signals

The ambient Internet of Things (AIoT), recently standardized by the third-generation partnership project (3GPP), demands a low-power wide-area communication solution. Ambient backscatter communication (AmBC) is a promising approach that enables backscatter devices (BDs) to communicate by reusing existing signals without additional spectrum or energy cost. This article investigates the feasibility of AmBC in the uplink of long-term evolution (LTE) cellular systems. We model the received BD signal, derive the optimal maximum a posteriori (MAP) detector, and propose simplified receiver architectures that achieve near-optimal performance with reduced complexity. A theoretical bit error rate (BER) analysis is developed, including a Gaussian approximation, and the achievable coverage is evaluated. The results show that AmBC can sustain a BER on the order of $10^{-2}$ at a reading distance of 1.5 m. Over-the-air experiments using commercial LTE uplink sounding reference signals (SRSs) further confirm the theoretical and simulation results. Overall, this work demonstrates that LTE cellular systems can natively support AmBC in the uplink, reinforcing its potential as a symbiotic radio (SR) paradigm for future low-power, spectrum-efficient AIoT connectivity.