Relacks: Reliable Backscatter Communication in Indoor Environments

The increasing number of embedded, plugged-in radios around homes and offices in everyday objects such as appliances, TVs, and smart speakers provides an excellent opportunity to bring ultra-low-power backscatter connectivity to billions of devices. However, backscatter links suffer from high loss due to two consecutive propagations and have to operate on narrow link-budget margins, which makes them more susceptible to multipath losses in indoor environments. To address this, we propose a closed-loop backscatter system that exploits diversity sources such as communication frequency and transceivers antennas based on the channel metrics to deliver reliable coverage over an entire area. We prototype a backscatter system with Bluetooth Low Energy (BLE) transceivers and BLE compatible tags and deploy it in several multipath rich indoor environments. Our evaluations show that we can successfully communicate with a backscatter tag in a 50m2 indoor area. The proposed algorithm for selecting communication parameters achieves an average 2.7 x success rate compared to the random selection while satisfying FCC output power requirements for frequency hopping transceivers.