Unitag: Enabling Multi-Frequency Backscatter

In this paper, we for the first time demonstrate how to realize multi-frequency backscatter communication for low power IoT devices. Our key innovation is an encoding rule that works from O(100) MHz to 2.4 GHz to cover most commercial communication bands such as BLE, LoRa and Wi-Fi. Based on the proposed method, backscatter devices can adaptively select one appropriate wireless protocol according to application scenarios. To this end, we reveal the fundamental reason why the existing backscatter tags only work in a specific frequency range and propose a universal multi-frequency communication method. We build hardware prototype and conduct experiments at several frequencies from 150 MHz to 2.4 GHz. Experimental results show that UniTag significantly improves communication performance at different frequencies in contrast to the existing methods, where the average bit error rate is only 13% to 50% of existing methods.