Collaborative Backscatter Based on Phase Channel Estimation in Passive RF Tag Networks

The RF tags offer ultra-low power cost of the communication due to the passive receiver based on envelope detector. The tag-to-tag link requires presence of excitation signal, either as a dedicated continuous wave exciter or an ambient RF signal. However, the link suffers from the limited range. The capability of RF tags to passively estimate the amplitude and phase of the wireless channel between pairs of communicating tags empowers these passive tags to provide a real-time, precise, fine-grained RF fingerprint of the environment. The phase estimation also enables collaboration between neighboring tags in order to improve the range and robustness of tag-to-tag link itself. We propose strategies that through the use of optimal collaborative reflection and backscatter of a cluster of tags improve the link range. We demonstrate that a single tag on a distance of 16 cm from the transmitting tag with optimal collaborative reflection improves the link range by 40%.