Laissez-Faire: Fully Asymmetric Backscatter Communication – Public Review

Laissez-Faire is a novel design for backscatter communication that enables much higher data rates. The key idea is simple and elegant. The authors note that low-power backscatter systems, e.g., RFIDs, transmit their signal using ON-OFF keying –i.e., they convey bits by transitioning the signal between two levels, up and down. However, since their bit rate is low (tens of kbps), they have a small number of transitions in a unit of time. The RFID reader on the other hand is a powerful device, and can sample the signal very fast (e.g., at tens of MHz). Thus, it can detect many more transitions per unit of time than there are in an RFID signal. This yields an opportunity for increasing the data rate of RFIDs but without jeopardizing their lowpower simple design. Specifically, we can have many RFIDs transmit concurrently so that we stack many transitions from different RFIDs in a unit of time. As long as the signals from different RFIDs do not experience a transition at exactly the same time, the reader can recover all transitions and hence all bits. The paper proposes this simple principle and builds on it to ensure the reader can tell which bits are from which RFID.