Wisent: Robust Downstream Communication and Storage for Computational RFIDs

TL;DR

Wisent is a novel protocol enabling fast, error-free downstream communication for CRFID devices by adaptively adjusting frame lengths, facilitating applications like wireless reprogramming in real-world environments.

Contribution

It introduces Wisent, a robust downstream communication protocol for CRFIDs that adaptively optimizes transfer times over legacy RFID systems, enabling wireless reprogramming.

Findings

Wisent achieves up to 16x faster transfer than non-adaptive methods.

It enables the first wireless reprogramming of CRFID devices.

Experimental validation on WISP 5 demonstrates practical effectiveness.

Abstract

Computational RFID (CRFID) devices are emerging platforms that can enable perennial computation and sensing by eliminating the need for batteries. Although much research has been devoted to improving upstream (CRFID to RFID reader) communication rates, the opposite direction has so far been neglected, presumably due to the difficulty of guaranteeing fast and error-free transfer amidst frequent power interruptions of CRFID. With growing interest in the market where CRFIDs are forever-embedded in many structures, it is necessary for this void to be filled. Therefore, we propose Wisent-a robust downstream communication protocol for CRFIDs that operates on top of the legacy UHF RFID communication protocol: EPC C1G2. The novelty of Wisent is its ability to adaptively change the frame length sent by the reader, based on the length throttling mechanism, to minimize the transfer times at varying channel conditions. We present an implementation of Wisent for the WISP 5 and an off-the-shelf RFID reader. Our experiments show that Wisent allows transfer up to 16 times faster than a baseline, non-adaptive shortest frame case, i.e. single word length, at sub-meter distance. As a case study, we show how Wisent enables wireless CRFID reprogramming, demonstrating the world's first wirelessly reprogrammable (software defined) CRFID.