C-Chirp: Towards Symmetric Cross-technology Communication over Asymmetric Channels

Abstract

Cross-Technology Communication (CTC) is an emerging technique that enables direct interconnection among incompatible wireless technologies. However, CTC channels established by existing methods are inherently asymmetric because of either the one-way nature of emulation in physical-level CTC or the asymmetric communication range caused by the asymmetric transmission power. In this paper, we focus on establishing symmetric CTC over asymmetric CTC channels. The bottleneck is the short communication range from the low-power and narrow-band technology to the high-power and wide-band technology because the asymmetric bandwidth and transmission power lead to serious symbol distortions. To compensate the inevitable distortions, we take advantage of the channel asymmetry and construct chirps in WiFi Channel State Information (CSI) to enhance the patterns used for conveying data. In this way, we can extend the communication range from ZigBee to WiFi. We theoretically build the model of CSI chirp based CTC and design c-Chirp, a novel CTC from ZigBee to WiFi. Due to channel asymmetry and discreteness, the WiFi receiver can only observe partial and distorted CSI chirps. To cope with this issue, we design a matching based chirp decoding method as well as an adaptation algorithm to reliably decode the symbols. We conduct extensive experiments to evaluate c-Chirp. The results show that c-Chirp can achieve a 60m communication range from ZigBee to WiFi, which is 6× longer than ZigFi, an existing representative CTC from ZigBee to WiFi.