A Fine-grained Modulation Technology for ZigBee Backscatter Communication

This paper presents the first symbol-level modulation technology for ZigBee backscatter communication. The developed backscatter tag, leveraging ambient ZigBee transmissions as radio frequency (RF) carrier excitation, conveys data by translating an excitation signal into a new ZigBee signal in neighboring ZigBee channels. This avoids the strong interference from the ambient excitation signals. The key enabling technique is a symbol-level codeword translation, which exploits square waves based on the difference between the excitation and tag data. A working prototype was successfully demonstrated to validate the modulation technology, which consists of two parts: an RF frontend circuit and an FPGA-based control circuit. Through extensive experiments and field studies, the evaluation shows that the bit error rates (BERs) can be controlled to be less than 0.1 when the communication distance is within 2 meters.