On Mitigating the Mismatch Between FSK Tags and GFSK Receivers in BLE Backscatter

This letter aims to significantly improve the communication performance of Radio Frequency Identification (RFID) tags that transmit to Bluetooth devices. Such tags are increasingly being researched in order to provide the benefits of RFID without the need for expensive stand-alone readers. Strictly speaking, these tags do not generate Bluetooth standards-specified waveforms, but are nevertheless compatible with standards-compliant receivers. Gaussian Frequency Shift Keying (GFSK) transmission is replaced by simpler FSK transmission from the tag. This letter analyzes the mismatch effects when FSK signals are demodulated by GFSK receivers. This letter also describes a new tag signaling technique that generates waveforms better matched to Bluetooth receivers than FSK waveforms. The novel technique can be implemented with tag hardware that can generate classical FSK waveforms. Bit error rate improvement of about 5 dB were observed in simulations. Tag coverage area is nearly doubled.