Robust Multi-Carrier Frame Synchronization for Localization Systems with Ultrasound

Time of arrival (TOA) based localization schemes compute the positions from the signal delay between senders and receivers in a network and thus have high requirements for the synchronization, in particular for the synchronization based on line-of-sight (LOS) signals. We propose an ultrasound system based on pure LOS synchronization and data transmission for sender identification. We use two carriers with 38 kHz, respectively 40 kHz, in a baseband OFDM scheme and by comparing the phase shift of both carriers we estimate with the Cramer-Rao lower bound a distance error between sender and receiver of 0.047 mm for a signal-to-noise ratio (SNR) of 10 dB. We transmit 8 bits in 1.5 ms for a robust localization, where we expect no intersymbol interferences for most realistic scenarios.