Doppler resilient modulation in a CDMA-based acoustic local positioning system

This paper proposes a Doppler resilient modulation approach that can be used in acoustic local positioning systems with Binary Phase-Shift Keying (BPSK) modulated signals for Time-of-Flight (ToF) estimation. The proposed approach is implemented in the receiver and can be performed in parallel with other classic techniques to improve the position estimation process. The technique is based on Differential Binary Phase-Shift Keying (DBPSK) modulation instead of the widely used BPSK modulation and presents a low computational complexity. The performance of the proposed technique is studied for BPSK-modulated Kasami codes with 63 and 255 bit length. Results have shown that the proposed technique is not only robust to Doppler effect but also to noise, multipath and multiple-access interference.