A Mobile Phone Uplink CPDP-DTDOA Positioning Method Using UAVs for Search and Rescue

This article proposes a mobile phone passive positioning system using unmanned aerial vehicles (UAVs) to detect the uplink signals based on orthogonal frequency-division multiplexing (OFDM) for search and rescue. Reducing the influence of time synchronization error on time of arrival (TOA) estimation, the system sets up a reference node to broadcast reference signals at the subframe of uplink signals. The differential time difference of arrival (DTDOA) estimation method is adopted to achieve high-precision positioning. At the same time, an efficient TOA estimation method for DTDOA called cross power delay profile (CPDP)estimation is proposed, which can reducethe computational effort of TOA estimation by up to 50% compared to conventional DTDOA. The performance and Cramer-Rao lower bound of CPDP-DTDOA estimation are compared with conventional DTDOA estimation and TDOA estimation. The effects of signal-to-noise ratio (SNR) and sampling rate on the performance of CPDP-DTDOA are evaluated. The experiment and simulation demonstrate that CPDP-DTDOA can achieve time synchronization and obtain unbiased TOA estimation even at low sampling rates when the reference signal is under line-of-sight (LOS) and high SNR, satisfying the low-power design for UAV platforms.