Patent ID: 9069058
Filing Date: 2015-06-30
Classification: G01S,H04B,H04L

Abstract:
1. A system for determining the position of a mobile receiver unit comprising: a plurality of static transmitter stations each configured to transmit an ultrasonic signal comprising a phase-shifting signature specific to the static transmitter station, wherein each signature comprises a first instance of a pattern, binary-phase-shift-key (BPSK)-encoded on a first carrier, and a second instance of a pattern, BPSK-encoded on a second carrier, wherein the beginning of the second instance is offset in time from the beginning of the first instance by a predetermined offset that is specific to the transmitter station, wherein the first and second carriers are at the same frequency, and wherein the first carrier is 90 degrees out of phase with the second carrier; a mobile receiver unit configured to receive an ultrasonic signal, comprising a phase-shifting signature, from one of the transmitter stations; a processing subsystem configured to use the received signature to identify the source transmitter station by cross-correlating the received signal with a reference copy of the pattern in the phase-shifting signature, to determine a complex correlation signal containing both in-phase and quadrature information, and by comparing said complex correlation signal with the same complex correlation signal shifted in time by an offset equal to the predetermined offset specific to the source transmitter station; and a processing subsystem configured to use the received signal and the identity of the source transmitter station to determine information relating to the position of the mobile receiver unit.