Real-time locating system and method using timing signal
View Patent ↗A location system includes a plurality of signal readers for receiving signals from a wireless transmitter to be located. The signals include a wideband, spread spectrum signal and a timing marker appended a predetermined time in front of the wideband, spread spectrum signal for indicating the presence of the wideband, spread spectrum signal. A location processor is operatively coupled to the signal readers for detecting the timing markers of signals and responsive to a detection of a timing marker, correlating a signal as a first-to-arrive signal and conducting differentiation of first-to-arrive signals to locate a wireless transmitter.
1. A location system comprising:
a plurality of signal readers for receiving signals from a wireless transmitter to be located wherein each signal reader time-stamps a signal with a time-of-arrival time stamp, each one of said signals consisting of a wideband, spread spectrum signal as a location pulse consisting of identification data for an object to be located to which the wireless transmitter is attached and a timing marker appended a predetermined time in front of the location pulse for indicating the presence of the location pulse and wherein the timing marker is timed at a predetermined range in front of the location pulse corresponding to a predetermined propagation distance to establish a known period of time to aid in finding the location pulse wherein a sampling window for edge detection as a range gate is determined by the timing of the timing marker; and
a location processor operatively coupled to said signal readers for processing the wideband, spread spectrum signal and responsive to a detection of the signal, correlating a signal as a first-to-arrive signal based on a time-of-arrival time stamp and conducting differentiation of first-to-arrive signals to locate the wireless transmitter.
2. A location system according to claim 1 , wherein said timing marker is timed about 80 to about 120 nanoseconds in front of the wideband, spread spectrum signal.
3. A location system according to claim 1 , wherein said timing marker is generated by a wireless local area network transmission.
4. A location system according to claim 3 , and further comprising an access point base station operative with the location processor and at least one signal reader.
5. A location system according to claim 1 , wherein said location processor comprises a matched filter correlator.
6. A location system according to claim 5 , wherein said matched filter correlator further comprises matched filter banks having parallel correlators that correlate a received communications signal with time offset versions of a reference spreading code.
7. A location system according to claim 1 , wherein said location processor further comprises a plurality of processors for distributing processing capability.
8. A location system according to claim 1 , wherein three signal readers are used for determining the location of the wireless transmitter.
9. A location system according to claim 1 , wherein each signal reader comprises a plurality of mutually diverse antennas for detecting signals at each signal reader.
10. A location system according to claim 1 , wherein each wireless transmitter comprises a tag transmitter that is coupled with the object to be located.