Abstract: A high accuracy search and tracking system that uses a round-trip messaging scheme in which the time of arrive (TOA) of ranging signals is accurately determined to yield the range estimates between a target communications device and one or more search communications devices. Successive ranging estimates are used by a search device to home in upon the target device. The physical location pinpoint communications system can be used alone, or in combination with other location estimation systems that can be used initially, or throughout the search and tracking process to pinpoint the physical location of the target device. The search radio(s) transmits ranging signals to the target radio which responds by transmitting reply ranging signals. Upon reception of the reply ranging signal, the search radio determines the range to the reference radio from the signal propagation time. Errors in TOA estimates can be minimized using advanced processing techniques, if required.

Abstract: Range measurements useful for determining a device's position are screened to eliminate unacceptable measurements. A two-stage range measurement screening technique involves a coarse screening stage that includes comparing the range measurement to an estimated expected range and a fine screening stage that includes comparing the range measurement to the computed fading-average range. Range measurements that fall within both coarse and fine screening windows are deemed acceptable and are supplied to a position tracking filter together with their estimated measurement accuracies. Range measurements that do not fall within either the coarse or fine screening window are discarded and do not corrupt the position solution. The accuracies of acceptable range measurements are determined from multiple factors including the measurement offset from a fading-average of previous range measurements and the standard deviation of the previous range measurements.

Abstract: Range measurements useful for determining a device's position are screened to eliminate unacceptable measurements. A two-stage range measurement screening technique involves a coarse screening stage that includes comparing the range measurement to an estimated expected range and a fine screening stage that includes comparing the range measurement to the computed fading-average range. Range measurements that fall within both coarse and fine screening windows are deemed acceptable and are supplied to a position tracking filter together with their estimated measurement accuracies. Range measurements that do not fall within either the coarse or fine screening window are discarded and do not corrupt the position solution. The accuracies of acceptable range measurements are determined from multiple factors including the measurement offset from a fading-average of previous range measurements and the standard deviation of the previous range measurements.

Abstract: A high accuracy search and tracking system that uses a round-trip messaging scheme in which the time of arrive (TOA) of ranging signals is accurately determined to yield the range estimates between a target communications device and one or more search communications devices. Successive ranging estimates are used by a search device to home in upon the target device. The physical location pinpoint communications system can be used alone, or in combination with other location estimation systems that can be used initially, or throughout the search and tracking process to pinpoint the physical location of the target device. The search radio(s) transmits ranging signals to the target radio which responds by transmitting reply ranging signals. Upon reception of the reply ranging signal, the search radio determines the range to the reference radio from the signal propagation time. Errors in TOA estimates can be minimized using advanced processing techniques, if required.