초록 ▼

A spread spectrum position location communication system determines the position of a mobile master radio using a round-trip messaging scheme in which the time of arrive (TOA) of ranging messages is accurately determined to yield the range estimates required to calculate the position of the mobile r

A spread spectrum position location communication system determines the position of a mobile master radio using a round-trip messaging scheme in which the time of arrive (TOA) of ranging messages is accurately determined to yield the range estimates required to calculate the position of the mobile radio via trilateration. The master radio transmits outbound ranging messages to plural reference radios which respond by transmitting reply ranging messages. Upon reception of the reply ranging message, the master radio determines the range to the reference radio from the signal propagation time calculated by subtracting the far-end turn around time from the round-trip elapsed time. Any combination of fixed or mobile radios of known positions can be used as the reference radios for another mobile radio in the system, thereby providing adaptability under varying transmission conditions. The individual radios do not need to be synchronized to a common time reference, thereby eliminating the need for highly accurate system clocks. By performing internal delay calibration, errors caused by difficult-to-predict internal transmitter and receiver delay variations can be minimized. Leading-edge-of-the-signal curve fitting and frequency diversity techniques minimize the effects of multipath interference on TOA estimates.

대표청구항 ▼

1. A mobile communication device capable of determining range to a reference communication device by exchanging ranging signals with the reference communication device, comprising:a transmitter configured to transmit to the reference communication device a sequence of outbound ranging signals at dif

1. A mobile communication device capable of determining range to a reference communication device by exchanging ranging signals with the reference communication device, comprising:a transmitter configured to transmit to the reference communication device a sequence of outbound ranging signals at different carrier frequencies; a receiver configured to receive from the reference communication device a sequence of reply ranging signals at the different carrier frequencies in response to the outbound ranging signals; and a processor configured to select from among the reply ranging signals a reply ranging signal at a carrier frequency providing a highest signal timing accuracy, said processor determining a time of arrival of the selected reply ranging signal and the range to the reference communication device from a round-trip signal propagation time of the selected reply ranging signal and a corresponding outbound ranging signal.