System and method for the detection and compensation of radio signal time of arrival errors

• US 20030008622A1
• Filed: 06/11/2001
• Published: 01/09/2003
• Est. Priority Date: 06/11/2001
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Amerga, Messay, Rick, Roland, Fernandez-Corbaton, Ivan J.
• Granted Patent: US 6,804,494 B2
• Time in Patent Office: Days
• US Class Current: 455/68
• CPC Class Codes: G01S 19/22 Multipath-related issues
• CPC Class Codes: G01S 19/40 Correcting position, velocity or attitude
• CPC Class Codes: G01S 19/42 Determining position
• CPC Class Codes: G01S 19/428 using multipath or indirect path propagation signals in position determination
• CPC Class Codes: G01S 19/46 the supplementary measurement being of a radio-wave signal type
• CPC Class Codes: G01S 5/0218 Multipath in signal reception
• CPC Class Codes: G01S 5/0273 using multipath or indirect path propagation signals in position determination
• CPC Class Codes: G01S 5/10 Position of receiver fixed by co-ordinating a plurality of position lines defined by path-difference measurements , e.g. omega or decca systemsG01S5/12 takes precedence ; beacons and receivers cooperating therewith G01S1/306, G01S1/308
• CPC Class Codes: H04B 1/1081 Reduction of multipath noise by equalising H04B7/005
• CPC Class Codes: H04B 1/711 the interference being multi-path interference
• CPC Class Codes: H04B 1/7117 Selection, re-selection, allocation or re-allocation of paths to fingers, e.g. timing offset control of allocated fingers
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 84/06 Airborne or Satellite Networks space-based or airborne stations H04B7/185

Abstract

A system and method are disclosed by which the effects of time of arrival errors may be reduced. In a mobile unit, such as a CDMA device, a correlation pulse is generated when a transmitted code matches a stored reference code. In the absence of multipath effects, correlation pulses are generated in response to the detection of multiple transmissions of the reference code from multiple transmitters. However, multipath effects distort the generated correlation pulses leading to errors in the time of arrival measurements. The present invention calculates the width of the correlation pulses and determines a delay correction factor based on the pulse width. The delay correction factor is added to the measured delay time to provide a more accurate delay time, thus permitting more accurate location measurements based on time of arrival. In alternative embodiments, other signal factors may also be used to apply delay correction factors. The actual location determination may be performed by the mobile unit, or any other positioning determining entity (PDE). The system is also capable of applying correction factors to time of arrival signals received from global positioning system (GPS) satellites.

Claims

1. A system for the correction of multipath errors in a telecommunication device, the system comprising:

an antenna capable of detecting telecommunications signals and generating detected electrical signals as a result thereof;

a receiver coupled to the antenna to receive the detected electrical signals;

an energy detector to analyze the received signals and to generate a correlation pulse when the received signals match a stored reference signal;

a timer to determine a time of arrival of the correlation pulse;

an analyzer to calculate a pulse width of the correlation pulse and to apply a correction factor to the time of arrival based on the pulse width to generate a corrected time of arrival.

2. The system of claim 1 wherein the analyzer converts the time of arrival into a delay time and the correction factor is a time delay correction factor applied to the delay time.

3. The system of claim 1 wherein the analyzer converts the time of arrival into a distance measurement and the correction factor is a distance delay correction factor applied to the distance measurement.

4. The system of claim 1, further comprising a data structure to store data relating a plurality of pulse width values to correction factors wherein the analyzer provides a measured pulse width value as an input to the data structure and retrieves a correction factor stored in association with the measured pulse width value.

5. The system of claim 1, further comprising a data structure to store a mathematical function relating pulse width to correction factors wherein the analyzer calculates the correction factor using the pulse width and the mathematical function.

6. A system for the correction of multipath errors in a telecommunication device location system, the system comprising:

a receiver to receive data transmitted from a remote transmitter located at an unknown distance from the receiver; and

an analyzer to analyze data associated with the received data and to generate location data related to a location of the receiver, the analyzer further calculating a correction factor based on a measured signal criteria to generate corrected location data.

7. The system of claim 6, further comprising a positioning determining entity to determine the location of the receiver based on the corrected location data and a known location of the remote transmitter.

8. The system of claim 6 wherein the location data is based on a time of arrival of the data received by the receiver.

9. The system of claim 8 wherein the time of arrival is calculated as a delay time and the correction factor is a time delay correction.

10. The system of claim 6 wherein the receiver generates a correlation pulse when the received data is correlated to a stored data pattern, the signal criteria being a pulse width of the correlation pulse.

11. The system of claim 10 wherein the signal analyzer models the correlation pulse as a quadratic equation having a plurality of coefficients, the coefficients being determined by amplitude values of the correlation pulse at predetermined times.

12. The system of claim 10 wherein the signal analyzer calculates a maximum amplitude of the correlation pulse and measures the pulse width at a predetermined level below the maximum amplitude.

13. The system of claim 6 wherein the receiver generates a signal strength indicator, the signal criteria being the signal strength indicator.

14. The system of claim 6 wherein the receiver is a portion of a cellular telephone operating in an 800 MHz band and the analyzer calculates the location data based on a time of arrival of data transmitted from the remote transmitter in the 800 MHz band.

15. The system of claim 6 wherein the receiver is a portion of a personal communication system telephone operating in an 1900 MHz band and the analyzer calculates the location data based on a time of arrival of data transmitted from the remote transmitter in the 1900 MHz band.

16. The system of claim 6 wherein the remote transmitter is a global positioning system (GPS) satellite and the receiver receives the data signals from the GPS satellite, the analyzer calculating the location data based on a time of arrival of data transmitted from the GPS satellite.

17. The system of claim 6 wherein the receiver is a portion of a code division multiple access CDMA) telephone and the analyzer calculates the location data based on a time of arrival of data transmitted from the remote transmitter in the 800 MHz band.

18. The system of claim 6, further comprising a data structure to store data relating signal criteria to correction factors wherein the analyzer provides a measure of the selected criteria as an input to the data structure and retrieves a correction factor stored in association with the measure of the selected criteria.

19. The system of claim 6, further comprising a data structure to store a mathematical function relating signal criteria to correction factors wherein the analyzer calculates the correction factor using the selected criteria and the mathematical function.

20. A method for the correction of multipath errors in a telecommunication device location system, the method comprising:

using a receiver to receive data transmitted from a remote transmitter located at an unknown distance from the receiver;

analyzing data associated with the received data and generating location data related to a location of the receiver; and

calculating a correction factor based on a measured signal criteria to generate corrected location data.

21. The method of claim 20, further comprising calculating the location of the receiver based on the corrected location data and a known location of the remote transmitter.

22. The method of claim 20 wherein the location data is based on a time of arrival of the received data.

23. The method of claim 20, further comprising generating a correlation pulse when the received data is correlated to a stored data pattern, the signal criteria being a pulse width of the correlation pulse.

24. The method of claim 20, further comprising calculating a maximum value of the correlation pulse and measuring the pulse width at a predetermined level below the maximum amplitude.

25. The method of claim 20, further comprising generating a signal strength indicator, the signal criteria being the signal strength indicator.

26. The method of claim 20 wherein the remote transmitter is a global positioning system (GPS) satellite and the receiver receives the data signals from the GPS satellite and calculating the location data is based on a time of arrival of data transmitted from the GPS satellite.

27. The method of claim 20, further comprising pre-storing data relating signal criteria to correction factors wherein calculating the correction factor comprises retrieving the correction factor stored in association with the selected criteria.

28. The method of claim 20, further comprising storing a mathematical function relating signal criteria to correction factors wherein calculating the correction factor uses the selected criteria and the mathematical function.