System and method for locating WiMAX or LTE subscriber stations
A system and method for estimating a location of a subscriber station receiving a first signal from a first base station and receiving a second signal from a second base station where the first and second base stations are nodes in a WiMAX or LTE network. A message may be received from the subscriber station containing first and second information, and a range ring determined from the first base station using the first information. A location hyperbola may be determined using the second information wherein the location hyperbola has the first and second base stations as foci. A location of the subscriber station may be estimated using the range ring and the location hyperbola.
1. A method for estimating a location of a subscriber station receiving a first signal from a first base station and receiving a second signal from a second base station where the first and second base stations are nodes in a WiMAX or LTE network, the method comprising:
(a) receiving from said subscriber station a message containing a first information and a second information;
(b) determining a range ring from said first base station using said first information;
(c) determining a location hyperbola using said second information wherein said location hyperbola has said first and said second base stations as foci; and
(d) estimating a location of said subscriber station using said range ring and said location hyperbola,
wherein the step of estimating a location of said subscriber station includes:
(i) determining a serving sector of said first base station for said subscriber station; and
(ii) if said range ring and said location hyperbola intersect plural times within said serving sector:
(A) determining plural sub-sectors for said serving sector;
(B) determining from said message a carrier-to-interference noise ratio (“CINR”) for each of a first and a second neighboring sector to said serving sector;
(C) determining a most likely sub-sector from said plural sub-sectors based on a comparison of said CINR for said first and second neighboring sectors; and
(D) estimating a location of said subscriber station as a point of intersection of said range ring and said location hyperbola that is within said most likely sub-sector.
2. The method of claim 1 wherein said message is a scanning result report message.
3. The method of claim 1 wherein said first information includes a round trip delay time value between said subscriber station and said first base station.
4. The method of claim 3 wherein said second information includes a relative time delay value observed at said subscriber station between said first and second signals.
5. The method of claim 1 wherein signals sent from said first and second base stations are synchronized to a common timing standard.
6. The method of claim 1 wherein said WiMAX or LTE network includes a Network Synchronization Unit (“NSU”) wherein said NSU is synchronized to a timing standard and located at a predetermined location.
7. The method of claim 6 wherein a time of arrival is determined at said NSU for said first signal and for said second signal.
8. The method of claim 6 wherein said WiMAX or LTE network includes a predetermined number N base stations and a predetermined number M NSUs wherein N>1 and N>M.
9. The method of claim 1 wherein said subscriber station is an Assisted-Global Positioning System (“A-GPS”) enabled subscriber station, and wherein a timing offset between said first and second signals is determined from said subscriber station message.
10. The method of claim 1 wherein plural additional subscriber stations are operating in said WiMAX or LTE network with each reporting their Global Positioning System (“GPS”) locations and subscriber station measurements to said WiMAX or LTE network to thereby allow said WiMAX or LTE network to determine synchronization between said base stations.
11. The method of claim 1 further comprising the step of:
determining a second location hyperbola using said second information wherein said second location hyperbola has said first base station and a third base station as foci, wherein the step of estimating a location of said subscriber station uses said range ring, said location hyperbola, and said second location hyperbola.
12. A system for estimating a location of a subscriber station receiving a first signal from a first base station and receiving a second signal from a second base station where the first and second base stations are nodes in a WiMAX or LTE network, comprising:
(a) a receiver for receiving from said subscriber station a message containing a first information and a second information;
(b) circuitry for determining a range ring from said first base station using said first information;
(c) circuitry for determining a location hyperbola using said second information wherein said location hyperbola has said first and said second base stations as foci; and
(d) circuitry for estimating a location of said subscriber station using said range ring and said location hyperbola,
wherein said circuitry for estimating a location of said subscriber station includes:
(i) circuitry for determining a serving sector of said first base station for said subscriber station; and
(ii) if said range ring and said location hyperbola intersect plural times within said serving sector:
(A) circuitry for determining plural sub-sectors for said serving sector;
(B) circuitry for determining from said message a carrier-to-interference noise ratio (“CINR”) for each of a first and a second neighboring sector to said serving sector;
(C) circuitry for determining a most likely sub-sector from said plural sub-sectors based on a comparison of said CINR for said first and second neighboring sectors; and
(D) circuitry for estimating a location of said subscriber station as a point of intersection of said range ring and said location hyperbola that is within said most likely sub-sector.
13. The system of claim 12 wherein said message is a scanning result report message.
14. The system of claim 12 wherein said first information includes a round trip delay time value between said subscriber station and said first base station.
15. The system of claim 14 wherein said second information includes a relative time delay value observed at said subscriber station between said first and second signals.
16. The system of claim 12 wherein signals sent from said first and second base stations are synchronized to a common timing standard.
17. The system of claim 12 wherein said WiMAX or LTE network includes a Network Synchronization Unit (“NSU”) wherein said NSU is synchronized to a timing standard and located at a predetermined location.
18. The system of claim 17 wherein a time of arrival is determined at said NSU for said first signal and for said second signal.
19. The system of claim 17 wherein said WiMAX or LTE network includes a predetermined number N base stations and a predetermined number M NSUs wherein N>1 and N>M.
20. The system of claim 12 wherein said subscriber station is an Assisted-Global Positioning System (“A-GPS”) enabled subscriber station, and wherein a timing offset between said first and second signals is determined from said subscriber station message.
21. The system of claim 12 wherein plural additional subscriber stations are operating in said WiMAX or LTE network with each reporting their Global Positioning System (“GPS”) locations and subscriber station measurements to said WiMAX or LTE network to thereby allow said WiMAX or LTE network to determine synchronization between said base stations.
22. The system of claim 12 further comprising:
circuitry for determining a second location hyperbola using said second information wherein said second location hyperbola has said first base station and a third base station as foci, wherein the circuitry for estimating a location of said subscriber station uses said range ring, said location hyperbola, and said second location hyperbola.