System and method for locating a mobile station in a wireless network

• US 20030119525A1
• Filed: 12/20/2001
• Published: 06/26/2003
• Est. Priority Date: 12/20/2001
• Status: Abandoned Application

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Rajkotia, Purva R.
• Application Number:
  US10/028,571
• Publication Number:
  US 20030119525A1
• Time in Patent Office: Days
• US Class Current: 455/456.1
• CPC Class Codes: G01S 1/026 of associated receivers
• CPC Class Codes: G01S 13/74 Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

A system and method is disclosed for locating a mobile station in a wireless network. A distance unit associated with a base station determines a one way travel time of a range signal from the base station to the mobile station and multiplies the one way travel time by the speed of light to obtain the distance from the base station to the mobile station. The one way travel time is equal to one half of a quantity that is equal to a two way travel time of a range signal minus a time value of a random backoff parameter of the mobile station. The distance resolution of the system is approximately two hundred forty four meters.

Claims

1. For use in wireless network communications system comprising a plurality of base stations and a plurality of mobile stations, an apparatus for determining a distance from a base station to a mobile station, said apparatus comprising:

a distance unit associated with said base station wherein said distance unit is capable of determining a one way travel time D of a signal from said base station to said mobile station; and

wherein said distance unit is capable of multiplying said one way travel time D by the speed of light to obtain said distance from said base station to said mobile station.

2. The apparatus as set forth in claim 1 wherein said distance unit is capable of determining said one way travel time D from:

3. The apparatus as set forth in claim 2 wherein said distance unit is capable of obtaining said two way travel time by subtracting an arrival time of said range signal at said base station from said mobile station from a transmission time of said range signal from said base station to said mobile station.

4. The apparatus as set forth in claim 2 wherein said random backoff parameter for said mobile station has a chip length value between zero chip lengths and five hundred eleven chip lengths.

5. The apparatus as set forth in claim 4 wherein a time value for one chip length value is eight hundred thirteen and eight tenths nanoseconds.

6. The apparatus as set forth in claim 1 wherein said distance unit is capable of obtaining a distance from said base station to said mobile station with a distance resolution of approximately two hundred forty four meters.

7. The apparatus as set forth in claim 2 wherein said distance unit is capable of adjusting a value of said two way travel time to correct a time difference of a signal comprising one of:

a multipath signal and a Doppler shifted signal.

8. A wireless network communications system comprising a base station and a mobile station, said base station comprising an apparatus for determining a distance from said base station to said mobile station, said apparatus comprising:

a distance unit associated with said base station wherein said distance unit is capable of determining a one way travel time D of a signal from said base station to said mobile station; and

wherein said distance unit is capable of multiplying said one way travel time D by the speed of light to obtain said distance from said base station to said mobile station.

9. The wireless network communications system as set forth in claim 8 wherein said distance unit is capable of determining said one way travel time D from:

10. The wireless network communications system as set forth in claim 9 wherein said distance unit is capable of obtaining said two way travel time by subtracting an arrival time of said range signal at said base station from said mobile station from a transmission time of said range signal from said base station to said mobile station.

11. The wireless network communications system as set forth in claim 9 wherein said random backoff parameter for said mobile station has a chip length value between zero chip lengths and five hundred eleven chip lengths.

12. The wireless network communications system as set forth in claim 11 wherein a time value for one chip length value is eight hundred thirteen and eight tenths nanoseconds.

13. The wireless network communications system as set forth in claim 8 wherein said distance unit is capable of obtaining a distance from said base station to said mobile station with a distance resolution of approximately two hundred forty four meters.

14. The wireless network communications system as set forth in claim 9 wherein said distance unit is capable of adjusting a value of said two way travel time to correct a time difference of a signal comprising one of:

a multipath signal and a Doppler shifted signal.

15. For use in wireless network communications system comprising a base station and a mobile station, a method of determining a distance from said base station to said mobile station comprising the steps of:

determining with a distance unit associated with said base station a one way travel time D of a signal from said base station to said mobile station; and

multiplying said one way travel time D by the speed of light to obtain said distance from said base station to said mobile station.

16. The method as set forth in claim 15 wherein the step of determining with a distance unit associated with said base station a one way travel time D of a signal from said base station to said mobile station comprises the step of:

calculating said one way travel time D from;

$D=\frac{1}{2}<br><br>\left[\left(\mathrm{two}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{way}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{travel}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{time}\right)-\left(\mathrm{random}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{backoff}\right)\right]$

wherein said two way travel time is a time of travel for a range signal to travel from said base station to said mobile station and to travel from said mobile station to said base station; and

wherein said random backoff is a time value of a chip length of a random backoff parameter of said mobile station.

17. The method as set forth in claim 16 further comprising the step of:

obtaining said two way travel time by subtracting an arrival time of said range signal at said base station from said mobile station from a transmission time of said range signal from said base station to said mobile station.

18. The method as set forth in claim 16 wherein said random backoff parameter for said mobile station has a chip length value between zero chip lengths and five hundred eleven chip lengths.

19. The method as set forth in claim 18 wherein a time value for one chip length value is eight hundred thirteen and eight tenths nanoseconds.

20. The method as set forth in claim 15 further comprising the step of:

obtaining with said distance unit a distance from said base station to said mobile station with a distance resolution of approximately two hundred forty four meters.

21. The method as set forth in claim 16 further comprising the step of:

adjusting in said distance unit a value of said two way travel time to correct a time difference of a signal comprising one of;

a multipath signal and a Doppler shifted signal.

22. The method as set forth in claim 15 wherein said distance unit determines a distance from said base station to said mobile station in less than ten seconds.

23. For use in wireless network communications system comprising a plurality of base stations and a plurality of mobile stations, a method for locating a mobile station in an area between three base stations, said method comprising the steps of:

determining with a distance unit associated with each of said three base stations a one way travel time D of a signal from each respective station to said mobile station where

$D=\frac{1}{2}<br><br>\left[\left(\mathrm{two}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{way}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{travel}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{time}\right)-\left(\mathrm{random}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{backoff}\right)\right]$

wherein said two way travel time is a time of travel for a range signal to travel from each respective base station to said mobile station and to travel from said mobile station to each respective base station;

wherein said random backoff is a time value of a chip length of a random backoff parameter of said mobile station;

multiplying each respective one way travel time D by the speed of light to obtain each respective distance from each respective base station to said mobile station; and

identifying a location of said mobile station within said area between said three base stations using said respective distances of said mobile station from said respective base stations.

24. The method as set forth in claim 23 wherein said location of said mobile station within said area between said three base stations has a distance resolution of approximately two hundred forty four meters.

25. The method as set forth in claim 23 wherein the step of identifying said location of said mobile station within said area between said three base stations using said respective distances of said mobile station from said respective base stations comprises the steps of:

providing said respective distances of said mobile station from said respective base stations to a distance unit within one of said three base stations; and

calculating in said distance unit a location of said mobile station from said respective distances of said mobile station from said respective base stations.

26. The method as set forth in claim 23 wherein the step of identifying said location of said mobile station within said area between said three base stations using said respective distances of said mobile station from said respective base stations comprises the steps of:

providing said respective distances of said mobile station from said respective base stations to a calculator unit not located within said three base stations; and

calculating in said calculator unit a location of said mobile station from said respective distances of said mobile station from said respective base stations.

27. For use in wireless network communications system comprising a plurality of base stations and a plurality of mobile stations, an apparatus for locating a mobile station in an area between three base stations, said apparatus comprising:

a distance unit associated with each of said three base stations wherein said distance unit is capable of determining a one way travel time D of a signal from each respective station to said mobile station where

$D=\frac{1}{2}<br><br>\left[\left(\mathrm{two}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{way}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{travel}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{time}\right)-\left(\mathrm{random}<br><br>\text{\hspace{1em}<br><br>}<br><br>\mathrm{backoff}\right)\right]$

wherein said two way travel time is a time of travel for a range signal to travel from each respective base station to said mobile station and to travel from said mobile station to each respective base station;

wherein said random backoff is a time value of a chip length of a random backoff parameter of said mobile station;

wherein said distance unit is capable of multiplying each respective one way travel time D by the speed of light to obtain each respective distance from each respective base station to said mobile station; and

wherein said distance unit is capable of identifying a location of said mobile station within said area between said three base stations using said respective distances of said mobile station from said respective base stations.

28. The apparatus as set forth in claim 27 wherein said location of said mobile station within said area between said three base stations has a distance resolution of approximately two hundred forty four meters.

29. The apparatus as set forth in claim 27 wherein said distance unit is capable of calculating a location of said mobile station from said respective distances of said mobile station from said respective base stations.

30. The apparatus as set forth in claim 27 further comprising:

a calculator unit coupled to said three base stations but not located within said three base stations, said calculator unit capable of receiving from said three base stations said respective distances of said mobile station from said respective base stations;

wherein said calculator unit is capable of calculating a location of said mobile station from said respective distances of said mobile station from said respective base stations.