Downlink observed time difference measurements

• US 6,490,454 B1
• Filed: 08/07/1998
• Issued: 12/03/2002
• Est. Priority Date: 08/07/1998
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Fischer, Sven, Larsson, Erik, Lundqvist, Patrik, Kangas, Ari
• Primary Examiner(s): MAUNG, NAY AUNG
• Application Number:
  US09/131,150
• Time in Patent Office: 1,579 Days
• Field of Search: 455/12.1, 455/67.4, 455/67.6, 455/422, 455/427, 455/432, 455/436, 455/456, 455/502, 455/503, 342/457, 370/324
• US Class Current: 455/456.1
• CPC Class Codes: G01S 1/026 of associated receivers
• 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: H04W 56/0075 based on arrival time vs. expected arrival time
• CPC Class Codes: H04W 64/00 Locating users or terminals or network equipment for network management purposes, e.g. mobility management

Abstract

A mobile communication station in a wireless communication network is used to measure the respective times of arrival of radio signals respectively transmitted by a plurality of radio transmitters in the network. The mobile communication station is provided with real time difference information indicative of differences between a time base used by a radio transmitter serving the mobile communication station and respective time bases used by the other radio transmitters. The mobile communication station determines, in response to the real time difference information and relative to the time base used by the radio transmitter serving the mobile communication station, a plurality of points in time at which the respective radio signals are expected to arrive the mobile communication station. For each radio signal, the mobile communication station monitors for arrival of the radio signal during a period of time after the point in time at which the radio signal is expected to arrive.

Claims

1. A method of using a mobile communication station in a wireless communication network to measure respective times of arrival of radio signals respectively transmitted by a plurality of radio transmitters in the network, comprising:

providing real time difference information indicative of when the radio signals are expected to arrive at the mobile communication station;

calculating at least one search window from said real time difference information; and

the mobile communication station monitoring for arrival of the radio signals during said at least one search window.

2. The method of claim 1, wherein said providing step includes providing real time difference information indicative of respective periods of time during which the respective radio signals are expected to arrive at the mobile communication station, and said monitoring step including the mobile communication station monitoring for arrival of each radio signal during the corresponding period of time.

3. The method of claim 1, wherein said providing step further includes:

providing real time difference information indicative of differences between a time base used by a radio transmitter serving the mobile communication station and respective time bases used by the radio transmitters being measured; and

in response to the real time difference information, determining, relative to the time base used by the serving radio transmitter, a plurality of points in time at which the respective radio signals are expected to arrive at the mobile communication station.

4. The method of claim 3, wherein said providing step further includes using the points in time to determine respective periods of time during which the respective radio signals are expected to arrive at the mobile communication station, and said monitoring step including the mobile communication station monitoring for arrival of each radio signal during the corresponding period of time.

5. The method of claim 4, wherein said using step includes the mobile communication station using the points in time to determine the respective periods of time.

6. The method of claim 4, wherein said using step includes accounting for respective distances to be traveled by the radio signals in order to reach the mobile communication station.

7. The method of claim 6, wherein said accounting step includes estimating, for each radio signal, a maximum possible distance of travel and a minimum possible distance of travel.

8. The method of claim 7, wherein said accounting step includes, for each radio signal, establishing a beginning point of the associated period of time based on the point in time at which arrival is expected and the minimum possible distance of travel, and establishing an ending point of the associated period of time based on the point in time at which arrival is expected and the maximum possible distance of travel.

9. The method of claim 3, wherein said determining step includes the mobile communication station determining the points in time.

10. The method of claim 3, wherein said radio signals are transmitted on time division multiple access channels, and said step of providing real time difference information includes expressing a real time difference using at least one of a frame number difference, a time slot number difference and a quarter bit number difference.

11. The method of claim 1, wherein the communication network is a cellular communication network.

12. The method of claim 11, wherein the communication network is a GSM network.

13. The method of claim 1, further comprising:

providing frequency information indicative of the respective frequencies of the measured radio signals.

14. A method of locating the position of a mobile communication station in a wireless communication network, comprising:

measuring at the mobile communication station respective times of arrival of radio signals respectively transmitted by a plurality of radio transmitters in the network, said measuring step further including;

providing real time difference information indicative of when the radio signals are expected to arrive at the mobile communication station;

calculating at least one search window based on the real time difference information; and

the mobile communication station monitoring for arrival of the radio signals during the at least one search window; and

using the measured times of arrival to locate the position of the mobile communication station.

15. The method of claim 14, further comprising:

providing frequency information indicative of the respective frequencies of the measured radio signals.

16. A method of determining the time of arrival of a radio signal at a radio communication station operating in a wireless communication network, comprising:

obtaining from the wireless communication network real time difference information from which an informational content of the radio signal can be determined but which real time difference information does not itself reveal the informational content of the radio signal;

determining the informational content of the radio signal in response to the real time difference information, the informational content indicative of at least one of the following;

an approximate expected arrival time of a synchronization burst relative to a time base used by a serving radio transmitter;

maximum bit information associated with the synchronization burst; and

a search window for the serving radio transmitter, the search window including the expected arrival time of the synchronization burst;

monitoring for arrival of the radio signal during the search window period; and

using the informational content of the radio signal to measure the time of arrival of the radio signal.

17. The method of claim 16, wherein said real time difference information includes information indicative of transmission timing of the radio signal.

18. The method of claim 16, wherein said real time difference information is indicative of a difference between a time base known to the radio communication station and a time base used by a radio transmitter from which the radio signal is to be transmitted.

19. The method of claim 16, wherein said real time difference information includes information indicative of a radio transmitter from which the radio signal is to be transmitted.

20. The method of claim 19, wherein the communication network is a GSM network, and wherein the information indicative of the radio transmitter includes a base station identity code (BSIC) which identifies a base station in the GSM network.

21. The method of claim 16, wherein the maximum bit information associated with the synchronization burst includes 78 encoded bits and 64 training bits.

22. An apparatus for use in locating the position of a mobile communication station in a wireless communication network, comprising:

a determiner for performing at least one of the following operations;

determining when each of a plurality of radio signals, respectively transmitted by a plurality of radio transmitters in the network, is expected to arrive at the mobile communication station; and

calculating at least one search windows for at least one of the plurality of radio transmitter;

a radio signal monitor for measuring respective times of arrival of the radio signals, said monitor provided in the mobile communication station and having an input coupled to said determiner to receive therefrom real time difference information indicative of when the radio signals are expected to arrive at the mobile communication station, said monitor responsive to said real time difference information to monitor for arrival of the radio signals during at least one respective search window period; and

an output for outputting the measured time of arrival information to a mobile location center, the mobile location center using the measured time of arrival information to determine the location of the mobile communication station.

23. The apparatus of claim 22, wherein said determiner is provided in the mobile communication station.

24. The apparatus of claim 22, wherein said determiner determines respective periods of time during which the respective radio signals are expected to arrive at the mobile communication station.

25. The apparatus of claim 22, wherein said determiner includes an input for receiving real time difference information indicative of differences between a time base used by a radio transmitter serving the mobile communication station and respective time bases used by radio transmitters which transmit the radio signals, said determiner responsive to the real time difference information for determining, relative to the time base used by the serving radio transmitter, a plurality of points in time at which the respective radio signals are expected to arrive at the mobile communication station.

26. The apparatus of claim 25, wherein said determiner is operable to use the points in time to determine respective periods of time during which the respective radio signals are expected to arrive at the mobile communication station.

27. The apparatus of claim 26, wherein said determiner is operable during determination of said periods of time to account for respective distances to be traveled by the radio signals in order to reach the mobile communication station, said determiner operable to estimate maximum possible distances of travel and minimum possible distances of travel and, for each radio signal, to establish a beginning point of the associated period of time based on the point in time at which arrival is expected and the minimum possible distance of travel, and to establish an ending point of the associated period of time based on the point in time at which arrival is expected and the maximum possible distance of travel.

28. The apparatus of claim 22, wherein the communication network is a cellular communication network.

29. The apparatus of claim 28, wherein the communication network is a GSM network.

30. An apparatus for measuring the time of arrival of a radio signal thereat, comprising:

an input for receiving real time difference information from which an informational content of the radio signal can be determined but which real time difference information does not itself reveal the informational content of the radio signal;

a determiner coupled to said input and responsive to said real time difference information for determining the informational content of the radio signal, the informational content of the radio signal indicative of at least one search window based upon the expected arrival time of a synchronization burst; and

a radio signal monitor for measuring the time of arrival of the radio signal, said monitor coupled to said determiner for using said informational content of the radio signal in measuring the time of arrival of the radio signal.

31. The apparatus of claim 30, wherein said real time difference information includes information indicative of transmission timing of the radio signal.

32. The apparatus of claim 30, wherein said real time difference information is indicative of a difference between a time base known to the apparatus and a time base used by a radio transmitter from which the radio signal is to be transmitted.

33. The apparatus of claim 30, wherein said real time difference information includes information indicative of a radio transmitter from which the radio signal is to be transmitted.

34. The apparatus of claim 33, wherein the communication network is a GSM network, and wherein the information indicative of the radio transmitter includes a base station identity code (BSIC) which identifies a base station in the GSM network.

35. The apparatus of claim 30, wherein the apparatus is a mobile radio communication station.

36. The apparatus of claim 30, wherein said input is further adapted to receive frequency information indicative of a frequency of the measured radio signal.

37. An apparatus for measuring the time of arrival of a radio signal thereat, comprising:

an input for receiving real time difference information from which an informational content of the radio signal can be determined but which real time difference information does not itself reveal the informational content of the radio signal;

a determiner coupled to said input and responsive to said real time difference information for determining the informational content of the radio signal, the informational content indicative of at least one of the following;

an approximate expected arrival time of a synchronization burst relative to a time base used by a serving radio transmitter;

maximum bit information associated with the synchronization burst; and

a search window for the serving radio transmitter, the search window including the expected arrival time of the synchronization burst; and

a radio signal monitor for measuring the time of arrival of the radio signal, said monitor coupled to said determiner for using said informational content of the radio signal in measuring the time of arrival of the radio signal, and further for monitoring for arrival of the radio signal during the search window period.

38. The apparatus of claim 37, wherein said real time difference information includes information indicative of transmission timing of the radio signal.

39. The apparatus of claim 37, wherein said real time difference information is indicative of a difference between a time base known to the apparatus and a time base used by a radio transmitter from which the radio signal is to be transmitted.

40. The apparatus of claim 37, wherein said real time difference information includes information indicative of a radio transmitter from which the radio signal is to be transmitted.

41. The apparatus of claim 40, wherein the communication network is a GSM network, and wherein the information indicative of the radio transmitter includes a base station identity code (BSIC) which identifies a base station in the GSM network.

42. The apparatus of claim 37, wherein the apparatus is a mobile radio communication station.

43. The apparatus of claim 37, wherein the monitor receives at least one of the following:

radio signals from the plurality of radio transmitters,

synchronization burst information including;

time of arrival information; and

maximum bit information, the maximum bit information including 78 encoded bits and 64 training bits; and

search window information.

44. The apparatus of claim 37, wherein said input is further adapted to receive frequency information indicative of a frequency of the measured radio signal.

45. A method of using a mobile communication station in a wireless communication network to measure respective times of arrival of radio signals respectively transmitted by a plurality of radio transmitters in the network, comprising:

providing the mobile communication station with real time difference information indicative of differences between a time base used by a radio transmitter serving the mobile communication station and respective time bases used by the other radio transmitters;

the mobile communication station calculating measurement search windows for each radio transmitter;

the mobile communication station determining, in response to the real time difference information and relative to the time base used by the radio transmitter serving the mobile communication station, a plurality of points in time at which respective radio signals are expected to arrive at the mobile communication station;

for each radio signal, the mobile communication station monitoring for arrival of the radio signal during the search window period; and

using the measured time of arrival information to determine the location of the mobile station.

46. The method of claim 45, further comprising:

providing, to the mobile communication station, frequency information indicative of the respective frequencies of the measured radio signals.