Downlink observed time difference measurements

• US 6,356,763 B1
• Filed: 11/04/1998
• Issued: 03/12/2002
• Est. Priority Date: 08/07/1998
• Status: Expired due to Term

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Lundqvist, Patrik, Cedervall, Mats, Fischer, Sven, Larsson, Erik, Kangas, Ari
• Primary Examiner(s): MAUNG, NAY AUNG
• Application Number:
  US09/186,192
• Time in Patent Office: 1,224 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, 370/320, 370/321
• 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 at 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 Code Division Multiple Access (CDMA) radio signals respectively transmitted by at least two radio transmitters in the network, said method comprising the steps of:

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;

providing the mobile communication station with information indicative of spreading codes used by the radio transmitter serving the mobile communication station and the other radio transmitters;

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 the respective CDMA radio signals are expected to arrive at the mobile communication station;

determining, by the mobile communication station, the spreading codes used by the radio transmitter serving the mobile communication station, from the information indicative of the spreading codes; and

for each CDMA radio signal, the mobile communication station monitoring, using the spreading codes, for arrival of the CDMA radio signal during a period of time after said point in time at which the CDMA radio signal is expected to arrive.

2. A method of using a mobile communication station in a wireless communication network to measure respective times of arrival of Code Division Multiple Access (CDMA) radio signals respectively transmitted by at least two radio transmitters in the network, said method comprising the steps of:

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

providing information indicative of spreading codes used by the at least two radio transmitters;

determining, by the mobile communication station and from the information indicative of the spreading codes, the spreading codes used by the at least two radio transmitters; and

the mobile communication station monitoring for arrival of the CDMA radio signals of broadcast channels associated with the at least two radio transmitters using the spreading codes and based upon the information indicative of when the CDMA radio signals are expected to arrive.

3. The method of claim 2, wherein said providing step includes providing 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.

4. The method of claim 2, 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.

5. The method of claim 4, 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.

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

7. The method of claim 5, wherein said using step includes accounting for respective distances to be traveled by the radio signals in order to reach the mobile communication station.

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

9. The method of claim 8, 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.

10. The method of claim 4, wherein said determining step includes the mobile communication station determining the points in time.

11. The method of claim 2, wherein the wireless communication network is a cellular communication network.

12. The method of claim 2, wherein the wireless communication network is a CDMA network.

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

receiving spreading code information;

determining from the received spreading code information the spreading codes used by at least two radio transmitters in the wireless communication network;

measuring at the mobile communication station respective times of arrival of Code Division Multiple Access (CDMA) radio signals respectively transmitted by the at least two radio transmitters in the network, including providing information indicative of when the CDMA radio signals are expected to arrive at the mobile communication station, and the mobile communication station monitoring for arrival of the CDMA radio signals using the spreading codes and based upon the information indicative of when the CDMA radio signals are expected to arrive; and

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

14. A method of determining the time of arrival of a Code Division Multiple Access (CDMA) radio signal from at least two radio transmitters at a radio communication station operating in a wireless communication network, said method comprising the steps of:

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

determining the informational content of the CDMA radio signal in response to the information;

receiving code group identification information and generating long codes therefrom;

monitoring for arrival of CDMA radio signals during a predetermined time interval in response to the information and the long codes; and

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

15. The method of claim 14, wherein said information includes information indicative of transmission timing of the CDMA radio signal.

16. The method of claim 15, wherein said transmission timing information is real time difference information 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 CDMA radio signal is to be transmitted.

17. The method of claim 14, wherein said information includes information indicative of a radio transmitter from which the CDMA radio signal is to be transmitted.

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

a determiner for determining when each of a plurality of Code Division Multiple Access (CDMA) radio signals from at least two radio transmitters is expected to arrive at the mobile communication station;

a radio signal monitor for measuring respective times of arrival of the CDMA radio signals, said radio signal monitor provided in the mobile communication station and having an input coupled to said determiner to receive therefrom information indicative of when the CDMA radio signals are expected to arrive at the mobile communication station, said monitor responsive to said information to monitor for arrival of the CDMA radio signals; and

a code generator coupled to said radio signal monitor for providing thereto codes, the radio signal monitor using the codes to monitor for arrival of the CDMA radio signals.

19. The apparatus of claim 18, wherein said determiner is provided in the mobile communication station.

20. The apparatus of claim 18, wherein said determiner determines respective periods of time during which the respective radio signals are expected to arrive at the mobile communication station.

21. The apparatus of claim 18, 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.

22. The apparatus of claim 21, 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.

23. The apparatus of claim 22, 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.

24. The apparatus of claim 18, wherein the wireless communication network is a cellular communication network.

25. The apparatus of claim 18, wherein the wireless communication network is a CDMA network.

26. The apparatus of claim 18, wherein said codes include spreading codes respectively associated with said CDMA radio signals.

27. The apparatus of claim 18, wherein said codes include codes carried by said CDMA radio signals.

28. The apparatus of claim 27, wherein said codes include code patterns respectively associated with radio transmitters used to produce the respective CDMA radio signals.

29. The apparatus of claim 18, wherein said code generator includes an input for receiving code identification information responsive to which said codes are provided.

30. The apparatus of claim 18, wherein said code generator is provided in the mobile communication station.

31. An apparatus for measuring the time of arrival of a Code Division Multiple Access (CDMA) radio signal thereat, comprising:

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

a determiner coupled to said input and responsive to said information for determining the informational content of the CDMA radio signal;

a code generator for receiving code group identification information and generating long codes therefrom; and

a radio signal monitor for measuring the time of arrival of the CDMA radio signal, said radio signal monitor coupled to said determiner for using said informational content of the CDMA radio signal in measuring the time of arrival of the CDMA radio signal, said radio signal monitor coupled to said code generator for receiving the long codes and for monitoring for arrival of the CDMA radio signals during a predetermined time interval in response to the information and the long codes.

32. The apparatus of claim 31, wherein said information includes information indicative of transmission timing of the CDMA radio signal.

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

34. The apparatus of claim 31, wherein said information includes information indicative of a radio transmitter from which the CDMA radio signal is to be transmitted.

35. The apparatus of claim 31, wherein the apparatus is a mobile radio communication station.

36. A method of using a mobile communication station in a wireless communication network to measure respective times of arrival of Code Division Multiple Access (CDMA) radio signals respectively transmitted by at least two radio transmitters in the network, comprising:

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

the mobile communication station monitoring for arrival of the radio signals in response to the information including the steps of;

correlating said radio signal with a first code that is periodically transmitted by the associated radio transmitter; and

simultaneously with said correlating step, correlating said radio signal with a code pattern that includes a plurality of second codes which are sequentially transmitted by the associated radio transmitter such that each of the second codes in the code pattern is transmitted simultaneously with one of said periodic transmissions of the first code.

37. The method of claim 36, including providing, for each radio transmitter, information indicative of a code group to which the radio transmitter belongs, and further including the mobile communication station determining said code pattern in response to said code group information.

38. The method of claim 36, including detecting said transmitted first and second codes by combining results of said correlating steps.

39. A system for measuring respective times of arrival of Code Division Multiple Access (CDMA) radio signals respectively transmitted by radio transmitters, said system comprising:

a serving radio transmitter providing information indicative of when the CDMA radio signals are expected to arrive, said serving radio transmitter periodically transmitting a first code and sequentially transmitting a plurality of second codes such that each of the plurality of second codes in a code pattern is transmitted simultaneously with a periodic transmission of the first code; and

a mobile communication station monitoring for arrival of the CDMA radio signals based upon the information provided by the serving radio transmitter, correlating the CDMA radio signals with the first code, substantially simultaneously correlating the CDMA radio signals with the code pattern that includes the plurality of second codes and determining the times of arrival of the CDMA radio signals based upon the correlated CDMA radio signals.

40. The system of claim 39, wherein said serving radio transmitter providing for each radio transmitter, information indicative of a code group to which each radio transmitter belongs, and further including the mobile communication station determining said code pattern in response to said code group information.

41. The system of claim 39, wherein said mobile communication station detecting said first and said second codes by combining results of the correlated radio signals.