Methods and systems for registering a wireless access terminal with a radio access network

• US 8,644,261 B1
• Filed: 02/04/2011
• Issued: 02/04/2014
• Est. Priority Date: 02/04/2011
• Status: Active Grant

• Current Assignee: Sprint Spectrum LP (Deutsche Telekom AG)
• Original Assignee: Sprint Spectrum LP (Deutsche Telekom AG)
• Inventors: Vargantwar, Sachin R.
• Primary Examiner(s): Shah, Chirag
• Assistant Examiner(s): Shivers, Ashley
• Application Number:
  US13/021,632
• Time in Patent Office: 1,096 Days
• Field of Search: None
• US Class Current: 370/332
• CPC Class Codes: H04W 48/20 Selecting an access point
• CPC Class Codes: H04W 60/04 using triggered events

Abstract

A method and system for determining whether an access terminal will perform a hand off to a target base station (BS) or register with a currently-serving BS and thereafter hand off to the target BS. In making that determination, the access terminal may make and compare pilot signal strength measurements. For a target BS transmitting a pilot signal detected to be stronger than a pilot signal transmitted by the currently-serving BS, the access terminal determines whether a distance between the target BS and a currently-registered BS exceeds a registration distance associated with the currently-registered BS. If the registration distance is exceeded, the access terminal registers with the currently-serving BS prior to handing off to the target BS such that the access terminal is more likely to receive page messages directed to the access terminal while it is registering with the currently-serving BS and handing off to the target BS.

Claims

1. A method comprising:

an access terminal registering with a first base station;

while the access terminal is registered with the first base station, the access terminal performing an idle-mode handoff to a second base station;

while the access terminal is registered with the first base station and while the second base station is a currently-serving base station for the access terminal, the access terminal detecting that a strength of a pilot signal transmitted by a third base station exceeds, by at least a handoff threshold, a strength of a pilot signal transmitted by the second base station;

the access terminal comparing a distance between the first base station and the third base station to a registration distance associated with the first base station; and

if the access terminal determines that the distance between the first base station and the third base station is greater than or equal to the registration distance associated with the first base station, then the access terminal registering with the second base station, otherwise, if the access terminal determines that the distance between the first base station and the third base station is less than the registration distance associated with the first base station, then the access terminal performing an idle-mode handoff from the second base station to the third base station.

2. The method of claim 1, further comprising:

while the access terminal is registered with the first base station but prior to the access terminal performing the idle-mode handoff to the second base station, the access terminal (i) detecting that the strength of the pilot signal transmitted by the second base station exceeds, by at least the handoff threshold, a strength of a pilot signal transmitted by a fourth base station, and (ii) determining that a distance between the first base station and the second base station is less than the registration distance associated with the first base station and then the access terminal responsively performing an idle-mode handoff from the fourth base station to the second base station.

3. The method of claim 1, further comprising, while the second base station is the currently-serving base station for the access terminal, the access terminal monitoring a forward paging channel of the second base station.

4. The method of claim 1, further comprising, while the second base station is the currently-serving base station for the access terminal, the access terminal monitoring a forward broadcast channel of the second base station.

5. The method of claim 1, further comprising, while the second base station is the currently-serving base station for the access terminal, the access terminal monitoring a forward control channel of the second base station.

6. The method of claim 1, wherein the handoff threshold comprises a dynamic handoff threshold.

7. The method of claim 1, wherein if the access terminal determines that the distance between the first base station and the third base station is greater than or equal to the registration distance associated with the first base station, the method further comprising the access terminal responsively performing an idle-mode handoff from the second base station to the third base station after the access terminal registers with the second base station.

8. The method of claim 1, further comprising:

the access terminal determining the registration distance associated with the first base station from among a plurality of registration distances associated with the first base station.

9. The method of claim 8,

wherein each registration distance of the plurality of registration distances is associated with a respective azimuth range of a plurality of azimuth ranges,

wherein an azimuth between a north reference line extending from the currently-registered base station and a ray extending from the currently-registered base station to the third base station is within a particular azimuth range of the plurality of azimuth ranges, and

wherein the registration distance associated with the first base station is associated with the particular azimuth range.

10. The method of claim 9, further comprising:

the access terminal receiving, from the currently-registered base station, a message arrangement comprising the plurality of azimuth ranges and the plurality of registration distances and responsively storing the plurality of azimuth ranges and the plurality of registration distances within a data storage device of the access terminal.

11. The method of claim 8,

wherein each registration distance of the plurality of registration distances is associated with a respective azimuth range of a plurality of azimuth ranges,

wherein an azimuth between a north reference line extending from the currently-registered base station and a ray extending from the currently-registered base station to the access terminal is within a particular azimuth range of the plurality of azimuth ranges, and

wherein the registration distance associated with the first base station is associated with the particular azimuth range.

12. An access terminal comprising:

a radio frequency (RF) transceiver that is operable to transmit communications to register the access terminal with a first base station;

a processor; and

a data storage device that contains computer-readable program instructions and a registration distance associated with the first base station,

wherein, while the access terminal is registered with the first base station, the access final is operable to perform an idle-mode handoff to a second base station,

wherein, while the access terminal is registered with the first base station and the second base station is a currently-serving base station for the access terminal, the processor is operable to execute computer-readable program instructions to detect that a strength of a pilot signal received by the RF transceiver from a third base station exceeds, by at least a handoff threshold, a strength of a pilot signal received by the RF transceiver from the second base station,

wherein the computer-readable program instructions are executable by the processor to compare a distance between the first base station and the third base station to the registration distance associated with the first base station, and

wherein if the processor determines that the distance between the first base station and the third base station is greater than or equal to the registration distance associated with the first base station, then the processor triggers the RF transceiver to transmit communications to register the access terminal with the second base station, otherwise, if the processor determines that the distance between the first base station and the third base station is less than the registration distance associated, with the first base station, then the processor triggers the access terminal to perform an idle-mode handoff from the second base station to the third base station.

13. The access terminal of claim 12, wherein the processor executes computer-readable program instructions to determine the distance between the first base station and the third base station from latitude and longitude data that represents a location of the first base station and latitude and longitude data that represents a location of the third base station.

14. The access terminal of claim 12, wherein the handoff threshold comprises a dynamic handoff threshold.

15. The access terminal of claim 12, wherein if the processor determines that the distance between the first base station and the third base station is greater than or equal to the registration distance associated with the first base station, then after the processor triggers the RF transceiver to transmit communications to register the access terminal with the second base station, the processor executes program instructions to perform an idle-mode handoff to the third base station.

16. The access terminal of claim 12, wherein the communications to register the access terminal with the second base station comprises data selected from the group consisting of (i) a location of the access terminal, (ii) a status of the access terminal, (iii) an identification of the access terminal, and (iv) a slot cycle of the access terminal.

17. The access terminal of claim 12, wherein the registration distance associated with the first base station is one of a plurality of registration distances associated with the first base station and stored in the data storage device.

18. A method comprising:

an access terminal registering with a first base station;

while the access terminal is registered with the first base station, the access terminal performing an idle-mode handoff to a second base station;

while the access terminal is registered with the first base station and while the second base station is a currently-serving base station for the access terminal, the access terminal detecting that a strength of a pilot signal transmitted by a third base station exceeds, by at least a handoff threshold, a strength of a pilot signal transmitted by the second base station;

the access terminal comparing a distance between the first base station and the third base station to a registration distance associated with the first base station; and

if the access terminal determines that the distance between the first base station and the third base station is greater than the registration distance associated with the first base station, then the access terminal registering with the second base station, otherwise, if the access terminal determines that the distance between the first base station and the third base station is less than or equal to the registration distance associated with the first base station, then the access terminal performing an idle-mode handoff from the second base station to the third base station.

19. The method of claim 18, further comprising:

while the access terminal is registered with the first base station but prior to the access terminal performing the idle-mode handoff to the second base station, the access terminal (i) detecting that the strength of the pilot signal transmitted by the second base station exceeds, by at least the handoff threshold, a strength of a pilot signal transmitted by a fourth base station, and (ii) determining that a distance between the first base station and the second base station is less than the registration distance associated with the first base station and then the access terminal responsively performing an idle-mode handoff from the fourth base station to the second base station.

20. The method of claim 18, further comprising, while the second base station is the currently-serving base station for the access terminal, the access terminal monitoring a forward paging channel of the second base station.

21. The method of claim 18, further comprising, while the second base station is the currently-serving base station for the access terminal, the access terminal monitoring a forward broadcast channel of the second base station.

22. The method of claim 18, further comprising, while the second base station is the currently-serving base station for the access terminal, the access terminal monitoring a forward control channel of the second base station.

23. The method of claim 18, wherein the handoff threshold comprises a dynamic handoff threshold.

24. The method of claim 18, wherein if the access terminal determines that the distance between the first base station and the third base station is greater than the registration distance associated with the first base station, the method further comprising the access terminal responsively performing an idle-mode handoff from the second base station to the third base station after the access terminal registers with the second base station.

25. An access terminal comprising:

a radio frequency (RF) transceiver that is operable to transmit communications to register the access terminal with a first base station;

a processor; and

a data storage device that contains computer-readable program instructions and a registration distance associated with the first base station,

wherein, while the access terminal is registered with the first base station, the access terminal is operable to perform an idle-mode handoff to a second base station,

wherein, while the access terminal is registered with the first base station and the second base station is a currently-serving base station for the access terminal, the processor is operable to execute computer-readable program instructions to detect that a strength of a pilot signal received by the RF transceiver from a third base station exceeds, by at least a handoff threshold, a strength of a pilot signal received by the RF transceiver from the second base station,

wherein the computer-readable program instructions are executable by the processor to compare a distance between the first base station and the third base station to the registration distance associated with the first base station, and

wherein if the processor determines that the distance between the first base station and the third base station is greater than the registration distance associated with the first base station, then the processor triggers the RF transceiver to transmit communications to register the access terminal with the second base station, otherwise, if the processor determines that the distance between the first base station and the third base station is less than or equal to the registration distance associated with the first base station, then the processor triggers the access terminal to perform an idle-mode handoff from the second base station to the third base station.