Methods and systems for temporarily modifying a macro-network neighbor list to enable a mobile station to hand off from a macro network to a femto cell

• US 7,929,970 B1
• Filed: 12/21/2007
• Issued: 04/19/2011
• Est. Priority Date: 12/21/2007
• Status: Active Grant

• Current Assignee: Sprint Spectrum LP (Deutsche Telekom AG)
• Original Assignee: Sprint Spectrum LP (Deutsche Telekom AG)
• Inventors: Prasad, Sunil, Gunasekara, Don
• Primary Examiner(s): Chang; Kent
• Assistant Examiner(s): Siddiqui; Kashif
• Application Number:
  US11/963,303
• Time in Patent Office: 1,215 Days
• Field of Search: 455437-444, 455522-525, 370/254, 370338-348
• US Class Current: 455/444
• CPC Class Codes: H04W 36/00835 Determination of neighbour cell lists
• CPC Class Codes: H04W 36/04 Reselecting a cell layer in multi-layered cells
• CPC Class Codes: H04W 84/045 using private Base Stations, e.g. femto Base Stations, home Node B

Abstract

Methods and systems are disclosed for temporarily modifying a macro-network neighbor list to enable a mobile station to hand off from a macro network to a femto cell. A method includes receiving a signal indicating that the mobile station detected coverage of a femto cell; after receiving the signal, adding the femto cell to the neighbor list, thereby enabling the mobile station to handoff to the femto cell; detecting that the mobile station completed handoff to the femto cell; and in response to detecting that the mobile station completed handoff to the femto cell, removing the femto cell from the neighbor list.

Claims

1. In a communications system that includes a mobile station and a macro network, wherein the macro network includes at least one macro coverage area serving the mobile station, and wherein the macro network includes a neighbor list corresponding to the at least one macro coverage area, a method comprising:

receiving, at the macro network, a signal indicating that the mobile station detected coverage of a femto coverage area;

after receiving the signal, adding the femto coverage area to the neighbor list at the macro network, thereby enabling the mobile station to hand off to the femto coverage area;

detecting, at the macro network, that the mobile station completed handoff to the femto coverage area; and

in response to detecting that the mobile station completed handoff to the femto coverage area, removing the femto coverage area from the neighbor list at the macro network.

2. In a communications system that includes a mobile station and a macro network, wherein the macro network includes at least one macro coverage area serving the mobile station, and wherein the macro network includes a neighbor list corresponding to the at least one macro coverage area, a method for temporarily modifying the neighbor list to enable the mobile station to hand off from the macro network to a femto coverage area, the method comprising:

receiving, at the macro network, a signal from the mobile station, wherein the signal identifies the femto coverage area, and wherein the femto coverage area is initially not included in the neighbor list;

in response to receiving the signal, temporarily modifying the neighbor list at the macro network to include the femto coverage area;

providing from the macro network to the mobile station an indication of the modified neighbor list, thereby enabling the mobile station to hand off from the macro network to the femto coverage area;

receiving, at the macro network, a message indicating that the mobile station completed handoff to the femto coverage area; and

in response to receiving the message indicating that the mobile station completed handoff to the femto coverage area, removing the femto coverage area from the modified neighbor list at the macro network.

3. The method of claim 2, wherein the step of receiving the signal from the mobile station occurs after the mobile station receives a pilot signal from the femto coverage area, the pilot signal identifying the femto coverage area and defining a pilot-signal strength that is above a predetermined threshold.

4. The method of claim 3, wherein the signal from the mobile station is a Pilot Strength Measurement Message (PSMM) that identifies the femto coverage area and includes an indication of the pilot-signal strength.

5. The method of claim 2, further comprising, in response to receiving the signal, determining whether the mobile station is authorized to be served by the femto coverage area.

6. The method of claim 5, wherein determining whether the mobile station is authorized to be served by the femto coverage area comprises:

referring to profile data corresponding to the mobile station; and

determining whether the profile data indicates that the mobile station is authorized to be served by the femto coverage area.

7. The method of claim 6, wherein the macro network includes the profile data.

8. The method of claim 2, wherein providing to the mobile station an indication of the modified neighbor list comprises sending to the mobile station a Neighbor List Update Message (NLUM) that includes the femto coverage area.

9. The method of claim 2, wherein receiving the message indicating that the mobile station completed handoff to the femto coverage area comprises receiving a Handoff Completion Message (HCM) from the mobile station.

10. The method of claim 2, further comprising modifying a handoff process for the mobile station such that the handoff process is biased toward handoff of the mobile station to the femto coverage area.

11. The method of claim 10, wherein the macro network stores a value indicating a threshold pilot-signal strength that must be exceeded to justify handoff to a given coverage area, and wherein modifying the handoff process for the mobile station comprises enabling the mobile station to handoff to the femto coverage area when a pilot-signal strength from the femto coverage area is lower than the threshold pilot-signal strength.

12. The method of claim 2, wherein the macro network is a radio access network.

13. The method of claim 2, wherein the femto coverage area includes a plurality of femto coverage areas.

14. A system for temporarily modifying a macro-network neighbor list to enable a mobile station to hand off from a macro network to a femto coverage area, wherein the macro network includes at least one macro coverage area serving the mobile station, and wherein the macro-network neighbor list corresponds to the least one macro coverage area, the system comprising, at the macro network:

a communication interface;

a processor; and

data storage containing (i) the macro-network neighbor list and (ii) instructions executable by the processor to;

(a) via the communication interface, receive a signal from the mobile station, wherein the signal identifies the femto coverage area, and wherein the femto coverage area is initially not included in the macro-network neighbor list;

(b) in response to receiving the signal, temporarily modify the macro-network neighbor list to include the femto coverage area;

(c) via the communication interface, provide to the mobile station an indication of the modified macro-network neighbor list, thereby enabling the mobile station to hand off from the macro network to the femto coverage area;

(d) via the communication interface, receive a message indicating that the mobile station completed handoff to the femto coverage area; and

(e) in response to receiving the message indicating that the mobile station completed handoff to the femto coverage area, remove the femto coverage area from the modified macro-network neighbor list.

15. The system of claim 14, wherein the step of receiving the signal from the mobile station occurs after the mobile station receives a pilot signal from the femto coverage area, the pilot signal identifying the femto coverage area and defining a pilot-signal strength that is above a predetermined threshold.

16. The system of claim 14, further comprising instructions to, in response to receiving the signal, determine whether the mobile station is authorized to be served by the femto coverage area.

17. The system of claim 14, wherein the instructions to provide to the mobile station the indication of the modified macro-network neighbor list comprise instructions to send to the mobile station a Neighbor List Update Message (NLUM) that includes the femto coverage area.

18. The system of claim 14, wherein the message is a Handoff Completion Message (HCM).

19. The system of claim 14, further comprising instructions to modify a handoff process for the mobile station such that the handoff process is biased toward handoff of the mobile station to the femto coverage area.

20. The system of claim 19, wherein the femto coverage area includes a plurality of femto coverage areas.