FEMTO CELL SIGNALING GATING

• US 20090280819A1
• Filed: 07/17/2008
• Published: 11/12/2009
• Est. Priority Date: 05/07/2008
• Status: Active Grant

• Current Assignee: AT&T Mobility II LLC (AT&T, Inc.), Microsoft Corporation
• Original Assignee: AT&T Mobility II LLC (AT&T, Inc.)
• Inventors: Brisebois, Arthur Richard, Huber, Kurt Donald
• Granted Patent: US 8,626,223 B2
• Time in Patent Office: Days
• US Class Current: 455/446
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04L 5/0078 Timing of allocation
• CPC Class Codes: H04W 48/08 Access restriction or access information delivery, e.g. discovery data delivery signalling during connection H04W76/00
• CPC Class Codes: H04W 52/244 Interferences in heterogeneous networks, e.g. among macro and femto or pico cells or other sector / system interference [OSI]
• CPC Class Codes: H04W 52/325 Power control of control or pilot channels
• CPC Class Codes: H04W 52/44 in connection with interruption of transmission
• CPC Class Codes: H04W 60/00 Affiliation to network, e.g. registration; Terminating affiliation with the network, e.g. de-registration
• CPC Class Codes: H04W 84/045 using private Base Stations, e.g. femto Base Stations, home Node B

Abstract

System(s) and method(s) are provided to manage signaling in a femto cell access point. A pilot signal power profile, or pilot signal gating, determines transmitted a time-dependent pilot signal power. The power profile displays a duty cycle well below 100% and a power depth, which is the amplitude between maximum and minimum pilot signal power, determined partially upon radio link conditions. The time-dependent power profile can be established through a schedule based at least in part on attachment data or subscriber input; machine-learning method facilitate inferring the schedule. Pilot signal gating profile can be reused in a femto cell deployment to broaden femto cell identification and thus facilitate macro-to-femto handover. Activating/deactivating pilot signal in a femto cell in the scheduled and synchronized manner provided herein leads to macro-femto interference mitigation and mobility improvement(s), and improved battery life of wireless devices that operate in a wireless environment that includes femto cells.

Claims

1. A method for managing signaling in a femto cell, the method comprising:

gating a pilot signal of a femto cell access point (AP) according at least in part to a predetermined pilot signal power time-dependent profile; and

conveying the gated pilot signal.

2. The method of claim 1, wherein gating a pilot signal of a femto cell AP based at least part on a predetermined pilot signal power profile further comprises:

generating a femto cell AP usage schedule; and

adjusting a power of the pilot signal according at least in part to the generated usage schedule.

3. The method of claim 2, wherein adjusting a power of the pilot signal according at least in part to the generated usage schedule comprises:

setting the power of the pilot signal to a first power level;

increasing the power of the pilot signal to a second power level when a mobile station attaches to the femto cell AP;

retaining the power of the pilot signal at the second power level when the subscriber station remains attached; and

resetting the power of the pilot signal to the first power level when the subscriber station detaches from the femto cell AP.

4. The method of claim 3, the power time-dependent profile is periodic with a duty cycle below 100%.

5. The method of claim 4, the power time-dependent profile has power depth determined at least in part on channel quality conditions, wherein the power depth is the difference among a maximum signal power (P_MAX) and a minimum (P_MIN) signal power.

6. The method of claim 5, wherein to facilitate response to induced interference conditions in a wireless environment in which the femto AP operates, P_MAX is reached from P_MIN within a first time interval determined by a first slope, and P_MIN is reached from P_MAX within a second time interval determined by a second slope.

7. The method of claim 3, generating a femto cell AP usage schedule further comprising:

tracking attachment events of a set of subscriber stations to the femto cell AP;

retaining the attachment events;

inferring a profile of attachment to the femto cell AP for a subscriber station in the set of subscriber stations to the femto cell AP based at least in part on the retained attachment events; and

generating the femto cell AP usage schedule based at least in part on the inferred profile of attachment.

8. The method of claim 7, wherein inferring a profile of attachment is based at least in part on machine-learning methods, the machine methods include at least one of a decision tree, a neural network, a regression analysis, a principal component analysis for feature and pattern extraction, a cluster analysis, a genetic algorithm, a game tree, a game matrix, pure and mixed strategies, Nash equilibria, or an evolutionary game theory.

9. The method of claim 1, further comprising establishing a pilot signal gating reuse plan for a set of femto cell APs.

10. The method of claim 9, further comprising:

identifying a set of femto cell APs that share a cell identification (ID) based at least in part on a received channel conditions report for the set of femto cells;

exploiting the pilot signal gating reuse to refine the identified set of femto cell APs;

identifying a femto cell AP in the refined set of femto cell APs that can serve a subscriber station for which macro-to-femto cell handover is requested; and

resolving requested macro-to-femto cell handover for the subscriber station and the identified femto cell AP.

11. The method of claim 10, identifying a femto cell AP in the refined set of femto cell APs is based at least in part on an access list of authorized mobile devices.

12. A system that controls signaling power in a femto cell, the system comprising:

a component that tracks attachment events from a macro cell to the femto cell;

a component that schedules a femto cell pilot signal gating based at least in part on the attachment events; and

a platform that conveys a femto cell pilot signal power profile based at least in part on the scheduled femto cell pilot signal gating.

13. The system of claim 12, wherein the component that schedules a femto cell pilot signal gating

(i) learns a profile of attachment to the femto cell based at least in part on tracked attachment events;

(ii) identifies a pattern in femto cell visitation history; and

(iii) generates the femto cell pilot signal gating based at least in part on the learned profile of attachment or the identified pattern in femto cell visitation history.

14. The system of claim 13, wherein the femto cell pilot gating is based at least in part on a femto cell ID (identification) code reuse distance.

15. The system of claim 14, the component that schedules a femto cell pilot signal learns a profile attachment based at least in part on machine-learning techniques.

16. The system of claim 15, the component that schedules a femto cell pilot signal identifies a pattern in femto cell visitation history based at least in part on machine-learning techniques.

17. The system of claim 16, the machine-learning techniques include at least one of a decision tree, a neural network, a regression analysis, a principal component analysis for feature and pattern extraction, a cluster analysis, a genetic algorithm, a game tree, a game matrix, pure and mixed strategies, Nash equilibria, or an evolutionary game theory.

18. The system of claim 12, the component that schedules a femto cell pilot signal

(a) schedules a transmitter power to a first pilot signal power level when a first subscriber station attaches to the femto cell;

and

(b) lowers the transmitter power to a second pilot signal power level when a last subscriber station detaches from the femto cell.

19. The system of claim 12, further comprising a management interface that facilitates generation of a femto cell pilot gating schedule.

20. The system of claim 12, the femto cell pilot signal power profile is a time-dependent profile that has a power depth determined at least in part on channel quality conditions, wherein the power depth is the difference among a maximum signal power (P_MAX) and a minimum (P_MIN) signal power.

21. The system of claim 20, the time-dependent power profile is periodic with a duty cycle below 100%.

22. The system of claim 21, wherein to facilitate response to induced interference conditions in a wireless environment in which the femto cell operates, P_MAX is reached from P_MIN within a first time interval determined by a first slope, and P_MIN is reached from P_MAX within a second time interval determined by a second slope.

23. The system of claim 22, further comprising a storage medium that retains a femto cell pilot gating schedule.

24. The system of claim 23, further comprising a component that generates a pilot signal gating reuse plan.

25. The platform of claim 24, wherein the pilot signal gating reuse plan is generated based at least in part on at least one of a historic attachment data, or a configuration deployment of femto cell identifications (IDs).

26. The system of claim 25, further comprising:

a component that identifies a set of femto cells with a common cell ID based at least in part on radio link condition for a femto radio access network;

a component that utilizes the pilot signal gating reuse plan to refine the identified set of femto cells;

a component that identifies a serving femto cell in the refined set of femto cells to serve a wireless device for which macro-to-femto cell handover is requested; and

a component that resolves the requested macro-to-femto cell handover for the wireless device and the identified serving femto cell.

27. The system of claim 26, wherein identification a the serving femto cell in the refined set of femto cells is based at least in part on an access list of authorized mobile devices.

28. A computer-readable medium including code instructions stored thereon that, when executed by a processor, cause the processor to carry out the following acts:

gating a pilot signal of a femto cell access point (AP) according at least in part to a predetermined pilot signal power time-dependent profile; and

conveying the gated pilot signal.

29. The computer-readable medium of claim 28, wherein gating a pilot signal of a femto cell AP based at least part on a predetermined signal power profile further comprises:

generating a femto cell AP usage schedule; and

adjusting a power of the pilot signal according at least in part to the generated usage schedule.

30. The computer-readable medium of claim 29, code instructions that, when executed by a processor, cause the processor to carry out the act of generating a femto cell AP usage schedule further include:

code instructions that when executed by the processor cause the processor to perform the following acts;

tracking attachment events of a set of subscriber stations to the femto cell AP;

retaining the attachment events;

learning a profile of attachment to the femto cell AP for a subscriber station in the set of subscriber stations to the femto cell AP based at least in part on the retained attachment events; and

generating the femto cell AP usage schedule based at least in part on the inferred profile of attachment.

31. The computer-readable of claim 30, wherein inferring a profile of attachment is based at least in part on machine-learning methods.

32. The computer-readable of claim 30, further comprising code instructions that, when executed by the processor, cause the processor to perform the following acts:

establishing a pilot signal gating reuse plan for a set of femto cell APs.

identifying a set of femto cell APs that share a cell identification (ID) based at least in part on a received channel conditions report for the set of femto cells;

utilizing the pilot signal gating reuse to refine the identified set of femto cell APs;

identifying a femto cell AP in the refined set of femto cell APs that can serve a subscriber station for which macro-to-femto cell handover is requested; and

resolving requested macro-to-femto cell handover for the subscriber station and the identified femto cell AP.