METHOD AND APPARATUS FOR DETERMINING THE IDENTITY OF A FEMTO CELL

• US 20130005326A1
• Filed: 06/30/2011
• Published: 01/03/2013
• Est. Priority Date: 06/30/2011
• Status: Active Grant

• Current Assignee: Viavi Solutions UK Limted (Lumentum Holdings Inc.)
• Original Assignee: Viavi Solutions UK Limted (Lumentum Holdings Inc.)
• Inventors: Flanagan, Michael Joseph
• Granted Patent: US 9,307,465 B2
• Time in Patent Office: Days
• US Class Current: 455/422.1
• 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

A femto cell is located within a macro cell of a wireless communication system. A method of identifying the femto cell comprises: determining at least one timing difference, the at least one timing difference being observed for communications between a wireless communication unit and each of a femto cell and at least one macro cell; and comparing the at least one observed timing difference to reference timing difference data. The identity of the femto cell may allow the location of the femto cell to be set as a geographical location for a wireless communication device that is within the footprint of the femto cell. The identity of the femto cell may allow hand in of an ongoing call, from the macro cell to the femto cell.

Claims

1. A method of identifying a femto cell of a cellular wireless communication system, the cellular wireless communication system comprising a plurality of macro cells, at least one femto cell associated with a macro cell, and a wireless communication unit, the method comprising the steps of:

determining at least one timing difference, the at least one timing difference being observed for communications between a wireless communication unit and each of a femto cell and at least one macro cell; and

comparing the at least one observed timing difference to reference timing difference data, to identify the femto cell.

2. The method of claim 1, wherein the method further comprises the steps of:

(i) receiving observed timing data for the femto cell and the at least one macro cell, from the wireless communication unit, and

(ii) determining the at least one observed timing difference, based at least partly on the observed timing data.

3. The method of claim 2, wherein:

(i) the observed timing data comprises a timing offset value for the femto cell and a timing offset value for the at least one macro cell; and

(ii) the method comprises determining an observed timing difference value for the femto cell and the at least one macro cell, by subtracting one of the timing offset values from the other.

4. The method of claim 1, wherein the reference timing difference data comprises reference timing difference values for one or more femto cells located at least partially within individual macro cells;

and the method further comprises;

(i) identifying the at least one macro cell with which the wireless communication unit can communicate; and

(ii) comparing the at least one observed timing difference to reference timing difference values for one or more femto cells, the one or more femto cells being at least partially within the at least one macro cell.

5. The method of claim 4, wherein the method further comprises the step of:

identifying the femto cell by identifying a reference timing difference value closest to the at least one observed timing difference.

6. The method of claim 1, wherein the method further comprises the step of:

determining an observed timing difference between a femto cell, and a macro cell that has a strongest signal strength for the wireless communication unit.

7. The method of claim 1, wherein the method further comprises the step of:

determining at least one observed timing difference between the femto cell, and each macro cell indicated as having a signal strength above a threshold value for the wireless communication unit.

8. The method of claim 1, wherein:

the method is performed in response to receiving an indication from the wireless communication unit of the presence of a femto cell.

9. The method for claim 8 wherein:

the method is performed in response to the receipt of a measurement report from the wireless communication unit, the measurement report comprising observed timing data for at least one femto cell using a femto cell primary scrambling code.

10. The method of claim 1, wherein the reference timing difference data comprises:

mapped data, the mapped data being created from data obtained by multiple wireless communication units of the cellular wireless communication system, whereby;

(i) each of the multiple wireless communication units uses a geo-location subsystem to identify a current location; and

(ii) the current location is stored together with observed timing difference data measured at the current location.

11. A method of determining the geographical location of a wireless communication unit, the wireless communication unit forming part of a cellular wireless communication system, the cellular wireless communication system further comprising a plurality of macro cells and at least one femto cell associated with a macro cell, the method further comprising the steps of:

(i) identifying a femto cell of a cellular wireless communication system, using the method of claim 1; and

(ii) setting a geographical location of the identified femto cell as a geographical location for the wireless communication unit.

12. A method of handing in an on-going call from a wireless communication unit to a femto cell of a cellular wireless communication system, the cellular wireless communication system comprising the wireless communication unit, a plurality of macro cells and at least one femto cell associated with a macro cell, the method further comprising the steps of:

(i) identifying a femto cell of a cellular wireless communication system, using the method of claim 1; and

(ii) handing in an on-going call from the wireless communication unit to the femto cell.

13. A network element within a wireless cellular communication network, the cellular wireless communication network comprising a plurality of macro cells and at least one femto cell associated with a macro cell, the network element comprising at least one signal processing module arranged to:

determine at least one timing difference, the at least one timing difference being observed for communications between a wireless communication unit and each of a femto cell and at least one macro cell; and

comparing the at least one observed timing difference to reference timing difference data, to identify the femto cell.

14. The network element of claim 13, further arranged to:

set a location of the identified femto cell as a geographical location for the wireless communication unit.

15. The network element of claim 14, further arranged to:

access a network configuration file, the network configuration file comprising latitude and longitude data for the at least one femto cell.

16. The network element of claim 13, further arranged to:

hand-in an on-going call from a macro cell to the identified femto cell.

17. The network element of claim 16, further arranged to:

access a femto cell configuration file, the femto cell configuration file comprising information identifying femto cells, including femto cell names or labels.

18. A tangible non-transitory computer program product having executable program code stored therein for programming signal processing logic to perform a method for identifying a femto cell of a cellular wireless communication system, the cellular wireless communication system comprising a plurality of macro cells, at least one femto cell associated with a macro cell, and a wireless communication unit, the code operable for:

determining at least one timing difference, the at least one timing difference being observed for communications between a wireless communication unit and each of a femto cell and at least one macro cell; and

comparing the at least one observed timing difference to reference timing difference data, to identify the femto cell.

19. The tangible non-transitory computer program product of claim 18, wherein the tangible computer program product comprises at least one of:

a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a Read Only Memory (ROM), a Programmable Read Only Memory (PROM), an Erasable Programmable Read Only Memory (EPROM), an Electrically Erasable Programmable Read Only Memory (EEPROM), and a Flash memory.