Servicing Cell Discovery During Out of Service

• US 20090275329A1
• Filed: 04/30/2008
• Published: 11/05/2009
• Est. Priority Date: 04/30/2008
• Status: Active Grant

• Current Assignee: Blackberry Limited
• Original Assignee: Blackberry Limited
• Inventors: SOKONDAR, Eniko, FARNSWORTH, Andrew, YOUNG, Gordon Peter
• Granted Patent: US 8,463,259 B2
• Time in Patent Office: Days
• US Class Current: 455/434
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information

Abstract

A user equipment is provided. The user equipment comprises a processor that, when the UE goes out of service area of a first cell, is configured to search for a suitable cell before the UE loses a connection to a network by checking for a suitable cell among cells proximate to the first cell, based on a timer before the UE loses the connection to the network.

Claims

1. A user equipment (UE), comprising:

a component that, when the UE goes out of a service area of a first cell, is configured to search for a suitable cell before the UE loses a connection to a network by checking for a suitable cell among cells proximate to the first cell based on a time before the UE loses the connection to the network.

2. The UE of claim 1, wherein the processor is further configured to check for coverage from a suitable cell proximate to the first cell about three to about seven seconds before the UE loses connection to the network.

3. The UE of claim 1, wherein the UE includes a Timer out of service timer, a T314 timer, a T315 timer and a T307 timer and the processor is further configured to check for coverage from a suitable cell from the cells proximate to the first cell before the Timer out of service timer, the T314 timer, the T315 timer or the T307 timer expires.

4. The UE of claim 3, wherein the processor is further configured to check for coverage from a suitable cell from the cells proximate to the first cell about three to about seven seconds before the Timer out of service timer, the T314 timer, the T315 timer or the T307 timer expires.

5. The UE of claim 3, wherein the processor is further configured to check for coverage from a suitable cell from the cells proximate to the first cell periodically before the Timer out of service timer, the T314 timer, the T315 timer or the T307 timer expires.

6. The UE of claim 1, wherein the processor is configured to check for coverage from a suitable cell from the cells proximate to the first cell periodically before the UE loses connection to the network.

7. The UE of claim 1, wherein the processor is further configured to search for a suitable cell shortly before the UE loses connection to the network by checking for coverage from a cell on the same frequency as the first cell.

8. The UE of claim 1, wherein the processor is further configured to search a suitable cell shortly before the UE loses connection to the network by checking for coverage from a suitable cell from at least one of a cell on one of a plurality of a frequencies supported by a registered public land mobile network (RPLMN) and a cell using a radio access technology (RAT) supported by the RPLMN.

9. The UE of claim 1, wherein the component is further configured to search for a serving cell before the UE loses the connection to the network by checking for coverage from at least one cell on the same frequency as the first cell, a cell on one of a plurality of frequencies supported by a registered public land mobile network (PLMN), a serving cell other than the first cell using a radio access technology (RAT) supported by the registered PLMN and different from the RAT used just prior to going out of service area.

10. The UE of claim 1, wherein the component is configured:

to search for a serving cell by checking each of a comprehensive set of cell frequencies,

after checking a predefined number of the comprehensive set of frequencies, to perform a targeted search for a serving cell by checking for coverage from at least one of a cell proximate to the first cell, a cell on the same frequency as the first cell, a cell on one of a plurality of frequencies supported by a registered public land mobile network (PLMN), a cell using a radio access technology (RAT) supported by the registered PLMN, and

to resume the search for a serving cell by checking each of the remaining comprehensive set of cell frequencies,

whereby the UE alternates between checking an additional predefined number of the comprehensive set of cell frequencies and performing the targeted search.

11. The UE of claim 1, wherein the component is further configured to search for a suitable cell periodically by checking for coverage from a cell adjacent to the first cell before the UE loses the connection to the network.

12. The UE of claim 4, wherein the component is further configured to search for a suitable cell by checking for coverage from a neighbor cell of the first cell about twenty-five seconds before the Timer out of service timer or the T307 timer expires and about fifteen seconds before the Timer out of service timer or the T307 timer expires.

13. A method of discovering a serving cell, comprising:

detecting an out of a service area condition of a first cell;

starting a Timer out of service timer; and

prior to expiration of the Timer out of service timer, checking for coverage from a cell proximate to the first cell, based on the Timer out of service timer.

14. The method of claim 13, wherein the checking for coverage from a cell proximate to the first cell is further restricted to checking for coverage from a cell adjacent to the first cell.

15. The method of claim 13, further including:

checking for coverage from a predefined number of cell frequencies contained in a comprehensive set of cell frequencies; and

after checking for coverage from the predefined number of cell frequencies contained in the comprehensive set of cell frequencies, checking for coverage from at least one of a cell proximate to the first cell, a cell on the same frequency as the first cell, a cell on one of a plurality of frequencies supported by a registered public land mobile network (PLMN), a cell using a radio access technology (RAT) supported by the registered PLMN,

whereby checking for coverage from at least one of the cell proximate to the first cell, the cell on the same frequency as the first cell, the cell on one of a plurality of frequencies supported by a registered public land mobile network (PLMN), the cell using a radio access technology (RAT) supported by the registered PLMN is repeated iteratively.

16. The method of claim 13, further including before expiration of the Timer out of service timer, checking for coverage from a cell on one of a plurality of frequencies supported by a registered public land mobile network (PLMN).

17. The method of claim 13, further including before expiration of the Timer out of service timer, checking for coverage from a cell using a radio access technology (RAT) supported by the registered PLMN.

18. The method of claim 13, further comprising checking the following before expiration of the Timer out of service timer:

coverage from at least one of a cell on the same frequency as the first cell,

a cell on one of a plurality of frequencies supported by a registered public land mobile network (PLMN),

a cell using a radio access technology (RAT) supported by the registered PLMN and different from the RAT used just prior to going out of service area.

19. The method of claim 18, further comprising periodically rechecking before expiration of the Timer out of service timer one or more of the following:

coverage from at least one of a cell on the same frequency as the first cell,

a cell on one of a plurality of frequencies supported by a registered public land mobile network (PLMN),

a cell using a radio access technology (RAT) supported by the registered PLMN.

20. The method of claim 13, further including:

starting a T307 timer; and

prior to expiration of the T307 timer, checking for coverage from a cell proximate to the first cell.

21. The method of claim 13, further including:

starting one of a T314 timer and a T315 timer; and

prior to expiration of the one of the T314 timer and the T315 timer, checking for coverage from a cell proximate to the first cell.