System search for full service while on a cell with limited service

Patent metadata

Field	Value
Publication number	US-9398520-B2
Application number	US-86598607-A
Country	US
Kind code	B2
Filing date	Oct 2, 2007
Priority date	Oct 2, 2007
Publication date	Jul 19, 2016
Grant date	Jul 19, 2016

Abstract

Techniques for performing system searches to find a suitable cell to receive full service while camped on a cell with limited service are described. Initially, a user equipment (UE) may camp on a first cell and receive limited service. The UE may perform a system search in background to find a suitable cell to receive full service. By performing the system search in background, the UE can receive paging messages and perform cell reselection and/or other tasks while the system search is pending and may also be able to obtain limited service with little or no delay when requested by a user. The UE may suspend the system search prior to each paging occasion, receive paging messages applicable for the UE, and then resume the system search. The UE may receive a request for limited service (e.g., emergency call), suspend or abort the system search, and obtain the requested limited service.

First claim

What is claimed is:

1. An apparatus comprising:
a receiver;
at least one processor configured to:
camp on a first cell and receive limited service via the first cell, wherein the limited service includes capability to originate emergency calls using the first cell;
perform a system search to find a suitable cell to receive full service, wherein the system search to find a suitable cell to receive full service is performed in background during the limited service such that search tasks are performed when no other tasks are to be performed;
process paging messages detected by the receiver while the system search is suspended, wherein the paging messages are received during user equipment-specific paging occasions assigned to a specific user equipment, wherein the system search is resumed based on search state information after the one or more paging occasions; and
in response to a first paging message of the paging messages indicating that the first cell has become barred, refrain from performing signal strength measurements of signals from a base station of the first cell during a barred timer duration; and

a memory coupled to the at least one processor.

2. The apparatus of claim 1 , wherein the at least one processor is configured to perform the system search over a time period covering multiple paging occasions, and to suspend the system search prior to each of the multiple paging occasions to process the paging messages detected by the receiver.

3. The apparatus of claim 2 , wherein the at least one processor is configured to save search state information prior to each paging occasion and to resume the system search based on the saved search state information after the paging occasion.

4. The apparatus of claim 1 , wherein the memory is configured to store an acquisition database including N entries, wherein N is an integer greater than 1, wherein each of the N entries includes information regarding a frequency channel and a previously acquired network, and wherein for the system search the at least one processor is configured to perform a first search based on the N entries in the acquisition database.

5. The apparatus of claim 4 , wherein for the system search the at least one processor is configured to perform a second search by scanning a set of frequency channels and attempting acquisition on each frequency channel received with sufficient signal strength.

6. The apparatus of claim 4 , wherein the apparatus is further configured to attempt acquisition on each frequency channel in a universal terrestrial radio access (UTRA) absolute radio frequency channel number list (UARFCN), comprising searching for a 256-chip primary synchronization code (PSC) sequence sent on a primary synchronization channel (SCH) by correlating received samples at the UE for each channel frequency with a locally generated PSC sequence at different time offsets.

7. The apparatus of claim 1 , wherein the at least one processor is configured to perform the system search to find a suitable cell in a last registered network or a home network.

8. The apparatus of claim 1 , wherein the at least one processor is configured to periodically perform system searches spaced apart by a predetermined search interval.

9. The apparatus of claim 1 , wherein the at least one processor is configured to perform system searches spaced apart by progressively longer search intervals, wherein the search intervals are spaced apart based on available battery power.

10. The apparatus of claim 1 , wherein the at least one processor is configured to communicate with the first cell via a first radio access technology and to perform the system search for the first radio access technology and at least one additional radio access technology.

11. The apparatus of claim 1 , wherein the at least one processor is configured to:
perform signal strength measurements of signals from base stations of neighbor cells during paging occasions, the signals detected by the receiver,
identify a second cell stronger than the first cell based on the signal strength measurements, and
perform cell reselection to the second cell.

12. The apparatus of claim 1 , wherein the at least one processor is configured to receive a request for limited service while the system search is pending, to suspend or abort the system search in response to the request, and to obtain the requested limited service.

13. The apparatus of claim 1 , wherein the at least one processor is configured to receive a request to originate an emergency call while the system search is pending, to suspend or abort the system search in response to the request, and to originate the emergency call.

14. The apparatus of claim 1 , wherein the at least one processor is configured to receive a paging message with system information indicating the first cell has become suitable to receive full service, to attempt registration via the first cell, and to abort the system search if pending and if the registration is successful.

15. The apparatus of claim 1 , wherein the at least one processor is configured to perform the system search while operating in an idle mode and camping on the first cell.

16. The apparatus of claim 1 , wherein the at least one processor is configured to perform the system search while operating in a connected mode and receiving limited service via the first cell.

17. The apparatus of claim 1 , wherein the at least one processor is configured to perform a first set of system searches spaced apart by a first search interval, and to perform a second set of system searches spaced apart by a second search interval longer than the first search interval, and wherein the first set of system searches is of a different type than the second set of system searches.

18. The apparatus of claim 1 , wherein the at least one processor is configured to perform telescopic full service searches with progressively longer search intervals.

19. A method comprising:
camping on a first cell and receiving limited service via the first cell, wherein the limited service includes capability to originate emergency calls using the first cell;
performing a system search to find a suitable cell to receive full service, wherein the system search to find a suitable cell to receive full service is performed in background during the limited service such that search tasks are performed when no other tasks are to be performed;
processing paging messages detected by a receiver while the system search is suspended, wherein the paging messages are received during user equipment-specific paging occasions assigned to a specific user equipment, wherein the system search is resumed based on search state information after the one or more paging occasions; and
in response to a first paging message of the paging messages indicating that the first cell has become barred, refrain from performing signal strength measurements of signals from a base station of the first cell during a barred timer duration.

20. The method of claim 19 , wherein the performing the system search comprises:
performing the system search over a time period covering multiple paging occasions; and
suspending the system search prior to each of the multiple paging occasions to process the paging messages detected by the receiver.

21. The method of claim 19 , further comprising:
storing an acquisition database including N entries, wherein N is an integer greater than 1, wherein each of the N entries includes information regarding a frequency channel and a previousl

Assignees

• Umatt Bhupesh Manoharlal
• Chikkappa Kiran
• Mittal Vineet
• Qualcomm Inc

Inventors

• Umatt Bhupesh Manoharlal
• Chikkappa Kiran
• Mittal Vineet

Classifications

• H04W68/00

  User notification, e.g. alerting and paging, for incoming communication, change of service or the like · CPC title

• H04W48/16 Primary

  Discovering, processing access restriction or access information · CPC title

• H04W68/02

  Arrangements for increasing efficiency of notification or paging channel · CPC title