Idle mode cell reacquisition and reselection

• US 20040043798A1
• Filed: 12/12/2002
• Published: 03/04/2004
• Est. Priority Date: 08/27/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Amerga, Messay, Halbhavi, Sudhir
• Granted Patent: US 7,133,702 B2
• Time in Patent Office: Days
• US Class Current: 455/574
• CPC Class Codes: H04B 1/70753 Partial phase search
• CPC Class Codes: H04B 1/70754 Setting of search window, i.e. range of code offsets to be searched H04B1/70758 takes precedence
• CPC Class Codes: H04B 1/70756 Jumping within the code, i.e. masking or slewing H04B1/70758 takes precedence
• CPC Class Codes: H04B 2201/70702 Intercell-related aspects
• CPC Class Codes: H04B 2201/70709 with discontinuous detection
• CPC Class Codes: H04W 48/20 Selecting an access point
• CPC Class Codes: H04W 52/0216 using a pre-established activity schedule, e.g. traffic indication frame
• CPC Class Codes: H04W 52/0219 where the power saving management affects multiple terminals
• CPC Class Codes: H04W 52/0245 according to signal strength
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

Techniques for cell reacquisition and reselection that increases time spent in low-power mode while effectively monitoring neighbor cells are disclosed. In one aspect, one or more windows around the expected location of the serving cell are searched in the period of time prior to the page indicator. In another aspect, intra-frequency neighbor cells are searched first to determine reselection candidates. Various other aspects are also presented. These aspects have the benefit of increasing time spent in low-power mode, thereby reducing power consumption and increasing standby time.

Claims

1. An apparatus comprising:

a searcher for locating a base station; and

a processor directing the searcher to locate a previously accessed base station within a first search window in response to a signal indicating the end of a low power time period, and for directing the searcher to locate the previously accessed base station within one or more second search windows when the previously accessed base station is not located within the first search window.

2. The apparatus of claim 1, further comprising a signal generator for generating the signal indicating the end of the low power time period.

3. The apparatus of claim 1, further comprising a demodulator for demodulating a signal from a located base station.

4. The apparatus of claim 3, further comprising a message decoder for decoding a page indicator message from a located base station, and wherein the processor generates a signal indicating the beginning of a low power time period when the page indicator indicates no page.

5. The apparatus of claim 4, wherein the processor directs the demodulator to demodulate a communication channel from the located base station signal when the page indicator indicates a page.

6. The apparatus of claim 1, wherein the processor directs the searcher to search for one or more base stations from a monitored list on the first frequency when the previously accessed base station is not located within the first or one or more second search windows.

7. The apparatus of claim 1, wherein the processor directs the searcher to search for any base station on the first frequency when the previously accessed base station is not located within the first or one or more second search windows.

8. The apparatus of claim 1, wherein the processor directs the searcher to search for one or more base stations from a monitored list on one or more second frequencies when the previously accessed base station is not located within the first or one or more second search windows.

9. The apparatus of claim 1, wherein the processor directs the searcher to search for one or more base stations from a monitored list on one or more alternate radio access technologies on the first or one or more second frequencies when the previously accessed base station is not located within the first or one or more second search windows.

10. A wireless communication device comprising:

a searcher for locating a base station; and

a processor directing the searcher to locate a previously accessed base station within a first search window in response to a signal indicating the end of a low power time period, and for directing the searcher to locate the previously accessed base station within one or more second search windows when the previously accessed base station is not located within the first search window.

11. A wireless communication system, including a wireless communication device, comprising:

a searcher for locating a base station; and

a processor directing the searcher to locate a previously accessed base station within a first search window in response to a signal indicating the end of a low power time period, and for directing the searcher to locate the previously accessed base station within one or more second search windows when the previously accessed base station is not located within the first search window.

12. A method of reacquisition, operable with a base station signal comprising a page indicator, the method comprising:

generating a wake-up signal at a predetermined time prior to the page indicator;

searching for a previously accessed base station within a plurality of search windows on a first frequency in response to the wake-up signal; and

demodulating the page indicator when the previously accessed base station is located within one of the plurality of search windows;

and wherein the pre-determined time is determined according to the time required to perform the search over the plurality of search windows.

13. The method of claim 12, further comprising searching for one or more base stations on the first frequency from a monitored list when the previously accessed base station is not located in one of the plurality of search windows.

14. The method of claim 12, further comprising searching for all base stations operating with the radio access technology of the previously accessed base station on the first frequency when the previously accessed base station is not located in one of the plurality of search windows.

15. The method of claim 12, further comprising searching for one or more base stations on one or more second frequencies from a monitored list when the previously accessed base station is not located in one of the plurality of search windows.

16. The method of claim 12, further comprising searching for one or more base stations operating with one or more alternate radio access technologies when the previously accessed base station is not located in one of the plurality of search windows.

17. The method of claim 12, further comprising performing cell reselection to a located base station when the located base station is not the previously accessed base station.

18. The method of claim 12, further comprising generating an out-of-service indicator when no base station is located.

19. The method of claim 12, further comprising generating a sleep signal when the demodulated page indicator indicates no page.

20. The method of claim 17, further comprising generating a sleep signal subsequent to cell reselection.

21. An apparatus, comprising:

means for generating a wake-up signal at a predetermined time prior to the page indicator;

means for searching for a previously accessed base station within a plurality of search windows on a first frequency in response to the wake-up signal; and

means for demodulating the page indicator when the previously accessed base station is located within one of the plurality of search windows;

and wherein the pre-determined time is determined according to the time required to perform the search over the plurality of search windows.

22. A wireless communication system, including a wireless communication device, comprising:

means for generating a wake-up signal at a predetermined time prior to the page indicator;

means for searching for a previously accessed base station within a plurality of search windows on a first frequency in response to the wake-up signal; and

means for demodulating the page indicator when the previously accessed base station is located within one of the plurality of search windows;

and wherein the pre-determined time is determined according to the time required to perform the search over the plurality of search windows.

23. Processor readable media operable to perform the following steps:

generating a wake-up signal at a predetermined time prior to the page indicator;

searching for a previously accessed base station within a plurality of search windows on a first frequency in response to the wake-up signal; and

demodulating the page indicator when the previously accessed base station is located within one of the plurality of search windows;

and wherein the pre-determined time is determined according to the time required to perform the search over the plurality of search windows.