Method and apparatus for performing acquisition in power save mode for wireless communication systems

• US 7,742,447 B2
• Filed: 06/14/2005
• Issued: 06/22/2010
• Est. Priority Date: 10/30/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Ekvetchavit, Thunyachate, Black, Peter J., Turner, Simon, Joshi, Abhay A., Hutchison, James A.
• Primary Examiner(s): Le; Danh C
• Application Number:
  US11/153,641
• Publication Number:
  US 20050232196A1
• Time in Patent Office: 1,834 Days
• Field of Search: 370/329, 370/328, 370/310, 455/550.1, 455/450
• US Class Current: 370/329
• CPC Class Codes: H04W 48/18 Selecting a network or a communication service
• CPC Class Codes: H04W 88/06 adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

Techniques to efficiently attempt acquisition of a packet data system (e.g., an IS-856 system). If a terminal has acquired one or more channels in a voice/data system (e.g., an IS-2000 system), then it can attempt acquisition on channels in the packet data system that are co-located with the acquired channels in the voice/data system. Multiple acquisition modes may be used, and on-going acquisition attempts on the co-located channels may be performed using one acquisition mode at a time in order to reduce power consumption. Acquisition attempts may be performed in a “ping-pong” manner to improve the likelihood of acquisition. For a ping-pong search, an acquisition attempt is made on the most recently acquired channel prior to an acquisition attempt on each of the remaining channels. Received signal strength estimates may also be obtained for selected channels and may be used to determine whether or not to attempt acquisition on these channels.

Claims

1. A wireless device comprising:

a control unit operative to determine a set of channels carrying encoded digital signals in a wireless communication system on which to attempt acquisition, initiate acquisition attempts on the channels in the set using a first digital signal acquisition mode, and then initiate acquisition attempts on the channels in the set using a second digital signal acquisition mode; and

a demodulator operative to process each of the channels in the set after a desired time delay and using a particular acquisition mode indicated by the control unit.

2. The device of claim 1, wherein the control unit is operative to toggle between the first and second acquisition modes.

3. The device of claim 1, wherein the first and second acquisition modes are associated with first and second sets of values for coherent and non-coherent integration intervals.

4. The device of claim 1, wherein the first acquisition mode is designed for a weak received signal with a low signal-to-noise ratio (SNR) and the second acquisition mode is designed for a received signal with a larger frequency offset.

5. The device of claim 1, wherein the channels in the set are sorted in an order determined by amount of elapsed time since the channels were last acquired.

6. The device of claim 1, wherein the wireless communication system is an IS-856 system.

7. An apparatus comprising:

means for determining a set of channels carrying encoded digital signals in a wireless communication system on which to attempt acquisition;

means for initiating acquisition attempts on the channels in the set using a first digital signal acquisition mode after a desired time delay; and

means for initiating acquisition attempts on the channels in the set using a second digital signal acquisition mode after the desired time delay.

8. The apparatus of claim 7, further comprising:

means for toggling between the first and second acquisition modes for the acquisition attempts on the channels in the set.

9. A wireless device comprising:

a control unit operative to determine a set of channels in a wireless communication system on which to attempt acquisition and to initiate acquisition attempts on the channels in the set, wherein acquisition is attempted on a first channel in the set prior to an acquisition attempt on each of the remaining channels in the set, wherein the channels in the set are sorted in an order determined by amount of elapsed time since the channels were last acquired, and wherein the first channel is a most recently acquired channel among the channels in the set; and

a demodulator operative to process each of the channels in the set after a desired time delay indicated by the control unit.

10. An apparatus comprising:

means for determining a set of channels in a wireless communication system on which to attempt acquisition;

means for sorting the channels in the set in an order determined by amount of elapsed time since the channels were last acquired, and wherein a first channel is a most recently acquired channel among the channels in the set; and

means for initiating acquisition attempts on the channels in the set, wherein acquisition is attempted on the first channel in the set after a first time delay and prior to an acquisition attempt on each of the remaining channels in the set, wherein the acquisition attempt on each of the remaining channels in the set is attempted after a second time delay.

11. A wireless device comprising:

a control unit operative to determine a set of channels in a wireless communication system on which to attempt acquisition, obtain received signal strength estimates for the channels in the set, and initiate acquisition attempts on the channels in the set based on the received signal strength estimates obtained for the channels, wherein the channels in the set are sorted in an order determined by amount of elapsed time since the channels were last acquired; and

a demodulator operative to process each of the channels in the set after a desired time delay indicated by the control unit and to provide symbols used to obtain a received signal strength estimate for the channel.

12. The device of claim 11, wherein the control unit is further operative to initiate scheduled acquisition attempts on the channels in the set based on a particular schedule.

13. The device of claim 12, wherein the control unit is further operative to initiate one or more micro searches, between successive scheduled acquisition attempts, to obtain one or more received signal strength estimates for one or more of the channels in the set.

14. The device of claim 12, wherein the control unit is operative to initiate a micro search, after each scheduled acquisition attempt, to obtain a received signal strength estimate for a selected channel.

15. The device of claim 14, wherein the selected channel is randomly selected from among the channels in the set.

16. The device of claim 14, wherein the selected channel is a channel in the set to be processed by a next scheduled acquisition attempt.

17. The device of claim 11, wherein the control unit is operative to initiate an acquisition attempt on a particular channel if the received signal strength estimate for the channel exceeds a particular threshold.

18. The device of claim 11, wherein the control unit is operative to initiate an acquisition attempt on a particular channel using a first acquisition mode if the received signal strength estimate for the channel exceeds a first threshold, and to initiate an acquisition attempt on the particular channel using a second acquisition mode if the received signal strength estimate for the channel is between a second threshold and the first threshold.

19. An apparatus comprising:

means for determining a set of channels in a wireless communication system on which to attempt acquisition;

means for sorting the channels in the set in an order determined by amount of elapsed time since the channels were last acquired;

means for obtaining received signal strength estimates for the channels in the set; and

means for initiating acquisition attempts on the channels in the set based on the received signal strength estimates obtained for the channels after a desired time delay.

20. A method for acquiring a wireless communication system, comprising:

determining a set of channels carrying encoded digital signals in the wireless communication system on which to attempt acquisition in an acquisition control unit;

initiating acquisition attempts on the channels in the set using a first digital signal acquisition mode after a desired time delay; and

initiating acquisition attempts on the channels in the set using a second digital signal acquisition mode after the desired time delay, wherein the acquisition attempts comprise;

receiving a forward link signal from a base station on a particular channel by an antenna;

digitizing the received forward link signal in a receiver unit to obtain data samples;

processing the data samples in a demodulator to obtain pilot estimates for the particular channel that the forward link signal was received; and

determining whether the pilot estimates is sufficient to support communication.

21. The method of claim 20, further comprising toggling between the first and second acquisition modes for the acquisition attempts on the channels in the set.

22. The method of claim 20, wherein the first and second acquisition modes are associated with first and second sets of values for coherent and non-coherent integration intervals.

23. The method of claim 20, wherein the first acquisition mode is designed for a weak received signal with a low signal-to-noise ratio (SNR) and the second acquisition mode is designed for a received signal with a larger frequency offset.

24. The method of claim 20, further comprising sorting the channels in the set in an order determined by an amount of elapsed time since the channels were last acquired.

25. A method for acquiring a wireless communication system, comprising:

determining a set of channels in the wireless communication system on which to attempt acquisition in an acquisition control unit, wherein the channels in the set are sorted in an order determined by amount of elapsed time since the channels were last acquired; and

initiating acquisition attempts on selected channels in the set, wherein acquisition is attempted on a first channel in the set after a first time delay and prior to an acquisition attempt on the remaining channels in the set, wherein an acquisition attempt on a second channel in the set is attempted after a second time delay, and wherein the acquisition attempts comprise;

receiving a forward link signal from a base station on the selected channel in the ser by an antenna;

digitizing the received forward link signal in a receiver unit to obtain data samples;

processing the data samples in a demodulator to obtain pilot estimates for the particular channel that the forward link signal was received; and

determining whether the pilot estimates is sufficient to support communication.

26. A method for acquiring a wireless communication system, comprising:

determining a set of channels in the wireless communication system on which to attempt acquisition in an acquisition control unit, wherein the channels in the set are sorted in an order determined by amount of elapsed time since the channels were last acquired;

obtaining received signal strength estimates for the channels in the set from a demodulator; and

initiating acquisition attempts on the channels in the set based on the received signal strength estimates obtained for the channels after a desired time delay.

27. The method of claim 26, further comprising initiating scheduled acquisition attempts on the channels in the set based on a particular schedule.

28. The method of claim 27, further comprising initiating one or more micro searches, between successive scheduled acquisition attempts, to obtain one or more received signal strength estimates for one or more of the channels in the set.

29. The method of claim 27, further comprising initiating a micro search, after each scheduled acquisition attempt, to obtain a received signal strength estimate for a selected channel.

30. The method of claim 29, further comprising randomly selecting the selected channel from among the channels in the set.

31. The method of claim 29, wherein the selected channel is a channel in the set to be processed by a next scheduled acquisition attempt.

32. The method of claim 26, further comprising initiating an acquisition attempt on a particular channel if the received signal strength estimate for the channel exceeds a particular threshold.

33. The method of claim 26, further comprising initiating an acquisition attempt on a particular channel using a first acquisition mode if the received signal strength estimate for the channel exceeds a first threshold, and initiating an acquisition attempt on the particular channel using a second acquisition mode if the received signal strength estimate for the channel is between a second threshold and the first threshold.

34. A computer program product, comprising:

computer-readable medium comprising;

code for causing a computer to determine a set of channels carrying encoded digital signals in a wireless communication system on which to attempt acquisition;

code for causing a computer to initiate acquisition attempts on the channels in the set using a first digital signal acquisition mode after a desired time delay; and

code for causing a computer to initiate acquisition attempts on the channels in the set using a second digital signal acquisition mode after the desired time delay.

35. The computer program product of claim 34, further comprising code for causing for causing a computer to toggle between the first and second acquisition modes for the acquisition attempts on the channels in the set.

36. The computer program product of claim 34, further comprising code for causing a computer to sort the channels in the set in an order determined by amount of elapsed time since the channels were last acquired.

37. A computer program product, comprising:

computer-readable medium comprising;

code for causing a computer to determine a set of channels in a wireless communication system on which to attempt acquisition;

code for causing a computer to sort the channels in the set in an order determined by amount of elapsed time since the channels were last acquired, and wherein a first channel is a most recently acquired channel among the channels in the set; and

code for causing a computer to initiate acquisition attempts on the channels in the set, wherein acquisition is attempted on the first channel in the set after a first time delay and prior to an acquisition attempt on each of the remaining channels in the set, wherein the acquisition attempt on remaining channels in the set is attempted after a second time delay.

38. A computer program product, comprising:

computer-readable medium comprising;

code for causing a computer to determine a set of channels in a wireless communication system on which to attempt acquisition;

code for causing a computer to sort the channels in the set in an order determined by amount of elapsed time since the channels were last acquired;

code for causing a computer to obtain received signal strength estimates for the channels in the set; and

code for causing a computer to initiate acquisition attempts on the channels in the set based on the received signal strength estimates obtained for the channels after a desired time delay.

39. The computer program product of claim 38, further comprising code for causing a computer to initiate scheduled acquisition attempts on the channels in the set based on a particular schedule.

40. The computer program product of claim 39, further comprising code for causing a computer to initiate one or more micro searches, between successive scheduled acquisition attempts, to obtain one or more received signal strength estimates for one or more of the channels in the set.

41. The computer program product of claim 39, further comprising code for causing a computer to initiate a micro search, after each scheduled acquisition attempt, to obtain a received signal strength estimate for a selected channel.

42. The computer program product of claim 41, further comprising code for causing a computer to randomly select the selected channel from among the channels in the set.

43. The computer program product of claim 38, further comprising code for causing a computer to initiate an acquisition attempt on a particular channel if the received signal strength estimate for the channel exceeds a particular threshold.

44. The computer program product of claim 38, further comprising code for causing a computer to initiate an acquisition attempt on a particular channel using a first acquisition mode if the received signal strength estimate for the channel exceeds a first threshold, and initiating an acquisition attempt on the particular channel using a second acquisition mode if the received signal strength estimate for the channel is between a second threshold and the first threshold.