Low latency frequency switching

• US 8,565,121 B2
• Filed: 10/25/2007
• Issued: 10/22/2013
• Est. Priority Date: 10/31/2002
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Shiu, Da-shan, Zhang, Li, Sy, Eugene, Malonado, David, Dhaliwal, Upkar
• Primary Examiner(s): Mesfin, Yemane
• Assistant Examiner(s): DAVENPORT, MON CHERI S
• Application Number:
  US11/924,578
• Publication Number:
  US 20080212553A1
• Time in Patent Office: 2,189 Days
• Field of Search: 370/254, 370/255, 370/335, 370/342, 370/350, 370/422, 370/441, 370/450, 370/453, 370/457, 370/462, 370/465, 370/479, 370/480, 370/481, 370/504
• US Class Current: 370/255
• CPC Class Codes: H03G 3/3036 in high-frequency amplifiers or in frequency-changers H03G3/3052, H03G3/32, H03G3/34 take precedence

Abstract

Techniques for improved low latency frequency switching are disclosed. In one embodiment, a controller receives a frequency switch command and generates a frequency switch signal at a time determined in accordance with a system timer. In another embodiment, gain calibration is initiated subsequent to the frequency switch signal delayed by the expected frequency synthesizer settling time. In yet another embodiment, DC cancellation control and gain control are iterated to perform gain calibration, with signaling to control the iterations without need for processor intervention. Various other embodiments are also presented. Aspects of the embodiments disclosed may yield the benefit of reducing latency during frequency switching, allowing for increased measurements at alternate frequencies, reduced time spent on alternate frequencies, and the capacity and throughput improvements that follow from minimization of disruption of an active communication session and improved neighbor selection.

Claims

1. A method comprising:

saving a current configuration of processing and tuning to a second frequency while active in a first communication mode associated with a first frequency;

processing measurements of a channel at a second communication mode after a associated synthesizer is settled in the second frequency; and

tuning back to the first frequency and reinitializing the active first communication mode at the saved current configuration without waiting for synthesizer settling at the first frequency in order to reduce system switch latency during inter-frequency switching or handoff.

2. The method of claim 1, wherein the saving of a current configuration includes identifying a time lag in the active communication mode.

3. The method of claim 1, wherein an expected time to tune, settle, and process measurements at the second communication mode is known a priori, the method further comprising a controller initiating a timer prior to the tuning to the second frequency which will expire after the measurements are taken at the second frequency but before settling of the associated synthesizer back to the first frequency.

4. The method of claim 1, wherein the taking of measurements includes measuring and calibrating the gain of a signal received by a receive chain while in the second communication mode.

5. A baseband processor comprising:

means for saving a current configuration of processing;

means for tuning to a second frequency while active in a first communication mode associated with a first frequency;

means for processing measurements of a channel after synthesizer settling in the second frequency and operating in a second communication mode; and

means for causing the synthesizer to tune back to the first frequency; and

means for reinitializing the active first communication mode at the saved current configuration without waiting for associated synthesizer to settle at the first frequency in order to reduce system switch latency during inter-frequency switching or handoff.

6. The baseband processor of claim 5, further comprising means for identifying a time lag in the active communication mode.

7. The baseband processor of claim 6, wherein the baseband processor is for use in a wireless communication device and the means for identifying a time lag involves identifying when the baseband processor is operating in compressed mode.

8. The baseband processor of claim 5, wherein the means for tuning to the first and second frequencies involves means for generating instructions to different synthesizers under control of the baseband processor.

9. The baseband processor of claim 5, wherein an expected time to tune, settle, and process measurements at the second communication mode is known a priori, the baseband processor further comprising means for initiating a timer prior to the tuning to the second frequency which will expire after the measurements are taken at the second frequency but before settling of the associated synthesizer back to the first frequency.

10. The baseband processor of claim 5, wherein the means for processing measurements includes means for measuring and calibrating the gain of a signal received by a receive chain while in the second communication mode.

11. The baseband processor of claim 5, wherein inter-frequency switching is performed during resource-to-resource handoff by a wireless communication device.

12. A wireless communication device for reducing system switch latency during handoff processing, comprising:

means for saving a current configuration of processing;

means for tuning to a second frequency while active in a first communication mode associated with a first frequency;

means for processing measurements of a channel after synthesizer settling in the second frequency and operating in a second communication mode; and

means for causing the synthesizer to tune back to the first frequency; and

means for reinitializing the active first communication mode at the saved current configuration without waiting for associated synthesizer to settle at the first frequency.

13. The wireless communication device of claim 12, further comprising means for identifying a time lag in the active communication mode.

14. The wireless communication device of claim 12, wherein the means for identifying a time lag involves identifying when the device is operating in compressed mode.

15. The wireless communication device of claim 12, wherein an expected time to tune, settle, and process measurements at the second communication mode is known a priori, the wireless communication device further comprising means for initiating a timer prior to the tuning to the second frequency which will expire after the measurements are taken at the second frequency but before settling of the associated synthesizer back to the first frequency.

16. The wireless communication device of claim 12, wherein the means for processing measurements includes means for measuring and calibrating the gain of a signal received by a receive chain while in the second communication mode.

17. A non-transitory computer-readable medium including computer-executable instructions to cause a wireless communication device to:

save a current configuration of processing and tune to a second frequency while active in a first communication mode associated with a first frequency;

process measurements of the channel at a second communication mode after the associated synthesizer is settled in the second frequency; and

tune back to the first frequency and reinitialize the active first communication mode at the saved current configuration without waiting for synthesizer settling at the first frequency in order to reduce system switch latency during inter-frequency or handoff processing.

18. A wireless communication device comprising:

a controller to provide switching between frequencies while in a first frequency associated with an active first communication mode; and

a receive chain (i) responsive to a first inter-frequency switch command from the controller generated after the controller has stored its current configuration in the active first communication mode to initiate tuning of a synthesizer to a second frequency, and, (ii) responsive to a second inter-frequency switch command from the controller to initiate tuning back to the first frequency and back to the active first communication mode prior to the synthesizer settling at the second frequency in order to reduce system switch latency during the inter-frequency switching.

19. The wireless communication device of claim 18, where the inter-frequency switching occurs when the wireless communication device is in compressed mode.

20. The wireless communication device of claim 19, where the wireless communication device is an integrated circuit.