Apparatus and method for maintaining synchronization between a receiver having a crystal oscillator and a transmitter

• US 9,113,475 B2
• Filed: 04/02/2014
• Issued: 08/18/2015
• Est. Priority Date: 03/18/2011
• Status: Active Grant

• Current Assignee: Marvell Asia Pte Limited (Marvell Technology Group Limited)
• Original Assignee: Marvell World Trade Limited (Marvell Technology Group Limited)
• Inventors: Ben-Eli, David
• Primary Examiner(s): FILE, ERIN M
• Application Number:
  US14/242,935
• Publication Number:
  US 20140211697A1
• Time in Patent Office: 503 Days
• Field of Search: 375/346
• US Class Current: 1/1
• CPC Class Codes: H04W 52/0235 where the received signal is a power saving command
• CPC Class Codes: H04W 76/28 Discontinuous transmission [DTX]; Discontinuous reception [DRX]
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A method includes, in a receiver that includes an uncompensated crystal oscillator, receiving signals from a transmitter by activating the receiver periodically at intervals corresponding to a specified wake-up time period. In response to detecting at the receiver that the specified wake-up time period is insufficient for maintaining synchronization between the receiver and the transmitter using the uncompensated crystal oscillator, an actual wake-up time period, smaller than the specified wake-up time period, is selected. The receiver is activated periodically according to the selected actual wake-up time period.

Claims

1. A method, comprising:

in a receiver that includes an uncompensated crystal oscillator, receiving signals from a transmitter by activating the receiver periodically at intervals corresponding to a specified wake-up time period;

in response to detecting at the receiver that the specified wake-up time period is insufficient for maintaining synchronization between the receiver and the transmitter using the uncompensated crystal oscillator, selecting an actual wake-up time period that is smaller than the specified wake-up time period; and

activating the receiver periodically according to the selected actual wake-up time period.

2. The method according to claim 1, comprising, upon activating the receiver according to the selected actual wake-up time period, resetting a frequency error between the transmitter and the receiver so as to retain the synchronization.

3. The method according to claim 1, comprising, in addition to activating the receiver according to the selected actual wake-up time period, activating the receiver and checking for the messages from the transmitter periodically according to the specified wake-up time period.

4. The method according to claim 3, wherein activating the receiver according to the specified wake-up time period comprises activating the receiver for a first time duration, and wherein activating the receiver according to the selected actual wake-up time period comprises activating the receiver for a second time duration that is shorter than the first time duration.

5. The method according to claim 1, wherein detecting that the specified time period is insufficient comprises down-converting the received signals using the uncompensated crystal oscillator, and assessing in the down-converted signals a frequency error that is caused at least partly by the uncompensated crystal oscillator.

6. The method according to claim 1, wherein selecting the actual wake-up time period comprises choosing the actual wake-up time period to be sufficiently short so as not to exceed a maximum frequency error specified for the receiver.

7. The method according to claim 1, wherein selecting the actual wake-up time period comprises decreasing the actual wake-up time period when an estimated frequency error between the transmitter and the receiver exceeds an upper frequency threshold, and increasing the actual wake-up time period when the estimated frequency error is below a lower frequency threshold.

8. The method according to claim 7, comprising setting the upper frequency threshold and the lower frequency threshold based on the specified wake-up time period.

9. The method according to claim 1, comprising, upon activating the receiver according to the selected actual wake-up time period but failing to successfully measure the signals from the transmitter on a first frequency, re-attempting to measure the signals on one or more second frequencies that are offset relative to the first frequency.

10. The method according to claim 1, comprising, upon activating the receiver according to the selected actual wake-up time period but failing to successfully measure the signals from the transmitter by coherently processing reference signals carried by the signals over a first coherent integration period, re-attempting to measure the signals by coherently processing the reference signals over a second coherent integration period, smaller than the first coherent integration period.

11. Apparatus, comprising:

a receiver, which comprises an uncompensated crystal oscillator and which is configured to receive signals from a transmitter; and

control circuitry, which is configured to activate the receiver periodically at intervals corresponding to a specified wake-up time period, and, in response to detecting that the specified wake-up time period is insufficient for maintaining synchronization between the receiver and the transmitter using the uncompensated crystal oscillator, to select an actual wake-up time period that is smaller than the specified wake-up time period and to activate the receiver periodically according to the selected actual wake-up time period.

12. The apparatus according to claim 11, wherein the control circuitry is configured to reset a frequency error between the transmitter and the receiver upon activating the receiver according to the selected actual wake-up time period, so as to retain the synchronization.

13. The apparatus according to claim 11, wherein the control circuitry is configured to activate the receiver and check for the messages from the transmitter periodically according to the specified wake-up time period, in addition to activating the receiver according to the selected actual wake-up time period.

14. The apparatus according to claim 13, wherein the control circuitry is configured to activate the receiver according to the specified wake-up time period for a first time duration, and to activate the receiver according to the selected actual wake-up time period for a second time duration that is shorter than the first time duration.

15. The apparatus according to claim 11, wherein the control circuitry is configured to detect that the specified time period is insufficient by down-converting the received signals using the uncompensated crystal oscillator, and assessing in the down-converted signals a frequency error that is caused at least partly by the uncompensated crystal oscillator.

16. The apparatus according to claim 11, wherein the control circuitry is configured to decrease the actual wake-up time period when an estimated frequency error between the transmitter and the receiver exceeds an upper frequency threshold, and to increase the actual wake-up time period when the estimated frequency error is below a lower frequency threshold.

17. The apparatus according to claim 11, wherein, upon activating the receiver according to the selected actual wake-up time period but failing to successfully measure the signals from the transmitter on a first frequency, the control circuitry is configured to re-attempt to measure the signals on one or more second frequencies that are offset relative to the first frequency.

18. The apparatus according to claim 11, wherein, upon activating the receiver according to the selected actual wake-up time period but failing to successfully measure the signals from the transmitter by coherently processing reference signals carried by the signals over a first coherent integration period, the control circuitry is configured to re-attempt to measure the signals by coherently processing the reference signals over a second coherent integration period, smaller than the first coherent integration period.

19. A mobile communication terminal comprising the apparatus of claim 11.

20. A chipset for processing signals in a mobile communication terminal, comprising the apparatus of claim 11.