Method and apparatus for calibrating sleep clocks
View Patent ↗Apparatus for use in a wireless network has a fast clock for operation in an active wakeup mode and a sleep clock for operation in a sleep mode. A calibration for the sleep clock is calculated based on the fast clock. A quality value for that new calibration is determined. If the quality value of the new calibration is higher than a quality value of an old calibration, the new calibration is used, and, if not, the new calibration is discarded and the old calibration is used. Alternatively or in addition, the length of time until the next calibration is estimated. It is then determined whether the new calibration is of sufficient quality to last for the estimated time until next calibration, and, if not, the calibration measurement period is extended.
1. An apparatus for use in a wireless network, the apparatus being associated with a fast clock for operation in an active wakeup mode and a sleep clock for operation in a sleep mode, the sleep clock having a current calibration and being periodically recalibrated, the apparatus comprising at least one controller configured to:
calculate a new calibration for the sleep clock based on the fast clock, the new calibration being calculated during a calibration measurement period; then
determine a quality value for the calculated new calibration for the sleep clock, wherein the quality value comprises the length of time that a calibration will remain acceptable;
estimate a length of time from the time of the new calibration until the next calibration for the sleep clock; and
determine whether the calculated new calibration is of sufficient quality to last for the estimated length of time from the time of the new calibration until the next calibration, and
when the calculated new calibration is determined not to be of sufficient quality to last until the next calibration,
extending the calibration measurement period, then
calculating another calibration for the sleep clock based on the fast clock during the extended calibration measurement period, and then
repeating the quality value determination using the calculated another calibration, the length of time estimation and the quality determination using the calculated, another calibration.
2. The apparatus according to claim 1 , the controller being further configured to determine whether the quality value of the calculated new calibration is higher than the quality value of the current calibration and,
if so, use the calculated new calibration and,
if not, discard the calculated new calibration and continue use of the current calibration.
3. The apparatus according to claim 1 , wherein the controller is further configured to calculate the quality value of a calibration by estimating how long the calibration is valid.
4. The apparatus according to claim 3 , wherein the controller is further configured to estimate how long a calibration will be valid based on an error allowed before a new calibration must be made and a length of the calibration measurement period.
5. The apparatus according to claim 3 , wherein the controller is further configured to estimate how long a calibration will be valid based on an error caused by temperature drift and an estimate of a length of time that the fast clock will not be running.
6. The apparatus according to claim 1 , wherein the controller is further configured to force a new calibration to be carried out if the current time equals or is larger than the time when the current calibration is no longer acceptable.
7. A method for use in a network apparatus associated with a fast clock for operation in an active wakeup mode and a sleep clock for operation in a sleep mode, the sleep clock having a current calibration and being periodically recalibrated, the method comprising:
calculating a new calibration for the sleep clock based on the fast clock, the new calibration being calculated during a calibration measurement period; then
determining a quality value for the calculated new calibration for the sleep clock, wherein the quality value comprises the length of time that a calibration will remain acceptable;
estimating a length of time from the time of the new calibration until the next calibration for the sleep clock;
determining whether the calculated new calibration is of sufficient quality to last for the estimated length of time from the time of the new calibration until the next calibration, and
when the calculated new calibration is determined not to be of sufficient quality to last until the next calibration,
extending the calibration measurement period, then
calculating another calibration for the sleep clock based on the fast clock during the extended calibration measurement period, and then
repeating the quality value determination step using the calculated another calibration, the length of time estimation step and the quality determination step using the calculated another calibration.
8. The method according to claim 7 , comprising:
determining whether the quality value of the calculated new calibration is higher than the quality value of the current calibration; and
if so, using the calculated, new calibration and,
if not, discarding the new calibration and continuing to use the current calibration.
9. The method according to claim 7 , wherein the quality value of a calibration is determined by estimating how long the calibration is valid.
10. The method according to claim 9 , further comprising estimating how long a calibration will be valid based on an error allowed before a new calibration must be made and a length of the calibration measurement period.
11. The method according to claim 9 , further comprising:
estimating how long a calibration will be valid based on an error caused by temperature drift and an estimate of the length of time that the fast clock will not be running.
12. The method according to claim 7 , further comprising forcing a new calibration to be carried out if the current time equals or is larger than the time when the current calibration is no longer acceptable.
13. An apparatus for use in a wireless network, the apparatus being associated with a fast clock for operation in an active wakeup mode and a sleep clock for operation in a sleep mode, the sleep clock having a current calibration and being periodically recalibrated, the apparatus comprising at least one controller configured to:
calculate a new calibration for the sleep clock based on the fast clock, the new calibration being calculated during a calibration measurement period; then
determine a quality value for the calculated new calibration by estimating how long the calibration is valid, wherein the quality value comprises the length of time that a calibration will remain acceptable;
when the calculated new calibration is determined not to be of sufficient quality to last until the next calibration,
extending the calibration measurement period, then
calculating another calibration for the sleep clock based on the fast clock during the extended calibration measurement period;
determine whether the quality value of the calculated new calibration is higher than a quality value of the current calibration; and,
if so, use the calculated new calibration and,
if not, discard the new calibration and continue to use the current calibration.
14. The apparatus according to claim 13 , wherein the controller is further configured to estimate how long a calibration will be valid based on an error allowed before a new calibration must be made and a length of the calibration measurement period.
15. The apparatus according to claim 14 , wherein the controller is further configured to estimate how long a calibration will be valid based on an error caused by temperature drift and an estimate of a length of time that the fast clock will not be running.
16. The apparatus according to claim 13 , wherein the controller is further configured to force a new calibration to be carried out if the current time equals or is larger than the time when the current calibration is no longer valid.
17. A method for use in a network apparatus associated with a fast clock for operation in an active wakeup mode and a sleep clock for operation in a sleep mode, the sleep clock having a current calibration and being periodically recalibrated, the method comprising:
calculating a new calibration for the sleep clock based on the fast clock, the new calibration being calculated during a calibration measurement period; then
determining a quality value for the calculated new calibration by estimating how long the calibration is valid, wherein the quality value comprises the length of time that a calibration will remain acceptable;
when the calculated new calibration is determined not to be of sufficient quality to last until the next calibration,
extending the calibration measurement period, then
calculating another calibration for the sleep clock based on the fast clock during the extended calibration measurement period;
determining whether the quality value of the calculated new calibration is higher than a quality value of the current calibration; and,
if so, using the new calibration and,
if not, discarding the new calibration and continuing to use the current calibration.
18. The method according to claim 17 , further comprising estimating how long a calibration will be valid based on an error allowed before a new calibration must be made and a length of the calibration measurement period.
19. The method according to claim 17 , further comprising:
estimating how long a calibration will be valid based on an error caused by temperature drift and an estimate of a length of time that the fast clock will not be running.
20. The method according to claim 17 , further comprising forcing a new calibration to be carried out if the current time equals or is larger than the time when the current calibration is no longer valid.