Method and apparatus for calibrating sleep clocks

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.

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.

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.