Patent ID: 8559421

Claim:
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.