Patent ID: 7190962
Filing Date: 2007-03-13
Classification: H04W,Y02D

Abstract:
1. A method for correcting a sleep clock of a wireless communications device to account for temperature induced errors by identifying and limiting probable multipath errors, the method comprising operations of: responsive to wakeup following a sleep state, measuring a difference between time reference output by a sleep clock and a network time reference and utilizing the difference to compute a current error in the sleep clock's frequency; determining whether predetermined criteria are satisfied by aspects of a current error including (1) magnitude and (2) character in relation to errors from previous sleep states; bounding a current error unless the criteria is met, the bounding operation comprising: utilizing a predetermined relationship between sleep state duration and predetermined sleep clock error maxima to identify an appropriate maximum error, and limiting magnitude of the current error to the identified maximum error; estimating a sleep clock's frequency utilizing inputs including the limited current error; utilizing a most recent estimate of the sleep clock's frequency whenever planning a wakeup time.