Patent ID: 6154642
Filing Date: 2000-11-28
Classification: H04L,H04W,Y02D

Abstract:
A digital wireless communications system comprising a first wireless radio station coupled to a network and a second wireless radio station arranged for wireless communication with the first wireless station via at least one time slot of a communications frame, in which system the first station comprises a master clock and is arranged to transmit messages to the second station comprising a synchronisation pattern, and in which system the second station comprises power management circuitry, local timing circuitry, and is at least controllable so as to operate in an active reception mode and in a power down mode, whereby the power down mode is adopted between reception of messages outside the active mode, the second station comprises register means for accumulating a timing error representing an accumulated difference between expected times of arrival of the synchronisation patterns and actual times of arrival of the synchronisation patterns, said timing error being accumulated during a predetermined time interval between reception of messages and before an expected reception of a next message, and the second station comprises means for at least substantially undoing the accumulated timing error before the expected reception of the next message by controlling the local timing circuitry in accordance with the accumulated timing error such that the timing error is compensated for just before the expected reception of the next message, said controlling of the local timing circuitry being performed within a first time period that is short with respect to a second time period between two successive messages, and said first time period ending at an instant before the expected reception of the next message, said instant being such that a ratio of a difference between said instant and a reception instant of a message preceding the next message, and of a difference between a reception instant of the next message and the reception instant of the message preceding the next message is close to one.