CA2173773A1 - Method and apparatus for regenerating the symbol clock of a cellular telephone following a sleep cycle - Google Patents

Abstract

A method for reducing power consumption in a cellular telephone by placing the receiver in a sleep mode when it is determined that the received signal has a sufficiently high quality. The duration of the sleep mode is extended by eliminating the need to resynchronize the receiver clock to the transmitter clock using dotting sequence and synchronizing data in the transmitted control data received after a sleep cycle. This is accomplished by resynchronizing the phase of the symbol clock to the phase of the transmitter clock after a sleep cycle utilizing the respective phase relationships to a low frequency, low power maintenance clock in the receiver which maintains time (and hence edge information) during the sleep mode until reception of the next data frame must begin. The maintenance clock is preferably an off-the-shelf oscillator of the type used in wrist watches. At a specified tick of this clock, which is known to the receiver before it goes to sleep, the high-speed system clocks are turned on in preparation for reception of the next frame of data. Since the phase relationship of the symbol clock to the maintenance clock prior to the sleep mode was known, the phase of the symbol clock is readily recreated after the sleep cycle from the known phase of the maintenance clock, which is never turned off.