Method and apparatus for regenerating the symbol clock of a cellular telephone following a sleep cycle
First Claim
1. A method for regenerating a receiver clock after a sleep cycle during which said receiver clock was deactivated, said regenerated receiver clock having a predetermined frequency and predetermined phase which has a predetermined relationship to a frequency and phase of a transmitter clock before and after said sleep cycle, comprising the steps of:
- measuring a time interval from a last clock tick of said receiver clock before deactivation of said receiver clock to a next following clock tick of a low power maintenance clock which is not deactivated during said sleep cycle;
generating a wake-up signal for said receiver clock at the end of said sleep cycle, said wake-up signal occurring after N clock ticks of said maintenance clock and causing said receiver clock to be restarted; and
computing a phase of said restarted receiver clock relative to a phase of said maintenance clock based on the relationship of said maintenance clock to said receiver clock prior to said sleep cycle.
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Accused Products
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.
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Citations
18 Claims
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1. A method for regenerating a receiver clock after a sleep cycle during which said receiver clock was deactivated, said regenerated receiver clock having a predetermined frequency and predetermined phase which has a predetermined relationship to a frequency and phase of a transmitter clock before and after said sleep cycle, comprising the steps of:
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measuring a time interval from a last clock tick of said receiver clock before deactivation of said receiver clock to a next following clock tick of a low power maintenance clock which is not deactivated during said sleep cycle; generating a wake-up signal for said receiver clock at the end of said sleep cycle, said wake-up signal occurring after N clock ticks of said maintenance clock and causing said receiver clock to be restarted; and computing a phase of said restarted receiver clock relative to a phase of said maintenance clock based on the relationship of said maintenance clock to said receiver clock prior to said sleep cycle. - View Dependent Claims (2, 3, 4)
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5. A receiver circuit for regenerating a receiver clock after a sleep cycle during which said receiver clock was deactivated, said regenerated receiver clock having a predetermined frequency and predetermined phase which has a predetermined relationship to a frequency and phase of a transmitter clock before and after said sleep cycle, comprising:
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a low power maintenance clock which is not deactivated during said sleep cycle; means for measuring a time interval from a last clock tick of said receiver clock before deactivation of said receiver clock to a next following clock tick of said maintenance clock; means for generating a wake-up signal for said receiver clock at the end of said sleep cycle, said wake-up signal occurring after N clock ticks of said maintenance clock and causing said receiver clock to be restarted; and a processor for computing a phase of said restarted receiver clock relative to a phase of said maintenance clock based on the relationship of said maintenance clock to said receiver clock prior to said sleep cycle. - View Dependent Claims (6, 7, 8, 9, 10, 11)
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12. A cellular telephone for operation in an environment wherein multiple copies of a message block are transmitted by a transmitting device, comprising:
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a radio transceiver; a demodulator; a symbol clock for driving demodulation by said demodulator; first means for adaptively determining the reliability of the reception of each copy of a received message block and for ignoring subsequent copies of said received message block and stopping said symbol clock for a sleep time if the reception of said received message block is found to be reliable; and second means, responsive to said first means, for regenerating said symbol clock after said sleep time whereby said regenerated symbol clock has a predetermined frequency and predetermined phase which has a predetermined relationship to a frequency and phase of a transmitter clock before and after said sleep time, said second means comprising a low power maintenance clock which is not deactivated during said sleep time and means, responsive to said maintenance clock, for generating a wake-up signal for said symbol clock after N clock ticks of said maintenance clock. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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Specification