Radiotelephone and method for clock calibration for slotted paging mode in a CDMA radiotelephone system

• US 6,016,312 A
• Filed: 02/28/1997
• Issued: 01/18/2000
• Est. Priority Date: 02/28/1997
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Callicotte, Mark J., Cahill, Stephen V., Storm, Brian D.
• Primary Examiner(s): Pham, Chi H.
• Assistant Examiner(s): NGUYEN, STEVEN H D
• Application Number:
  US08/808,275
• Time in Patent Office: 1,054 Days
• Field of Search: 370/335, 370/342, 370/350, 370/503, 370/311, 370/320, 370/324, 370/321, 375/208, 375/200, 375/356, 375/357, 455/38.3, 455/38.1, 455/38.2, 455/343, 455/574
• US Class Current: 370/311
• CPC Class Codes: H04M 19/08 with current supply sources at the substations generating ringing current H04M19/04
• CPC Class Codes: H04W 52/0274 by switching on or off the equipment or parts thereof
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A radiotelephone (104) in a radiotelephone system (100) enters a low power sleep mode and times the duration of the sleep mode using a sleep clock generator (205) having a coarse resolution. The radiotelephone synchronizes timing of the radiotelephone to system timing using an oscillator (116) having a fine resolution. The radiotelephone then exits the low power sleep mode synchronized with system timing.

Claims

1. A method for operating a mobile station in a code division multiple access (CDMA) radiotelephone system including a plurality of base stations transmitting a short pseudorandom noise (PN) sequence including a system timing indicator comprising a PN roll boundary of the short PN sequence, the method comprising the steps of:

(a) determining an offset between a fine resolution clock and a coarse resolution clock;

(b) entering a low power sleep mode;

(c) timing a sleep duration using the coarse resolution clock;

(d) synchronizing the fine resolution clock of the mobile station to the PN roll boundary of the short PN sequence by correlating to a short PN sequence generated in the mobile station;

(e) adjusting timing of the mobile station by combining timing of the coarse resolution clock and the offset;

(f) exiting the low power sleep mode with the fine resolution clock synchronized with the system timing indicator.

2. A method as recited in claim 1 wherein step (b) comprises the step of inactivating the fine resolution clock.

3. A method as recited in claim 2 wherein the method further comprises the step of activating the fine resolution clock at a time sufficiently before step (d) to allow the fine resolution clock to stabilize.

4. A method as recited in claim 1, further comprising the steps of:

storing an offset time corresponding to a difference between timing of the system timing indicator and timing of the coarse resolution clock;

determining a wakeup time;

at a prewake time corresponding to the difference in the wakeup time and the offset time, starting a reference timer which expires at the wakeup time; and

in response to expiration of the reference timer, exiting the low power sleep mode.

5. A method as recited in claim 4 further comprising the step of configuring the reference timer to expire substantially synchronously with a next received system timing indicator.

6. A method for operating a mobile station in a code division multiple access (CDMA) radio communication system including a plurality of base stations, transmitting a short pseudorandom noise (PN) sequence including a system timing indicator comprising a PN roll boundary of the short PN sequence, the method comprising the steps of:

aligning a short PN sequence of the mobile station with the system timing indicator so as to allow reference clock synchronization;

synchronizing a reference clock signal to the system timing indicator at a first clock rate;

producing a sleep clock signal at a second clock rate, the second clock rate being less than the first clock rate;

measuring timing accuracy of the sleep clock signal using the reference clock signal;

determining an offset between the reference clock signal and the sleep clock signal based on the timing accuracy;

adjusting the sleep clock signal timing by combining the timing accuracy of the sleep clock signal and the offset; and

entering a low power sleep mode for a time duration that is based on the adjusted sleep clock signal.

7. A method as recited in claim 6 wherein the step of measuring timing accuracy comprises the steps of:

summing reference clock edges;

summing sleep clock edges; and

relating sleep clock edges to reference clock edges to estimate the timing accuracy of the sleep clock signal.

8. A method as recited in claim 7 wherein the step of relating comprises multiplying the first clock rate by a ratio of sleep clock edges to reference clock edges to form an estimate of the second clock rate.

9. A method as recited in claim 6 wherein the method further comprises the steps of producing one or more output timing signals synchronized to the system timing indicator.

10. A method as recited in claim 6 wherein the mobile station includes a reference oscillator for producing the reference clock signal and wherein the step of entering a low power sleep mode comprises inactivating the reference oscillator.

11. A radiotelephone configured for operation in a code division multiple access (CDMA) radiotelephone system including a plurality of base stations, transmitting a short pseudorandom noise (PN) sequence including a system timing indicator comprising a PN roll boundary of the short PN sequence, the radiotelephone comprising:

a PN code generator providing a short PN sequence to align with the system timing indicator;

a reference oscillator for generating a reference clock signal synchronized to the system timing indicator using the short PN sequence from the PN code generator at a first rate;

a sleep clock generator for generating a sleep clock signal;

a reference timer for counting periods of the reference clock signal;

a sleep timer for counting periods of the sleep clock signal;

a controller for determining timing accuracy of the sleep clock generator by relating the periods of the sleep clock signal to the periods of the reference clock signal, the controller determining an offset between the reference clock signal and the sleep clock signal; and

a sleep time controller for placing the radiotelephone in a low power sleep mode having a duration based on the timing accuracy of the sleep clock generator, the sleep time controller adjusting the duration by combining timing of the sleep clock signal and the offset.

12. The radiotelephone of claim 11, further comprising

a timing controller for producing an output timing signal synchronized to the system timing indicator.

13. A radiotelephone as recited in claim 12 further comprising:

a sleep latch coupled to the sleep timer for storing contents of the sleep timer at a first predetermined time;

a reference latch coupled to the reference timer for storing contents of the reference timer at the first predetermined time; and

an offset latch coupled to the reference timer for storing contents of the reference timer at a second predetermined time, the offset latch storing a time from a last received system timing reference to the second predetermined time.

14. A code division multiple access (CDMA) radiotelephone operable in a CDMA radiotelephone system including a plurality of base stations, transmitting a short pseudorandom noise (PN) sequence including a system timing indicator comprising a PN roll boundary of the short PN sequence, the CDMA radiotelephone comprising:

a sleep clock which produces a coarse resolution clock signal;

a PN code generator providing a short PN sequence which is aligned with the system timing indicator;

an oscillator which produces a fine resolution clock signal, the oscillator being synchronized to the system timing indicator using the short PN sequence from the PN code generator;

a timing controller which places a portion of the CDMA radiotelephone including the oscillator in a low power sleep mode, the timing controller determining an offset between the fine resolution clock signal and the coarse resolution clock signal, the timing controller timing duration of the low power sleep mode in response to the coarse resolution clock signal adjusted by combining the coarse resolution clock signal and the offset; and

a clock edge synchronizer which synchronizes timing of the CDMA radiotelephone to the system timing indicator of the CDMA radiotelephone system using the fine resolution clock signal, the clock edge synchronizer removing the portion of the CDMA radiotelephone from the low power sleep mode synchronized with the system timing indicator.

15. A CDMA radiotelephone as recited in claim 14 wherein the clock edge synchronizer comprises:

an offset register for storing an offset time corresponding to a difference between timing of a received system timing indicator and timing of the coarse resolution clock signal;

a sleep timer for timing duration of the low power sleep mode and producing a match signal at a prewake time; and

a reference timer which times the offset time after the sleep timer produces the match signal,

the clock edge synchronizer removing the portion of the CDMA radiotelephone from the low power sleep mode upon expiration of the reference timer.

16. A CDMA radiotelephone as recited in claim 15 further comprising:

a modem for detecting system timing indicators transmitted by the CDMA radiotelephone system,

the offset time corresponding to a difference between timing of a last received system timing indicator and a last edge of the coarse resolution clock signal.

17. A CDMA radiotelephone as recited in claim 16 wherein the reference timer expires substantially synchronously with a next received system timing indicator.