Synchronization of time base units

• US 7,751,447 B2
• Filed: 01/03/2005
• Issued: 07/06/2010
• Est. Priority Date: 01/13/2004
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: ST-Ericcson SA (Telefonaktiebolaget LM Ericsson)
• Inventors: Heinle, Frank, Bening, Andreas
• Primary Examiner(s): Ferris; Derrick W
• Assistant Examiner(s): Ghowrwal; Omar
• Application Number:
  US10/585,803
• Publication Number:
  US 20070165594A1
• Time in Patent Office: 2,010 Days
• Field of Search: 370/503, 370/310, 370/345, 370/350, 370/464, 370/498, 370/520, 455/231, 455/502
• US Class Current: 370/503
• CPC Class Codes: H03L 7/00 Automatic control of frequency or phase; Synchronisation
• CPC Class Codes: H04J 3/0694 Synchronisation in a TDMA node, e.g. TTP

Abstract

Due to emerging cellular standards, such as UMTS, TDMA and WLAN, there is more and more need for so-called multi-mode mobile phones, i.e. phones which support not only one air interface but at least two. According to an exemplary embodiment of the present invention, a simplified synchronization of a plurality of time base units in a receiving station, such as a multi-mode mobile phone, is provided, in which the plurality of time base units is synchronized by performing a calibration of one first time base unit only and then using the calibration for synchronizing the other time base units with the calibrated first time base unit. Since the synchronization of the various time base units can be performed by software, the number of hardware components for synchronization may be significantly reduced.

Claims

1. A method of synchronizing a first and a second time base unit in a receiving station, the method comprising the steps of:

awakening the first time base unit from a sleep-mode to an operational-mode, where in sleep-mode the first time base unit uses timing signals at a first clock rate from a first reference clock;

after the first time base unit is awoken and while the first time base is in operational-mode, receiving timing signals at a second clock rate from a second reference clock at the first time base unit, wherein the second clock rate is higher than the first clock rate, and wherein the first time base unit uses the timing signals at the second clock rate in operational-mode;

performing a calibration of the first time base unit, independently of the second time base unit, after the first time base unit is awoken based at least on the timing signals at the second clock rate from the second reference clock, resulting in a calibrated first time base unit; and

adjusting the second time base unit based at least on the calibration of the first time base unit to synchronize the second time base unit with the calibrated first time base unit, wherein the second time base unit is communicatively isolated from the first reference clock and communicatively coupled to the first time base unit and the second reference clock.

2. The method of claim 1 wherein adjusting the second time base unit based at least on the calibration of the first time base unit to synchronize the second time base unit with the calibrated first time base unit includes:

estimating a time of a first occurrence of a frame synchronization signal of the calibrated first time base unit, resulting in an estimated time of the first occurrence of the frame synchronization signal of the calibrated first time base unit; and

transmitting the estimated time of the first occurrence of the frame synchronization signal of the calibrated first time base unit to a counter of the second time base unit.

3. The method of claim 2, further comprising:

after estimating the time of the first occurrence of the frame synchronization signal of the calibrated first time base unit, writing the estimated time of the first occurrence of the frame synchronization signal of the calibrated first time base unit into a memory of the second time base unit; and

copying content of the memory into the counter of the second time base unit at the first occurrence of the frame synchronization signal, resulting in synchronization of the first and second time base units.

4. The method of claim 1 wherein the receiving station further comprises a first and a second supported system and a system controller;

wherein the first supported system corresponds to the first time base unit and the second supported system corresponds to the second time base unit; and

further comprising;

generating a wake-up signal that is triggered by one of the first time base unit and an external event while the first time base unit is in sleep-mode;

after generation of the wake-up signal, transmitting the wake-up signal to the system controller; and

transmitting an activation signal to the first and second supported systems from the system controller after receiving the wake-up signal.

5. The method of claim 4 wherein the first time base unit comprises a calibration unit;

wherein the second time base unit comprises no calibration unit; and

further comprising;

transmitting a calibration command to the calibration unit from the system controller; and

receiving the calibration command at the first time base unit, wherein the calibration unit performs the calibration of the first time base unit after receiving the calibration command from the system controller.

6. The method of claim 4, wherein the first time base unit and the first supported system correspond to one of GSM, EDGE, TDMA, WLAN, TD-SCDMA, Bluetooth, and UMTS;

and wherein the second time base unit and the second supported system correspond to another one of GSM, EDGE, TDMA, WLAN, TD-SCDMA, Bluetooth, and UMTS.

7. The method of claim 4, further comprising:

clocking the first time base unit at the first clock rate; and

clocking the second time base unit at the second clock rate.

8. A communication system for synchronizing a first and a second time base unit, the communication system comprising:

a transmitting station; and

a receiving station that includes the first and second time base units, the receiving station configured to provide the first time base unit with timing signals at a first clock rate from a first reference clock during a sleep-mode of the first time base unit and with timing signals at a second clock rate, which is higher than the first clock rate, from a second reference clock during an operational-mode of the first time base unit and configured to perform a calibration of the first time base unit, independently of the second time base unit, after the first time base unit is awoken from sleep-mode based at least on the timing signals at the second clock rate from the second reference clock, resulting in a calibrated first time base unit, and configured to adjust the second time base unit based at least on the calibration of the first time base unit to synchronize the second time base unit with the calibrated first time base unit, wherein the second time base unit is communicatively isolated from the first reference clock and communicatively coupled to the first time base unit and the second reference clock.

16. The communication system of claim 8 wherein the receiving station is configured to:

estimate a time of a first occurrence of a frame synchronization signal of the calibrated first time base unit, resulting in an estimated time; and

transmit the estimated time to a counter of the second time base unit at the first occurrence of the frame synchronization signal, resulting in synchronization of the first and second time base units.

17. The communication system of claim 8 wherein the first time base unit corresponds to one of GSM, EDGE, TDMA, WLAN, TD-SCDMA, Bluetooth, and UMTS;

and wherein the second time base unit corresponds to another one of GSM, EDGE, TDMA, WLAN, TD-SCDMA, Bluetooth, and UMTS.

9. A receiving station for a plurality of communication systems, comprising:

a first reference clock providing timing signals at a first clock rate;

a second reference clock providing timing signals at a second clock rate, which is higher than the first clock rate;

a first time base unit having a sleep-mode and an operational-mode and being communicatively coupled to the first reference clock and the second reference clock, the first time base unit being configured to receive and use the timing signals provided by the first reference clock at the first clock rate during the sleep-mode of the first time base unit, and the first time base unit being configured to receive and use the timing signals provided by the second reference clock at the second clock rate during the operational-mode of the first time base unit;

a second time base unit having a sleep-mode and an operational-mode and being communicatively isolated from the first reference clock and being communicatively coupled the second reference clock and the first time base unit, the second time base unit being configured to receive and use the timing signals provided by the second reference clock at the second clock rate during the operational-mode of the second time base unit;

wherein the first time base unit includes a calibration unit configured to perform a calibration of the first time base unit after the first time base unit is awoken from sleep-mode based at least on the timing signals at the second clock rate from the second reference clock and independently of the second time base unit, resulting in a calibrated first time base unit; and

wherein the receiving station is configured to adjust the second time base unit based at least on the calibration of the first time base unit to synchronize the second time base unit with the calibrated first time base unit.

18. The receiving station of claim 9 wherein the receiving station is configured to:

estimate a time of a first occurrence of a frame synchronization signal of the calibrated first time base unit, resulting in an estimated time; and

transmit the estimated time to a counter of the second time base unit at the first occurrence of the frame synchronization signal, resulting in synchronization of the first and second time base units.

19. The receiving station of claim 9 wherein the first time base unit corresponds to one of GSM, EDGE, TDMA, WLAN, TD-SCDMA, Bluetooth, and UMTS;

and wherein the second time base unit corresponds to another one of GSM, EDGE, TDMA, WLAN, TD-SCDMA, Bluetooth, and UMTS.

10. A computer readable medium having a software program for performing a synchronization of a first time base unit and a second time base unit stored therein, wherein a receiving station comprises the first and second time base units, the software program including instructions that cause a processor, when executing the software program, to:

provide the first time base unit with timing signals at a first clock rate from a first reference clock during a sleep-mode of the first time base unit and with timing signals at a second clock rate from a second reference clock during an operational-mode of the first time base unit, wherein the second clock rate is higher than the first clock rate;

perform a calibration of the first time base unit after the first time base unit is awoken from sleep-mode based at least on the timing signals at the second clock rate from the second reference clock, resulting in a calibrated first time base unit; and

adjust the second time base unit based at least on the calibration of the first time base unit to synchronize the second time base unit with the calibrated first time base unit, wherein the second time base unit is communicatively isolated from the first reference clock and communicatively coupled to the first time base unit and the second reference clock.

20. The computer readable medium of claim 10 wherein the software program stored therein include further instructions to cause the processor, when executing the software program, to:

estimate a time of a first occurrence of a frame synchronization signal of the calibrated first time base unit, resulting in an estimated time; and

transmit the estimated time to a counter of the second time base unit at the first occurrence of the frame synchronization signal, resulting in synchronization of the first and second time base units.

11. A receiving station of a mobile communications device that communicates with a plurality of communication systems, the receiving station comprising:

a low frequency reference clock providing low frequency timing signals;

a high frequency reference clock providing high frequency timing signals;

a first time base unit corresponding to a first communications system of the plurality of communication systems communicatively coupled to the high frequency clock and to the low frequency clock, the first time base unit being configured to use the high frequency timing signals, which are received from the high frequency reference clock, to calibrate the first time base unit after the first base unit is awoken from a respective sleep-mode and being configured to use the low frequency timing signals, which are received from the low frequency reference clock, during a respective sleep-mode;

a second time base unit corresponding to a second communications system of the plurality of communication systems communicatively coupled to the high frequency clock but not communicatively coupled to the low frequency clock, the second time base unit being configured to be adjusted based at least on a calibration of the first time base unit after the second time base unit is awoken from a respective sleep-mode, wherein the first and the second time base units are further configured to use the high frequency timing signals from the high frequency reference clock during respective operational-modes; and

wherein the first time base unit is calibrated independently of the second time base unit.

12. The receiving station of claim 11, further comprising:

a system controller communicatively coupled to the first and the second time base units and configured to estimate a time of a first occurrence of a frame synchronization signal of the first time base unit based at least on the calibration of the first time base unit and configured to provide the estimated time to the second time base unit.

13. The receiving station of claim 11 wherein the first time base unit includes a calibration unit communicatively coupled to the high frequency reference clock and configured to calibrate the first time base unit based at least on a command received from a system controller and the high frequency timing signals from the high frequency reference clock.

14. The receiving station of claim 13 wherein the second time base unit includes a memory that stores an estimated time of a first occurrence of the frame synchronization signal of the first time base unit.

15. The receiving station of claim 14 wherein the second time base unit includes a counter into which contents of the memory are copied at the first occurrence of the synchronization signal of the first time base unit.