Method and apparatus for providing a time adjustment to a wireless communication system

• US 6,208,871 B1
• Filed: 02/27/1998
• Issued: 03/27/2001
• Est. Priority Date: 02/27/1998
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Hall, Scott Maurice, Krzystyniak, Michael Anthony, Warner, Shawn Allison
• Primary Examiner(s): Hunter, Daniel S.
• Assistant Examiner(s): Gantt, Alan T.
• Application Number:
  US09/032,005
• Time in Patent Office: 1,124 Days
• Field of Search: 455/517, 455/13.2, 455/456, 370/335
• US Class Current: 455/517
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
• CPC Class Codes: H04W 56/001 Synchronization between nodes

Abstract

In a wireless communication system including at least a first (101) and a second base transceiver station (201), a method for providing time adjustment to the second base transceiver station (201) is presented. The method includes supplying an identity of the first and second base transceiver station to a mobile station (103), and based on the identity, tracking a first signal from the first base transceiver station (101) and a second signal from the second base transceiver station (201) by the mobile station (103). The method further includes determining a timing adjustment calculation based on a first time offset of the first and a second time offset of the second signal by the mobile station. And finally, the method includes transmitting the timing adjustment calculation to the second base station transceiver (201), the timing adjustment subsequently used to adjust the timing of the second base station transceiver (201).

Claims

1. In a wireless communication system, comprising at least a first and a second base transceiver station, a method for providing a time adjustment to the second base transceiver station, the method comprising the steps of:

receiving an identity of the first and second base transceiver station at a mobile station, wherein the step of receiving the identity comprises the step of receiving a first base station identity number and a first PN short code time offset of the first base station transceiver, and a second base station identity number and a second PN short code time offset of the second base station transceiver, wherein the second base station transceiver adjusts a timing such that the second base station transceiver is synchronized in time to the first base station transceiver;

tracking a first signal from the first base transceiver station and a second signal from the second base transceiver station by the mobile station, based on the identity, to yield a first and second time offset wherein the step of tracking the first signal by the mobile station comprises the steps of;

acquiring a pilot channel of the first signal from the first base station transceiver via correlation to a PN short code by the mobile station;

decoding a sync channel of the first signal to verify the first PN short code time offset and the first base station identity number via coherent demodulation provided by the pilot signal;

decoding a paging channel of the first signal to acquire a neighbor list comprised of PN short code time offsets associated with neighboring base station transceivers, including at least the second base station transceiver;

enabling a phase lock loop algorithm in the mobile station to begin adjusting a local oscillator frequency of the mobile station to synchronize to an oscillator frequency of the first base station transceiver;

initiating a timer in the mobile station upon enabling the phase lock loop algorithm;

freezing the phase lock loop algorithm upon expiration of the timer, thereby yielding a stable free running local oscillator frequency in the mobile station which is substantially equal to the oscillator frequency of the first base transceiver station;

extracting a first time offset from the first signal by a mobile station controller; and

terminating tracking of the first signal by the mobile station;

determining a timing adjustment calculation based on the first time offset of the first signal and the second time offset of the second signal by the mobile station; and

transmitting the timing adjustment calculation to the second base station transceiver.

2. The method according to claim 1, wherein the mobile station is a random mobile station comprising a mobile station controller for calculating a timing adjustment calculation.

3. The method according to claim 1, wherein the step of tracking the second signal by the mobile station comprises the steps of:

acquiring a pilot channel of the second signal from the second base station transceiver via correlation to the PN short code by the mobile station;

decoding a sync channel of the second signal to verify the first PN short code time offset and the second base station identity number via coherent demodulation provided by the pilot signal; and

decoding a paging channel of the second signal to acquire a neighbor list comprised of PN short code time offsets associated with neighboring base station transceivers, including at least the first base station transceiver.

4. The method according to claim 3, wherein the step of tracking the second signal further comprises the steps of:

enabling the phase lock loop algorithm of the mobile station to begin adjusting a local oscillator frequency of the mobile station to synchronize to an oscillator frequency of the second base station transceiver; and

extracting a second time offset from the second signal by a mobile station controller.

5. The method according to claim 4, wherein the step of determining a timing adjustment calculation based on the first time offset of the first signal and the second time offset of the second signal comprises the steps of:

calculating a time offset difference between the first and second PN short code time offsets to form a desired time offset;

calculating a time offset difference between the first time offset and the second time offset to form a measured time offset; and

comparing the desired time offset to the measured time offset by the mobile station controller to determine the timing adjustment calculation.

6. The method according to claim 5, wherein the step of transmitting the timing adjustment calculation to the second base station transceiver comprises the steps of:

transmitting an access channel message to the second base transceiver station, the access channel message comprising the timing adjustment calculation;

receiving the channel access message by the second base station receiver; and

adjusting, based on the timing adjustment calculation, the second time offset to be equivalent to the second PN short code time offset thereby yielding a PN short code time offset in the second base transceiver station which is synchronized to the PN short code time offset of the first base station.

7. The method according to claim 5, wherein the step of transmitting the timing adjustment calculation to the second base station transceiver further comprises the steps of:

transmitting an access channel message to the second base transceiver station, the access channel message including the timing adjustment calculation;

averaging, in the second base transceiver station, the timing adjustment calculation with a previous timing adjustment calculation to form a new timing adjustment calculation; and

adjusting, based on the new timing adjustment calculation, the second time offset to be equivalent to the second PN short code time offset thereby yielding a PN short code time offset in the second base transceiver station which is synchronized to the PN short code time offset of the first base station.

8. The method according to claim 6, wherein the step of transmitting the access channel message further comprises the steps of:

enabling the phase lock loop algorithm in the mobile station to begin adjusting its local oscillator frequency to synchronize to the local oscillator frequency of the second base station transceiver; and

synchronizing the mobile station to the second time offset to enable access channel messaging.

9. The method according to claim 1, wherein the wireless communication system is a home base cordless phone system comprising a plurality of base transceiver stations including at least the first and second base transceiver stations.

10. The method according to claim 1, wherein the wireless communication system comprises a code division multiple access system.

13. The method according to claim 10, wherein the step of tracking the second signal further comprises the steps of:

enabling the phase lock loop algorithm in the mobile station to begin adjusting the local oscillator frequency of the mobile station to synchronize to a oscillator frequency of the second base station transceiver; and

extracting a second time offset from the second signal by a mobile station controller.

14. The method according to claim 13, wherein the step of determining the timing adjustment calculation based on the first time offset of the first signal and the second time offset of the second signal comprises the steps of:

calculating a time offset difference between the first and second PN short code time offsets to form a desired time offset;

calculating a time offset difference between the first time offset and the second time offset to form a measured time offset; and

comparing the desired time offset to the measured time offset by the mobile station controller to form the timing adjustment calculation.

15. The method according to claim 14, wherein the step of transmitting the timing adjustment calculation to the second base station transceiver comprises the steps of:

transmitting an access channel message to the second base transceiver station, the access channel message including the timing adjustment calculation;

receiving the access channel message by the second base transceiver station; and

adjusting, based on the access channel message, the second time offset to prevent alignment in time of the second time offset with the first time offset.

16. The method according to claim 15, wherein the step of adjusting further comprises the step of:

adjusting, based on the access channel message, the oscillator frequency of the second base station transceiver, to prevent alignment in time of the second time offset with the first time offset.

11. In a wireless communication system, comprising at least a first and a second base transceiver station, a method for providing a time adjustment to the second base transceiver station, the method comprising the steps of:

receiving an identity of the first and second base transceiver station at a mobile station, wherein the step of receiving the identity comprises the step of receiving a first base station identity number and a first PN short code time offset of the first base station transceiver, and a second base station identity number and a second PN short code time offset of the second base station transceiver, wherein the second base station transceiver adjusts a timing such that the second base station transceiver is unsynchronized in time to the first base station transceiver;

tracking a first signal from the first base transceiver station and a second signal from the second base transceiver station by the mobile station, based on the identity, to yield a first and second time offset, wherein the step of tracking the first signal by the mobile station comprises the steps of;

acquiring a pilot channel of the first signal from the first base station transceiver via a first signal strength measurement and correlation to a PN short code time offset by the mobile station;

decoding a sync channel of the first signal to verify the first base station identity number via coherent demodulation provided by the pilot signal;

enabling a phase lock loop algorithm in the mobile station to begin adjusting a local oscillator frequently of the mobile station to synchronize to an oscillator frequency of the first base station transceiver;

initiating a timer in the mobile station upon enabling the phase lock loop algorithm;

freezing the phase lock loop algorithm upon expiration of the timer, thereby yielding a stable free running local oscillator frequency in the mobile station which is substantially equal to the oscillator frequency of the first base transceiver station;

extracting a first time offset from the first signal by a mobile station controller; and

terminating tracking of the first signal by the mobile station;

determining a timing adjustment calculation based on the first time offset of the first signal and the second time offset of the second signal by the mobile station; and

transmitting the timing adjustment calculation to the second base station transceiver.

12. The method according to claim 11, wherein the step of tracking the second signal by the mobile station comprises the steps of:

acquiring a pilot channel of the second signal from the first base station transceiver via second signal strength measurement and correlation to the PN short code time offset by the mobile station; and

decoding a sync channel of the second signal by the mobile station to verify the second base station identity number via coherent demodulation provided by the pilot signal.

17. In a wireless communication system, comprising at least a first and a second base transceiver station, the first base transceiver station synchronized to a system reference time, and the second base transceiver station unsynchronized to the system reference time, the system reference time including a system reference oscillator frequency and an absolute reference time, a method for providing wireless communication system synchronization to the second base transceiver station, the method comprising the steps of:

receiving an identity of the first and second base transceiver station at a mobile station, wherein the step of receiving the identity comprises the steps of;

receiving a first base station identity number and a first PN short code time offset of the first base station transceiver;

receiving a second base station identity number and a second PN short code time offset of the second base station transceiver;

receiving a first distance between the first base transceiver station and the mobile station, and;

receiving a second distance between the second base transceiver station and the mobile station;

tracking a first signal from the first base transceiver station by the mobile station, based on the identity;

synchronizing the mobile station to the system reference time via the first signal;

determining an actual time offset with respect to the absolute reference time, of a second signal from the second base transceiver station by the mobile station; and

based on the actual time offset, synchronizing the second base transceiver station to the system reference time.

18. The method according to claim 17, wherein the step of receiving the identity further comprises the step of receiving a first distance between the first base transceiver station and the mobile station and a second distance between the second base transceiver station and the mobile station.

19. The method according to claim 17, wherein the step of tracking the first signal by the mobile station comprises the steps of:

acquiring a pilot channel of the first signal from the first base station transceiver via correlation to a PN short code by the mobile station;

decoding a sync channel of the first signal by the mobile station to verify the first PN short code time offset and the first base station identity number via coherent demodulation provided by the pilot signal; and

decoding a paging channel of the first signal to acquire a neighbor list comprised of PN short code time offsets associated with neighboring base station transceivers, including at least the second base station transceiver.

20. The method according to claim 17, wherein the step of synchronizing the mobile station to the system reference time via the first signal comprises the steps of:

enabling a phase lock loop algorithm in the mobile station to begin adjusting its local oscillator frequency to synchronize to the system reference oscillator frequency of the first base station transceiver;

initiating a timer in the mobile station upon enabling the phase lock loop algorithm;

freezing the phase lock loop algorithm upon expiration of the timer, thereby yielding a stable free running local oscillator frequency in the mobile station which is substantially equal to the system reference oscillator frequency of the first base transceiver station; and

terminating tracking of the first signal by the mobile station.

21. The method according to claim 17, wherein the step of synchronizing the mobile station to the system reference time via the first signal comprises the steps of:

initiating a pilot searcher algorithm in the mobile station to control adjustment of a phase lock loop algorithm of the mobile station such that the local oscillator frequency of the mobile station is substantially equal to the system reference oscillator frequency of the first base transceiver station; and

continuing tracking of the first signal by the mobile station.

22. The method according to claim 17, wherein the step of determining an actual time offset with respect to the absolute reference time of the second signal comprises the steps of:

tracking the second signal from the second base transceiver station by the mobile station based on the identity of the second base station transceiver; and

extracting the actual time offset from the second signal by a mobile station controller.

23. The method according to claim 22, wherein the step of tracking the second signal further comprises the steps of:

assigning a receiver in the mobile station to demodulate at least one signal at the second PN short code time offset;

acquiring a pilot channel of the at least one signal via correlation to a PN short code by the mobile station;

decoding a sync channel of the at least one signal by the mobile station to verify the second PN short code time offset and the second base station identity number via coherent demodulation provided by the pilot signal; and

verifying acquisition of the at least one signal by the receiver, based in the identity.

24. The method according to claim 23 wherein the mobile station is a fixed location monitoring mobile at a fixed location for synchronizing the second base transceiver station.

25. The method according to claim 24, wherein the step of synchronizing the second base transceiver station to the system reference time comprises the steps of:

calculating a time offset difference between the first and second PN short code time offsets to form a desired time offset;

calculating a difference between the actual time offset and the desired time offset of the second base transceiver station, by the mobile station controller to form a timing adjustment calculation;

transmitting an access channel message to the second base transceiver station, the access channel message comprising the timing adjustment calculation;

adjusting, based on the timing adjustment calculation, the actual time offset to be equivalent to the second PN short code time offset thereby yielding a PN short code time offset which is synchronized to the absolute reference time of the first base station; and

adjusting, based on the timing adjustment calculation, the local oscillator frequency of the second base transceiver station thereby yielding a local oscillator frequency in the second base station transceiver which is substantially equal to the system reference oscillator frequency of the first base station.

26. The method according to claim 25, wherein the step of transmitting the access channel message further comprises the steps of:

enabling a phase lock loop algorithm in the mobile station to begin adjusting its local oscillator frequency to synchronize to the local oscillator frequency of the second base station transceiver; and

synchronizing the fixed location monitoring mobile to the actual time offset to enable access channel messaging.

29. The apparatus according to claim 26, wherein the identity comprises a first base station identity number and a first PN short code time offset of the first base station transceiver, and a second base station identity number and a second PN short code time offset of the second base station transceiver.

30. The apparatus according to claim 26, wherein the mobile station receiver further comprises:

a means for acquiring a pilot channel of the second signal from the second base station transceiver via correlation to a short code; and

a means for decoding a sync channel of the second signal to verify the first PN short code time offset and the second base station identity number via coherent demodulation provided by the pilot signal.

31. The apparatus according to claim 19, wherein the mobile station receiver comprises:

a means for acquiring a pilot channel of the first signal from the first base station transceiver via correlation to a short code;

a means for decoding a sync channel of the first signal to verify the first PN short code time offset and the first base station identity number via coherent demodulation provided by the pilot signal; and

a means for decoding a paging channel of the first signal to acquire a neighbor list comprised of PN short code offsets associated with neighboring base station transceivers, including at least the second base station transceiver.

27. In a wireless communication system, comprising at least a first and a second base transceiver station, the first base transceiver station synchronized to a system reference time, and the second base transceiver station unsynchronized to the system reference time, the system reference time including a system reference oscillator frequency and an absolute reference time, an apparatus for providing wireless communication system synchronization to the second base transceiver station, the apparatus comprising:

means for conveying an identity of the first and second base transceiver station;

a mobile station adapted to receive the identity, the mobile station comprising

a mobile station receiver adapted to track a first signal from the first base transceiver station and a second signal from the second base transceiver station, based on the identity, and to synchronize the mobile station to the system reference time via the first signal, wherein the mobile station receiver further comprises;

means for acquiring a pilot channel of the second signal from the second base station transceiver via correlation to a short code; and

means for decoding a sync channel of the second signal to verify the first PN short code time offset and the second base station identity number via coherent demodulation provided by the pilot signal; and

a mobile station controller adapted to determine an actual time offset with respect to the absolute reference time, of the second signal, calculate a timing adjustment calculation based on the actual time offset, and coordinate transmission of an access channel message, the access channel message comprising the timing adjustment calculation;

a second base transceiver station receiver for reeving and acknowledging the access channel message; and

a second base transceiver station phase lock loop algorithm for producing a correction signal based on the timing adjustment calculation, the correction signal synchronizing the second base transceiver station to the system reference time.

28. In a wireless communication system, comprising at least a first and a second base transceiver station, the first base transceiver station synchronized to a system reference time, and the second base transceiver station unsynchronized to the system reference time, the system reference time including a system reference oscillator frequency and an absolute reference time, an apparatus for providing wireless communication system synchronization to the second base transceiver station, the apparatus comprising:

a means for conveying an identity of the first and second base transceiver station;

a mobile station for receiving the identity, the mobile station comprising

a mobile station receiver for tracking a first signal from the first base transceiver station and a second signal from the second base transceiver station, based on the identity, and

synchronizing the mobile station to the system reference time via the first signal,

a mobile station controller for determining an actual time offset with respect to the absolute reference time, of the second signal,

calculating an timing adjustment calculation based on the actual time offset, and

coordinating transmission of an access channel message the access channel message comprising the timing adjustment calculation;

a second base transceiver station receiver for receiving and acknowledging the access channel message; and

a second base transceiver station phase lock loop algorithm for producing a correction signal based on the timing adjustment calculation, the correction signal synchronizing the second base transceiver station to the system reference time.