Synchronization of multiple base stations in a wireless communication system

• US 8,005,072 B2
• Filed: 03/30/2006
• Issued: 08/23/2011
• Est. Priority Date: 10/30/1998
• Status: Expired due to Fees

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Denney, Lisa V., Quigley, Thomas J., Dworkin, David R., Lee, Robert J., Hebsgaard, Anders
• Primary Examiner(s): Pham; Chi H
• Assistant Examiner(s): BOAKYE, ALEXANDER O
• Application Number:
  US11/392,806
• Publication Number:
  US 20060182148A1
• Time in Patent Office: 1,972 Days
• Field of Search: 370/337, 370/350, 370/324, 370/480, 370/486, 370/490, 370/503, 370/509, 370/512, 370/270, 370/420, 370/510, 370/487, 370/489, 370/520, 370/50, 375/222, 725/111, 725/112, 725/109, 455/438, 455/435
• US Class Current: 370/352
• CPC Class Codes: H04B 1/1036 with automatic suppression of narrow band noise or interference, e.g. by using tuneable notch filters H04B1/123 takes precedence; filter circuits H03H
• CPC Class Codes: H04J 3/0664 unidirectional timestamps
• CPC Class Codes: H04J 3/067 Details of the timestamp structure
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
• CPC Class Codes: H04L 12/2801 Broadband local area networks
• CPC Class Codes: H04L 2025/03808 Transmission of equaliser coefficients
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end

Abstract

A plurality of CMTS devices are linked together and synchronized to facilitate communication between the respective CMTS devices and respective downstream cable modems. According to one embodiment of the invention, one of the CMTS devices is designated as a master device, and the other CMTS devices are designated as slave devices. The respective CMTS devices are connected to each other by means of a synchronization bus. The master CMTS device then generates and broadcasts a future time stamp value, which is received by the respective slave CMTS devices. When the time stamp counter in the master CMTS device reaches the transmitted value, a control signal is broadcast over the synchronization bus. The slave CMTS devices then retrieve the time stamp value and reset their respective local time stamp counters to the received value. In this manner, the CMTS devices are synchronized.

Claims

1. A wireless communication system, comprising:

a first base station having a first time counter; and

a second base station having a second time counter;

wherein the first base station provides a signal in response to a value of the first time counter corresponding to predetermined time stamp information;

wherein the second base station sets the second time counter based on the signal provided by the first base station; and

wherein the second time counter is used to generate timing information for transmission by the second base station.

2. The wireless communication system of claim 1, wherein the second base station synchronizes the second time counter with the first time counter based on the signal.

3. The wireless communication system of claim 1, further comprising:

a third base station having a third time counter;

wherein the third base station sets the third time counter based on the signal provided by the first base station.

4. The wireless communication system of claim 3, wherein the first, second, and third base stations are connected via a synchronization bus.

5. The wireless communication system of claim 1, wherein the first base station generates the signal based on time stamp information received from a processor.

6. The wireless communication system of claim 5, wherein the processor updates the time stamp information in response to a lapse of a predetermined amount of time.

7. A wireless communication system, comprising:

a first base station to transmit MAP information to a plurality of subscriber stations, the MAP information including identifiers associated with respective uplink channels that are connected to the subscriber stations; and

a second base station connected to an uplink channel, wherein the second base station filters the MAP information based on an identifier of the MAP information that is associated with the uplink channel that is connected to the second base station.

8. The wireless communication system of claim 7, wherein the second base station stores a portion of the MAP information that is associated with the uplink channel that is connected to the second base station.

9. The wireless communication system of claim 7, wherein the second base station disregards a portion of the MAP information that is not associated with the uplink channel that is connected to the second base station.

10. The wireless communication system of claim 7, wherein the first base station transmits the MAP information to the second base station.

11. A base station, comprising:

means for storing time stamp information;

a first time counter configured for counting a local time of the base station;

means for setting the first time counter based on the time stamp information and a time signal provided by a second time counter configured for counting a local time of a second base station, wherein the time signal is based on a time stamp value at the second time counter that corresponds to the time stamp information; and

means for generating timing information for transmission using the first time counter.

12. The base station of claim 11, wherein the means for setting includes means for synchronizing the first time counter with the second time counter based on the time signal.

13. The base station of claim 11, wherein the time stamp information is associated with a future time stamp.

14. The base station of claim 11, further comprising:

means for updating the time stamp information in response to a lapse of a predetermined amount of time.

15. A system for synchronizing a plurality of base stations, comprising:

a first base station including a counter, the first base station configured to communicate with a plurality of subscriber stations via at least one downlink channel and at least one uplink channel;

a plurality of second base stations coupled to the first base station, wherein each second base station includes a respective counter and is configured to receive communications from a plurality of subscriber stations via at least one uplink channel; and

a processor programmed to calculate a future time stamp value and to transmit the future time stamp value to each of the first and second base stations;

wherein the first base station is configured to compare the future time stamp value with the value of the counter of the first base station, and to transmit a signal to each second base station when the counter of the first base station and the future time stamp have equal values, the second base stations being operative in response to the signal to load the future time stamp value to the respective counters.

16. The system of claim 15, wherein the processor is programmed to calculate a future time stamp value for the first base station and a different future time stamp value for the second base stations, where the values are offset by a predetermined number of clock cycles.

17. The system of claim 15, wherein the processor is programmed to query the first base station for its current time stamp value, and to calculate the future time stamp value based on the current time stamp value of the first base station.

18. The system of claim 15, wherein the processor is programmed to transmit the future time stamp value a predetermined amount of time prior to reaching the future time stamp value.

19. The system of claim 18, wherein the processor is programmed to transmit the future time stamp value between approximately eight and approximately 64 clock cycles prior to reaching the future time stamp value.

20. The system of claim 15, wherein the processor is programmed to generate a new future time stamp value once every predetermined amount of time.

21. The system of claim 20, wherein the processor is programmed to generate a new future time stamp value once per millisecond.

22. The system of claim 15, wherein the processor is included in the first base station.

23. The system of claim 15, comprising:

a register to store a current time stamp value;

means for storing data to the register using a first clock domain; and

means for reading the data from the register using a second clock domain.