Method and apparatus for the synchronization of multiple cable modem termination system devices

• US 7,035,251 B2
• Filed: 06/01/2004
• Issued: 04/25/2006
• Est. Priority Date: 10/30/1998
• Status: Expired due to Term

• Current Assignee: Avago Technologies International Sales 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
• Assistant Examiner(s): Boakye, Alexander O.
• Application Number:
  US10/856,829
• Publication Number:
  US 20040218589A1
• Time in Patent Office: 693 Days
• Field of Search: 370/324, 370/480, 370/486, 370/490, 370/503, 370/509, 370/512, 370/270, 370/419, 370/420, 370/510, 370/489, 370/352, 370/432, 370/493, 375/222, 725/111
• 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 communication system, comprising:

a master cable modem termination system device having a first counter; and

a first slave cable modem termination system device having a second counter;

wherein the first slave cable modem termination system device sets the second counter based on a signal provided by the master cable modem termination system device; and

wherein the second counter is used to generate timing information for transmission by the first slave cable modem termination system device.

2. The communication system of claim 1, wherein the first slave cable modem termination system device synchronizes the second counter with the first counter based on the signal.

3. The communication system of claim 1, wherein the master cable modem termination system device provides the signal in response to a value of the first counter corresponding to predetermined time stamp information.

4. The communication system of claim 1, further comprising:

a second slave cable modem termination system device having a third counter;

wherein the second slave cable modem termination system device sets the third counter based on the signal provided by the master cable modem termination system device.

5. The communication system of claim 4, wherein the master cable modem termination system device and the first and second slave cable modem termination system devices are connected via a synchronization bus.

6. The communication system of claim 1, wherein the master cable modem termination system device generates the signal based on time stamp information received from a processor.

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

8. A communication system, comprising:

a first cable modem termination system device to transmit MAP information to a plurality of cable modems, the MAP information including identifiers associated with respective upstream channels that are connected to the cable modems; and

a second cable modem termination system device connected to an upstream channel, wherein the second cable modem termination system device filters the MAP information based on an identifier of the MAP information that is associated with the upstream channel that is connected to the second cable modem termination system device.

9. The communication system of claim 8, wherein the second cable modem termination system device stores a portion of the MAP information that is associated with the upstream channel that is connected to the second cable modem termination system device.

10. The communication system of claim 8, wherein the second cable modem termination system device disregards a portion of the MAP information that is not associated with the upstream channel that is connected to the second cable modem termination system device.

11. The communication system of claim 8, wherein the first cable modem termination system device transmits the MAP information to the second cable modem termination system device.

12. A method, comprising:

storing time stamp information at a first slave cable modem termination system device having a first counter;

setting the first counter of the first slave cable modem termination system device based on a signal provided by a master cable modem termination system device having a second counter; and

generating timing information for transmission by the first slave cable modem termination system device using the first counter.

13. The method of claim 12, wherein setting the first counter includes synchronizing the first counter with the second counter based on the signal.

14. The method of claim 12, wherein storing the time stamp information includes storing the time stamp information associated with a future time stamp.

15. The method of claim 12, wherein setting the first counter is performed in response to detecting a time stamp value at the second counter that corresponds to the time stamp information.

16. The method of claim 12, further comprising:

setting a third counter of a second slave cable modem termination system device based on the signal provided by the master cable modem termination system device.

17. The method of claim 16, further comprising:

connecting the master cable modem termination system device and the first and second slave cable modem termination system devices via a synchronization bus.

18. The method of claim 12, further comprising:

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

19. A method, comprising:

transmitting MAP information including identifiers associated with respective upstream channels from a first cable modem termination system device to cable modems connected to the upstream channels; and

filtering the MAP information at a second cable modem termination system device based on an identifier of the MAP information that corresponds with an upstream channel that is connected to the second cable modem termination system device.

20. The method of claim 19, further comprising:

storing a portion of the MAP information that corresponds with the upstream channel that is connected to the second cable modem termination system device at the second cable modem termination system device.

21. The method of claim 19, further comprising:

disregarding a portion of the MAP information that does not correspond with the upstream channel that is connected to the second cable modem termination system device at the second cable modem termination system device.

22. The method of claim 19, further comprising:

transmitting the MAP information from the first cable modem termination system device to the second cable modem termination system device, wherein filtering the MAP information at the second cable modem termination system device is performed in response to transmitting the MAP information from the first cable modem termination system device to the second cable modem termination system device.