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

• US 20060182148A1
• Filed: 03/30/2006
• Published: 08/17/2006
• Est. Priority Date: 10/30/1998
• Status: Active Grant

• 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
• Granted Patent: US 8,005,072 B2
• Time in Patent Office: Days
• US Class Current: 370/503
• 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 system for synchronizing plural cable modem termination devices, comprising:

a master cable modem termination system device, said device having at least one downstream channel and at least one upstream channel for communicating with plural cable modems, said master device further including a counter;

plural slave cable modem termination system devices connected to the master cable modem termination system device, wherein each slave device has at least one upstream channel for receiving communications from plural cable modems, each slave device further including a counter;

a processor programmed to calculate a future time stamp value and to transmit said value to each of the master and slave devices;

wherein the master device is designed to compare the future time stamp value with the value of the counter, and to transmit a signal to each slave device when the counter of the master device and the future time stamp have equal values, the slave devices being operative in response to said signal to load the future time stamp value to the respective counters.

2-24. -24. (canceled)