Method and apparatus for upstream burst transmission synchronization in cable modems
US6556591B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jul 19, 2001 |
| Grant date | Apr 29, 2003 |
| Priority date | — |
| Expiry date | Jul 19, 2021 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N21/4385
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A system for synchronizing the upstream burst transmission in a cable system to a time specified by the cable head end is disclosed. The system includes a free running counter within a cable modem (CM) or network interface unit (NIU), along with logic to capture the value of this free running counter at the time a frame of MPEG-2 SYNC data arrives, to create a time tag stored in memory. A computer within the cable modem or network interface unit has access to the time tags in memory and the contents of a time synchronization message from the head end, also stored in memory. The computer contains a program to calculate the value of the local counter that corresponds to a time to transmit commanded by the cable system head end. The system includes logic within the CM or NIU to initiate an upstream burst transmission when the value of the local counter becomes equal to a calculated value, thus causing the cable modem to initiate its upstream burst transmission precisely at the time commanded by the head end.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.