Method and apparatus for digital transmission incorporating scrambling and forward error correction while preventing bit error spreading associated with descrambling
US6349138B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Apr 23, 1997 |
| Grant date | Feb 19, 2002 |
| Priority date | — |
| Expiry date | Apr 23, 2017 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N7/173
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
The specification relates to a method and apparatus supporting multiple access, bi-directional data and multimedia transfer described over a hybrid fiber/coax (HFC) network, though applicable to transmissions over other media as well. The protocol associated with the present invention supports downstream broadcast transmission from headend to cable modem, and also provides for allocation of bandwidth for cable modems to transmit back to the headend. The protocol supports different access modes such as STM, ATM, and VL; within each subframe of a subframe/frame/masterframe structure. The protocol is utilized over a system which provides for forward error correction (FEC) and scrambling/descrambling, while eliminating the deleterious effects on the error correcting capability of the FEC due to the bit error spreading associated with a scrambling/descrambling function. The protocol adapts to changing demands for a mix of circuit and packet mode applications and allocates upstream and downstream bandwidth in response to the a variety of bursty and isochronous traffic sources.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.