Digital Signals over RF Channels Cont


Data-over-Cable Service Interface Specification (DOCSIS):

• RF interface specification of minimum recommended technical performance requirements for data

• Cable modem termination system (CMTS) and cable modem (CM) vendors must pass certification

• CableLabs tests and grants (or withholds) DOCSIS "Certified" or "Qualified" status

• Cable operators purchase certified/qualified equipment to ensure interoperability with vendors

- Reference:

• A variation is Euro-DOCSIS standards that use 7 MHz and 8 MHz for cable plants

© 2004 Cisco Systems, Inc. All rights reserved. BCRAN v2.1—4-9

Data-over-Cable Service Interface Specifications (DOCSIS) defines specific bandwidths for data signals (200 kHz, 400 kHz, 800 kHz, 1.6 MHz, and 3.2 MHz) that the cable operator can use.

The cable TV industry assigns the available spectrum to serve two purposes. Under the National Television Standards Committee (NTSC) standard, the North American TV standard, each country can determine its own splits and frequency assignments. DOCSIS specifications are based on NTSC TV channel plans. Euro-DOCSIS specifications are written for Phase Alternating Line (PAL) based deployments.

There are three DOCSIS standards currently used:

■ DOCSIS 1.0 was the first standard.

■ DOCSIS 1.1 was the standard needed to deploy VoIP packet cable with end-to-end quality.

■ DOCSIS 2.0, a standard in progress, will be able to provide 30 Mbps in the upstream path.

For more information, refer to the following:

www cablemodem com/specifications/specifications10 html_

www cablemodem com/specifications/specifications11 html_

www cablemodem com/specifications/specifications20 html_

There is a separate set of standards for Euro-DOCSIS. This standards variation defines the physical layers as they fit into 7-MHz and 8-MHz plants around the world. Euro-DOCSIS standards specify 108 to 810 MHz for the downstream. These Euro-DOCSIS standards are:

■ SP-RFI-C01 -01119 for DOCSIS 1.0, now ANSI/SCTE 22-1 2002

■ SP-RFIv1. 1-I08-0203 01 for DOCSIS 1.1, now ANSI/SCTE 23-1 2002

0 0

Post a comment