ITU-T J.122 PDF

This Recommendation defines the second generation of radio-frequency interface specifications for high-speed data-over-cable systems.

There are differences in the cable spectrum planning practices adopted for different networks in the world. Therefore, three options for physical layer technology are included, which have equal priority and are not required to be interoperable. One technology option is based on the downstream multi-programme television distribution that is deployed using 6 MHz channelling, and supports upstream transmission in the 5-42 MHz region. The second technology option is based on a multi-programme television distribution using 8 MHz channel spacing and supports upstream in the 5-65 MHz region. The third technology option is based on 6 MHz channel spacing and supports upstream in the 10-55 MHz region. All options have equal status. The first of these options is defined in clauses 4, 6 and 7, whereas the second and third are defined by replacing the content of those clauses with the content of Annex F or Annex J. Compliance with this Recommendation requires compliance with only one of these implementations. It is not required that equipment built to one option shall interoperate with equipment built to another.

These optional physical-layer technologies allow operators some flexibility within any frequency planning, EMC and safety requirements that are mandated for their area of operation. For example, the 6 MHz downstream-based option defined by clauses 4, 6 and 7 might be deployable within an 8 MHz channel plan.

Frequency planning, safety and EMC requirements are a national matter and are not covered by this Recommendation. Compliance remains the operators' responsibility.

All optional physical-layer technologies are required to be backwards compatible with the earlier versions of those options defined in [DOCS9], [DOCS11] and [DOCS12].

NOTE – The structure and content of this Recommendation have been organized for ease of use by those familiar with the original source material; as such, the usual style of ITU-T recommendations has not been applied.