ANSI SCTE 133-2017 pdf free download – Downstream RF Interface for Cable Modem Termination System.
5FUNCTIONAL ASSUMPTIONS
This section describes the characteristics of a cable television plant, assumed to be for the purpose of operating adata-over-cable system. It is not a description of EQAM or CMTS parameters. The data-over-cable system MUSTbe interoperable within the environment described in this section.
Whenever there is a reference in this section to frequency plans or compatibility with other services, or conflictswith any legal requirement for the area of operation, the latter shall take precedence.Any reference to NTSC analogsignals in six MHz channels does not imply that such signals are physically present.
5.1Broadband Access Network
A coaxial-based broadband access network is assumed. This may take the form of either an all-coax or hybridfiberlcoax (HFC) network. The generic term “cable network” is used here to cover all cases.
A cable network uses a shared-medium, “tree-and-branch” architecture, with analog transmission.The keyfunctional characteristics assumed in this document are the following:
.Two-way transmission
.A maximum opticaL/electrical spacing between the DRFI-compliant device and the most distant CM of 100
miles in each direction, although typical maximum separation may be 10-15 miles
.A maximum differential opticalelectrical spacing between the DRFI-compliant device and the closest and most
distant modems of 100 miles in each direction, although this would typically be limited to 15 miles
At a propagation velocity in fiber of approximately 1.5 ns/ft, 100 miles of fiber in each direction results in a round-trip delay of approximately 1.6 ms. For further information, see [DOCSIS2],Appendix VIII.
5.2Equipment Assumptions
5.2.1 Frequency Plan
In the downstream direction, the cable system is assumed to have a pass band with a lower edge between 50 and 54MHz and an upper edge that is implementation-dependent but is typically in the range of 300 to 870 MHz.Withinthat pass band, NTSC analog television signals in six-MHz channels are assumed present on the Standard (STD),HRC, or IRC frequency plans of [CEA-542-B], as well as other narrowband and wideband digital signals.
5.2.2Compatibility with Other Services
The CM and EQAM or CMTS MUST coexist with the other services on the cable network, for example:
1. TheyMUST be interoperable in the cable spectrum assigned for EQAM or CMTS-CM interoperation, while thebalance of the cable spectrum is occupied by any combination of television and other signals, and
2. They MUST NOT cause harmful interference to any other services that are assigned to the cable network in
spectrum outside of that allocated to the EQAM or CMTS. The latter is understood as:
No measurable degradation (highest level of compatibility),
.No degradation below the perceptible level of impairments for all services (standard or medium level
of compatibility), or
No degradation below the minimal standards accepted by the industry (for example, FCC for analogvideo services) or other service provider (minimal level of compatibility).
5.2.3 Fault Isolation Impact on Other Users
As downstream transmissions are on a shared-media, point-to-multipoint system, fault-isolation procedures should take into account the potential harmful impact of faults and fault-isolation procedures on numerous users of the dataover-cable, video, and other services.
For the interpretation of harmful impact, see Section 5.2.2 above.ANSI SCTE 133 pdf download.