FYI - IPCDN terminology

[Walid Dabbous <Walid.Dabbous@sophia.inria.fr>]

INTERNET-DRAFT  IPCDN Terms of Reference              28 July 97

********
Upstream       The set of frequencies used to send data from a sub-
********       scriber to the headend.

**********
Downstream     The set of frequencies used to send data from a headend
**********     to a subscriber.

Subsplit       A frequency allocation plan where 5-42 MHz is used for
               upstream data and 50+MHz is used for downstream data.

Midsplit       A frequency allocation plan where 5-108 MHz is used for
               upstream data and 178+ is used for downstream data.

Cable Modem    Any device which modulates and demodulates digital data
               onto a CATV plant.
*******
Headend        Central distribution point for a CATV system.  Video sig-
*******        nals are received here from satellite (either co-located
               or remoted), frequency converted to the appropriate chan-
               nels, combined with locally originate signals, and
               rebroadcast onto the HFC plant. For a CATV data system,
               the headend is the typical place to link between the HFC
               system and any external data networks.

Distribution HubA smaller or remote headend distribution point for a
               CATV system.  Video signals are received here from
               another site (headend), and redistributed.  Sometimes a
               small number of locally originated signals are added.
               Such signals might be city information channels, HFC
               cable modem signals or the like.

Optical Node   A device used to convert broadband RF (radio frequency,
               e.g. television signals) to/from a fiber optic signal.

Fiber Node     Also "Node".  An optical node located in the outside
               plant distribution system which terminates the fiber
               based downstream signal as an electrical signal onto a
               coaxial RF cable.  Each fiber node is defined to support
               a certain service area, either defined by number of homes
               passed, or total amplifier cascade (# of active amplif-
               iers in the longest line from the node to the end of the
               line.)

Trunk Line     A CATV "backbone" coaxial cable.  This runs from an Opti-
               cal Node and through a specific neighborhood or serving
               area.

Branch Line    Also "Feeder Cable". A coax cable which runs from a trunk
               line to a subscriber drop point.



M. StJohns                                                      [Page 2]



INTERNET-DRAFT  IPCDN Terms of Reference              28 July 97

***
Tap            A passive device which divides the signal between the
***            trunk or feeder lines and splits the signal into ports
               for subscriber drop access.

Drop           A subscriber access point.  From the tap to the home and
               the actual coax connection and wiring in the subscribers
               home.

Amplifier      Amplifiers are used on coaxial segments of a CATV plant
               to restore signal levels lost due to attenuation through
               distance.  Unfortunately amplifiers amplify noise as well
               as signal.

Channel        A specific frequency allocation and bandwidth. Downstream
               channels used for television in the US are 6MHz wide
               (NTSC).  International systems such as PAL and SECAM use
               8Mhz wide channels.

CATV           Originally Community Antenna Television.  Now used to
               refer to any cable (coax/fiber) based system provision of
               television services.

Homes Passed   The number of homes or offices potentially servicable by
               a cable system either on a per node or per system basis.

Telephony ReturnA variant of a cable data system where the return path
               from the subscriber cable modem goes via a dialup (or
               ISDN) connection instead of over an upstream channel.