The description of the components associated with cable systems essentially equates to defining additional terminology. Typical components include:
■ Antenna site—A location containing a cable provider's main receiving and satellite dish facilities. This site is chosen based on potential for optimal reception of transmissions over the air, via satellite, and via point-to-point communication.
■ Headend—A master facility where signals are received, processed, formatted, and distributed over to the cable network. This includes both the transportation and distribution networks. This facility is typically heavily secured and sometimes "lights-out," meaning that it is not regularly staffed.
■ Transportation network—The means and media by which remote antenna sites are connected to the headend facility. Alternately, this could be a headend facility connection to the distribution network. The transmission media may be microwave, coaxial supertrunk, or fiber optic.
■ Distribution network—In typical cable system architectures, consists of trunk and feeder cables. The trunk is the backbone cable (usually 0.75-inch diameter) over which the primary connectivity is maintained. In many networks, the distribution network tends to be a hybrid fiber-coaxial network.
■ Node—Performs optical-to-RF conversion of CATV signal as needed. Feeder cables (typically 0.5-inch diameter) originate from nodes that branch off into individual communities to provide services to anywhere between 100 and 2000 customers each.
■ Subscriber drop—Connects the subscriber to the cable service network via a connection between the feeder portion of a distribution network and the subscriber terminal device (for example, TV set, VCR, high-definition TV set-top box, or cable modem). The subscriber drop components consist of the physical coaxial cabling, grounding and attachment hardware, passive devices, and a set-top box.
These components tend to be relatively easy to understand in concept. In practice, these are implemented in differing manners depending on the cable provider. Regardless of the chosen architecture, the concepts remain the same. Figure 3-1 illustrates typical cable provider architecture.
Traditional Coaxial Network
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