Cable television systems have moved far beyond simple delivery of television programming to include high-speed data services, voice telephony, networking, transactional delivery of digital video under the interactive control of customers, and targeted advertising delivery, to name a few. To manage this complex business, what was formerly known simply as the “headend” has also evolved into a hierarchy of national, regional, and local signal processing centers. Similarly, the subscriber’s premise has evolved to often include local distribution networks that allow communication among devices as well as with the external network. In the near future, communications will be provided by operators to multiple, diverse end terminals, including wireless devices. Our previous book, Modern Cable Television Technology: Voice, Video and Data Communications, 2nd ed. (Morgan Kaufmann, 2004) covered the entire range of technologies involved in a cable system and should be consulted for topics lying outside the scope of this volume.

At some point in this network, the modulated radio frequency (RF) signals that are to be transported to customer homes are delivered to a linear distribution network whose purpose is to deliver those same signals with no further per-signal processing and with as little degradation as economically possible. This book is devoted to that portion of the system, which we have referred to generically as the “hybrid fiber/coax (HFC) plant,” although it need not always include both fiber optics and coaxial transport and may occasionally include microwave links. The HFC plant is designed to be as transparent as possible and is characterized by its bidirectional RF bandwidth, the maximum level of various impairments to the transported signals, the number of homes or customers who share common signals, its reliability and availability, and its ability to scale to provide greater per-subscriber bandwidth as needed. It is this portion of a cable television system that distinguishes it from, for instance, a direct-to-home satellite system; that is, a satellite provider is limited to a one-way broadband path that, because of the characteristics of satellite antennas, delivers signals in common to millions of homes and, because of the characteristics of those signals, requires signal processing for every in-home television receiver.

Because of the limitations of its networks, direct broadcast satellite (DBS) systems are practically limited to video distribution as their primary business. By contrast, cable operators have the luxury of a two-way path with the ability to deliver a unique spectrum of signals to each small group of homes with a quality that is sufficiently high to support both analog video- and bandwidth-efficient digital modulation schemes. The HFC plant thus supports both broadcast and high-usage-rate transactional and two-way services. New fiber-based telephone networks have many of the same advantages as cable, although with a different network architecture. In particular, some telephone carriers use a combination of linear and digital optical transport on different wavelengths sharing a single fiber. These emerging fiber-deep (including fiber to the home) networks are also covered in this volume.

CATV originally stood for Community Access Television but is now more commonly known as Cable TV. CATV is one of the most common methods of transmitting television signals to a consumer’s home, using radio frequency signals transmitting through coaxial cable. More recently, CATV can also transmit over optical fiber, which utilizes light pulses to send and receive signals. CATV origins date back to 1924 when some cable broadcasting was done using cable in European cities. In 1948, community antennas were built where over-the-air signal reception was limited. The community antenna received the over-the-air signal and then transmitted it to households by cable. Today, CATV offers analog and digital channels (including high definition). Receiving digital channels requires a cable box for conversion.

cable television, is generally, any system that distributes television signals by means of coaxial or fiber-optic cables. The term also includes systems that distribute signals solely via satellite. Cable television systems originated in the United States in the late 1940s and were designed to improve the reception of commercial network broadcasts in remote and hilly areas. During the 1960s they were introduced in many large metropolitan areas where local television reception is degraded by the reflection of signals from tall buildings. Commonly known as community antenna television (CATV), these cable systems use a “community antenna” to receive broadcast signals (often from communications satellites), which they then retransmit via cables to homes and establishments in the local area subscribing to the service. Subscribers pay a specified monthly service charge in addition to an initial installation fee. Since the mid-1970s there has been a proliferation of cable-television systems offering special services. Besides bringing high-quality signals to subscribers, the systems provide additional television channels. Some of these systems can deliver 50 or more channels because they distribute signals occurring within the normal television broadcast band as well as nonbroadcast frequencies. A frequency-conversion device is connected to the television set of the subscriber to accommodate these signals of nonbroadcast frequencies. The increased number of channels allows expanded programming, including broadcasts from distant cities, continuous weather and stock-market reports, programs produced by community groups and educational institutions, and access to pay-TV program materials such as recent motion pictures and sports events not telecast by other broadcasters.

Another feature offered by more and more cable operators is two-way channel capability, which enables subscribers to communicate with programming facilities or information centers within the system. Using the cable connection, home viewers can, for example, participate in public opinion polls or call up various kinds of written and graphic materials (e.g., citations from reference books, concert schedules, and recipes). The latter feature is offered by systems called videotex, which were first introduced in Great Britain and West Germany. Two-way cable television systems increasingly allow subscribers with home computers to link up with computer networks, giving the subscribers access to data banks and permitting them to interact with other online users. Cable operators have also experimented with video compression, digital transmission, and high-definition television (HDTV).

In the United States, government deregulation of the cable-television industry in the 1990s allowed cable companies to experiment with telephony and allowed telephone companies to distribute cable-television programming.