mers could obtain cable service with the same TV sets they use to receive over-the-air broadcast TV signals, cable operators recreate a portion of the over-the-air radio frequency (RF) spectrum within a sealed cable line. The older coax-only cable systems typically operate with 330 MHz or 450 MHz of capacity (Ostergard, 1998). While the newer, more expensive hybrid fiber-optic/coax (HFC) systems can operate at 750 MHz or more (Ostergard, 1998). HFC networks combine both fiber-optic and coaxial cable lines. About half of the cable subscribers in North America are connected to HFC cable systems. HFC networks cost much less than a pure fiber-optic network, but provide many of fiber's reliability and bandwidth benefits. The fiber-optic portion of the HFC network is a star configuration where optical fiber feeder lines run from the cable head-end to groups of 500 to 2,000 subscribers (Van Matre, 1999). These groups of subscribers are called cable nodes or cable loops. A trunk-and-branch configuration of coaxial cable runs from the optical-fiber feeders to reach each subscriber. Because CATV systems were originally designed primarily to send signals downstream, only a small amount of the available bandwidth was allocated for upstream transmissions. There is very little need for upstream communication in CATV system that is used solely for television signal transmission. The allocated upstream bandwidth is a narrow 5 to 42 MHz band residing at the lower end of the cable TV RF spectrum (Barnes, 1997). Downstream cable TV program signals begin at 50 MHz, which is the equivalent of channel 2 for over-the-air television signals. Each standard television channel occupies 6 MHz of RF spectrum. So a traditional coaxial cable system with 400 MHz of downstream bandwidth can carry the equivalent of 60 analog TV channels, and a modern HFC system with 700 MHz of downstream bandwidth has the capacity for 110 channels (Salent, 1999). To deli...
