Analog video and audio have long been the mainstream signals in cable systems. With the appearance of scrambled programming and addressable subscriber decoders, cable systems silently entered the digital world.
As in any communications system, the cable networks must contend with and compensate for imperfect or noisy signals. The analog world can tolerate noise much easier than the digital world. Moreover, analog methods for digital noise filtering are ineffective against errors in digital data channels. This paper examines digital error control, its effects on customers and equipment, and presents an overview of a few techniques used by equipment designers to improve data reliability and system performance.