A digital video system for the CATV industry

A ditigal pulse code modulator (PCM) system is proposed to implement long-haul video system for the CATV industry. A comparison is made between PCM system and wide-band FM system in terms of repeaterability versus additional occupied signal bandwidth. This is followed by a noise analysis of coaxial cable to determine the correct PCM format and bit information rate. An 80- megabit system is selected, which uses an 8-bit code in a four-level, eight-level, eight-level pulse sequence per video sample. The selected PCM system is then evaluated for its performance on both a long-haul cable system and a long-haul microwave system. Performance calculations are made on a 500-mile cable system in terms of error rate and its related video signal-to-noise ratio. Repeater spacings are computad for various configurations, including the replacement of the digital regenerators with analog amplifiers. Additional performance calculations are then made on a 3000-mile microwave system, including the effect of simultaneous Rayleigh fading.