Coaxial cable distribution plant performance simulation

The CATV system delivers analog video signals from a centralized headend through a tree- and-branch fiber/coax network. That architecture is very cost effective for delivering broadcast video channels to a vast area. The introduction of interactive TV, data and telephony services requires an upstream link from customers to the headend. Although equipment for upstream transmission is available, CATV systems are primarily engineered for the delivery of one way analog broadcast TV programs. In this paper, issues related to two-way digital transmission through the coaxial cable distribution plant are examined. The objective is to establish a reliable computer modeling environment for the study and simulation of general and advanced transmission systems over the coaxial cable distribution plant. The discussions are focused on three general topics: the coaxial cable distribution plant transmission channel, the corresponding noise environment, and applicable transmission system architectures. Two- port network models are developed for the components (coaxial cable, taps, etc.) of the coaxial cable distribution plant. A realistic distribution plant channel model can be constructed based on these component models. The distribution plant noise level is analyzed based on thermal noise level, amplifier noise figure, and the funneling effect. The upstream ingress noise model is also developed. Three advanced transmission systems, adaptive transmitter, frame based equalization, and discrete multitone (DMT), are presented. End to end computer simulation results are presented using QPSK upstream.