Prototyping Quadrature Amplitude Modulation for Two-way Communication on CATV Networks

Recently, coaxial cable networks have received much attention in the context of interactive application [1,2]. In countries with a high penetration of CATV (e.g. Belgium >90%), the cable network forms a viable alternative to classical telephone networks. Envisaged applications are telephony, interactive television, home-shopping, video-ondemand, high-speed Web browsing, etc. The interactive nature of these services requires however two-way communication on a network that initially was only intended for a one-way broadcasting of television signals. What is aimed at now, is a low bit-rate upstream link (from the subscriber to the head-end station) and a high bit-rate downstream link (from the head-end station to the local subscribers). Particularly the first problem is challenging because very little is known about the upstream channel, and communication standards are still under development [3]. The projected frequency band for upstream communication is in the 5-25 MHz range, see also Figure 1. upstream