Headends and Hubs
Simple cable plants that serve a single geographic area can be represented as having a single source for video signal, often a satellite, antenna, or other type of receiver. This source, called the headend, transmits data through a set of fiber nodes throughout the geographic region. Each fiber node then connects to a coaxial distribution network that delivers video to individual subscriber premises. Each fiber node is often analogous to a group of subscribers such as an apartment complex, city block, office building, or neighborhood.
Many MSOs, formed by the consolidation of several geographically disparate cable plants, face challenges when distributing information between local cable networks. To help solve the issues of distance without reducing the economies of scale present in large MSOs, a hierarchical network of distribution points is typically deployed, as shown in Figure 13-3. In a large MSO there usually exists a set of redundant headends where video signals are received. Satellite receivers, decoders, and other expensive equipment can serve many subscriber regions. These large headends are often called super headends and transmit data to several smaller headends for final delivery. Some distribution points, called hubs, are smaller than headends but serve as points at which the core video distribution network is connected through fiber transmitter/receivers to individual fiber nodes. Super headends, headends, and hubs together allow for a small set of signal sources to be used to serve a large number of subscribers in many areas, while maintaining a high level of television service availability.
Figure 13-3 Hierarchical Headend Architecture
Figure 13-3 Hierarchical Headend Architecture
- ^ □□□□ Redundant Headend
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