Hierarchical distribution of video with dynamic port allocation

A two-level distribution network for broadcast and interactive video is proposed. This two-level design replaces a large switch by a network of smaller switches, facilitating switch growth and enhancing switch reliability. The second-level switches (or the local switches) can be located at convenient places in their respective service districts, reducing the overall circuit mileage of the video distribution system. Video requests can be proposed independently by the local switches, rendering a large call processor at the central switch unnecessary. A traffic model for this network is formulated, and the optimum capacities of the central and local switches are determined for a given blocking requirement. Adding a small crosspoint switch between the two levels allows the output ports of the central switch to be dynamically allocated to the local switches. It is shown that this sharing of output ports can significantly reduce the size of the central switch