DIGITAL SIGNAL BROADCASTING

摘要

A distribution network groups television program signals into service tiers. To provide these from unsynchronized MPEG streams without resynchronization, each stream, representing a single program signal is encapsulated into ATM cells with a virtual path(VP) identification of each ATM cell corresponding to the service tier and a virtual channel (VC) identification corresponding to the respective program signal. Payloads in cells having the same VP are scrambled using a scrambling key allocated to that VP and hence to the corresponding service tier, and are unscrambled by entitled subscribers using the scrambling key which is supplied to them individually using public/private encryption techniques.