Upstream transmissions in a two-way communications network are effected from subscriber terminals in upstream packets having one of a plurality of different separately acknowledgeable acknowledgment tags. Downstream acknowledgments of upstream messages are contained in CA packets multiplexed with product...http://www.google.de/patents/US5517502?utm_source=gb-gplus-sharePatent US5517502 - Upstream transmission using multiple transmission tags and downstream acknowledgements in conditional access packets
