Upstream Cable Modems: the Intelligent Physical Layer

The most difficult challenge in upgrading CATV networks for broadband interactive multimedia services lies in the upstream communication path from the customer premises to the headend. This article points out that upstream cable modems are first-of-a-kind modems, which feature intelligent physical layer on top of the basic high speed modem functionalities. After introducing the topic we elaborate the design of a QAM upstream cable modem that combines high spectral efficiency with fast acquisition. The design will be treated, together with the advanced design methodology used for system description, simulation, verification and implementation.