DOCSIS2.0: Where Upstream. Network and Application Needs Meet

摘要

Since its creation in 1997, the Data Over Cable Service Interface Specification (DOCSIS) has become the worldwide standard for data transmission over cable television infrastructures. Announced in December 2001, DOCSIS 2.0 significantly enhanced previous versions by defining an improved upstream channel physical layer (PHY). The upstream channel provides a data link from the cable subscriber's customer premises equipment (CPE) to the cable modem termination systems (CMTSs) at the cable operator's headend or hub site. DOCSIS 2.0 made no changes to the downstream channel PHY. It continues to provide the link between the CMTS and CPE at raw data rates up to 42.88 Mbps (55.62 Mbps for Euro-DOCSIS). The upstream PHY defined by DOCSIS 2.0 allows raw data rates up to 30.72 Mbps over a single channel. Compared to DOCSIS 1.0, this represents a 50 percent increase in spectral efficiency and 300 percent increase in throughput of a single carrier. DOCSIS 2.0 enhancements increase system capacity and provide cable operators with the potential to reduce the number of upstream ports at the CMTS and thereby improve statistical multiplexing performance. The upshot of these developments is that cable operators are able to reduce their cost per bit.