Cable Modem Termination System
A cable modem termination system (short: CMTS ) is a component that is usually in a cable headend ( English headend ), and data transmission , such as access to the Internet or Voice over Cable is the cable users and service. Depending on the expansion stage, a CMTS can serve up to 150,000 households (as of spring 2014).
Essential assemblies of a CMTS
MAC processor
The MAC processor is responsible for managing the cable modems .
Scheduler
In close coordination with the MAC processor, the scheduler is responsible for the management of the upstream channel resources.
WAN interface
The WAN interface forms the interface to the IP network. The interface can be implemented both as a router and as a bridge.
Downstream modulator
The downstream modulator or transmission unit modulates the data coming from the Internet onto a carrier and sends the data to the cable modem . The transmitter unit works in a frequency range of 88–860 MHz for DOCSIS and 88–1012 MHz for EuroDOCSIS.
Upstream demodulator
The upstream demodulator or receiver unit receives the data sent from the cable modem to the CMTS. Depending on the number of nodes or coax cells, which in turn depends on the size of the cable network and the number of cable modems operated, there are one or more upstream demodulators. The receiving unit works in a frequency range of 5–65 MHz according to the European standard (EuroDOCSIS) or in a frequency range of 5–42 MHz according to the US standard (DOCSIS).
Interconnection of downstream and upstream
In order to switch the number of upstreams and downstreams to one physical line, these are brought together via directional couplers ( English power combiners ).
literature
- Laubach, Mark E. / Farber, David J. / Dukes, Stephen D .: Delivering Internet Connections over Cable. New York 2001. ISBN 0-471-38950-1
- Keller, Andres: "Data transmission in the cable network", Heidelberg, 2005. ISBN 3-540-22501-3