Cisco DNCS System Release 2.7 3.7 4.2 Guia Do Desenho
1-18
Introducing DOCSIS
4000358 Rev B
System Elements and Interfaces,
Continued
DHCT Interfaces
A DOCSIS-capable Explorer DHCT has an integrated cable modem and DHCT CPE.
When a DHCT is initialized in DOCSIS or Mixed DOCSIS/DAVIC mode, the cable
modem acts as a “front end” for communication to the DHCT. From the CMTS’s
perspective, the DHCT is the CPE “behind” the cable modem.
The following diagram shows a conceptual model of the interfaces in a DOCSIS-
The following diagram shows a conceptual model of the interfaces in a DOCSIS-
capable DHCT.
Communication Paths in the DOCSIS-Capable Explorer DHCT
Use of the communication paths differs with the DHCT’s communication mode. A
Use of the communication paths differs with the DHCT’s communication mode. A
Mixed DOCSIS/DAVIC-capable Explorer DHCT uses three receivers to
simultaneously receive analog and digital A/V services and DOCSIS and DAVIC
downstream data.
The DHCT has a QAM-16/QPSK transmitter to send data upstream. The three
The DHCT has a QAM-16/QPSK transmitter to send data upstream. The three
downstream receivers perform the following functions:
•
•
The primary in-band receiver tunes to analog and digital A/V services.
•
The secondary in-band receiver tunes to downstream DOCSIS high-speed data.
•
The downstream DAVIC QPSK receiver tunes to out-of-band data when the
DHCT is operating in DAVIC or Mixed DOCSIS/DAVIC mode.
The upstream transmitter sends data either to the DAVIC QPSK demodulator in
DAVIC mode or to the DOCSIS CMTS in either a Mixed DOCSIS/DAVIC or
DOCSIS mode.