ZXDSL 9210 (V3.1) Broadband Universal Access Equipment Technical Manual
A-4
A.15 Very high-speed Digital Subscriber Line (VDSL)
The IP-based VDSL generally adopts QAM. It uses its unique
modulation/demodulation hardware to connect both ends of existing twisted pairs and
creates a 3-channel duct: A high-speed uplink channel, a high-speed downlink channel
(to subscriber premises), and a low-frequency channel (0kHz to 900kHz). The
low-frequency channel ensures that voice communication or ISDN still runs normally
even if the VDSL connection fails.
A.16 Video on Demand (VOD)
Also called the interactive television on demand system, VOD plays video programs as
required by users. This changes the situation in which the user watched television
programs passively.
VOD applications are the most striking vehicle on the broadband multimedia network
expressway. VOD can also be applied in the cell LANs or broadband networks of cable
TV.
The VOD system consists of three parts: Server terminal system, network system, and
customer terminal system.
VOD provides various media information flows for terminal users to expand people’s
information channels and enrich people’s spiritual life. It will play more and more
important roles in entertainment (in hotels, hospitals, and airports), company trainings,
remote market research, and advertisement services.