Zte ZXDSL 9210 (V3.1), Техническое руководство

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the bi-directional transmission rate of the VDSL can reach 10 Mbps. There may
be greater coverage when the line width becomes larger. Just like ADSL, VDSL
may share the same subscriber line with ordinary telephone services. Because of
small distance, the VDSL technology overcomes some ADSL problems such as
low line selection ratio and unstable rate.
As a trend of the ADSL technology, VDSL is the most advanced digital
subscriber line technology at present. The VDSL technology transmits signals
over a pair of twisted copper wires. With the frequency-division multiplexing
technology, the VDSL technology transmits uplink/downlink signals of
telephone and VDSL within different frequency bands. Low frequency bands
transmit ordinary telephone and narrowband ISDN services; medium frequency
bands transmit images of downlink channels or high-speed data information;
high frequency bands transmit information of uplink digital channels. Different
service signals at the transmitting end are modulated into different frequency
bands and then transmitted over twisted pair cables to the receiving end, where
they are demodulated and filtered to regenerate the original signals. Therefore,
as long as you configure a VDSL Modem at the central office and one at the
subscriber premises, telephone services can be added to channels by means of
POTS splitters and couplers. And the HDTV digital images or multi-channel
code-compressed MPEG images can be transmitted to the subscriber premises
via VDSL downlink channels.
Compared with the ADSL technology, the VDSL technology features simple
network construction scheme, convenient use and high transmission rate (10
times higher than that of ADSL). The transmission distance of VDSL is slightly
smaller than that of the ADSL technology. The interference between its
transmission code elements is greatly reduced due to shortened transmission
distance. This simplifies requirements for digital signal processing and reduces
transceiver costs as compared with those in the ADSL system. In the meantime,
because of its shorter transmission distance, the VDSL technology overcomes
some ADSL problems, such as low line selection ratio and unstable rate.
By combining the VDSL and Ethernet technologies, high-speed Ethernet signals
can be transmitted over ordinary telephone lines, and users can be connected to
Internet just by means of VDSL terminal adapters without rewiring the costly
Category 5 twisted pair. The combination of the VDSL and Ethernet