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by Dinesh Thakur Category: Computer Network

VDSL modems (Very high bit rate DSL) achieve speeds much higher than ADSL modems, but a few blocks away. Their capacity is several tens of megabits per second. VDSL modems can make the output of a PON (Passive Optical Network) to extend their connection to the user. PON being in ATM technology, VDSL modems must in this case accept the ATM frame.

The flow rates may be asymmetrical or symmetrical at the option of the user. According to the proposals of ANSI, the asymmetric flow should reach 6.4Mbit/s in the uplink direction and 52Mbit/s in the downlink direction for a distance of 300m. For a distance of 1000m, it should be possible to obtain half of the previous flow rates. The frequency band between 300 and 700kHz is devoted to the rising band. The part of the spectrum between 700kHz and 30MHz is used for the downlink band. The lower part of the spectrum is reserved for telephone speech or the passage of a narrow band ISDN interface.
As in the case of ADSL, a filter used to separate the telephone part, that goes to a telephone distribution frame, and the data part, that goes to the equivalent of a DSLAM, which may use the optical fiber of the PON to achieve the technical premises of the operator.
The enterprise network, at the exit of VDSL modem, can be of two types: ATM or Ethernet. In the first case, the ATM frames are directly sent over the network by an ATM switch connected to the modem. In the second case, an Ethernet hub is set up, complete with a router.

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