Page 20 - Broadband Internet The Basics for Next Generation Networks (NGN) in Telecommunication.

ADSL Access

Architecture

Illustrates the architecture ADSL

ADSL Access Architecture

ADSL transceiver unit centrally, ADSL transceiver remote unit (at the user), splitters

for providing both the telephone service (POTS – Plain Old Telephony Service) and
the ADSL service, and a multiplexer of DSLs called DSLAM (Digital Subscriber Line
Access Multiplexer) on the side of the operator.
Terminal (downlink), the telephone (POTS) signals and ADSL signals are
transferred to the users.

Splitters on both sides of the subscriber line (local loop) are used for frequency
multiplexing/demultiplexing of POTS and ADSL signals.
This is achieved by using a low pass filter with upper frequency boundary around 4

kHz (frequency range of the POTS subscriber line is 0–4 kHz).
The splitter is used to ensure the operation of POTS services even in case of failure
of ADSL service.
In the uplink direction, POTS and ADSL signals are multiplexed on the side of the
user and the signals are transmitted by the same twisted pair telephone line to the

ADSL network elements on the operator’s side.
On the side of the operator, multiplexed POTS and ADSL signals are transmitted to
the DSLAM, which first uses a splitter to separate (demultiplex) POTS and ADSL

signals.
There are two outputs of the splitter: one is for POTS signal and the other for ADSL
signal that is carried to an ADSL modem.
In the uplink direction aggregated traffic (by using concentrators) from all users
connected to the DSLAM is transmitted over IP (ATM-Asynchronous Transfer Mode)

backbone network which is connected to the Internet.
In the downlink direction the aggregated traffic is separated to individual ADSL
modems used for individual local loops.

The DSLAM splitters in this case are used to multiplex POTS and ADSL signals on
the subscriber line in the downlink direction.
At the end-user premises the received signal is demultiplexed by using splitter, so
POTS signals are transferred to a telephone device connected to the splitter while
ADSL signals are transferred to the user’s ADSL modem.

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