27-06-2012, 11:44 AM
ATM Passive Optical Networks and Integrated VDSL
[attachment=25694]
INTRODUCTION
The combination of competition, resulting from
deregulation, and the opportunities provided by
emerging technologies is driving the evolution of
telecommunications networks to support new
high-bandwidth services. High-capacity optical
fiber systems are already commonplace in the core
network, where multiplexing and concentration
enable the infrastructure to be shared between
many customers. In the access network it is much
more difficult to share resources since it is a fundamental
requirement, for the final drop at least,
to provide a separate line for each customer. For
traditional national operators with a legacy network,
deploying optical fiber to each customer in
order to support high-bandwidth services would
involve a high capital outlay. One of the biggest
challenges currently facing network operators,
therefore, is to find a cost-effective solution for
supporting broadband access that enables the networking
jigsaw to be completed and facilitates the
transition to the broadband era.
VDSL
VDSL transmission uses advanced modulation
— carrierless amplitude and phase(CAP),
quadrature amplitude modulation (QAM), or
discrete multitone (DMT) — to support highbit-
rate transmission over twisted copper pairs
[4]. Bit rates of 6.5–13 Mb/s are likely to be sufficient
to support most high-bandwidth applications
in the near future, and 26–52 Mb/s gives
sufficient capacity for future upgrades.
VDSL can be used in either symmetric or
asymmetric mode. Symmetric operation is compatible
with the requirements of business customers,
where VDSL is used to provide legacy
leased-line-type services. Asymmetric operation
is more appropriate for residential customers,
where Internet, home shopping, and video on
demand applications will predominate.
ATM PON
In the ATM PON system as specified by the Full
Services Access Networks Consortium (FSAN), a
single optical fiber connects the exchange equipment
(optical line terminal, OLT) to an optical
splitter that supplies the signal to a number of
ONUs [6]. The ONUs may be placed at the customer
premises, but a more economic solution
may be to locate them in a street cabinet and use
VDSL over copper pairs for the final drop.
There has been great interest in ATM PON
systems from operators around the world, leading
to the setting up of FSAN. This consortium
consists of telecommunications operators and
suppliers; the aim is to generate common specifications
to encourage the introduction of full-service
access networks.
ATM PON AND VDSL FOR BROADBAND ACCESS
The combination of an ATM PON and VDSL
allows a flexible set of deployment options that
can be tailored to particular conditions and constraints.
VDSL used in conjunction with an
ATM PON allows broadband access to customers
sharing an optical fiber, together with
reuse, at least in part, of the local copper loop.
It is usually assumed that there will be a difference
between business and residential cabinets
in the number of customers they connect,
with a small number for business and a larger
number for residential. However, since residential
penetration is expected to be low initially,
the residential ONU will typically be located at
the wiring cabinet, which serves approximately
400 customers (FTTCab).
VDSL NTU FEATURES
The architecture of the VDSL NTU is shown in
. It can be seen that the architecture of the
VDSL NTU is similar to that of the VDSL line
card. The main difference between the two is
that the UTOPIA bus on the NTU is expanded
to accommodate the user interface drivers, such
as the ATM-25 switch port controller and the E1
interworking element.
[attachment=25694]
INTRODUCTION
The combination of competition, resulting from
deregulation, and the opportunities provided by
emerging technologies is driving the evolution of
telecommunications networks to support new
high-bandwidth services. High-capacity optical
fiber systems are already commonplace in the core
network, where multiplexing and concentration
enable the infrastructure to be shared between
many customers. In the access network it is much
more difficult to share resources since it is a fundamental
requirement, for the final drop at least,
to provide a separate line for each customer. For
traditional national operators with a legacy network,
deploying optical fiber to each customer in
order to support high-bandwidth services would
involve a high capital outlay. One of the biggest
challenges currently facing network operators,
therefore, is to find a cost-effective solution for
supporting broadband access that enables the networking
jigsaw to be completed and facilitates the
transition to the broadband era.
VDSL
VDSL transmission uses advanced modulation
— carrierless amplitude and phase(CAP),
quadrature amplitude modulation (QAM), or
discrete multitone (DMT) — to support highbit-
rate transmission over twisted copper pairs
[4]. Bit rates of 6.5–13 Mb/s are likely to be sufficient
to support most high-bandwidth applications
in the near future, and 26–52 Mb/s gives
sufficient capacity for future upgrades.
VDSL can be used in either symmetric or
asymmetric mode. Symmetric operation is compatible
with the requirements of business customers,
where VDSL is used to provide legacy
leased-line-type services. Asymmetric operation
is more appropriate for residential customers,
where Internet, home shopping, and video on
demand applications will predominate.
ATM PON
In the ATM PON system as specified by the Full
Services Access Networks Consortium (FSAN), a
single optical fiber connects the exchange equipment
(optical line terminal, OLT) to an optical
splitter that supplies the signal to a number of
ONUs [6]. The ONUs may be placed at the customer
premises, but a more economic solution
may be to locate them in a street cabinet and use
VDSL over copper pairs for the final drop.
There has been great interest in ATM PON
systems from operators around the world, leading
to the setting up of FSAN. This consortium
consists of telecommunications operators and
suppliers; the aim is to generate common specifications
to encourage the introduction of full-service
access networks.
ATM PON AND VDSL FOR BROADBAND ACCESS
The combination of an ATM PON and VDSL
allows a flexible set of deployment options that
can be tailored to particular conditions and constraints.
VDSL used in conjunction with an
ATM PON allows broadband access to customers
sharing an optical fiber, together with
reuse, at least in part, of the local copper loop.
It is usually assumed that there will be a difference
between business and residential cabinets
in the number of customers they connect,
with a small number for business and a larger
number for residential. However, since residential
penetration is expected to be low initially,
the residential ONU will typically be located at
the wiring cabinet, which serves approximately
400 customers (FTTCab).
VDSL NTU FEATURES
The architecture of the VDSL NTU is shown in
. It can be seen that the architecture of the
VDSL NTU is similar to that of the VDSL line
card. The main difference between the two is
that the UTOPIA bus on the NTU is expanded
to accommodate the user interface drivers, such
as the ATM-25 switch port controller and the E1
interworking element.