Information Technology Reference
In-Depth Information
Table 1. Comparison of ADSL, ADSL2+, VDSL1 and VDSL2
ADSL
ADSL2+
VDSL1
VDSL2
Downstream (Mbps)
8
25
100
100
Upstream (Mbps)
1
1
50
100
Range (feet)
>15000
>15000
5000
12000
ported by Schrier (Government Technology, 2009)
for the case of United States, the core of a na-
tional broadband strategy is fibre-optic cable in
every home and business place in the country.
According to Schrier's report, such a network is
an investment that would last 50 years or more.
The network would support many value added
services, such as high-definition video streaming,
video conferencing station, teleworking, etc.
Furthermore, fibre networks would also support
high-speed wireless connections, because wireless
access points can be added at any place the fibre
terminates (such as home and business place).
There are many variations concerning the
business model concerning the management of
the passive and active layers of the networks as
well as their services. The main emphasis is on
open access to in-building, last drop, last mile
fibres. Also there is a preference for point-to-
point topologies focused on competitive access
to passive components.
Furthermore, there is a technological debate
concerning optical networks. More specifically,
the telecommunications industry, having ten years'
experience with both active and passive optical
networks, debates about the pros and cons of
each solution. Optic FTTH can be implemented
with both Passive Optical Networks (PONs) and
Ethernet Point-to-Point (PtP) fibre optic networks.
A PON (Kramer, 2005) is a point-to-multipoint,
Fibre To The Premises (FTTP) network architec-
ture. This architecture uses unpowered optical
splitters to enable a single optical fibre to serve
multiple premises. The typical amount of premises
is from 32 to 128. A PON consists of an Optical
Line Terminal (OLT) at the service provider's
central office and a number of Optical Network
Units (ONUs) near end users. A PON configura-
tion uses less fibre and central office equipment
than point to point architectures. The standards
in this area are the following:
BPON (Broadband Passive Optical
Network).
EPON or GEPON (Ethernet PON).
GPON (Gigabit PON).
Table 2 compares BPON, EPON and GPON
(Marcheck, 2006; Li, 2005).
Except the above standards, presented in Table
2,there are two new standards, namely IEEE
802.3av-2009 and SCTE IPS910. IEEE 802.3av-
2009 (10G-EPON, 10 Gigabit Ethernet PON) has
been approved at September 2009. This standard
has been created by IEEE P802.3av 10G-EPON
Task Force (http://www.ieee802.org/3/av/). It is
backward compatible with 802.3ah EPON.
10GigEPON uses separate wavelengths for 10G
and 1G downstream traffic. 802.3av will con-
tinue to use a single wavelength for both 10G and
1G upstream with TDMA separation. SCTE
IPS910 (RFoG, RF over Glass) is an SCTE (So-
ciety for Cable Telecommunications Engineers,
http://www.scte.org/) Interface Practices Subco-
mittee standard in development for Point to
MultiPoint (P2MP) operations. Its proposed
wavelength plan is compatible with data PON
solutions including EPON, GEPON and 10G-
EPON. RFoG offers an FTTH PON like archi-
tecture for MSOs without having to select or
deploy a PON technology.
 
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