DSL for Nxt Gen Broadband

DISSERTATION
DSL for Nxt Gen Broadband
Submitted in partial fulfillment of the requirements of
M.S. degree program in Telecommunication & Software Engineering
By
A.Anthony Praveen Thilak
ID. Number: 2008HZ97076
Under the Supervision of
Belal Shamim
Project Manager
Tech Mahindra Limited
Dissertation work carried out at
Tech Mahindra Ltd, Pune
BIRLA INSTITUTE OF TECHNOLOGY AND SCIENCE
Pilani (Rajasthan) India
December 2010

DSL for Nxt Gen Broadband 2008HZ97076
SEMB ZG629T DISSERTATION
DSL for Nxt Gen Broadband
Submitted in partial fulfillment of the requirements of
M.S. degree program in Telecommunication and Software Engineering
By
A.Anthony Praveen Thilak
ID No. 2008HZ97076
Under the supervision of
Belal Shamim
Project Manager
Tech Mahindra Limited
Dissertation work carried out at
Tech Mahindra Limited, Pune
BIRLA INSTITUTE OF TECHNOLOGY AND SCIENCE
PILANI (RAJASTHAN)
December 2010
Tech Mahindra | MS Dissertation Page 2

BIRLA INSTITUTE OF TECHNOLOGY AND SCIENCE, PILANI
CERTIFICATE
This is to certify that the Dissertation entitled ‘DSL for Nxt Gen Broadband’ and
submitted by A.Anthony Praveen Thilak ID No. 2008HZ97076 in partial fulfillment of
the requirements of SEMB ZG629T Dissertation embodies the bonafide work done by him
her under my supervision.
Signature of the Supervisor: _______________
Name: Belal Shamim
Designation: Project Manager
Date: __________

Acknowledgements
This project would not have been possible without the contribution of a few prodigious
hearts and especially my organization. I would like to express my greatest gratitude to the
people who have helped & supported me throughout my MS Dissertation and the course.
A special thank of mine goes to Tech Mahindra for providing the opportunity to work
with the IT industry and along with that helping me to complete my MS.
BITS: For providing the best curriculum with the current global market needs.
Belal Shamim for supervising my dissertation and giving all the aid, confidence,
encouragement and generous support.
Rajesh Mahajan and Rajesh Tarkunde for their suggestions, time, guidance and all the
support that they provided during the complete tenure of dissertation.
TELUS WH-DSL Team: The team which made sure my tenure of MS goes smoothly also
few suggestions to enhance the features.
I wish to thank my parents and friends for their undivided support and interest which
inspired and encouraged me to go my own way, without whom my MS Degree would not
have been reality. At last but not the least I want to thank God who made all things
possible...

BIRLA INSTITUTE OF TECHNOLOGY & SCIENCE, PILANI
SECOND SEMESTER 2009-10
BITS ID No. of Student: 2008HZ97076
Name of Student: A.Anthony Praveen Thilak
Dissertation Title: DSL for Nxt Gen Broadband
Name of Supervisor: Belal Shamim
Abstract:
This report reviews the modern developments in the principal broadband access
technologies and to assess the capabilities of those technologies to meet the future
requirements of the consumer. The Internet market continues to explode, consumer and
business demand for greater bandwidth and faster connection speeds, which has led to
several technological approaches. Prominent among them are digital subscriber line (DSL)
technologies, which are being installed at an unprecedented rate. Addressing one of the
most important topics to the telecom and information industries today, ‘DSL for Nxt
broadband’ provides an overview of DSL deployment and explores the forces driving the
rapid growth of broadband and high-speed access in homes and businesses. We will
compare and contrast different technologies available in providing ultimate broadband
connectivity to every end customer whether for a home based purpose or business utility.
The report provides an examination of regulatory constraints, technology hurdles, market
drivers and competing technologies, as it offers in-depth discussion about the future of
DSL.
This report proposes that broadband be defined beyond the traditional notion of a specific
type of network connectivity or minimum transmission speed. Rather, it proposes that
broadband be viewed as an ecosystem that includes its networks, the services that the
networks carry, the applications they deliver, and users.
Services like Internet Protocol Television (IPTV) require high downstream as well as
upstream transmission rates, which make cost-effective deployment of voice, data, and
high-speed Internet services a necessity. Digital Subscriber Line (DSL) service is one of
the most exciting technologies to come to market in the area of information access. The
concept is as elegant as it is simple - DSL achieves broadband speeds over ordinary phone
lines. G.SHDSL is a new international standard for single-pair, high-speed DSL, as defined
in the ITU-T Standard G.991.2. G.SHDSL is the technology for future where there is a
requirement for higher-speed bandwidth in both directions.

Table of Contents
1.0 Overview
2.0 Study of Broadband and its importance
2.1 Broadband Basics
2.2 Wired-line or Fixed Line Technologies
2.2.1 Hybrid Fiber Coax (HFC): Cable TV & Cable Modems
2.3 Wireless Technologies
2.4 Importance of DSL in future Broadband
3.0 xDSL
3.1 Introduction
3.2 Types of DSL and its significance
3.2.1 Asymmetric DSL (ADSL)
3.2.2 Symmetric DSL (SDSL)
3.2.3 ISDN DSL or IDSL
3.2.4 DSL Architecture
4.0 Stable and Sustainable DSL for Future
4.1 Overview: G.Shdsl - Symmetric High Speed DSL
4.2 Key Features
4.2.1 Symmetrical, High-Speed, Cost-Effective Bandwidth
4.2.2 Spectral Compatibility
4.2.3 Carrier Advantages
4.2.4 Signaling - Handshake Capability
4.2.5 Interoperability
4.2.6 Best replacement for T-1 or E-1 services
4.2.7 Alternative to Fiber
4.2.8 VoDSL
4.3 Architectural Changes
4.3.1 G.Shdsl WAN Interface Card for the Cisco 1700 Series
4.3.1.1 Features
4.3.1.1.1 Business-Class Security
4.3.1.1.2 Integrated Voice and Data over G.Shdsl
4.3.1.1.3 Support for Analog and Digital Voice Interfaces

4.3.1.1.4 Standards-Based Voice Technology
4.3.1.1.5 DSLAM Interoperability
4.4 Diverse Consumer Category
4.4.1 Business Users
4.4.1.1 Multi-line Voice over DSL (VoDSL)
4.4.1.2 Web hosting
4.4.1.3 Videoconferencing
4.4.1.4 VPN Services
4.4.1.5 Remote LAN Access
4.4.2 Residential Users
4.4.2.1 Extended reach for remote customers
4.4.2.2 Residential Gateway Access
4.4.2.3 Internet Gaming
4.4.2.4 Peer-to-Peer Services
4.4.3 MxU Feeder Applications
4.4.4 E1/T1 Replacement
4.5 Why G.Shdsl?
5.0 Conclusion
6.0 References
7.0 Glossary and Acronym List

List of Figures
S.No Description Page No.
Figure 2.1 Typical voice band modem link 13
Figure 2.2
Cable TV, Hybrid Fiber Coax (HFC) Network
Architecture
14
Figure 2.3 Network architectures for various forms of xDSL 15
Figure 2.5 Wireless Architecture – Block Diagram 18
Figure 3.1 DSL Reference Model – Block Diagram 22
Figure 3.2 ADSL reference model 24
Figure 3.3 ADSL Loop Architecture 25
Figure 3.4 DSL Network 26
Figure 3.5
DSL Architecture 28
Figure 4.1
Comparison of rates and distances with other DSL
technologies
31
Figure 4.2 Spectral Efficiency of G.Shdsl 32
Figure 4.3 Future Networks with G.Shdsl 34
Figure 4.4 Cisco WAN Interface Card 36
Figure 4.5 Simplified Leased Line Network with G.Shdsl 42
List of Tables
S.No Description Page No.
Table 2.1 xDSL bandwidth versus distance capabilities 16
Table 2.2 Types of fixed line technologies and their features 18
Table 2.3 WiMAX Bandwidth performance 19

1.0 Overview
Nurturing the development of a universally networked society connected over high-
capacity networks is a widely shared goal among both developed and developing countries.
High capacity networks are seen as strategic infrastructure, intended to contribute to high
and sustainable economic growth and to core aspects of human development. In the pursuit
of this goal, various countries have, over the past decade and a half, deployed different
strategies, and enjoyed different results.
Two broad definitions of “broadband” have emerged for the purpose of planning, the
transition to next-generation networks.
The first emphasizes is on the deployment of substantially higher capacity networks. This
sometimes translates into a strong emphasis on bringing fiber networks ever closer to the
home. High capacity is mostly defined in terms of download speeds, although some
approaches also try to identify a basket of applications whose supportability defines the
quality of the desired next generation infrastructure.
The second emphasis is on ubiquitous seamless connectivity. This approach accentuates
user experience rather than pure capacity measures. Just as the first generation transition
from dial-up to broadband included both the experience of much higher speeds, and the
experience of “always on,” so too next generation connectivity will be typified not only by
very high speeds, but also by the experience that connectivity is “just there”: connecting
anyone, anywhere, with everyone and everything, without having to think about it.
Thus providing a high capacity and ubiquitous network connectivity for every end user
irrespective of the consumer size is the primary call. ‘DSL for Nxt Gen Broadband’ is an
in-depth resource designed to explain the current available architecture of broadband
technologies and the requirements of the future generation for a sustainable data
transmission.
The methodology observed to attain such a goal and propose a suitable technology is listed
below.
• Review the available broadband architecture and study its types
• Impact of DSL technology in current broadband structure
• Explore the various DSL technologies available
• Emphasize the importance of DSL over other technologies
• Design the parameters for the proposal of a sustainable broadband technology
• Identify and elaborate the best DSL for future broadband

G.SHDSL, known as Single-pair High-speed Digital Subscriber Line (ITU) or Symmetric
High-bit rate Digital Subscriber Loop (DSL Forum), is used to cost-effectively transport
broadband services over a single copper pair or over bonded multi-pairs. G.SHDSL is
suited for all voice embedded data transmission services and this report strives to justify the
fact that G.SHDSL is the best DSL Broadband technology for future considering several
parameters which prove to satisfy all the modern day requirements.

2.0 Study of Broadband and its importance
“Change in technology is happening every moment.
The world is changing as the cellular phone becomes the computer”
Whether reading the latest news on an iPad, tweeting on an HTC Incredible or watching
video clips on YouTube, our collective need for bandwidth is seemingly insatiable and this
isn’t going to change anytime soon. Broadband has taken our Internet experience much
beyond downloads and give you access to a lot of useful applications and is a necessary
infrastructure that allows businesses to participate in the global economy. Businesses are
less likely to locate or grow without affordable broadband.
According to a recent study, the average broadband connection is now generating 14.9 GB
of Internet traffic per month, up 31 percent from last year when it was 11.4 GB per month.
And while a majority of this traffic is coming from online video-streaming not P2P, the
trends show that we are using the Internet for more than just that. Communication services
such as Skype only increase the daily usage of the Internet. Add to the mix addictive sites
like Facebook, Zynga and Groupon, and you can see that the Internet is becoming deeply
embedded in our lives. There is an interesting dynamic of the web, the peak traffic that is
equivalent of prime time on television. Peak-hour Internet traffic is 72 percent higher than
Internet traffic during an average hour. In an average day, Internet “prime time” ranges
from approximately 9 p.m. to 1 a.m. (for the local time zone) around the world.
Here are some of the key findings from the study.
• Peer-to-peer (P2P) file sharing is now 25 percent of global broadband traffic,
down from 38 percent last year.
• Video, which includes streaming video, Flash, and Internet TV — represents 26
percent, compared to 25 percent for P2P.
• Over one-third of the top 50 sites by volume are video sites.
• Contrary to popular belief, none of the top 50 global web sites (by traffic
volume) featured explicit adult content.
• Ten of the top 50 sites were associated with software updates and downloads
(security and application enhancements).
Cisco is predicting that video calling will exceed 1 percent of consumer internet traffic by
end of 2010; Apple’s FaceTime is only going to help achieve this goal. In summary, I think
all these numbers can be tied to my initial assertion: Broadband is the magical driver of all
things on the Internet. Thanks to broadband, everything, including the web, changes. Such
a powerful technology has its own history and importance.

2.1 Broadband Basics
The public switched telephone network (PSTN) was originally designed to carry voice
signals, and the bandwidth of these signals was limited to the frequency range from
approximately 200 Hz to 3.4 kHz (with some variations, depending on location). Although
a voice signal is analog by its nature, digitization of many of the links in the telephone
network is very common now, particularly in the trunk network between telephone
company central offices (COs) which is heavily based on optical fiber and microwave
links. For the most part, a voice signal travels in analog form from the originating user to
the local CO across a copper twisted pair (the local loop), where it is digitized by a codec
(“coder/decoder”) and then it is transmitted over the trunk network to the CO serving the
user at the other end. Here it is converted from digital form back to analog by another
codec before being transmitted across this user’s local loop to the receiving telephone.
The 1950s saw the introduction of voice band modems for the purpose of transmitting data
across the PSTN. Early modems (for example, the Bell 103) transmitted at low bit rates
(300 bits per second (bit/s)) using frequency shift keying (FSK) modulation. Modem
technology quickly developed to provide higher bit rates and also enabled full-duplex
transmission. For example, the CCITT (now ITU-T) V.22 standard provided for
communication at 1200 bit/s, and the later V.22bis recommendation extended this to 2400
bit/s. Subsequent developments led toV.32 (9600 bit/s),V.32bis (14, 400 bit/s), and
laterV.34, which uses very sophisticated signal processing techniques to achieve bit rates
up to 33.6 kbit/s, with various fall-back options. In the late 1990s, pulse coded modulation
(PCM) modems were developed and standardized as ITU-T RecommendationV.90. This
recommendation provides for up to 56 kb it/s in the downstream direction (from the CO to
the user), where an all-digital path is assumed to exist between the data source and the CO
serving the user. This is a reasonable assumption in practice, because many information
sources, such as Internet service providers (ISPs), have direct digital connections to the
PSTN. InV.90, the upstream direction of transmission uses V.34 modulation, limiting
upstream bandwidth to 33.6 kbit/s. The figure below shows a block diagram of a typical
voice band modem communication link.
However, there is a limit to what is achievable within the existing PSTN framework with
its limited bandwidth, users (both residential and commercial) continue to demand ever-
increasing bit rates for many different applications, so the local loop of the PSTN as it
stands has essentially become a bottleneck. Residential users demand faster transmission
rates for Internet access, and the multitude of applications it enables (Web browsing, e-
mail, online shopping and gaming, and many other applications).
User requirements for higher-speed local access have driven the need for transmission
systems capable of providing transmission speeds of hundreds of kilobits, or even
megabits, per second which raises the necessity of Broadband technology. There are
several modes of broadband services, basically different technologies involved in bringing
broadband to the end customer.

Figure 2.1 Typical voice band modem link
The term broadband refers to a telecommunications signal of greater bandwidth, in some
sense, than another standard or usual signal (and the broader the band, the greater the
capacity for traffic). On an extensive view broadband refers to telecommunication that
provides multiple channels of data over a single communications medium, typically using
some form of frequency or wave division multiplexing. Broadband is often called high-
speed Internet, because it usually has a high rate of data transmission relative to dial-up
access over a modem. In general, any connection to the customer of 256 Kbit/s (0.256
Mbit/s) or more is considered broadband Internet.
Broadband solutions can be classified into two main groups.
Wired-line or Fixed Line Technologies
Wireless Technologies
2.2 Wired-line or Fixed Line Technologies
The fixed line solutions communicate via a physical network that provides a direct “wired”
connection from the customer to the service supplier. The best example of this is the plain
old telephone system (POTS) where the customer is physically connected to the operator
by a pair of twisted copper cables. Fixed line broadband technologies rely on a direct
physical connection to the subscriber’s residence or business. Many broadband
technologies such as cable modem and xDSL (digital subscriber line) have evolved to use
an existing form of subscriber connection as the medium for communication. Cable modem
systems use existing hybrid fiber-coax Cable TV networks. xDSL systems use the twisted
copper pair traditionally used for voice services by the POTS. In general, all these
aforementioned technologies strive to avoid any upgrades to the existing network due to the
inherent implications for capital expenditure.

2.2.1 Hybrid Fiber Coax (HFC): Cable TV & Cable Modems
Digital cable TV networks are able to offer bi-directional data transfer bandwidth in
addition to voice and digital TV services. Using a cable modem in the customer premise
and a Cable Modem Termination System (CMTS) at the network’s head-end, the well-
established HFC standard, DOCSIS 1.1, provides for a data transmission service with
speeds of up to a 30 Mbps on one 8 MHz channel (6 MHz is used in the US) using QAM
modulation techniques. The recently proposed HFC standard, DOCSIS 3.0, may be capable
of 100 Mbps of bandwidth per channel in the near future. Data transmission over Cable TV
networks has the advantage that where the coaxial cable is in good condition and RF
amplifiers exist (or can be installed) to extend the network reach, relatively high
bandwidths can be provided to the end user without distance limitations. However, a cable
TV broadband service relies on shared network architecture; this result in the limitation that
the amount of bandwidth delivered to the customer is dependent on how many people share
the connection back to the head-end. Typically a service of 1 Mbps downstream and 128
kbps upstream is offered (more recently a 3-5 Mbps downstream service has become
available), but up to 1000 users may share the connection to the head-end and so the actual
bandwidth obtained can be lower due to excessive loading.
Fig
ure 2.2 Cable TV, Hybrid Fiber Coax (HFC) Network Architecture
2.2.2 Digital Subscriber Line (xDSL)
DSL technology uses the existing copper telephone infrastructure to facilitate high speed
data connections. DSL equipment achieves this by dividing the voice and data signals on
the telephone line into three distinct frequency bands. For example with Asymmetric DSL
(ADSL), voice conversations are carried in the 0 to 4 KHz (3 KHz in U.S.) band (as they
are in all POTS circuits), the upstream data channel is carried in a band between 25 and

160 KHz and the downstream data channel begins at 240 KHz and goes up to about
1.1MHz. Complex data modulation techniques enable data rates of up to 12Mbps. DSL
access modules (DSLAMS) are placed in the local exchange or at nodes in the access
network to transmit and receive the data signals. However xDSL has the disadvantage that
it is a distance-sensitive technology. As the connection length from the user to the DSLAM
increases, the signal quality decreases and the connection speed goes down.
There a number of different DSL technologies, the key ones are ADSL, SDSL (symmetric),
VDSL (Very high bit rate DSL) and ADSL2+. More recently, ADSL2++ has been
introduced. ADSL technology can provide maximum downstream speeds of up to 12 Mbps
and upstream speeds of up to 640 Kbps at a distance of about 0.3 km. The ultimate distance
limit for ADSL service is 5.4 km, but at this distance transmission speeds are limited to
approximately 500 Kbps. For business applications it is possible to get Symmetric DSL
(SDSL) which allows high speed download and uploads, but again the maximum available
bandwidth is around 3Mbps. With VoD requiring at least 3Mbps and HDTV requiring
approximately 15 to 20 Mbps, clearly neither ADSL or SDSL can meet the bandwidth
requirements for HDTV and may well struggle to provide VoD and/or a basic video service
over the full network.
Figure 2.3 Network architectures for various forms of xDSL
VDSL and the more recently introduced ADSL2+ can offer bandwidths high enough to
allow video services. VDSL can offer up to 52 Mbps, but only over very short distances.
Therefore in order to offer VDSL to a significant proportion of the population the
DSLAMs need to be relocated to street cabinets (closer to the subscriber) and fiber feeds
installed to the street cabinets. The cost of this upgrade and laying fiber to the cabinets
means that VDSL is prohibitively expensive relative to ADSL technology and VDSL
deployments have been limited.

Table 2.1 xDSL bandwidth versus distance capabilities
ADSL2+ however, is standardized and allows transmission of sufficient bandwidth for
some video services, over greater distances than VDSL, without the need for DSLAM
relocation. As a result ADSL2+ is becoming the upgrade path for operators wishing to
improve upon their standard ADSL service offerings.
Figure 2.4 End-to-end networks
The below tabulation explains briefly the features of every different wired line / fixed line
technology, among which technologies like VDSL, BPL and FTTH are for high end
customers of greater bandwidth requirements.

Technology Spectrum UsageCapacity Max Range Advantages Limitations
Hybrid
Fiber Coax
(HFC):
Cable TV
& Cable
Modems
7-860MHz (7-
550 MHz) 6MHz
per Channel
40 Mbps per
channel, upgrade
path to 50 Mbps
proposed.
Typical bandwidth
per user 0.5 – 3
Mbps
Amplifiers are
installed to
extended range.
This is cost
effective
typically up to
100 Km.
Uses existing
cable TV
network.
Limited
bandwidth per
channel,
bandwidth is
shared by many
users, very low
upstream data
rates.
ADSL Up to 1.1MHz 12 Mbps @ 0.3Km
8.4Mbps @ 2.7Km
6.3Mbps @ 3.6Km
2 Mbps @ 4.8Km
1.5Mbps @ 5.4Km
Max 5.4 Km Uses existing
POTS network
Limited
bandwidth
which is
distance
sensitive, lower
upstream rates
VDSL Up to 1.1MHz 52 Mbps @ 0.3Km
26 Mbps @ 0.9Km
13 Mbps @ 1.3Km
Max 1.3 Km Mainly uses
existing POTS
network
Limited
distance;
requires fiber
feeds.
Bandwidth is
highly distance
sensitive.
ADSL 2+ Up to 2.2MHz 26 Mbps @ 0.3Km
20 Mbps @ 1.5Km
7.5Mbps @ 2.7Km
Max 2.7 Km Uses existing
POTS network
Bandwidth is
highly distance
sensitive.
BPL 1-30 MHz Max 200 Mbps
Typical 2-3 Mbps
1-3 Km Uses existing
power lines
Expensive
power line
upgrades
FTTH THz Up to 1Gbps per
channel per fiber.
20 Km Relatively
unlimited
bandwidth
Requires new
fiber access
network overlay
Table 2.2 Types of fixed line technologies and their features
2.3 Wireless Technologies

In general, wireless broadband refers to technologies that use point-to-point or point-to-
multipoint microwave in various frequencies between 2.5 and 43 GHz to transmit signals
between hub sites and an end-user receiver. While on the network level, they are suitable
for both access and backbone infrastructure, it is in the access network where wireless
broadband technology is proliferating. As a consequence, the terms “wireless broadband”
and “wireless broadband access” are used interchangeably. There are a wide range of
frequencies within which wireless broadband technologies can operate, with a choice of
licensed and unlicensed bands. Generally speaking, higher frequencies are advantaged
relative to lower frequencies as more spectrum is available at high frequencies and smaller
antennas can be used, enabling ease of installation. Higher bandwidth systems use
frequencies above 10 GHz. However, high frequency systems are severely attenuated by
poor weather conditions (e.g. rain or fog) and therefore suffer from distance limitations.
Figure 2.5 Wireless Architecture – Block Diagram
Wireless technologies can be broadly categorized into those requiring line-of-sight (LOS)
and those that do not. Point-to-point microwave, Local Multipoint Delivery System
(LMDS), Free Space Optics (FSO), and Broadband Satellite all require line-of-sight for
reliable signal transmission while cellular technologies like GSM, CDMA, 3G, WiFi,
WiMAX, and fixed wireless broadband technologies like Multipoint Multichannel
Distribution System (MMDS) require no line-of-sight between the transmission hub and
receiving equipment. Clearly, the non-line-of-sight (NLOS) technologies provide
advantages in terms of ease of deployment and wider network coverage.
Wireless may seem like the obvious choice for a (fixed position) local access technology,

because it does not require the installation of a transmission medium. This can be
particularly important in developing countries, where the level of installed communications
infrastructure significantly lags behind that in developed countries.
However, there are a number of issues that have hampered the deployment of wireless local
access. For example, the available radio spectrum is becoming increasingly congested,
forcing broadband wireless access systems to move to higher frequencies, where line-of-
sight (LOS) operation may become necessary. This applies, for example, with the local
multi-point distribution system (LMDS) and similar systems operating between 20 and 40
GHz. Furthermore, there are still challenges and costs associated with deploying the
necessary infrastructure where it is required, for example, planning issues associated with
location of base stations, as well as the challenge of developing user-friendly customer
premises equipment (CPE).
Table 2.3 – WiMAX Bandwidth performance
Table 2.3 shows that standard WiMAX equipment aims to deliver between 8 and 11 Mbps
of upstream and downstream bandwidth per channel but only over a range of 1 to 2 km for
NLOS operations. Equivalent indoor self-install standard WiMAX solutions aim to achieve
similar bandwidths but only over 0.3 to 0.5 km of range. The latest generation of full-
featured WiMAX equipment aims to deliver a bidirectional bandwidth of up to 11 Mbps
over 3 to 9 km with NLOS capability and the same bandwidth over a 1 to2 km range for
NLOS indoor self-install applications.
Systems operating at lower frequencies, where non-LOS transmission is more reliable,
have also been deployed (e.g., microwave multi-point distribution system (MMDS) in the
region of 2–4 GHz), though greater bandwidth efficiency may be required to increase bit
rates. On the other hand, fading and multi-path propagation make it more difficult to use
higher-order modulation to achieve the necessary spectral efficiency. At the same time, the
fact that the transmitter and receiver are in fixed locations means that directional (and
multiple) antennae may be used to increase performance.

Each broadband technology has its own unique characteristics, including advantages and
disadvantages. In some deployment scenarios, the choice of technology is obvious, being
driven by factors such as the nature if the terrain or expense of rights of way (ROW).
However, in many other circumstances, the choice is not exactly simple, and it depends
very much on the type of services to be provided, the penetration rate, the availability of
alternatives, and other economical and technical considerations. In the below table, we
compare the major broadband technologies on spectrum usage, capacity, coverage/reach,
advantages and limitations.
2.4 Importance of DSL in future Broadband
The demand for bandwidth has led to several technological approaches developed to
provide broadband access to business and residential customers, and though DSL has
numerous advantages, other means of obtaining high-speed access might be preferable. The
main aspiration is to provide broadband access to as many people as possible, DSL as a
technology wins the market in all the features. Considering a few parameters as listed
below, DSL proves to be better among other technologies.
 Speed
 Cost
 Availability
 Cost of Service
 Speed: Video and other applications are continuing to drive up broadband speed
requirements, and data service providers have to stay ahead of the curve unless they want
to get leapfrogged by the next killer app.
 Cost: The cost of upgrading networks run into the $billions. While enterprise
customers are willing to pay a premium for high speeds, there isn't a lot of price/speed
elasticity among consumers. Cost is a factor that could both slow network expansion and
broadband adoption.
 Availability: Broadband service is always slowest to reach less populated areas,
due to economies of scale. The most popular broadband options aren't available in some
rural communities. This will drive demand for technologies that serve these areas, such as
satellite and most likely WiMAX in the future. DSL will break these shackles and will be
available for every end user irrespective of the geographical nature.

 Quality of Service: For some applications, service disruption is just not acceptable.
Wireline broadband technology has always had an advantage over wireless here, but there
are differences even among different wireline technologies (i.e. DSL and dedicated lines
generally get better marks from customers than cable, although reliability is very similar)
Some broadband technologies, like satellite and EV-DO, are reaching the upper edge of
their theoretical speeds, while fiber, cable, and WiMAX have a long way to go before
maxing out.
3.0 xDSL
Digital Subscriber Line (DSL) is a broadband connection that uses the existing telephone
line. DSL provides high-speed data transmissions over the twisted copper wire, the so-
called “lastmile” or “local loop” that connects a customer’s home or office to their local
telephone company Central Offices (COs). It provides greatest loop coverage for the lowest
cost and enables high speed digital transmission on conventional telephone lines. DSL
connection transmits data in a frequency band above voice telephony which manages to

squeeze more information through a standard phone line -- and lets you make regular
telephone calls even when you're online.
3.1 Introduction
The range of DSL technologies is quite broad, and this breadth can be somewhat confusing
to the uninitiated. This section briefly describes the different types of DSL technology. In
simple terms, DSL technologies can be subdivided into two broad classes:
• Symmetric. Same data rates transmitted in both directions (downstream and upstream).
This is a typical requirement of business customers.
• Asymmetric. In this case, there is asymmetry between the data rates in the downstream
and upstream directions, with the downstream data rate typically higher than the upstream
(usually appropriate for applications such as Web browsing).
This division is quite crude however, and, to confuse matters, some of the various
technologies are capable of both asymmetric and symmetric operation. To further
complicate things, many DSL systems are capable of multi-rate operation, which adds a
further dimension of variability.
Point to note is that symmetric DSLs generally use baseband modulation such as pulse
amplitude modulation (PAM), where the bandwidth of the transmitted signal extends all the
way down to 0 Hz (notwithstanding the effect of any coupling transformers or other
filtering), whereas the asymmetric technologies generally use pass band modulation, which
avoids the lowest frequencies that would be used by voice band services such as analog
telephony.
Figure 3.1 DSL Reference Model – Block Diagram
This is generally because the residential users who would typically make use of asymmetric
DSLs still need to be able to make use of “lifeline” POTS, even when the DSL service is
unavailable (for example, due to a power failure in the customer premises).
A block diagram of a typical DSL configuration is shown in the above Figure. Note that the
term “digital subscriber line” generally refers to the analog local loop between each
customer premises and its local central office, and a DSL modem is required at each end of
the loop. Furthermore, the DSL service can be regarded as being provided by means of an
“overlay” network that is not part of the normal switched telephone network. This means

that the service provider CO needs to be able to separate the DSL service from the POTS
service, with the voice service being sent onward by means of the ordinary trunk network,
whereas the data carried by the DSL may be sent to a data network that is separate from the
switched voice network. The CO will generally provide DSL service to the user premises
using a DSL access multiplexer (DSLAM), the DSLAM usually contains many DSL
modems serving multiple customers.
The key point to note here is that in essence, a “digital subscriber line” exists on a single
local loop between the customer premises and the central office, unlike the voice band
modem case where, technically, the modem link includes two local loops (plus the network
elements in between). All varieties of DSL have a specified environment in which they are
expected to operate reliably. This specified environment includes the types of loops over
which the service is expected to operate, as well as a definition of the expected noise
environment (including impulse noise and crosstalk). DSL technologies that have been
developed in recent times are also expected to be spectrally compatible with services
already in use in the loop plant, in the sense that the presence of the new DSL will not
unduly degrade the performance of existing services. The modulation techniques most
commonly used and the parameters define a quality service to the end customers, in
particular, the signal-to-noise ratio (SNR) required for these modulation techniques to
operate with some specific probability of error is discussed in detail. These SNR
requirements impose fundamental performance limits that can be achieved in practical DSL
systems. Basic DSL performance requirements are usually specified in terms of acceptable
bit error ratio (BER) with specified noise margin while operating in certain conditions. The
BER usually used in DSL development is 10^-7, and the noise margin is usually either 5 or
6 dB. The noise margin specification means that the system is expected to operate at an
actual BER no greater than the specified BER when the noise is increased by a level equal
to the noise margin. Typically, the specified test conditions mirror anticipated worst-case
conditions. The inclusion of the noise margin means that DSL systems generally operate in
normal conditions with BER much less than 10^-7, and it also allows for reliable operation
when the noise conditions are worse than normal (e.g., due to the presence of unexpected
sources of noise).
3.2 Types of DSL and its significance
General categories of DSL: symmetric and asymmetric. Symmetric DSL provides the same
service bit-rate in both upstream and downstream direction. Asymmetric DSL (ADSL)
provides more downstream bit-rate (from the network to the user) than upstream bit-rate.
DSL can be divided mainly into three types, Asymmetric DSL (ADSL), Symmetric DSL
(SDSL) and ISDN digital subscriber line (IDSL).
3.2.1 Asymmetric DSL (ADSL)

ADSL (Asymmetric Digital Subscriber Line) is a technology for transmitting digital
information at a high bandwidth on existing phone lines to homes and businesses, which is
capable of providing data rates of up to 8 Mbit/s downstream (i.e., toward the consumer)
and up to 896 kbit/s in the upstream direction. As with symmetric DSL, ADSL technology
has been standardized by the various regional and global standardization bodies; both DMT
and single-carrier technologies were originally proposed for ADSL, though the standards
are based on DMT modulation. The North American recommendation can be found in
[ANSI T1 1998], and the European recommendation developed by ETSI TM6 is in [TS 101
388 2002]. Furthermore, ITU-T has also created Recommendation G.992.1 (“G.dmt”)
[ITU-T G.991.1 1999] to cover this type of “full-rate” ADSL, incorporating many of the
features of the regional standards.
Figure 3.2 ADSL reference model
Delivery of ADSL services requires a single copper pair configuration of a standard voice
circuit with an ADSL modem at each end of the line, creating three information channels –
a high speed downstream channel, a medium speed upstream channel, and a plain old
telephone service (POTS) channel for voice. Data rates depend on several factors including
the length of the copper wire, the wire gauge, presence of bridged taps, and cross-coupled
interference. The line performance increases as the line length is reduced, wire gauge
increases, bridge taps are eliminated and cross-coupled interference is reduced.
Transmission uses one pair of wires. Unlike regular dialup phone service, ADSL provides
continuously-available, "always on" connection. ADSL is asymmetric in that it uses most
of the channel to transmit downstream to the user and only a small part to receive
information from the user.
3.2.1.1 Physical connectivity
At the central office, a main distribution frame collects the cables from many subscribers
and uses a splitter to distribute the data traffic to a DSLAM and routes the regular
telephone traffic over an E1/T1 connection to the public switched telephone network
(PSTN). The DSLAM mixes DSL services from different subscribers into ATM virtual
circuits. Often, a DSLAM concentrator is used in cases where an ILEC or CLEC has many
DSLAMs distributed over a large geographic area. The DSLAM contains ATU-Cs where
ADSL signals are multiplexed onto a high-speed interface connected to an ATM network.
This ATM network provides access to the internet through internet service providers

(ISPs). The DSL provider bundles the traffic destined for a given ISP and sends it over an
E3/T3 or an STM-1/OC-3c connection.
Figure 3.3 ADSL Loop Architecture
A broadband remote access server (BRAS) terminates the subscriber’s IP session and
directs it to the Internet backbone. In most cases, POTS splitters at the network interface
device (NID) and central office allow the copper loop to be used simultaneously for high-
speed ADSL and POTS service. The POTS channel is split from the ADSL channel by a
passive, low-pass/high-pass filter that separates the signals – low frequency for POTS and
high frequency for ADSL – routing each to a separate wire pair. The splitter also protects
the ADSL signal from POTS transients originating from handsets going on-hook and off-
hook. ADSL service may be installed without using a “splitter” at the NID. Instead, micro
filters are placed in-line with the phone jack at each telephone location. While this
configuration sacrifices some level of performance, it allows the customer to self-install the
CPE. Typically, micro filters are packaged with the ADSL modem in a self-install kit.
This type of DSL connection gives the consumer more bandwidth when it comes to
downloading as compared to uploading. Because of the reduced upload rate, Internet
service providers are able to offer greater bandwidth in terms of downloading. This
technology is best used by residential customers since they normally use more bandwidth
for downloading. The normal rate for downloading is at 5 Mbps and 1 Mbps when
uploading. Examples of Asymmetric DSL are: RADSL, VDSL and ADSL/G.Lite.
• RADSL (Rate-Adaptive DSL) - is an ADSL technology from Westell in which
software is able to determine the rate at which signals can be transmitted on a given
customer phone line and adjust the delivery rate accordingly. Westell's FlexCap2 system
uses RADSL to deliver from 640 Kbps to 2.2 Mbps downstream and from 272 Kbps to

1.088 Mbps upstream over an existing line.
• VDSL (Very high data rate DSL) - is a developing technology that promises much
higher data rates over relatively short distances (between 51 and 55 Mbps over lines up to
1,000 feet or 300 meters in length). It's envisioned that VDSL may emerge somewhat after
ADSL is widely deployed and co-exist with it.
3.2.2 Symmetric DSL (SDSL)
SDSL is a form of Digital Subscriber Line (DSL) service that provides equal bandwidth for
both uploads and downloads. Originally developed in Europe, SDSL was one of the earliest
forms of DSL to not require multiple telephone lines, and is based on 2B1Q technology,
essentially a single-pair version of HDSL capable of operation at a number of different bit
rates. Symmetric DSL connections are more popularly used in business because they have
higher requirements or needs when it comes to data transfers as compared to home Internet
users. Normally, Symmetric DSL can offer up to 1.5 Mbps both for download and
upload. Examples of Symmetric DSL are: HDSL, SDSL/G-Lite and SHDSL.
Figure 3.4 DSL Network
SDSL possesses all of the common characteristics of DSL, including an "always on"
combination of voice and data services, availability limited by physical distance, and high
speed access compared to analog modems. SDSL supports data rates up to 3,088 Kbps.
HDSL (High bit-rate DSL) - is the earliest variation of DSL to be used for wideband digital
transmission within a corporate site and between the telephone company and a customer.
The main characteristic of HDSL is that it is symmetrical: an equal amount of bandwidth is
available in both directions. For this reason, the maximum data rate is lower than for
ADSL. HDSL can carry as much on a single wire of twisted-pair as can be carried on a T1
line in North America or an E1 line in Europe (2,320 Kbps). UDSL (Unidirectional DSL) -
is a proposal from a European company. It's a unidirectional version of HDSL.
SDSL is faster than ADSL. The bandwidth of SDSL can be as high as 7 mbps in both
directions while ADSL can have the bandwidth of up to 1 mbps from uploading side.
SDSL is a good choice for the heavy loaded high speed data transferring from both the
direction but it more expensive than ADSL and its speed also vary according to distance. It

can run over one pair of copper wire within maximum 3 kilometer. SDSL (Single-line
DSL) - is apparently the same thing as HDSL with a single line, carrying 1.544 Mbps (U.S.
and Canada) or 2.048 Mbps (Europe) each direction on a duplex line. It is considered to be
the "business grade" DSL because of its symmetric speeds. SDSL is slower than ADSL but
usually marketed with Service Level Agreement (SLA) such as the network will be
guaranteed up for 99.5%, and there will be a 24-hour response time for every problem.
3.2.3 ISDN DSL or IDSL
Another type of DSL Internet Service is the so called IDSL which is actually a hybrid DSL
(ISDN technology) that was designed at the same time when the other forms of DSL
Internet technologies were made. IDSL however is not used that much because of the low
speeds that it offers, actually only a maximum of 128 Kbps.
3.2 DSL Architecture
A typical DSL service architecture is illustrated in Figure 3.5. Basically DSL is the last
mile coverage of the complete telecommunication network; the plain components are
shown below.
When deployed directly from the central office (CO), as is done with most ADSL
deployment today, the achievable data rate is typically limited by the loop length of the
twisted pair. The advantage of this architecture is complete re-use of existing copper
infrastructure, resulting in minimum upfront equipment and deployment costs. However, in
order to provide more bandwidth for advanced video applications, it is desirable to install
fiber from the CO to cross connect boxes, or nodes, in the neighborhood and then utilize
the existing copper twisted pairs from the cross connect nodes to the individual customer
premises.
In the architecture illustrated, the network consists of Customer Premise Equipment (CPE),
the Network Access Provider (NAP) and the Network Service Provider (NSP). CPE refers
to end-user workstations (such as a PC) together with an ADSL modem or ADSL
terminating unit router (ATU-R). The NAP provides ADSL line termination by using DSL
access multiplexers (DSLAMs).

Figure 3.5 DSL Architecture
The DSLAM forwards traffic to the local access concentrator, which is used for Point-to-
Point Protocol (PPP) tunneling and Layer 3 termination. From the Layer 2 Tunneling
Protocol Access Concentrator (LAC), services extend over the ATM core to the NSP.
In-depth discussion of the DSL architecture is out of scope of this report.

4.0 Proposed Model: Stable and Sustainable DSL for Future
Modern day applications, such as Internet access, remote LAN access, teleconferencing,
workgroup and data sharing, telecommuting and numerous varieties of digital video
services and the increasing volume of traditional data are driving demand for high-speed
data network access on both upstream and downstream. G.SHDSL, a symmetric, multi-rate
DSL combining the best of SDSL and HDSL2, it's aimed at users of DSL for voice, data
and Internet access services. It includes many of the features of HDSL2/4 and ETSI SDSL,
including symmetric bit rates, multi-rate operation, and the use of 16-level trellis-coded
(TC) PAM.
4.1 Overview: G.Shdsl - Symmetric High Speed DSL
Having given a clear scrutiny on the various broadband technologies and specifically in-
detail about the DSL technology in the above sections this report will elaborate on its
endeavor for proposing a stable and sustainable DSL broadband technology which will not
only cater the needs of a residential customer but also on the business application
perspective. Earlier the interest towards this technology was more focused on business and
oriented on its applications. The purpose of this report is to emphasize the fact that the
technological developments in the fast world today needs symmetrical data transmission
and not asymmetrical as the olden days. Prior, these asymmetrical speeds suited the home
user, since the usual kinds of traffic sent from homes are e-mails and requests for Web
pages, which consume relatively small amounts of bandwidth. The higher "downstream"
speed also allows people to more easily receive larger incoming applications like streaming
radio, MP3 files and graphics files. May be a decade back importance was more on
downstream and not on upstream but services like Internet Protocol Television (IPTV),
video calling, online gaming, web hosting etc require high downstream as well as upstream
transmission rates.
ADSL can receive information at up to 8mbps but can only transmit at a rate of 0.8mbps
this makes G.Shdsl to be a better technology for future. Way back in Sept 2001, an article
released in http://news.cnet.com explained on the importance and future developments
which could happen on G.Shdsl but due to lack of technological developments then, it did
not concentrate on the importance and value of residential customers who are also potential
buyers of this symmetric high-speed digital subscriber line. ADSL was considered being far
from extinction since it is widely used among residential consumers, which outnumber
business customers. Now there is a need for symmetrical DSL technology which will
eventually change this belief. Besides being faster and stretching longer distances,
G.SHDSL carries an international pedigree. G.Shdsl (Symmetrical High-Data-Rate DSL) is
based on the International Telecommunications Union (ITU) G.991.2 global industry
standard. Speed and distance are other factors that strengthen G.SHDSL; it delivers
symmetrical data rates from 192 Kbps up to 2.3 Mbps on single wire pair or up to 4.6mbps
in some cases (dual pair). It transports T1, E1, ISDN, ATM, and IP signals, making it ideal
for both business and residential applications. Bandwidth is more than T1 and it is cheaper.

In addition, the G.SHDSL signal has a greater distance reach from the central office than
ADSL and proprietary SDSL connections, allowing service providers to capture more
customers. It can also be deployed nearly twice as far from the central office (CO) than
SDSL, which is limited to a maximum distance of 18,000 feet.
Current view is that applications will test downstream limits equal to upstream limits, one
of several versions of DSL high-speed Net access, the technology is being considered for
use by some of the largest U.S. service providers, including SBC Communications, for its
ability to serve a greater number of customers. Analysts believe some U.S. carriers may
begin using this full-fledged in the contemporary era.
To add significance to the understanding, mentioned below are some of the statements
released by technologists from US.
"The European market will see this. And the (U.S. local phone companies) are looking at
deploying it to replace their business offerings now," said Pat Hurley, a DSL analyst at
TeleChoice, a communications industry market research firm.
"Cisco G.SHDSL business-class solutions enable our service provider customers to
increase their profitability on DSL services by better addressing the largely untapped
market of small and medium business that are clamoring for cost-effective broadband
connections," said Enzo Signore, Director of Marketing for the Cisco DSL business unit.
Signore added that G.SHDSL offers ISPs the potential for increased profits through
managed data services, firewall security, VPNs, voice over IP (VoIP) and distance learning.
The Cisco solution has already been adopted by a number of ISPs, including U.S.
based NTELOS, Intraconnect of Greece and BBned of the Netherlands. Paris-
based Alcatel joined the party and set off a G.SHDSL board that allows telcos using Alcatel
equipment to offer symmetric service for little more than the cost of ADSL services.
Everett Brooks, DSL Forum SHDSL working group chairman, said over time, SHDSL
offers service providers a very cost-effective means of deploying symmetrical DSL
services. In the coming years, expect to see more equipment manufacturers and ISPs
announce G.SHDSL offerings. It's truly a global standard now, as a result the worldwide
market driving the price down.
4.2 Key Features:
G.Shdsl is based on HDSL and is specified in the International Telecommunications Union
(ITU) recommendation number G.991.2 titled Single-Pair High-Speed Digital Subscriber
Line Transceivers. Symmetrical WAN speeds up to 2.3 Mbps over a single copper pair and
up to 4.6 Mbps over two copper pairs using ITU-T G.991.2 and is spectrally compatible to
all other DSL technologies with the use of TC-PAM line coding. It combines the best of the
legacy services into a single, robust technology that can be used for both full and fractional
E1/T1 lines, Digital Added Main Lines (multiple voice channels), and video conferencing
applications using a single twisted pair of wires. Using Cisco High-Speed WAN Interface

Cards, Symmetrical WAN speeds of 2.304 Mbps per pair up to 9.2 Mbps over four pairs on
the 4-pair G.SHDSL WAN interface card (HWIC-4SHDSL) by bonding with Inverse
Multiplexing over ATM (IMA) can be achieved. Other key features listed below.
Features like Extensive ATM class-of-service (CoS) and IP quality-of-service (QoS)
support, Operation possible when connected to a DSL access multiplexer (DSLAM), Toll-
quality voice over data through ATM Adaption Layer 5 (AAL5) and voice over IP (VoIP),
Single RJ-11 connector on 2-pair G.SHDSL HWIC (HWIC-2SHDSL) and single RJ-45
connector on 4-pair G.SHDSL HWIC (HWIC-4SHDSL), ability to sustain up to 8
permanent virtual circuits (PVCs) per HWIC and support for wetting current makes the
Cisco High-Speed WAN Interface Cards to be a premier and enhances the features of
G.Shdsl.
4.2.1 Symmetrical, High-Speed, Cost-Effective Bandwidth
G.Shdsl (Symmetrical High-Data-Rate DSL) delivers symmetrical data rates from 192
Kbps up to 2.3 Mbps on single wire pair or up to 4.6mbps in some cases (dual pair). Speeds
vary, depending on the loop length and line conditions. More traditional WAN links, such
as leased-line and ISDN, provide similar service, but often at a much higher monthly cost.
Figure 4.1 Comparison of rates and distances with other DSL technologies
The G.Shdsl delivers symmetrical connectivity and provides the necessary bandwidth for
business applications such as VoIP, videoconferencing, and toll bypass at a lower monthly
charge. G.SHDSL enable cost-effective deployment of voice, data, and high-speed Internet
services; fully compliant with the ITU-T G.991.2 G.SHDSL standard.
The Figure below shows the rates and distances that can be achieved by a number of
DSL technologies and illustrates how SHDSL provides full symmetric service rates a
distances greater than other DSLs, and without repeaters to 4 km.

4.2.2 Spectral Compatibility
Spectral compatibility is a function of the degree of overlap between the received signal
and the crosstalk signal, and the relative strengths of the signals. A number of factors
influence the severity of crosstalk on a pair of wires and in effect, interfere with the desired
signal. Factors such as loop length, the effect of echo cancellation (EC) versus frequency
division multiplexing (FDM) transmission are applicable.
Different types of DSL in a cable utilize different bandwidth. Depending on the energy of
the signals and the spectral placement, the different types of DSL systems may or may not
be compatible with each other. The crosstalk effect that one DSL system has on another in
the cable defines the spectral compatibility. In the design of DSL systems, spectral
compatibility is important because the deployment of any new DSL services should not
degrade the performance of other services in the cable. Likewise, the existing services in
the cable should not prevent the new DSL from meeting its performance objectives.
Figure 4.2 Spectral Efficiency of G.Shdsl
Figure 4.2 exemplifies the improved power spectral density (PSD) characteristics and
efficiency of SHDSL. The PSD represents the amount of energy required to send
information. With a reduced amount of energy across a band of frequencies, the potential
for interference with an ADSL customer is greatly reduced while requiring less power.
Therefore SHDSL presents less of a disturbance to ADSL equipped loops, and ensures
overall spectral compatibility with existing deployments.
The SHDSL standard was developed not only to address interoperability issues but also
into consideration the spectral characteristics of the existing line coding and transmission
techniques in common use within the existing networks. SHDSL or G.991.2 is based on

modifications to HDSL2 and uses TC-PAM, providing 16 levels of encoding rather than the
4 levels provided by 2B1Q and thereby improving spectral efficiency. Trellis coding,
Viterbi decoding and Tomlinson pre-coding provide improved bit error rates and SNR
(Signal Noise Ratio).
4.2.3 Carrier Advantages
Market changes day-in-day-out, embracing new standards for expanded distances, adaptive
rates, lower power, ease of deployment and revenue generating capabilities has been a
usual custom. SHDSL offers a wide range of benefits in deploying advanced services.
The deployment of new high-value business services out of existing installed base of
DSLAMs with minor changes influences least capital investment. Symmetric bandwidth
supports applications that require high performance in both directions which has been the
vital nature. Single pair design with dual pair option, and rate-adaptive capability provides
network design and deployment flexibility an edge over other technologies. Eliminates
need for E1/T1 repeaters on loops fewer than 18000 feet. Enhanced reach capabilities allow
an offering of consistent services to a wider range of customers, making a profit factor for
service providers. Superior spectral compatibility with other transmission technologies
eases deployment limitations, reduces criticality of accurate loop records and eliminates the
need for troublesome binder group segregation. Transport cost savings for existing services
such as leased or private lines.
G.SHDSL generally provides 20% to 30% increase in reach over HDSL at the same
deliverable data rates. The SHDSL standard supports the use of line powered repeaters,
therefore allowing very long DSL customer reach. Multiple repeaters (up to 7) can be used
to achieve extremely long distances. DSL services can be provided to
customers well beyond 30000 ft. Additionally, when G.SHDSL multilink technologies are
used, such as four-wire, Inverse Multiplexing for ATM and permanent-virtual-circuit
bonding, G.SHDSL's reach is more than double HDSL's.
4.2.4 Signaling - Handshake Capability
The biggest advantage of G.SHDSL is its rate-adaptive capability. The handshake protocol
available in G.SHDSL negotiates the highest achievable data rate given the copper loop
conditions. It has advantage over earlier symmetric DSL approaches includes the use of the
signaling standard, G.994.1, “Handshake Procedures for DSL Transceivers”, frequently
referred to as G.hs. G.hs defines signals, messages and procedures for exchange between
DSL equipment. The use of this signaling capability occurs after the DSL equipment has
gone through its power initialization phase and enters the mode where it needs to
automatically establish certain operational characteristics before signal can be exchanged.
G.hs procedures are utilized to enable rate adaptation.
The bandwidth and therefore data rate that can be supported on that particular copper loop

can be adjusted to attain a certain bit error rate based on a Service Level Agreement (SLA),
or achieve longer loop lengths or reach. In this manner, rate adaptive operation and power
adjustments are made automatically. At the completion of initialization and handshake
procedures, the DSL equipment enters SHOWTIME. SHOWTIME is used to describe the
mode where the user and network can begin communications over the access network. The
TC-PAM line code, which is the foundation for G.Shdsl, allows for easy interoperation due
to the low complexity level of the transceivers. G.Shdsl TCPAM line code is capable of
increasing reach by 30 percent. Hence G.SHDSL is the most preferred DSL technology
used in campus networks for its extended reach and multi-rate support.
4.2.5 Interoperability
Interoperability is one of the main features of the G.Shdsl which makes it to inter-operate
with other DSL standards and the network equipments used by them. Worldwide standard
drives wider availability of fully interoperable equipment. G.SHDSL is compatible with
ADSL, causing little noise or crosstalk between cables. Therefore, G.SHDSL services can
be mixed with ADSL in the same cables without much - if any - interference.
One of the best paradigms of the interoperability feature of G.Shdsl is the compatibility of
Cisco High-Speed WAN Interface Cards with the legacy DSLAMs like
 Alcatel ASAM 7300
 ECI HiFocus SAM 480
 Lucent Stinger FS
4.2.6 Best replacement for T-1 or E-1 services
Legacy services such as E1/T1 require the use of many repeaters, approximately every
1000m or 3000 – 4000 ft, which is complicated to deploy, power and maintain. On a
business user perspective G.Shdsl will offer a reduced service-level agreement compared
with T-1 or E-1 services, at a lower monthly cost. It is also important to note that symmetric
DSL standards were developed to support a repeater mode. By using SHDSL as a repeater
technology for really long loops, not only are fewer repeaters required for a given distance
but also the reach of DSL service is nearly unlimited.
Figure 4.3 is an illustration of the service provider/carrier network and the access
application environment that SHDSL can support. Systems that utilize SHDSL can support
numerous types of symmetric access applications. While SHDSL has been targeted
primarily as the high-speed symmetric service for business and SOHO customers, it is also
applicable for selected applications in the residential market.

Figure 4.3 Future Networks with G.Shdsl
Since services are handled in the digital domain, bandwidth can be dynamically allocated
between voice, data and video applications.
It is significant to note that globally, starting in 2002, there were approximately 196 million
E1/T1 subscriber access lines in use according to Cahners In-Stat. In the future, the
majority of these lines are candidates for upgrade with SHDSL to leverage ability to
support new or higher speed applications than can be supported over E1/T1 lines, and to
lower operational costs.
4.2.7 Alternative to Fiber
SHDSL is an excellent high bandwidth alternative to Fiber.
DSL is comparatively inexpensive because it runs over copper networks that are already in
place. Service providers can avoid the expense of laying fiber, enabling the operator to
offer high-speed services at a lower price than if they had to invest and deploy new
transmission facilities. Techniques such as bonding and IMA enable higher data rates.
Bonding generally involves the use of a second pair. When an E1/T1 (which is 4-wire or
two pair) customer is upgraded, only one pair is required with SHDSL to support the
equivalent service rates. By utilizing the “spare” pair, the service rate to that customer can
be doubled with bonding. With IMA, many pairs can be multiplexed together to support
even higher rates to the customer. Copper loops to customer locations are far more
prevalent than T3/E3 or fiber. SHDSL provides an important new tool in the service
provider/carrier service portfolio.

4.2.8 VoDSL
Even without compression, a large number of voice channels can be placed on DSL
channels, which makes the technology very attractive. For example, up to 24/32 voice
channels can be transmitted over 1.5/2.0 Mbps DSL. DSL signals at the customer side are
delivered into an integrated access device (IAD), which forwards them over twisted pair to
the carrier. The signals go to the carrier' DSLAM and then to an access switch that
forwards voice via a voice gateway to the Public Switched Telephone Network (PSTN) and
data to the appropriate data network.
4.3 Architectural Changes
The major change will be over the access router and the customer premises equipment.
Implementation can be of any branded network equipment, here considering a cisco
interface card and router the employment is explained. The Cisco G.Shdsl WAN Interface
Cards for the Cisco 1700/2600/3700 Series are handy.
Cisco Systems has also announced that it’s adding G.SHDSL capabilities to its CPE
routers. The routers are part of an end-to-end solution with G.SHDSL line cards for the
Cisco 6000 IP DSL Switch family.
4.3.1 G.Shdsl WAN Interface Card for the Cisco 1700 Series
The Cisco 1700 Series with a single-pair high-bit-rate digital-subscriber-line (G.Shdsl)
WAN interface card (WIC) is the industry's first multiservice router to deliver business-
class broadband service with scalable performance, flexibility, and security for small-
medium businesses and small enterprise branch offices. Together with the integrated
G.Shdsl WIC (WIC-1SHDSL), the Cisco 1700 is the perfect solution for a variety of
businesses that require high-speed business-class DSL access on a secure, high-
performance modular platform.
Figure 4.4 Cisco WAN Interface Card
Combined with the WIC-1SHDSL, the Cisco 1700 delivers cost-effective, high-speed,
symmetrical bandwidth at a lower monthly cost than most traditional WAN circuits. This
provides businesses with the necessary bandwidth for such critical traffic as voice and
videoconferencing, and allows customers to take advantage of the cost savings of
integrating voice and data traffic on the same WAN link. Service providers can benefit by

offering differentiated service levels through service-level agreements (SLAs) at a more
competitive price.
The G.Shdsl standard (ITU G.991.2) represents the first DSL standard accepted worldwide
and is the latest in DSL technology. The G.Shdsl WIC is based on ITU recommendation
G.991.2 and, therefore, allows for better interoperability with third-party vendors.
The dual WAN ports on the Cisco 1700 Series platforms allow for flexibility in installing
WAN access lines. Multiple G.Shdsl WICs can be configured per router chassis to provide
additional bandwidth through a second WAN link, and supply connectivity to additional
sites or service providers. With the broad array of WICs available for the Cisco 1700
platform, flexible configurations, including asymmetric DSL (ADSL), dial, ISDN, E1/T1,
and Frame Relay are also possible. Secondary WAN links can, therefore, be used to
provide more available bandwidth or redundancy for mission-critical applications.
In addition, the Cisco 1700 Series incorporates Cisco IOS®
Firewall Technology (Cisco
Secure Integrated Software) supporting stateful firewall and intrusion-detection
functionality. With an always-on DSL connection, Internet security is a critical component
in protecting corporate resources from malicious attacks.
4.3.1.1 Features
The features of the Interface Card are explained in detail below.
4.3.1.1.1 Business-Class Security
G.Shdsl can be optimized with Cisco 1700 for virtual private networks (VPNs). VPNs
allow for secure use of any shared network incorporating the same policies and levels of
security and performance as a private network.
4.3.1.1.2 Integrated Voice and Data over G.Shdsl
Service providers increase revenue by building differentiated service options based on
premium, standard or best-effort service classes. This requires a QoS mechanism to
differentiate service levels and prioritize traffic accordingly. The Cisco 1700 with G.Shdsl
WIC provides ATM CoS features that enable service providers to manage their core ATM
network infrastructures and deliver scalable, cost-effective services with QoS guarantees to
their customers. Permanent-virtual-circuit (PVC) traffic shaping and queuing allow further
optimization of the existing bandwidth between customers and various services.
Many customers require IP QoS to differentiate between high- and low-priority traffic. The
Cisco 1700 with G.Shdsl WIC supports VoIP over DSL with IP QoS map to ATM CoS.
These enhanced QoS features enable data and voice traffic to be transmitted on the same
virtual circuit, thus allowing for further reduction of monthly recurring WAN charges.

4.3.1.1.3 Support for Analog and Digital Voice Interfaces
Cisco 175x (1750 and 1751) routers feature one voice-interface-card (VIC) slot and two
WAN/voice-interface-card (WIC/VIC) slots. Cisco 1751 VICs include dual-port foreign
exchange station (FXS), foreign exchange office (FXO), ear and mouth (E&M), and direct
inward dial (DID), all of which provide the analog voice interface to legacy telephony
equipment (phones, fax, private branch exchange [PBX], and key telephone system [KTS])
and the Public Switched Telephone Network (PSTN). It provides users a cost-effective way
to migrate toward a packet-based multiservice infrastructure without deeming legacy
telephony equipment obsolete. Cisco 1751 supports digital voice with dual-port ISDN
Basic Rate Interface (BRI) NT/TE VIC (network and user-side Q.931 BRI). This enables
users to easily connect ISDN PBXs and KTSs to a multiservice network with a minimum
of configuration changes on the PBX. In addition, users can immediately take full
advantage of multiservice capabilities, such as telephony toll-bypass applications and full
gateway integration within Cisco AVVID (Architecture for Voice, Video and Integrated
Data). The Cisco 1750 does not support digital voice interfaces (BRI) or analog DID, but
does support the other voice interfaces referenced in this section.
4.3.1.1.4 Standards-Based Voice Technology
The voice functionality of the Cisco 1700 with the G.Shdsl WIC, which is based on H.323
standards, enables third parties to develop applications to a standard protocol. This results
in an ecosystem of compatible voice applications such as enhanced call control via
gatekeepers, service billing, and network management. Such an ecosystem provides a
complete solution for rapid deployment of intranet voice services for branch offices and
enterprise teleworkers.
4.3.1.1.5 DSLAM Interoperability
The G.Shdsl is based on the Globespan chipset and operates either back to back or
connected to a Cisco 6160 and 6260 DSLAM. Interoperability testing with third-party
vendors' DSLAMs is likely to be conducted on an on-going basis. Additional information
on this will be provided when testing is completed. Customers can deploy G.Shdsl WICs in
a back-to-back configuration to take advantage of existing copper wiring in a building,
campus, or neighbourhood where DSLAM aggregation equipment is either not needed or
not financially justified. In back-to-back mode, one side of the connection is configured in
server mode and provides functionality similar to that of a DSLAM.
4.4 Diverse Consumer Category
Symmetric High Speed DSL has a varied consumer platform; its technological nature has
the edge over numerous broadband technologies available in the market. Listed below are
the most important ones.

4.4.1 Business Users
SHDSL is suited to voice and data applications that need high upstream and downstream
bit-rates and is well matched to the following business services/applications.
4.4.1.1 Multi-line Voice over DSL (VoDSL)
A Voice over DSL service requires the use of a CPE / IAD (Integrated Access Device) that
typically provides 4-16 voice ports in addition to the data port(s) on the unit. VoDSL with
multiple voice channels places stringent requirements on the upstream link requires
guaranteed bandwidth (QoS) and is better suited to a symmetric connection than to an
asymmetric to operate successfully.
4.4.1.2 Web hosting
Application where a web server is located at subscriber’s premises and is connected to the
Internet via the DSL link, it requires a high bandwidth connection in the upstream
direction.
4.4.1.3 Videoconferencing
A videoconferencing service can run data, text and video over (typically) an ISDN link.
DSL has the capability to offer the same service but with a higher data rate hence giving
improved video quality and/or multiple videoconferences on the same line. As
videoconference service is usually two way process, symmetric DSL service (SHDSL) is
best suited to this application.
4.4.1.4 VPN Services
A virtual private network (VPN) is a private data network that makes use of the public
telecommunication infrastructure, maintaining privacy through the use of a tunnelling
protocol and security procedures. SHDSL is well suited to the provision of VPN services
interconnecting smaller branch offices where higher speed access provided by E3/T3 or
fiber access is either not available or too expensive when copper pairs are readily available
4.4.1.5 Remote LAN Access
Remote LAN (Local Area Network) Access is typically used by telecommuters and in the
SOHO environment to access the corporate network. This technology is also applicable to
campus locations to interconnect between buildings such as hospitals, universities, and
airports. In these applications, data packets are exchanged symmetrically in both directions.
SHDSL is suitable for Remote LAN Access because it enables end users to upload
information as fast as it can be downloaded. Rates range from 192Kbps to 4.6Mbps
depending on the service ordered and/or the reach. The SOHO environment within the

USA is typically characterized as having 8 – 16 lines and in Europe typically 6-8 lines.
Symmetric access using just one or two pairs can support the same number of POTS and
ISDN channels while using the remaining bandwidth to provider even higher speed
corporate data or Internet access.
4.4.2 Residential Users
The following points highlight attributes making SHDSL applicable for certain residential
users. Because SHDSL uses the POTS bandwidth, alternative mechanisms have been
developed to support voice (details go beyond the scope of this paper). In the event of the
loss of power, emergency Lifeline service (e.g E-911 in US) is generally not supported.
However, SHDSL provides a remote powering option and it can be utilized to provide one
emergency line.
4.4.2.1 Extended reach for remote customers
Unlike ADSL, SHDSL technology can achieve higher rates at longer distances, and also
supports the use of signal repeaters. This enables users outside the range of ADSL to be
offered DSL service where in the past service could not be provided. On average, SHDSL
provides 3000 – 4000 ft increased reach over previous symmetric technologies such as
SDSL (2B1Q). When this is put into perspective of the serving area, this translates to
approximately 40 % increase in coverage area. More serving area, more customers served,
more revenue opportunities for service providers.
4.4.2.2 Residential Gateway Access
A residential gateway is a term used to describe Customer Premises Equipment (CPE)
installed in a home that provides access to/from the home for multiple services (Internet
access, home video surveillance, home automation, etc.)
4.4.2.3 Internet Gaming
Online gaming is driven by client-server architecture, targeted marketing, and the Web’s
global reach. Internet gaming is convenient for end users since it can be done from the
comfort of their own homes. In this competitive application environment, one user is
competing against a game server (or another player in the future). In the gaming
community where ranking levels are used, every 5 ms (milliseconds) of delay or slower
packet transmission response results in a lower ranking level. Asymmetric service where
the upstream link speed is much slower than the downstream link skews the player’s
performance ranking due to the slower upstream speed. Symmetric service is required for
successful Internet gaming. Start-up costs are relatively low including a cheap server and
some unsophisticated interactive software on the client side, which can be licensed from
many sources.

4.4.2.4 Peer-to-Peer Services
Someone who runs a business from their home and needs to share information with clients
would fall into the category of Peer-to-Peer Services e.g. media file sharing. SHDSL is
best-suited for these types of services in that it enables the user to share large files with
clients and receive large files from clients – SHDSL enables smooth two-way
communication.
4.4.3 MxU Feeder Applications
The multi-unit building market, generically identified as MxU stands for Multiple Dwelling
Unit (MDU) and Multiple Tenant Unit (MTU). MDUs include apartment houses,
condominiums, and commercial multi-tenant office buildings. The customers that benefit
include tenants, IT service providers, NSPs (Network Service Providers), and ISPs
(Internet Service Providers). Tenants benefit by receiving Internet services more
conveniently at faster speeds. IT service providers benefit by expanding end-user services
such as video and virtual gaming in conjunction with billing services. NSPs and ISPs
benefit by expanding service boundaries for community applications like E-commerce and
local network applications.
MTUs consist of mainly hotels. The customers that benefit from SHDSL deployment
within hotels include hotel operators that can sell new services over existing cabling
without compromising revenues from voice services and guests, especially business
travellers, who can access corporate Intranets and use e-mail over much more convenient
connections than currently possible. SHDSL with Inverse Multiplexing over ATM (IMA)
fills an important void by enabling SHDSL over multiple lines multiplexed together to
offer higher speed service rates between the MxU location and the network without
installing E3/T3 line or constructing fiber to the building.
The advantages include:
 Minimize time to market by reusing the existing copper wiring already connected to
the customer location.
 Minimize disruptions to tenants in the MxU because no new cable construction is
necessary.
 Enable the use of SHDSL technology across different MxU segments, residential
versus business
 Lower deployment costs with the MxU representing a converged communication
platform, and lower maintenance costs with new support tools.
 Provides higher reliability and redundancy with multiple copper pairs back into the
network.

4.4.4 E1/T1 Replacement
Price is one reason DSL is taking the commercial market by storm. DSL is available at a
fraction of the cost of E1/T1 service, which generally is not affordable for most small
businesses. The primary reason why SHDSL service is more economical is related to the
fact that there is no need for repeaters approximately every 1000 meters or every 3000 –
4000 ft, which is required with E1/T1. To order a new E1/T1 line, there is significant delay
and costs because the service provider must install these repeaters in the outside plant and
involves multiple truck rolls. SHDSL does not require repeaters under 18000 ft and can be
installed on existing copper loops thereby significantly reducing time to service as well as
being a lower cost technology. Furthermore, SHDSL only uses one copper pair to provide
equivalent E1/T1 service rates where E1/T1 service requires two pairs.
Figure 4.5 Simplified Leased Line Network with G.Shdsl
Figure 4.5 shows how the use of SHDSL can simplify the network architecture.
The SHDSL standard includes a provision for carrying E1/T1 within the SHDSL payload,
thus SHDSL is able to provide E1/T1 type services. CPE vendors have developed CPE
units are available on the market today. Some carriers/service providers are still using
E1/T1 equipment from the 1980s, which is quickly becoming obsolete. SHDSL provides
these carriers with a cost reduced and simplified alternative solution for providing
equivalent service and/or can provide higher-speed, higher-bandwidth intensive service
rates up to 4.6Mbps.

4.5 Why G.Shdsl?
As the claim for greater transmission speeds continues to grow, service providers/carriers
are also beginning to place new importance on flexibility and programmability. For ISPs,
ILECs, and CLECs, the goal is to increase revenue by adding new services and applications
to their current portfolio of existing services, and expanding their Internet access. G.Shdsl
technology is evolving to meet these needs.
In an evolving society there is always room for new ideas, the main standardization bodies
like ITU, Committee T1 and ETSI are currently working on the next generation of their
respective standards. In order to widen the possible field of application, higher data rates,
multi channel bonding and new payload classes such as Packet Transport are being
addressed.
 Security: Unlike cable modems, each subscriber can be configured so that it will
not be on the same network. In some cable modem networks, other computers on the cable
modem network are left visibly vulnerable and are easily susceptible to break ins as well
as data destruction.
 Integration: G.Shdsl will easily interface with ATM, Nx64, and WAN technology.
Telecommuting may get even easier than its earlier categories.
 High bandwidth on both upstream and downstream.
 Cost effective as compared to other broadband technologies.
Till date internet access has been a more asymmetric service. But now the modern day user
and his requirements grow for symmetric types of applications, particularly in the SOHO
and residential environments:
 Voice
 Peer-to-peer file sharing (e.g. – collaborative projects between a satellite office
location and a main office of an organization or consumer file swapping)
 Business data traffic (E-Mail, LAN)
 Leased line replacement (T1, E1)

5.0 Conclusion
“Necessity is the mother of invention”
Demand makes everything; need demands invention. Inevitable need leads to high-speed
bandwidth requirement and it continues to grow at a rapid pace, driven mostly by growth in
data, as the Internet and related networks become more central to businesses. Broadband is
the answer for all of them and what type of broadband in the billion dollar question, this
report answers that to a certain extent. Today's telecom industry is undergoing a bandwidth
shortage driven mostly by the continuing explosion of the Internet and data markets. The
rapid growth of distributed business applications; the proliferation of private networks, e-
commerce, and bandwidth-intensive applications such as multimedia, videoconferencing,
and video-on-demand; and the continuing deregulation and privatization of the
telecommunications networks throughout the world are all helping to fuel the demand for
bandwidth.
Spectral compatibility, standards, interoperability, self-installation of modems, auto
configuration and provisioning are the four key ingredients to a success deployment of
DSL.
G.Shdsl is the access technology of choice for high-speed symmetric service offerings by
the service providers for businesses, Small Office Home Office (SOHO) customers and
Residential Customer. By utilizing SHDSL technology, service providers can offer services
that combine greater reach performance and spectral compatibility with other transmission
technologies in the same binder, as well as lower power and rate adaptation within their
respective networks for high-speed symmetric service offerings. Until recently, most of the
current deployments of Symmetric DSL (SDSL) have been proprietary and based on two-
binary one-quaternary (2B1Q) modulation over a single twisted pair. SHDSL provides both
equipment manufacturers and service providers with a shared common definition for a
worldwide multi-rate symmetric service, and provides greater deployment and service
flexibility for service providers.
To conclude, with below advantages as the justification factors this report proposes
G.Shdsl to be the best DSL and best broadband technology for future.
• Rate adaptation - Symmetrical service up to 2.3 mbps
• Standardization
• Greater reach -30% longer reach than SDSL
• Spectral compatibility
• Affordable T1/E1 alternative
• Low power
• Repeatable
• Application flexibility -Multi-rate (192kb/s - 4.6mbps) unlike HDSL

• More upstream bandwidth for bandwidth intensive applications
6.0 References
Books:
• The DSL Bible - Ron Gilster (Author)
• Understanding DSL Technology - Thomas Starr (Author), John M.
Cioffi (Author), Peter J. Silverman (Author)
• DSL for Dummies – David Angell (Author)
• DSL Advances - Thomas Starr (Author), John Cioffi (Author), Massimo Sorbara
(Author)
• Implementation and applications of DSL technology - Philip Golden
(Author), Krista S. Jacobsen (Author)
• End-to-end DSL architectures - Wayne C. Vermillion (Author)
• Telecommunications essentials - Lillian Goleniewski (Author), Kitty Wilson
Jarrett (Author)
Website:
• http://www.cisco.com/
• www.find-docs.com
• www.en.wikipedia.org
• http://www.juniper.net
• www.networktutorials.info
• www.networkcomputing.com
• www.howstuffworks.com
• www.webopedia.com
• http://compnetworking.about.com
• http://whatis.techtarget.com

• http://www.von.com/EBooks.aspx
• http://www.broadbandreports.com/
Also referred several Tutorials and White Papers by:
• George H. Dobrowski, GlobespanVirata
• Soum Mukherjee, HyperEdge
• Jimmy Engstrom, Ericsson
• Sascha Lindecke, Infineon
• Andrew Nicholson, Nokia
• Barry Dropping, Symmetricom
• The Evolution of Broadband: DSL and Beyond by Judith Hellerstein

7.0 Glossary and Acronym List
2B1Q 2 bits, 1 Quaternary
Line code for HDSL
3G Third Generation ( Mobile Communication System)
ANSI American National Standards Institute
ASCII A standard for digitizing text. An 8 bit character set which
contains the alphabet, numbers and all other printable characters
ADSL Asymmetric Digital Subscriber Line
AAL5 ATM Adaptation Layer 5
ATM Asynchronous Transfer Mode
Bit Either a 1 or 0, a small unit of data
BPL Broadband over power lines
Bridge Tap Accidental Connection of another local loop to the primary
loop. Becomes a transmission line stub and hurts DSL
performance.
Byte 8 bits
CAP Carrierless Amplitude Phase Modulation (CAP). Transmission
method used by some ADSL systems. Not approved by
standards bodies.
CLEC Competitive Local Exchange Carrier
CMTS Cable Modem Termination System
CPE Customer Premises Equipment / Customer Provided Equipment
CODEC Coder / Decoder
CO Central Office
CoS Class-of-service
DMT Discrete MultiTone Modulation. Transmission method used by
ADSL systems. Approved by standard’s bodies
DSL Digital Subscriber Line
DSLAM DSL Access Multiplexer
E1 Dedicated Leased Line - 2.048Mbits/Second
ETSI European Telecommunications Standards Institute
FDM Frequency Division Multiplexing
FTTH Fiber to the Home
FTTN Fiber to the Neighbourhood
G.Shdsl Symmetrical High-Data-Rate DSL
HDSL High bit-rate Digital Subscriber Lines
HDTV High Definition TV
ILEC Incumbent Local Exchange Carrier
IMA Inverse Multiplexing for ATM (Asynchronous Transmission
Mode)
IPTV Internet Protocol Television
ISP Internet Service Provider

ITU International Telecommunications Union. Develops and
maintains telecommunication standards.
Kbps Kilobits per second, 1000 bits per second
LAN Local Area Network
LAC Layer 2 Tunneling Protocol Access Concentrator
Mbps Megabits per second, 1 million bits per second
MMDS Multipoint Multichannel Distribution System
Modem Modulator/Demodulator. Device that transmits and receives data
over a line.
MTU Multiple Tenant Unit
MxU/MDU Multiple Dwelling Unit
NAP Network Access Provider
NLOS Non-line-of-sight
NSP Network Service Provider
P2P Peer-to-peer
PAM Pulse Amplitude Modulation
PPP Point-to-Point Protocol
POTS Plain Old Telephone Service. ‘Normal’ voice telephone service.
PSTN Public Switch Telephone Network
QAM Quadrature Amplitude Modulation. Line code for DMT ADSL
systems.
QoS Quality-of-Service
RF Radio Frequency
Simplex Transmission method where data is sent exclusively in one
direction on a pair of wires.
SDSL Symmetric DSL
SLA Service-level Agreement
SOHO Small Office / Home Office
T1 A transmission line that transmits data at 1.544 Mbps. Leased
Lines
VDSL Very high bit rate DSL
VoDSL Voice Over DSL
WAN Wireless Access Network / Wide Area Network
WIC WAN Interface Card

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