Module: Current Trends in Networking
Lesson: Wired Broadband Technologies
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Wired Broadband Technologies
Wired Broadband Technologies
It is often required to access a resource that is in the core of a network. Such access requires
connectivity from the “edge” of the network. Different network access technologies that are
broadly grouped as wired and wireless access technologies serve the varied access needs. Of
these, broadband denotes one set of technologies that provides the means of both wired and
wireless access.
This lesson starts by introducing the term “broadband” and distinguishes it from the term
“narrowband”. Common broadband data access technologies available to end users in their
homes or offices are introduced. These are:
Broadband over Cable TV
Digital Subscriber Line (DSL)
Broadband over Power Line (BPL)
Fibre to the Home (FTTH)
For each technology, the fundamental principles, the means of delivering a broadband data
signal, and the technical frame are discussed.
By the end of this lesson you will be able to:
demonstrate an understanding of existing wired broadband technologies
acquire a technical understanding of emerging trends in wired and cable technologies.
Begin the lesson by viewing a presentation giving you an overview of broadband technologies.
https://vimeo.com/245756735/74f8fbbf8f
Transcript
What is broadband?
Currently, the term broadband denotes a high-speed network access facility to access the
Internet. Homes, offices and individuals use broadband, when stationary and when mobile. It
also denotes the evolution of the network access technology from the era of the public
switched telephone networks (PSTN) that were used to provide access to networks via a dialup modem. The speeds were limited by the transmission technologies and the media used.
Formally, the term broadband, in contrast to the term “narrowband”, refers to a band of
frequencies that can traverse a given media - wired or wireless. Both these terms represent the
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frequency bandwidth of the signals used to transmit the data (Figure 1.01). Note that this holds
good for both wired and wireless communications. Narrowband connections provide data at a
slower rate, while broadband connections offer a higher data rate. Narrowband and
broadband, or wideband, are terms which refer to the amount of bandwidth used to transfer
information.
Figure 1.01 - Narrowband and broadband frequency bandwidth
An example of narrowband access is the dial-up access used before broadband was available.
In the context of voice calls, the quality of voice calls can be enhanced when using broadband
or wideband. A typical narrowband call filters the voice data between 300 Hz and 3400 Hz. A
wideband call (or a high-definition (HD) call) provides a bandwidth range between 50 Hz and
7000 Hz. Figure 1.02 illustrates this concept.
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Figure 1.02 - Frequency bands for narrowband and wideband (HD) voice
In present day usage, the term broadband is used as a marketing term for Internet access
providers to provide improved access to Internet services. The services that are promised on a
typical broadband subscription are:
faster worldwide web browsing
faster downloading of films, documents, photographs, and other large files
telephony, radio, television, and videoconferencing
virtual private networks and remote system administration
on-line gaming, particularly interaction-intensive multi-player online role-playing games.
The choice of narrowband vs broadband for access to a network is made based on the
application. For applications such as Internet access, there is a need for a high data rate and
the volume of data transferred is substantially large. Broadband access is generally preferred.
In contrast, for an application that has low volumes of data transfer, a low periodicity of transfer
(unlike an almost continuous transfer in the case of broadband access) and low data rate,
narrowband is preferred. Recently, some applications in the Internet of Things (IoT) have such
characteristics. They are termed as rId8
narrowband IoT or NB-IoT
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With this background, let us now explore the various wired broadband technologies available.
Critically compare broadband technologies with narrowband technologies with respect to
achieving higher data rates and long-range reliable connectivity.
There are many more physical factors that limit the implementation of broadband systems.
These issues are prompting the debate over narrowband or broadband solutions. All
applications share a set of most-desired parameters: communications that have the highest
data rate, use the least spectrum, consume the least amount of power, have the longest
range, and are the most resistant to interference. To ensure a high data rate, however, the
frequency spectrum used must be increased. This step invariably lowers the power, range,
and resistance to interference. These tradeoffs comprise the critical differences between
broadband and narrowband RF communications.
Please refer to the article below (DeLisle, 2014), which critically compares the two
technologies to aid your research.
Broadband over cable TV
Historically, most television was broadcast using analogue radio transmissions. However, there
have also been a number of systems that deliver the signal to the end-user’s equipment (the
television) via a cable rather than a radio signal. Of course, there is a cable connecting the
aerial to your TV anyway. What we are referring to here is a system where there is no aerial on
your house. A typical cable network is illustrated in Figure 1.03. The satellite TV signals
received at the provider end are transmitted to various locations on a fibre network and then
distributed locally on coaxial cable networks. The networks use amplifiers at periodic lengths to
boost the signal strength and enable them to travel over long distances. The term “hybrid” is
used since the media used for interconnectivity is a mix of fibre and coaxial cables.
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Figure 1.03 - A typical hybrid cable network
A cable connects the “head end” where the cable provider is located to the user, where the
content is delivered. Typically, in cable networks, the TV signals received in a regional head
end (RHE) are distributed to local head ends (LHE), which in turn distribute the signal to the
residential customers via co-axial cables. Figure 1.04 illustrates the architecture of a cable
network.
Figure 1.04 - Cable Network Architecture
In the early days of cable TV, the network used analogue signals. The key technological
development was the switch to digital transmission. This enables a cable to carry many more
channels and allows each channel to carry different services, such as data for an Internet
connection and voice telephone facilities. The basic technology broadcasts MPEG-2 encoded
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streams over a co-axial or fibre cable using multiplexing techniques. In the recent past,
MPEG-4 encoding is becoming a standard and experiments are being done to broadcast 4K
quality transmission on cable.
In most cases, the cable operator will install co-axial/fibre optic trunk cables along the street
and have nodes providing connections to the drop cables at intervals. The co-axial drop cables
then feed to user premises where a set top box separates the data and TV signals. It is
common to have an Ethernet port on the set top box, providing the data connection that can
then be distributed via standard Ethernet technology.
The data service is commonly carried over one or more channels within the multiplex and there
are various standards for doing this. The key set is the Data Over Cable Service Interface
Specification (DOCSIS) family.
The commercial development of digital television is tied up with local legislation, which varies
from country to country. However, the basic pattern is the same. In the early days of broadcast
media (radio and TV), governments restricted the supplier companies in many ways. These
include restricting the number of channels they could carry and the areas they could service. It
was also common to prohibit the carrying of other services such as telephone, to protect
monopolies in telephone operation.
Cable standards and performance
The services, interfaces and performance standards for the cable network services are
specified in the Data over Cable Services Interface Specifications, called as DOCSIS. It
concerns the interface standards for cable modems that interconnect the cable operator with
the customer’s television set or a digital computer, typically a desktop or a laptop. DOCSIS is
a technology developed by CableLabs for transfer of data over coaxial cable that are
developed and used for cable TV connection. Cable Operators across the world have adopted
DOCSIS standards for providing Internet data, voice, and video services using existing cable
TV systems.
Over the last two decades, DOCSIS technology has evolved from the initial 1.0 version with
top speeds of 42 Mbps to DOCSIS 3.0, which can provide more than 100 Mbps for Internet,
telephony, and video services. The current version of the standard is DOCSIS 3.1. This version
supports speeds of up to 10 Gbps downstream and up to 1 Gbps upstream. It is a strong
contender to fibre optic cable. As with other data communications, there are a range of
standards that ratify these protocols. The main ones are ITU Recommendation J.112
(DOCSIS), J.122 (DOCSIS v2.0) and J.222 (DOCSIS 3.0).
DOCSIS architecture
A DOCSIS architecture comprises two components: a cable modem (CM) located at the
customer premises, and a cable modem termination system (CMTS) located at a control point.
A control point can be, for example, a CATV headend, a hub, service office, and the like. A
typical CMTS is a device which hosts downstream and upstream ports (it is functionally similar
to the DSLAM used in DSL systems). For duplex communication between a CMTS and CM,
two physical ports are required (unlike Ethernet, where one port provides duplex
communications). Because of the noise in the return (upstream) path, a CMTS has more
upstream ports than downstream ports - the additional upstream ports provide ways of
minimizing noisy lines (until DOCSIS 2.0, they were required to provide higher upstream
speeds as well).
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How does DOCSIS work?
The Physical Layer used to be carried on either 6MHz or 8MHz channels for downstream data
in DOCSIS 3.0 and earlier. Upstream uses between 200kHz and 3.2MHz channels but version
2 increased this to 6.4MHz. Data is modulated using Quadrature Amplitude Modulation (QAM)
at either 64 or 256 levels downstream. The upstream channel is much slower so it can rely on
Quadrature phase-shift keying (QPSK) or 16 level QAM for version 1. Version 2 and 3
increased the upstream data rates by making use of up to 64 level QAM. DOCSIS 3.1
abandoned this schema in favour of 20KHz and 50KHz wide subcarriers using orthogonal
frequency-division multiplexing (OFDM) to increase handling of suboptimal channel conditions
such as attenuation and interference.
Downstream communications are allocated dedicated channels within the multiplex and are
therefore uncontended. The data link layer controls access to the line for upstream
communications deterministically by using time division multiple access (TDMA) technology. If
an upstream message is waiting, the device makes a request for time slots which are then
allocated according to demand. This results in fewer collisions than pure contentions systems
like carrier sense multi-access with collision detection (CSMA/CD) used in older Ethernet
networks. At the data link layer, it is also possible to employ channel bonding both up and
downstream on version 3.0.
Performance
The exact performance, as always, varies depending on the details of implementation and
overheads. In particular, there may be contention as end user lines are merged in the street
when they access the fibre. The figures here are raw data rates.
Figure 1.05 - Typical speeds for DSL versions
The standard DOCSIS standard (using 6 MHz channels) gives a downstream data rate of up to
42.88 Mbit/s. The EuroDOCSIS standard (using 8 MHz channels) gives 57.20 Mbit/s
downstream. The upstream rates are the same for both systems at 10.24 Mbit/s (Figure 1.04).
DOCSIS version 3.0 allows up to 8 downstream and 4 upstream channels to be bonded.
Figure 1.06 shows the typical downstream speeds for 4 channel and 8 channel bonding.
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Figure 1.06 - Typical speeds for DSL 3.0 with channel bonding
TeamNANOG (2013) provides a good overview of the DOCSIS 3.1 and its implementation.
The DOCSIS standards are available online. You can look them up, along with other
information on DOCSIS and cable modems - refer to CableLabs (2017).
There are also some very detailed technical descriptions of DOCSIS operation, including a bit
by bit decoding of the protocols available. Refer to The Volpe Firm (2017) for examples, or
search on DOCSIS.
Digital Subscriber Line (DSL)
Digital Subscriber Line, DSL, is a set of technologies that is used to transmit digital data over
existing phone lines, without interfering with the telephone services. The phone lines are
unshielded twisted pair lines, unlike the coaxial cables used for CATV networks. These
technologies can now deliver data rates up to 50 Mbps.
Obviously, a different connection technology is required to support the need for higher
bandwidth utilisation by the users. However, in order to provide a different connection
technology, you might need to run a new connection to every user. This was impractical
because of cost and time. A solution was needed that used the current telephone wire that
already ran to subscribers’ houses. That solution was digital subscriber line (DSL).
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In some sense, it can be regarded as a stop-gap solution. Ideally, we would run an optical fibre
to each subscriber premises and provide all digital communications via that. (Fibre will be
explained later in this lesson.) However, this would cost a huge amount of money and take a
long time to roll out. In some parts of the UK, all new houses are being built with fibre to the
property, but the vast majority of older homes still have to be serviced.
How does DSL work?
The telephone system was designed to convey speech and offers a baseband system
operating up to about 3400Hz. Originally the technology could not handle a wider bandwidth.
The modern speech telephone is almost always digital until the final step between the last
exchange and your telephone, which is usually analogue. This final stage is called the local
loop and is still designed to handle baseband up to 3400Hz.
However, the entire system in a modern phone network, including the local loop, is capable of
handling a much wider bandwidth, up to 10MHz in good conditions. The normal telephone
does not use this bandwidth, but the cables and other equipment can carry it. This means that
we have a ready-made connection into the home which has a significant spare bandwidth that
we can use for Internet traffic.
The technique is a variation on frequency division multiplexing, where the lowest band of the
communications system (in practice up to 20kHz) is reserved for baseband voice
communication and the remainder of the available bandwidth (over 25kHz to allow a guard
band) is used for data communications.
DSL Architecture
Figure 1.07 - DSL Architecture
The ADSL functions at the network end are performed by an ADSL Terminal Unit-Central office
(ATU-C) together with a splitter function (S-C). The ATU-C interfaces with the network
switching, transport, and multiplexing functions and network operations. It may be in a central
office or in a remote location as an extension of a carrier system. The ATU-C functions are
usually integrated within a higher-level network element, e.g. DSL access multiplexer
(DSLAM). DSLAM contains the access interface (network termination - NT) to the appropriate
transit network, e.g., ATM, Frame Relay, etc. ADSL functions at the customer end (remote
end) are performed by an ADSL Terminal Unit-Remote end type (ATU-R) together with a
splitter function (S-R). Note that the ATU-C and ATU-R are the corresponding end points at the
local exchange and the customer premises. The ATU-R is usually within the cable modem at
the customer premises and the ATU-C is part of the DSLAM. The architecture of DSL is
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illustrated in Figure 1.07. Figure 1.08 illustrates a real-life interconnectivity of the components
of the DSL service both at the customer end as well as at the provider end.
Figure 1.08 - DSL functional components at the local & remote ends
At the customer premises, ATU-R may present the interfaces to the local distribution for
broadband services via service modules (SM) and “set-top” boxes. The SM contains
necessary decoders and terminal interfaces for the given service and customer control
interfaces.
Splitters are three-node devices, that allow the telephony signals and the ADSL signal to
reside on the same copper loop without interfering one with the other. The splitter provides a
low pass filter to the basic voice and control telephony signal (below 4kHz) and a high pass
filter for the ADSL signals, starting approximately at 25kHz or above. Most POTS splitter
designs are passive, that is without powering requirements. The advantages of passive filters
are in their reliability, because they enable a continuous telephone service even if the modem
fails (for example, due to a power outage).
ADSL and SDSL
Many variations on DSL have been developed, some of which are commercially available,
others existing only in theory. The key difference is between symmetric and asymmetric DSL
(SDSL and ADSL). This distinguishes how the available data bandwidth is divided between
upstream (going out of your property) and downstream (coming into your property) channels.
ADSL provides a much higher bandwidth for the downstream channel, giving a much higher
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data rate for downloads than for uploads. Most service providers provide ADSL services when
they mention they provide broadband services. When subscribing for a broadband service, it is
important to check the downstream and upstream data rates to see if they match your
requirements.
ADSL2 and ADSL2+ are variations of the same technology. ADSL2 and ADSL2+ can provide
downstream data rates of 12 Mbps and 24 Mbps, respectively. These speeds are available
across loop distances of 5,000 and 6,000 metres. These technologies use channel bonding aggregating several channels for higher bandwidth on the downstream and upstream enabling the providers to offer different tiered data rate services to their subscribers. The
corresponding ITU standards for these technologies are G.992.3 and G.992.4 (2002) for
ADSL2 and G.992.5 (2003).
Symmetric DSL provides the same bandwidth in each direction. Although less common, there
are circumstances where this might be useful. Hosting services such as your own web server,
it may be possible to have a SDSL connection to provide a satisfactory upstream speed for
customers accessing your website.
In general, SDSL is provided to small businesses who need better than ADSL upstream rates
but do not need or want the higher costs of dedicated T1/E1 links.
Most SDSL services do not carry voice as well, but use the entire bandwidth of the link for
data.
In a battle of bandwidth in the last mile, fibre has clearly won over copper. However, the latest
standard by ITU-T called the G.fast has changed the game for copper. Discuss the G.fast
technology and how it could enhance the broadband speeds on the last mile and the benefits
it offers to the domestic users. Share your findings on the discussion forum of Lesson 1.
G.fast standard along with vectoring techniques, is aimed at injecting new life into existing
telephone wire infrastructure in the predominantly copper ‘last mile’ areas. For operators with
copper assets in the access network, one primary reason for G.fast is that it allows them to get
to market more quickly with viable offerings able to compete, in ‘value-for-money’ terms, with
end-to-end fibre (FTTH, fibre to the home). Additionally, speed to market is coupled with a
lower cost of deployment, making use of existing telephone wiring. Use the article (Johnson,
2014) for additional reference.
Very high bit rate Digital Subscriber Line (VDSL)
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Figure 1.09 - DSL configurations, speeds and standards
VDSL and VDSL2 provide data rates faster than ADSL/ADSL2+ with a distance limit of 1.5
kms. Figure 1.09 illustrates the various technologies and the data rates associated with them.
The theoretical downstream and upstream data rates are 200 Mbps. The practical data rates
observed are about 100 Mbps. VDSL2 supports a wider frequency range of 30 MHz in
comparison to VDSL’s 12 Mhz frequency range. Both VDSL generations quickly deteriorate
after certain distances. At 1 km, both VDSL versions begin to exhibit similar speeds. At
approximately 1.6 km, VDSL’s performance becomes comparable to ADSL2+. Take a look at
Figure 1.10 for the variation of speed with respect to the distance.
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Figure 1.10 - Variation of DSL speeds with distance
The higher bit rates are achieved by port-bonding and vectoring. This simply means that two or
more ports, each of a certain speed and connected to the same destination device can be
considered as one single link and therefore an aggregated speed. For example, if each port is
capable of 100 Mbps, then two bonded ports would give an aggregate of 200 Mbps. Vectoring
is used to remove crosstalk and interference that causes reduced performance. It measures
the amount of crosstalk on the network links and applies anti-phase signals to cancel them out.
This is similar to how noise-cancelling headphones work.
VDSL2 supports 8 distinct “profiles” with varying maximum downstream and upstream
throughput as well as different bandwidth frequencies and transceiver power. Different profiles
are optimal for different deployment scenarios. Figure 1.11 illustrates the various profiles
available. Notice that the profile names indicate the bandwidth available for that specific profile,
as part of the name.
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Figure 1.11 - VDSL profiles
G.fast
G.fast is the latest standardised evolution of DSL connections. It uses digital signal processing
technology that has demonstrated fibre-like bandwidth of up to 1 Gbps download trial speeds
over existing landline copper cabling of around 100m, and up to 400 Mbps download trial
speeds over around 300m in lab trials. G.fast and XG.FAST are being viewed as a possible
future for DSL-based network connections (which currently use VDSL2).
Nokia’s XG.FAST development equipment, in laboratory tests, have achieved a little over
3.5Gbps aggregate (upstream + downstream) trial speeds over a single 100m Copper Pair.
Beyond this, XG.FAST even has demonstrated the potential to reach total throughput trial
download speeds of up to 10Gbps, but those multi-gigabit trial speeds are only demonstrated
over short lengths of twisted-pair copper cabling - (30m to 50m). Figure 1.12 illustrates the
results of the trials by British Telecom in 2015. Notice the degradation in speeds with the
increase in distance. Also, notice the impact of vectoring on the performance.
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Figure 1.12 - G.fast trials run by British Telecom
However, G.fast currently has a shorter range than VDSL2, which can present challenges.
Skipio (2015) provides an illustrative comparison between the two technologies.
Read the article titled Fighting fibre with G.Fast (Walko, 2016). The high-speed DSL options
have provided the feasibility of providing a high-speed last mile (from the local
exchange/wiring cabinet to the home) on copper instead of having to lay new fibre optic
cables. Discuss on the lesson one forum how the DSL technologies could facilitate this and
save the providers additional investment in laying fibre optic cables.
Consider that the copper cables are now able to provide Gigabit speeds on the last mile.
These speeds are similar to those available on fibre optic cables. This means that the
providers do not need to invest in laying new media. The existing media can be used by
changing the end equipment at the local exchange/cabinet and the home. However, there are
distance limitations to consider.
Broadband over Power Line
To get Internet access, you must already have an electricity supply to power your computer.
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Whilst this could be from your own local generator, from solar panels or wind generators or
similar, for most people the electricity supply comes via a cable-based distribution grid. This
leads to an obvious question - can we send data down the same cable as power? The
straightforward answer is - yes.
Broadband over Power Line (BPL) has a number of other names such as Power Line Digital
Subscriber Line (to try to fit it in with DSL services - somewhat tenuously!), Power Line
Communication (PLC), etc.
Power lines for power
First, we need a little background on power lines. Electricity is distributed over long distances
(typically over about 500km) by high voltage networks operating at 100kV or above. This helps
reduce power losses as higher voltages can mean lower currents and it is current that
generates heat which wastes power. (This is a gross simplification, but it will do for our
discussions. If you want to know more - look it up. Type the term “What is power transmission
losses” in Google’s search box)
For local distribution, say within a town, this is stepped down to about 11kV - 100kV depending
on where you are. Some large users such as big industrial consumers may take their feed at
this level.
For distribution to domestic users and small businesses, the voltage is stepped down again by
local sub-stations to the standard for your country. In most of Europe it is 230V, in the USA and
Canada it is 110V. Other areas vary - look yours up if you do not already know it.
Within your house, you will have one or more power line networks distributing electricity to wall
sockets, lighting and high consumption appliances like cookers and showers. Again, the exact
setup varies from country to country.
Power lines for data
It is possible to have data over power lines right across the distribution network through high-,
medium- and low-voltage networks, but in practice the transformer systems used to step the
voltages make this rather tricky, so we’ll stick to sending data over a single stage of the power
network.
Home LAN over power lines
There are several systems available commercially that will allow you to use your home power
cables to carry LAN data. Typically, these provide an interface between standard wired
Ethernet and the power lines, replacing the standard UTP cable with mains cables.
The big advantages are that you have an Ethernet port on your computer already and you can
connect Ethernet switches and hence printers and ADSL/cable modems etc. Also, the cabling
is already in your house. With the increase in home entertainment systems and the
convergence of these with computer technology, this offers significant benefits.
The main problems are to do with security and interference. Depending on how your home is
wired up, your next-door neighbour (or anyone else in your street or on your substation) may
be able to see your communications. Your data transmissions may interfere with devices
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taking power from the line, such as televisions.
There are several standards available for home data over power lines, most of which come
under the banner of HomePlug. These will provide physical layer data rates of up to 200 Mbit/s
with a media access control layer (MAC layer - the one that Ethernet quotes) at around 80
Mbit/s. So, they are not quite as fast as standard 100 Mbit/s Ethernet but not far off. New
developments including HomePlug AV2 will push this up to around 600 Mbit/s physical and
240 Mbit/s MAC, giving comparable performance with standard UTP Ethernet.
However, this is a different prospect from supplying Internet access.
Internet access over power line
Often marketed as Broadband over Power Line (BPL), this provides an Internet data service
carried over the electricity lines that come to your home. Figure 1.13 shows how the signals
arrive from the Internet provider to the home.
Figure 1.13 - Broadband over power lines (BPL)
The main advantage is that you already have the cables in place. This is particularly useful if
you are in a remote area where there is no cable-TV and the telephone exchange is a long
way away (see previous units on DSL and cable-TV Internet connections).
Disadvantages include the lack of standards (meaning that different manufacturers’ and
suppliers’ systems are incompatible), unpredictable quality of power lines in data
communication terms and variations in the power distribution network itself. However, the
existence of BPL does keep some pressure on telecoms and cable-TV companies to distribute
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their networks to more remote areas. The other big problem is noise. Power lines are very
noisy, carrying high voltages (compared with computer and data communication voltages) with
big spikes. Modern power supplies in computers, televisions etc. use a switching technology to
step down from the home voltage (110V, 240V etc.) to that needed by the device (often 5V or
12V) and these generate signals on the line. The actual cable is not shielded or a twisted pair,
so it picks up RF interference over long distances. There are also issues with BPL data signals
interfering with radio communications.
Note: do not confuse data over power lines with Power over Ethernet. This is the other way
around, where a data cable - typically Ethernet UTP cable - is used to carry a small amount of
power to supply a remote device such as a Wi-Fi access point. This removes the need to run a
separate power supply line to these devices which are often installed in awkward places like
roof spaces.
Although mobility is a factor in the choice of a DSL provider, checking error rates at the
customer location is more appropriate. Error rates affect the data throughputs which is of
primary consequence to the customer.
Fibre to the Home (FTTH)
This is fibre to anywhere, as the same technology applies wherever the end user may be.
Most Internet connections, to home users and small businesses at least, are supplied via a
metal cable over the last mile or local loop. This may be your telephone line (technically a
twisted pair cable although most are not twisted much at all) or your cable-TV connection (coaxial cable from the street junction to your set top box). However, as discussed above, these
are somewhat hybrid technologies that are making the best of what is easily available. If you
are starting from scratch without such infrastructure in place, it is better to put in the best
technology for the job. That is optical fibre.
Fibre to where?
In fact, most of the telecoms network is fibre anyway, so the term fibre to the x already applies
as fibre to the exchange or fibre to the node (FTTN). We then just take the fibre further,
replacing copper cable with optical cable for each hop. It makes sense to do this gradually,
moving from the infrastructure network in steps to the end user. Depending on the local
implementation, this results in fibre to the cabinet (FTTC - the box at the end of your street),
fibre to the building (FTTB - usually in a multiple occupancy property like a block of flats - then
distribute to each flat with copper, often UTP Ethernet), and eventually fibre to the home
(FTTH).
Why fibre?
Optical fibre has a number of advantages over copper cable. The signal is carried by light
rather than electrical signals. It is less susceptible to interference, has much higher bandwidth
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and hence data rates, a much longer range and is much harder to hack into as there is no
“leakage” of electromagnetic radiation from the cable. However, it is more expensive to buy
and harder to install. The end connection needs to be accurately machined and this means
cables have to be made up to the correct length.
Technology
As with BPL, there are a number of ways of implementing fibre to the home. From an end user
point of view, you get a fibre optic pair (one for transmit and one for receive) connected to a
dedicated box and providing 100 Mbit/s or 1 Gbit/s data rate. This is commonly done with
standard Ethernet over fibre protocols. Thus, the technology is just standard Ethernet over
fibre. It is not the technology that is holding up this roll out but the installation of the fibre
cables.
Fibre to the desk
It is also possible to deliver fibre to the desk. Although it is not common to go as far as the
desk, Ethernet networks are commonly connected using fibre optic backbones to link switches.
The increased range and data rates over fibre make this a good option but the extra cost
usually means it is not worth running the fibre to the desktop. Most PCs do not have the speed
to take advantage of this; however, many servers do and some applications such as rendering
video may also benefit.
Interacting with your classmates and tutor
Use the discussion forum for this lesson to discuss the following questions with other students:
Which of the broadband technologies would you prefer if you could choose freely? Why?
What factors that are not mentioned in the text should be considered when choosing what
broadband technology to proliferate? For example, how farsighted is a focus on
infrastructure building costs? How likely is it that future progress in broadband technology
will supersede the current leading technologies?
Do you know of other broadband technologies that are not described in the lesson text?
Summary
This lesson provides an overview of broadband data access for end users. It elaborates on
broadband data access and how this is provided using current technology, i.e. Broadband over
Cable TV, Digital Subscriber Line, Broadband over Power Line, and Fibre to the Home. Each
technology is based on a different connection with its own advantages, limitations and
challenges. From the provider’s perspective, the high-speed DSL technologies are a good
alternative to implementing a fibre-based last mile, which requires a large investment in cable
laying as well as the end equipment.
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2021 Arden University Ltd. All rights reserved
Read the article titled Fibre-Wireless (FiWi) Broadband Access Networks in an Age of
Convergence: Past, Present, and Future (Maier 2014). How do mixed media networks help to
proliferate broadband access? Reflect upon the various factors that enable to extend the
broadband service provision.
Further and wider reading
Viewing
Sckipio, 2015. G fast versus VDSL [video, online] Available from: [Accessed 2 October 2017]
TeamNANOG, 2013. DOCSIS 3.1 High Level Overview [video, online] Available from:
https://www.youtube.com/watch?v=gCw2jORPN-s [Accessed 2 October 2017]
ZCorum, 2015. G.Fast Technology - a DSL overview with Scott Helms and Rick Yuzzi. [video,
online] Available from: [Accessed 2 October 2017]
Key text
Ma Y., Jia Z. (2017) Evolution and Trends of Broadband Access Technologies and FiberWireless Systems. In: Tornatore M., Chang GK., Ellinas G. (eds) Fiber-Wireless Convergence
in Next-Generation Communication Networks. Optical Networks. Springer, Cham
Wider reading
Versatek, 2016. G.Fast Chipsets Give Copper a New Lease on Life Online. Accessed
22/09/2017
References
CableLabs, 2017. Full Duplex DOCSIS 3.1 [online]. California: CableLabs. Available from:
https://www.cablelabs.com/full-duplex-docsis/ [Accessed 2 October 2017]
DeLisle J, 2014, What’s the difference between broadband and narrowband RF
communications? [online] Microwaves & RF Available from: http://www.mwrf.com/systems/wh
at-s-difference-between-broadband-and-narrowband-rf-communications [Accessed 2 October
2017]
Johnson, O., 2014. Is copper the future of Fibre? G.Fast and the Battle of Bandwidth. [online]
ITUblog. Available from: https://news.itu.int/copper-future-fibre-g-fast-battle-bandwidth/
[Accessed 16 June 2021]
Krsti, V. and Stojanovi, M., 2000. Digital Subscriber Line Technology: Network Architecture,
Deployment Problems and Technical Solutions invited paper, Proceedings TELFOR, pp.38-45.
[online] Available from: http://static.pupin.rs/2018/07/Telfor_2000_06.pdf [Accessed 16 Jun
2021]
©
2021 Arden University Ltd. All rights reserved
Maier, M., 2014. Fiber-wireless (FiWi) broadband access networks in an age of convergence:
Past, present, and future. Advances in Optics, 2014. [online] Available from: - Fibre-Wireless
(FiWi) Broadband Access Networks in an Age of Convergence: Past, Present, and Future
[Accessed 2 October 2017]
Martin Maier, Fiber-Wireless (FiWi) Broadband Access Networks in an Age of Convergence:
Past, Present, and Future, Advances in Optics, vol. 2014, Open Access, Article ID 945364, 23
pages, 2014. doi:10.1155/2014/945364 [online] Available from:
http://downloads.hindawi.com/archive/2014/945364.pdf [Accessed 2 October 2017]
The Volpe Firm, 2017. DOCSIS Tutorial Series - All things DOCSIS [online]. Georgia: The
Volpe Firm. Available from: https://volpefirm.com/docsis-basics-tutorial-series [Accessed 2
October 2017]
Walko, J., 2016. Fighting fibre with G.Fast. [online] New Electronics. Available from:
http://www.newelectronics.co.uk/article-images/146176/P12-14.pdf [Accessed 2 October
2017]
©
2021 Arden University Ltd. All rights reserved
©
2021 Arden University Ltd. All rights reserved
©
2021 Arden University Ltd. All rights reserved
©
2021 Arden University Ltd. All rights reserved
©
2021 Arden University Ltd. All rights reserved
©
2021 Arden University Ltd. All rights reserved
©
2021 Arden University Ltd. All rights reserved
©
2021 Arden University Ltd. All rights reserved
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