2. INTRODUCTION OF THE TOPIC
The use of high bandwidth applications is increasing rapidly, with increased
consumer demand for streaming content such as video on demand, as well as peer-
to-peer file sharing,3G , MP3,IPTV all these require bandwidth.
For ISP's who are bandwidth limited, the "all you can eat" model may become
unsustainable as demand for bandwidth increases. Fixed costs represent 80-90% of
the cost of providing broadband service, and although most ISP's keep their cost
secret, the total cost (January 2008) is estimated to be about $0.10 per gigabyte.
Currently about 5% of users consume about 50% of the total bandwidth.
Some ISPs have begun experimenting with usage based pricing, notably a Time
Warner test in Beaumont, Texas. Bell Canada has imposed bandwidth caps on
customers, with pricing ranging from $1 to $7.50 per gigabyte for usage over certain
limits. For comparison, note that a typical standard-definition movie is 700mb-1.2GB,
while a high-definition movie is 6GB-12GB. This could conceivably result in a charge
of $90 to view a movie
Increasingly, all forms of electronic information telephony, data traffic, and
TV and radio are being converted into digital format, making it possible for a single
network to handle all of them. Also, there Is a continuing demand to transport more
information, more quickly. The result is a need for communication links with huge
bandwidth. Broadband is a possible answer.
Broad connectivity options
High-speed Internet access and Remote LAN access are just the beginning of
broadband. Other applications that will be made possible include videoconferencing,
desk-to-desk video, interactive CAD, and collaborative working. 3G wireless
networks (based on broadband) will lead to applications such as mobile multimedia,
mobile videoconferencing, etc.
Service providers will be able to provide demand-based differentiated services such
as Internet access combined with voice and video on demand to customers, and in
turn benefit from improved revenues. Demand-based services will allow users to
choose the bandwidth they require.
Here Is how broadband wireless networks will provide solutions.
2
3. Disaster control and management The Gujarat earthquake is a case in point of
where broadband wireless networks could have been deployed. Ad hoc wireless
broadband networks would have come in handy in Gujarat when all means of
communication failed, especially for sending multimedia information. This could be
online help from a surgeon to a medic who Is providing aid to disaster victims; or
schedules, distribution plans, and remote monitoring of relief material.
Military and defence Wireless broadband networks would enable military to
exchange multimedia information while on the move. In many tactical scenarios, the
effective use of these networks may become the difference between victory and
defeat.
Mobile videoconferencing For the busy business managers of the future and for
telecommuting workers operating from anywhere, wireless broadband data
communication may become a great asset.
Remote monitoring of industrial plants Engineers can monitor industrial plants right
from their mobile handset, rather than go to the plant or its monitoring station.
As you can see, broadband access can lead to more useful applications for end
users and new revenue generation models for network operators providing
broadband services.
3
5. BROADBAND OVERVIEW
Broadband is often called high-speed Internet, because it usually has a high
rate of data transmission. In general, any connection to the customer of 256 kbit/s
(0.256 Mbit/s) or more is considered broadband Internet. The International
Telecommunication Union Standardization Sector (ITU-T) recommendation I.113 has
defined broadband as a transmission capacity that is faster than primary rate ISDN,
at 1.5 to 2 Mbit/s. The FCC definition of broadband is 200 kbit/s (0.2 Mbit/s) in one
direction, and advanced broadband is at least 200 kbit/s in both directions. The
Organization for Economic Co-operation and Development (OECD) has defined
broadband as 256 kbit/s in at least one direction and this bit rate is the most common
baseline that is marketed as "broadband" around the world. There is no specific
bitrate defined by the industry, however, and "broadband" can mean lower-bitrate
transmission methods. Some Internet Service Providers (ISPs) use this to their
advantage in marketing lower-bitrates connections as broadband.
In practice, the advertised bandwidth is not always reliably available to the
customer; ISPs often allow a greater number of subscribers than their backbone
connection can handle, under the assumption that most users will not be using their
full connection capacity very frequently. This aggregation strategy works more often
than not, so users can typically burst to their full bandwidth most of the time;
however, peer-to-peer (P2P) file sharing systems, often requiring extended durations
of high bandwidth, stress these assumptions, and can cause major problems for
ISPs who have excessively overbooked their capacity. For more on this topic, see
traffic shaping. As take up for these introductory products increases, telcos are
starting to offer higher bit rate services. For existing connections, this most of the
time simply involves reconfiguring the existing equipment at each end of the
connection.
As the bandwidth delivered to end users increases, the market expects that video on
demand services streamed over the Internet will become more popular, though at
the present time such services generally require specialized networks. The data
rates on most broadband services still do not suffice to provide good quality video,
5
6. as MPEG-2 video requires about 6 Mbit/s for good results. Adequate video for some
purposes becomes possible at lower data rates, with rates of 768 kbit/s and 384 kbit/
s used for some video conferencing applications, and rates as low as 100 kbit/s used
for videophones using H.264/MPEG-4 AVC. The MPEG-4 format delivers high-
quality video at 2 Mbit/s, at the high end of cable modem and ADSL performance.
Increased bandwidth has already made an impact on newsgroups: postings to
groups such as alt.binaries.* have grown from JPEG files to entire CD and DVD
images. According to NTL, the level of traffic on their network increased from a daily
inbound news feed of 150 gigabytes of data per day and 1 terabyte of data out each
day in 2001 to 500 gigabytes of data inbound and over 4 terabytes out each day in
2002.
Technology
The standard broadband technologies in most areas are DSL and cable
modems. Newer technologies in use include VDSL and pushing optical fiber
connections closer to the subscriber in both telephone and cable plants. Fiber-optic
communication, while only recently being used in fiber to the premises and fiber to
the curb schemes, has played a crucial role in enabling Broadband Internet access
by making transmission of information over larger distances much more cost-
effective than copper wire technology. In a few areas not served by cable or ADSL,
community organizations have begun to install Wi-Fi networks, and in some cities
and towns local governments are installing municipal Wi-Fi networks. As of 2006,
high speed mobile Internet access has become available at the consumer level in
some countries, using the HSDPA and EV-DO technologies. The newest technology
being deployed for mobile and stationary broadband access is WiMAX.
6
7. Multilinking Modems
It is possible to roughly double dial-up capability with multilinking technology.
What is required are two modems, two phone lines, two dial-up accounts, and ISP
support for multilinking, or special software at the user end. This option was popular
with some high-end users before ISDN, DSL and other technologies became
available.
Diamond and other vendors had created dual phone line modems with bonding
capability. The speed of dual line modems is faster than 90 kbit/s. To use this
modem, the ISP should support line bonding. The Internet and phone charge will be
twice the ordinary dial-up charge.
Load Balancing takes two internet connections and feeds them into your network as
one double speed, more resilient internet connection. By choosing two independent
internet providers the load balancing hardware will automatically use the line with
least load which means should one line fail, the second one automatically takes up
the slack.
ISDN
Integrated Service Digital Network (ISDN) is one of the oldest high-speed
digital access methods for consumers and businesses to connect to the Internet. It is
a telephone data service standard. Its use in the United States peaked in the late
1990s prior to the availability of DSL and cable modem technologies. Broadband
service is usually compared to ISDN-BRI because this was the standard high-speed
access technology that formed a baseline for the challenges faced by the early
broadband providers. These providers sought to compete against ISDN by offering
faster and cheaper services to consumers.
A basic rate ISDN line (known as ISDN-BRI) is an ISDN line with 2 data
"bearer" channels (DS0 - 64 kbit/s each). Using ISDN terminal adapters (erroneously
called modems), it is possible to bond together 2 or more separate ISDN-BRI lines to
reach speeds of 256 kbit/s or more. The ISDN channel bonding technology has been
used for video conference applications and high-speed data transmission.
Primary rate ISDN, known as ISDN-PRI, is an ISDN line with 23 DS0 channels and
total speed of 1,544 kbit/s (US standard). ISDN E1 (European standard) line is an
7
8. ISDN lines with 30 DS0 channels and total speed of 2,048 kbit/s. Because ISDN is a
telephone-based product, a lot of the terminology and physical aspects of the line
are shared by the ISDN-PRI used for voice services. An ISDN line can therefore be
"provisioned" for voice or data and many different options, depending on the
equipment being used at any particular installation, and depending on the offerings
of the telephone company's central office switch. Most ISDN-PRI's are used for
telephone voice communication using large PBX systems, rather than for data. One
obvious exception is that ISPs usually have ISDN-PRI's for handling ISDN data and
modem calls.
It is mainly of historical interest that many of the earlier ISDN data lines used 56 kbit/
s rather than 64 kbit/s "B" channels of data. This caused ISDN-BRI to be offered at
both 128 kbit/s and 112 kbit/s rates, depending on the central office's switching
equipment.
Wired Ethernet
Where available, this method of broadband connection to the Internet would indicate
that the Internet access is very fast. However, just because Ethernet is offered
doesn't mean that the full 10, 100, or 1000 Mbit/s connection is able to be utilized for
direct Internet access. In a college dormitory for example, the 100 Mbit/s Ethernet
access might be fully available to on-campus networks, but Internet access speeds
might be closer to 4xT-1 speed (6 Mbit/s). If you are sharing a broadband connection
with others in a building, the access speed of the leased line into the building would
of course govern the end-user's speed.
However, in certain locations, true Ethernet broadband access might be available.
This would most commonly be the case at a POP or a datacenter, and not at a
typical residence or business. When Ethernet Internet access is offered, it could be
fiber-optic or copper twisted pair, and the speed will conform to standard Ethernet
speeds of up to 10 Gbit/s. The primary advantage is that no special hardware is
needed for Ethernet. Ethernet also has a very low latency.
Rural broadband
One of the great challenges of broadband is to provide service to potential
customers in areas of low population density, such as to farmers and ranchers. In
cities where the population density is high, it is easy for a service provider to recover
8
9. equipment costs, but each rural customer may require expensive equipment to get
connected. A similar problem existed a century ago when electrical power was
invented. Cities were the first to receive electric lighting, as early as 1880, while in
the United States some remote rural areas were still not electrified until the 1940s,
and even then only with the help of federally funded programs like the Tennessee
Valley Authority (TVA).
Several rural broadband solutions exist, though each has its own pitfalls and
limitations. Some choices are better than others, but are dependent on how
proactive the local phone company is about upgrading their rural technology.
Wireless Internet Service Provider (WISPs) are rapidly becoming a popular
broadband option for rural areas.
Satellite Internet
This employs a satellite in geostationary orbit to relay data from the satellite
company to each customer. Satellite Internet is usually among the most expensive
ways of gaining broadband Internet access, but in rural areas it may only compete
with cellular broadband. However, costs have been coming down in recent years to
the point that it is becoming more competitive with other high-speed options.
Satellite Internet also has a high latency problem caused by the signal having to
travel 35,000 km (22,000 miles) out into space to the satellite and back to Earth
again. The signal delay can be as much as 500 milliseconds to 900 milliseconds,
which makes this service unsuitable for applications requiring real-time user input
such as certain multiplayer Internet games and first-person shooters played over the
connection. Despite this, it is still possible for many games to be played, but the
scope is limited to real-time strategy or turn-based games. The functionality of live
interactive access to a distant computer can also be subject to the problems caused
by high latency. These problems are more than tolerable for just basic email access
and web browsing and in most cases are barely noticeable.
There is no simple way to get around this problem. The delay is primarily due
to the speed of light being only 300,000 km/second (186,000 miles per second).
Even if all other signaling delays could be eliminated it still takes the electromagnetic
9
10. wave 233 milliseconds to travel from ground to the satellite and back to the ground, a
total of 70,000 km (44,000 miles) to travel from you to the satellite company.
Since the satellite is usually being used for two-way communications, the total
distance increases to 140,000 km (88,000 miles), which takes a radio wave 466 ms
to travel. Factoring in normal delays from other network sources gives a typical
connection latency of 500-700 ms. This is far worse latency than even most dial-up
modem users' experience, at typically only 150-200 ms total latency.
Most satellite Internet providers also have a FAP (Fair Access Policy).
Perhaps one of the largest cons against satellite Internet, these FAPs usually throttle
a user's throughput to dial-up speeds after a certain "invisible wall" is hit (usually
around 200 MB a day). This FAP usually lasts for 24 hours after the wall is hit, and a
user's throughput is restored to whatever tier they paid for. This makes bandwidth-
intensive activities nearly impossible to complete in a reasonable amount of time
(examples include P2P and newsgroup binary downloading).
Cellular broadband
Cellular phone towers are very widespread, and as cellular networks move to third
generation (3G) networks they can support fast data; using technologies such as
EVDO, HSDPA and UMTS.
These can give broadband access to the Internet, with or without a cell phone
because Cardbus, ExpressCard, and USB cellular modems are available, as are
cellular broadband routers, which allow more than one computer to be connected to
the Internet using one cellular connection.
Advantages
1. The only broadband connection available on many cell phones and PDA's
2. Mobile wireless connection to the Internet
3. Available in all metropolitan areas, most large cities, and along major
highways. (See a map)
4. No need to aim an antenna in most cases
5. The antenna is extremely small compared to a satellite dish
6. Low latency compared to satellite Internet
7. Higher availability than WiFi "Hot Spots"
8. A traveler who already has cellular broadband will not need to pay different
WiFi Hot Spot providers for access.
10
11. Power-line Internet
This is a new service still in its infancy that may eventually permit broadband Internet
data to travel down standard high-voltage power lines. However, the system has a
number of complex issues, the primary one being that power lines are inherently a
very noisy environment. Every time a device turns on or off, it introduces a pop or
click into the line. Energy-saving devices often introduce noisy harmonics into the
line. The system must be designed to deal with these natural signaling disruptions
and work around them.
Broadband over power lines (BPL), also known as Power line communication, has
developed faster in Europe than in the US due to a historical difference in power
system design philosophies. Nearly all large power grids transmit power at high
voltages in order to reduce transmission losses, then near the customer use step-
down transformers to reduce the voltage. Since BPL signals cannot readily pass
through transformers, repeaters must be attached to the transformers. In the US, it is
common for a small transformer hung from a utility pole to service a single house. In
Europe, it is more common for a somewhat larger transformer to service 10 or 100
houses. For delivering power to customers, this difference in design makes little
difference, but it means delivering BPL over the power grid of a typical US city will
require an order of magnitude more repeaters than would be required in a
comparable European city.
The second major issue is signal strength and operating frequency. The system is
expected to use frequencies in the 10 to 30 MHz range, which has been used for
decades by licensed amateur radio operators, as well as international shortwave
broadcasters and a variety of communications systems (military, aeronautical, etc.).
Power lines are unshielded and will act as transmitters for the signals they carry, and
have the potential to completely wipe out the usefulness of the 10 to 30 MHz range
for shortwave communications purposes.
Wireless ISP
This typically employs the current low-cost 802.11 Wi-Fi radio systems to link
up remote locations over great distances, but can use other higher-power radio
communications systems as well.
11
12. Traditional 802.11b was licensed for omni directional service spanning only 100-150
meters (300-500 ft). By focusing the signal down to a narrow beam with a Yagi
antenna it can instead operate reliably over a distance of many miles.
Rural Wireless-ISP installations are typically not commercial in nature and are
instead a patchwork of systems built up by hobbyists mounting antennas on radio
masts and towers, agricultural storage silos, very tall trees, or whatever other tall
objects are available. There are currently a number of companies that provide this
service. A wireless Internet access provider map for USA is publicly available for
WISPS.
iBlast
iBlast was the brand name for a theoretical high-speed (7 Mbit/s), one-way digital
data transmission technology from Digital TV station to users that was developed
between June 2000 to October 2005.
WorldSpace
WorldSpace is a digital satellite radio network based in Washington DC. It covers
most of Asia and Europe plus all of Africa by satellite. Beside the digital audio, user
can receive one way high speed digital data transmission (150 Kilobit/second) from
the Satellite.
Pricing
Traditionally, ISPs have used an "all you can eat" or flat rate model, with pricing
determined by the maximum bitrate chosen by the customer. However the use of
high bandwidth applications is increasing rapidly, with increased consumer demand
for streaming content such as video on demand, as well as peer-to-peer file sharing.
For ISP's who are bandwidth limited, the "all you can eat" model may become
unsustainable as demand for bandwidth increases. Fixed costs represent 80-90% of
the cost of providing broadband service, and although most ISP's keep their cost
secret, the total cost (January 2008) is estimated to be about $0.10 per gigabyte.
Currently about 5% of users consume about 50% of the total bandwidth.
Some ISPs have begun experimenting with usage based pricing, notably a Time
Warner test in Beaumont, Texas. Bell Canada has imposed bandwidth caps on
customers, with pricing ranging from $1 to $7.50 per gigabyte for usage over certain
12
13. limits. For comparison, note that a typical standard-definition movie is 700mb-1.2GB,
while a high-definition movie is 6GB-12GB. This could conceivably result in a charge
of $90 to view a movie.
Broadband worldwide
Broadband technologies
Fiber-optic communication
List of device bandwidths
Public switched telephone network (PSTN)
Baseband
Narrowband
Local loop
Back-channel, a low-speed, or less-than-optimal, transmission channel in the
opposite direction to the main channel
Broadband implementations
Digital Subscriber Line (DSL), digital data transmission over the wires used in
the local loop of a telephone network
Local Multipoint Distribution Service, broadband wireless access technology
that uses microwave signals operating between the 26 GHz and 29 GHz bands
WiMAX, a standards-based wireless technology that provides high-throughput
broadband connections over long distances
Power line communication, wireline technology using the current electricity
networks
Satellite Internet access
Cable modem, designed to modulate a data signal over cable television
infrastructure
Fiber to the premises, based on fiber-optic cables and associated optical
electronics
High-Speed Downlink Packet Access (HSDPA), a new mobile telephony
protocol, sometimes referred to as a 3.5G (or "3½G") technology
Evolution-Data Optimized (EVDO), is a wireless radio broadband data
standard adopted by many CDMA mobile phone service providers
13
14. Future broadband implementations
White Spaces Coalition a group of technology companies aiming to deliver
broadband internet access via unused analog television frequencies
Broadband applications
Broadband telephony
Broadband radio
14
16. INDIAN BROADBAND MARKET
The telecom world may still be marveling at India's mobile telephony growth, which
at 100 million connections has emerged as the fastest growing in the world, but the
other scorching growth story in the country's telecom sector could well be broadband
over wireless.
That's the conclusion Canada-based broadband telecom research firm Maravedis
Inc. and its Indian counterpart Tonse Telecom arrived at in their just released report
on the Indian broadband market.
The report forecasts that the next phenomenal telecom growth story in India lies in
broadband wireless access (BWA) segment, which could experience the same
explosive growth as mobile telephony experienced over the last three years.
"Our analysis of the Indian broadband market has revealed that although broadband
has seen grown quite a bit in the past year it has seen nothing yet," said Adlane
Fellah, CEO and founder of Maravedis, that claims to be a world leader in market
research and analysis of the global broadband, BWA and WiMax markets.
“But if India can bring in the right conditions, broadband, particularly over
wireless access, would follow the same explosion as mobile phones experienced in
India lately."
The mobile phone made its debut in the country in 1995 and struggled for the first
three years to touch the 1 million mark in 1998. Growth started perking up thereafter
to reach 3 million in 2000, 5 million in 2001, and 10 million in 2002.
But finally due to a variety of reasons like a new telecom policy that removed the
problems of mobile operators and the crashing of handset prices, mobile telecom
subscription exploded in the country to reach 100 million in June 2006.
And now, analysts even project that India's monthly net mobile subscriber additions
could overtake those of China in the next few months. China added 5.6 million
mobile subscribers in May, while India's mobile-phone subscriber base grew by 4.25
million (June figures not released yet) that month.
However, according to Sridhar Pai, the co-author of the report, to achieve that kind of
growth the Indian government has to take the first steps, which are opening up the
spectrum-radio waves that carry the voice/data- for WiMax so that broadband can
16
17. proliferate over wireless using specifically the WiMax technology, and formulates
policies so that prices of end user equipments -- like computers and modems -- fall
to make them more affordable for Indians.
WiMax is defined as Worldwide Interoperability for Microwave Access. It is a
standards-based wireless technology that provides high-throughput broadband
connections over long distances. WiMax can be used for a number of applications,
including "last mile" broadband connections, hotspots and cellular backhaul, and
high-speed enterprise connectivity for business.
Broadband services were launched in India in 2005 and now cover about 300 Indian
cities with a combined 1.5 million connections. But even as wireless telephony was
growing at scorching rate then, India chose to introduce broadband using the ADSL
or asymmetric digital subscriber line technology that basically uses existing copper
telephone lines thus restricting its data transfer speed and reach.
"In a country as congested as India the ADSL technology can only grow to a certain
extent," Pai said, "and in fact it has already reached saturation."
Which is why, even as 1.5 million broadband connections in about a year look
reasonably satisfactory by Indian standards, the number is piffling considering that
India now has 50 million fixed line and 100 million mobile users, said the report.
However, while low broadband penetration is a clear opportunity, its main hurdle is
availability of spectrum. Currently, telecom operators and the government are
engaged in a war over spectrum allocation. While the operators are clamoring for
more spectrum for expansion and improvement their quality of services, the
government that "owns" most the spectrum through the country's space and defense
sectors, is still undecided on how to allocate this scare resource.
The report said that even if the government has recently announced allocation of
spectrum on the 3.3 to 3.4 GHz band range, the country needs 3.4 to 3.5 GHz --
which is the WiMax spectrum -- for a profitable business case.
Meanwhile activity in the broadband wireless access space seems to be hectic
already, in anticipation of the government announcing its new spectrum allocation
policy expected by the year end.
For instance, five Indian operators, Bharti TeleVentures, Reliance Telecom, the
NASDAQ-listed SIFY Ltd, the state-owned BSNL and Tata Group-owned VSNL have
acquired Broadband wireless licenses in 3.3 GHz range and are in various stages of
trials.
17
18. The report says that VSNL has also announced Phase 1 pre-WiMax deployment
although there is clearly insufficient spectrum.
Global telecom companies too have joined the fray. Intel is reportedly making
"significant progress" in working closely with the Indian government in bringing the
country's rural broadband goals to reality, while Motorola is strengthening its
presence in the hinterlands through its extensive broadband wireless access projects
for state governments.
Alcatel has joined the bandwagon too by entering into a joint venture recently with a
government-owned telecom research outfit to focus on exclusive BWA/WiMax
solutions that are tailor made for India "at Indian price points."
"Although the Indian broadband arena is emerging, it offers huge potential for those
that can demonstrate perseverance, patience and commitment," said the report,
which has projected that assuming India releases WiMax spectrum by this year end,
the annual BWA/WiMax equipment market opportunity -- a mere $6 million in 2005 --
could increase to $256 million in 2012.
"By then India could have accumulated 18 million BWA subscribers making the
country one of the top three WiMax markets in the world,"
Special reference to rural broadband
One of the great challenges of broadband is to provide service to potential
customers in areas of low population density, such as to farmers and ranchers. In
cities where the population density is high, it is easy for a service provider to recover
equipment costs, but each rural customer may require expensive equipment to get
connected.
Several rural broadband solutions exist, though each has its own pitfalls and
limitations. Some choices are better than others, but are dependent on how
proactive the local phone company is about upgrading their rural
technology.Wireless Internet Service Provider (WISPs) are rapidly becoming a
popular broadband option for rural areas.
According to the report in November provided by Voice and data magazine rural
broadband area has been referred to as Gold Mines for resources and revenues and
major service providers instead of taking governments help have offered government
18
19. to help out in the successful implementation of broadband in Rural India withspecial
attention to the areas of
a) Healtcare
b) Education
C) Entertainment-IPTV, Gaming, Video Streaming servers
d) Communication-VOIP
All these is not possible without the successful implementation of Broad band in
India hence concluding we can say that with growth and progress of the economy in
India Broadband is is the underlying need which has been well understood ,hence
there lies a huge potencial market and technology for the success of broadband.
WiMAX
WiMAX, the Worldwide Interoperability for Microwave Access, is a
telecommunications technology aimed at providing wireless data over long distances
in a variety of ways, from point-to-point links to full mobile cellular type access. It is
based on the IEEE 802.16 standard, which is also called WirelessMAN. The name
"WiMAX" was created by the WiMAX Forum, which was formed in June 2001 to
promote conformance and interoperability of the standard. The forum describes
WiMAX as "a standards-based technology enabling the delivery of last mile wireless
broadband access as an alternative to cable and DSL" (and also to HSPA).
Uses
The bandwidth and reach of WiMAX make it suitable for the following potential
applications:
Connecting Wi-Fi hotspots with each other and to other parts of the Internet.
Providing a wireless alternative to cable and DSL for last mile broadband
access.
Providing high-speed data and telecommunications services.
Providing a diverse source of Internet connectivity as part of a business
continuity plan. That is, if a business has a fixed and a wireless Internet connection,
19
20. especially from unrelated providers, they are unlikely to be affected by the same
service outage.
Providing nomadic connectivity.
Broadband access
Many companies are closely examining WiMAX for "last mile" connectivity at high
data rates. The resulting competition may bring lower pricing for both home and
business customers or bring broadband access to places where it has been
economically unavailable. Prior to WiMAX, many operators have been using
proprietary fixed wireless technologies for broadband services.
WiMAX access was used to assist with communications in Aceh, Indonesia, after the
tsunami in December 2004. All communication infrastructure in the area, other than
Ham Radio, was destroyed, making the survivors unable to communicate with
people outside the disaster area and vice versa. WiMAX provided broadband access
that helped regenerate communication to and from Aceh.
WiMAX was used by Intel to assist the FCC and FEMA in their communications
efforts in the areas affected by Hurricane Katrina.
Subscriber units
WiMAX subscriber units are available in both indoor and outdoor versions from
several manufacturers. Self-install indoor units are convenient, but radio losses
mean that the subscriber must be significantly closer to the WiMAX base station than
with professionally-installed external units. As such, indoor-installed units require a
much higher infrastructure investment as well as operational cost (site lease,
backhaul, maintenance) due to the high number of base stations required to cover a
given area. Indoor units are comparable in size to a cable modem or DSL modem.
Outdoor units are roughly the size of a laptop PC, and their installation is comparable
to a residential satellite dish.
With the advent of mobile WiMAX, there is an increasing focus on portable units.
This includes handsets (similar to cellular smartphones) and PC peripherals (PC
Cards or USB dongles). In addition, there is much emphasis from operators on
consumer electronics devices (game terminals, MP3 players and the like); it is
notable this is more similar to Wi-Fi than 3G cellular technologies.
Mobile handset applications
20
21. Some cellular companies are evaluating WiMAX as a means of increasing bandwidth
for a variety of data-intensive applications.
Sprint Nextel announced in mid-2006 that it would invest about US$ 5 billion in a
WiMAX technology buildout over the next few years.[3] As of November 9,
2007 this project in partnership with Clearwire has been shelved, but the project
could be revived with or without Clearwire now that Sprint has hired Dan Hesse as
its new CEO. On December 5, 2007, Bin Shen, Sprint's VP of Product Management
and Partnership Development, announced that Sprint's WiMAX network will go live in
a soft launch in Chicago, Baltimore, and Washington DC. Full commercial launch is
still expected to be approximately spring of 2008. NYT reports that Sprint's soft
launch in the three test markets went live as of January 11, 2008. Sprint hopes to
use WiMAX as a springboard past its competitors and past concerns about its
shrinking user base and concerns about the financial wisdom of the large WiMAX
deployment.
Backhaul/access network applications
WiMAX is a possible replacement candidate for cellular phone technologies
such as GSM and CDMA, or can be used as a layover to increase capacity. It has
also been considered as a wireless backhaul technology for 2G, 3G, and 4G
networks in both developed and developing nations.
"Backhaul" for remote cellular operations is typically provided via satellite, and in
urban areas via one or several T1 connections. WiMAX is mobile broadband and as
such has much more substantial backhaul need. Therefore traditional backhaul
solutions are not appropriate. Consequently the role of very high capacity wireless
microwave point-to-point backhaul (200 or more Mbit/s with typically 1 ms or less
delay) is on the rise. Also fiber backhaul is more appropriate.
Deploying WiMAX in rural areas with limited or no internet backbone will be
challenging as additional methods and hardware will be required to procure sufficient
bandwidth from the nearest sources -- the difficulty being in proportion to the
distance between the end-user and the nearest sufficient internet backbone.
Given the limited wired infrastructure in some developing countries, the costs to
install a WiMAX station in conjunction with an existing cellular tower or even as a
21
22. solitary hub are likely to be small in comparison to developing a wired solution. Areas
of low population density and flat terrain are particularly suited to WiMAX and its
range. For countries that have skipped wired infrastructure as a result of prohibitive
costs and unsympathetic geography, WiMAX can enhance wireless infrastructure in
an inexpensive, decentralized, deployment-friendly and effective manner.
Technical information
WiMAX is a term coined to describe standard, interoperable implementations
of IEEE 802.16 wireless networks, similar to the way the term Wi-Fi is used for
interoperable implementations of the IEEE 802.11 Wireless LAN standard. However,
WiMAX is very different from Wi-Fi in the way it works.
MAC layer/data link layer
In Wi-Fi the media access controller (MAC) uses contention access — all
subscriber stations that wish to pass data through a wireless access point (AP) are
competing for the AP's attention on a random interrupt basis. This can cause
subscriber stations distant from the AP to be repeatedly interrupted by closer
stations, greatly reducing their throughput. This makes services such as Voice over
IP (VoIP) or IPTV, which depend on an essentially-constant Quality of Service (QoS)
depending on data rate and interruptibility, difficult to maintain for more than a few
simultaneous users.
In contrast, the 802.16 MAC uses a scheduling algorithm for which the subscriber
station need compete once (for initial entry into the network). After that it is allocated
an access slot by the base station. The time slot can enlarge and contract, but
remains assigned to the subscriber station, which means that other subscribers
cannot use it. In addition to being stable under overload and over-subscription
(unlike 802.11), the 802.16 scheduling algorithm can also be more bandwidth
efficient. The scheduling algorithm also allows the base station to control QoS
parameters by balancing the time-slot assignments among the application needs of
the subscriber stations.
Physical layer
22
23. The original version of the standard on which WiMAX is based (IEEE 802.16)
specified a physical layer operating in the 10 to 66 GHz range. 802.16a, updated in
2004 to 802.16-2004, added specifications for the 2 to 11 GHz range. 802.16-2004
was updated by 802.16e-2005 in 2005 and uses scalable orthogonal frequency-
division multiple access (SOFDMA) as opposed to the OFDM version with 256 sub-
carriers (of which 200 are used) in 802.16d. More advanced versions, including
802.16e, also bring Multiple Antenna Support through Multiple-input multiple-output
communications (MIMO) See WiMAX MIMO. This brings potential benefits in terms
of coverage, self installation, power consumption, frequency re-use and bandwidth
efficiency. 802.16e also adds a capability for full mobility support. The WiMAX
certification allows vendors with 802.16d products to sell their equipment as WiMAX
certified, thus ensuring a level of interoperability with other certified products, as long
as they fit the same profile.
Most commercial interest is in the 802.16d and .16e standards, since the lower
frequencies used in these variants suffer less from inherent signal attenuation and
therefore give improved range and in-building penetration. Already today, a number
of networks throughout the world are in commercial operation using certified WiMAX
equipment compliant with the 802.16d standard.
23
24. Architecture
The WiMAX Forum has defined an architecture that defines how a WiMAX network
connects with other networks, and a variety of other aspects of operating such a
network, including address allocation, authentication, etc. An overview of the
architecture is given in the illustration. This defines the following components:
SS/MS: the Subscriber Station/Mobile Station
ASN: the Access Service Network
BS: Base station, part of the ASN
ASN-GW: the ASN Gateway, part of the ASN
CSN: the Connectivity Service Network
HA: Home Agent, part of the CSN
AAA: AAA Server, part of the CSN
NAP: a Network Access Provider
24
25. NSP: a Network Service Provider
plus a number of interconnections (or reference points) between these, labeled R1 to
R5 and R8.
It's important to note that the functional architecture can be designed into various
hardware configurations rather than fixed configurations. For example, the
architecture is flexible enough to allow remote/mobile stations of varying scale and
functionality and Base Stations of varying size - e.g. femto, pico, and mini BS as well
as macros.
Comparison with Wi-Fi
Possibly due to the fact both WiMAX and Wi-Fi begin with the same two
letters, are based upon IEEE standards beginning with "802.", and both have a
connection to wireless connectivity and the Internet, comparisons and confusion
between the two are frequent. Despite this, the two standards are aimed at different
applications.
WiMAX is a long-range system, covering many kilometers that typically uses
licensed spectrum (although it is also possible to use unlicensed spectrum) to deliver
a point-to-point connection to the Internet from an ISP to an end user. Different
802.16 standards provide different types of access, from mobile (similar to data
access via a cellphone) to fixed (an alternative to wired access, where the end user's
wireless termination point is fixed in location.)
Wi-Fi is a shorter range system, typically hundreds of meters, that uses
unlicensed spectrum to provide access to a network, typically covering only the
network operator's own property. Typically Wi-Fi is used by an end user to access
their own network, which may or may not be connected to the Internet. If WiMAX
provides services analogous to a cellphone, Wi-Fi is more analogous to a cordless
phone.
WiMAX and Wi-Fi have quite different Quality of Service (QoS)
mechanisms. WiMAX uses a mechanism based on setting up connections between
the Base Station and the user device. Each connection is based on specific
scheduling algorithms, which means that QoS parameters can be guaranteed for
25
26. each flow. Wi-Fi has introduced a QoS mechanism similar to fixed Ethernet, where
packets can receive different priorities based on their tags. This means that QoS is
relative between packets/flows, as opposed to guaranteed.
WiMAX is highly scalable from what are called "femto"-scale remote
stations to multi-sector 'maxi' scale base that handle complex tasks of management
and mobile handoff functions and include MIMO-AAS smart antenna subsystems.
Due to the ease and low cost with which Wi-Fi can be deployed, it is sometimes
used to provide Internet access to third parties within a single room or building
available to the provider, often informally, and sometimes as part of a business
relationship. For example, many coffee shops, hotels, and transportation hubs
contain Wi-Fi access points providing access to the Internet for customers.
Spectrum allocation issues
The 802.16 specification applies across a wide swath of the RF spectrum,
and WiMAX could function on any frequency below 66 GHz, (higher frequencies
would decrease the range of a Base Station to a few hundred meters in an urban
environment).
There is no uniform global licensed spectrum for WiMAX, although the WiMAX
Forum has published three licensed spectrum profiles: 2.3 GHz, 2.5 GHz and 3.5
GHz, in an effort to decrease cost: economies of scale dictate that the more WiMAX
embedded devices (such as mobile phones and WiMAX-embedded laptops) are
produced, the lower the unit cost. (The two highest cost components of producing a
mobile phone are the silicon and the extra radio needed for each band.) Similar
economy of scale benefits apply to the production of Base Stations.
In the unlicensed band, 5.x GHz is the approved profile. Telecom
companies are unlikely to use this spectrum widely other than for backhaul, as they
do not own and control the spectrum.
In the USA, the biggest segment available is around 2.5 GHz, and is already
assigned, primarily to Sprint Nextel and Clearwire. Elsewhere in the world, the most-
likely bands used will be the Forum approved ones, with 2.3 GHz probably being
most important in Asia. Some countries in Asia like India and Indonesia will use a
mix of 2.5 GHz, 3.3 GHz and other frequencies.
26
27. Analog TV bands (700 MHz) may become available for WiMAX use, but
await the complete rollout of digital TV, and there will be other uses suggested for
that spectrum. In the USA the FCC auction for this spectrum began in January 2008
and, as a result, the biggest share of the spectrum went to Verizon Wireless and the
next biggest to AT&T. EU commissioner Viviane Reding has suggested re-allocation
of 500–800 MHz spectrum for wireless communication, including WiMAX.
WiMAX profiles define channel size, TDD/FDD and other necessary
attributes in order to have inter-operating products. The current fixed profiles are
defined for both TDD and FDD profiles. At this point, all of the mobile profiles are
TDD only. The fixed profiles have channel sizes of 3.5 MHz, 5 MHz, 7 MHz and 10
MHz. The mobile profiles are 5 MHz, 8.75 MHz and 10 MHz. (Note: the 802.16
standard allows a far wider variety of channels, but only the above subsets are
supported as WiMAX profiles.)
Since October 2007, the Radiocommunication Sector of the International
Telecommunication Union (ITU-R) has decided to include WiMAX technology in the
IMT-2000 set of standards. This enables spectrum owners (specifically in the
2.5-2.69 GHz band at this stage) to use Mobile WiMAX equipment in any country
that recognizes the IMT-2000.
Spectral efficiency
One of the significant advantages of advanced wireless systems such as WiMAX is
spectral efficiency. For example, 802.16-2004 (fixed) has a spectral efficiency of 3.7
(bit/s)/Hertz, and other 3.5–4G wireless systems offer spectral efficiencies that are
similar to within a few tenths of a percent. The notable advantage of WiMAX comes
from combining SOFDMA with smart antenna technologies. This multiplies the
effective spectral efficiency through multiple reuse and smart network deployment
topologies. The direct use of frequency domain organization simplifies designs using
MIMO-AAS compared to CDMA/WCDMA methods, resulting in more-effective
systems.
Silicon implementations
A critical requirement for the success of a new technology is the availability of
low-cost chipsets and silicon implementations.
27
28. Intel is a leader in promoting WiMAX, and has developed its own chipset. However, it
is notable that most of the major semiconductor companies have to date been more
cautious of involvement and most of the solutions come from specialist smaller or
start-up suppliers. For the client-side these include ApaceWave, GCT
Semiconductor, Altair Semiconductor, Beceem, Comsys, Runcom, Motorola with TI,
NextWave, Sequans, Redpine signals, Wavesat, Coresonic & SySDSoft. Both
Sequans and Wavesat manufacture solutions for both clients and network while TI,
DesignArt, and picoChip are focused on WiMAX chip sets for base stations. The
large number of suppliers during introduction phase of WiMAX demonstrates the low
entry barriers for IPR.
Standards
The current WiMAX incarnation, Mobile WiMAX, is based upon IEEE Std
802.16e-2005, approved in December 2005. It is an amendment of IEEE Std
802.16-2004, and so the actual standard is 802.16-2004 as amended by
802.16e-2005 — the specifications need to be read together to understand them.
IEEE Std 802.16-2004 addresses only fixed systems. It replaced IEEE Standards
802.16-2001, 802.16c-2002, and 802.16a-2003.
IEEE 802.16e-2005
IEEE 802.16e-2005 improves upon IEEE 802.16-2004 by:
Adding support for mobility (soft and hard handover between base stations).
This is seen as one of the most important aspects of 802.16e-2005, and is the very
basis of 'Mobile WiMAX'.
Scaling of the Fast Fourier Transform (FFT) to the channel bandwidth in
order to keep the carrier spacing constant across different channel bandwidths
(typically 1.25 MHz, 5 MHz, 10 MHz or 20 MHz). Constant carrier spacing results in
a higher spectrum efficiency in wide channels, and a cost reduction in narrow
channels. Also known as Scalable OFDMA (SOFDMA). Other bands not multiples of
1.25 MHz are defined in the standard, but because the allowed FFT subcarrier
numbers are only 128, 512, 1024 and 2048, other frequency bands will not have
exactly the same carrier spacing, which might not be optimal for implementations.
Improving NLOS coverage by utilizing advanced antenna diversity
schemes, and hybrid-Automatic Retransmission Request (HARQ)
28
29. Improving capacity and coverage by introducing Adaptive Antenna Systems
(AAS) and Multiple Input Multiple Output (MIMO) technology
Increasing system gain by use of denser sub-channelization, thereby improving
indoor penetration
Introducing high-performance coding techniques such as Turbo Coding and
Low-Density Parity Check (LDPC), enhancing security and NLOS performance
Introducing downlink sub-channelization, allowing administrators to trade
coverage for capacity or vice versa
Enhanced Fast Fourier Transform algorithm can tolerate larger delay
spreads, increasing resistance to multipath interference .Adding an extra QoS class
(enhanced real-time Polling Service) more appropriate for VoIP applications.
802.16d vendors point out that fixed WiMAX offers the benefit of available
commercial products and implementations optimized for fixed access. It is a popular
standard among alternative service providers and operators in developing areas due
to its low cost of deployment and advanced performance in a fixed environment.
Fixed WiMAX is also seen as a potential standard for backhaul of wireless base
stations such as cellular, Wi-Fi or even Mobile WiMAX.
SOFDMA (used in 802.16e-2005) and OFDM256 (802.16d) are not
compatible so most equipment will have to be replaced if an operator wants or needs
to move to the later standard. However, some manufacturers are planning to provide
a migration path for older equipment to SOFDMA compatibility which would ease the
transition for those networks which have already made the OFDM256 investment.
Intel provides a dual-mode 802.16-2004 802.16-2005 chipset for subscriber units.
This affects a relatively small number users and operators.
3G and 4G cellular phone systems
Both major 3G systems, CDMA2000 and UMTS, compete with WiMAX. Both aim to
offer DSL-class Internet access in addition to phone service. UMTS has also been
enhanced to compete directly with WiMAX in the form of UMTS-TDD, which can use
WiMAX oriented spectrum and provides a more consistent, if lower bandwidth at
peak, user experience than WiMAX.
29
30. 3G cellular phone systems usually benefit from already having entrenched
infrastructure, being upgraded from earlier systems. Users can usually fall back to
older systems when they move out of range of upgraded equipment, often relatively
seamlessly.
The major cellular standards are being evolved to so-called 4G, high bandwidth, low
latency, all-IP networks with voice services built on top. With GSM/UMTS, the move
to 4G is the 3GPP Long Term Evolution effort. For AMPS/TIA derived standards
such as CDMA2000, a replacement called Ultra Mobile Broadband is under
development. In both cases, existing air interfaces are being discarded, in favour of
OFDMA for the downlink and a variety of OFDM based solutions for the uplink, much
akin to WiMAX.
In some areas of the world the wide availability of UMTS and a general desire for
standardization has meant spectrum has not been allocated for WiMAX: in July
2005, the EU-wide frequency allocation for WiMAX was blocked.
Mobile Broadband Wireless Access
Mobile Broadband Wireless Access (MBWA) is a technology being developed by
IEEE 802.20 and is aimed at wireless mobile broadband for operations from 120 to
350 km/h. The 802.20 standard committee was first to define many of the methods
which were later funneled into Mobile WiMAX, including high speed dynamic
modulation and similar scalable OFDMA capabilities. It apparently retains fast hand-
off, Forward Error Correction (FEC) and cell edge enhancements.
The Working Group was temporarily suspended in mid 2006 by the IEEE-SA
Standards Board since it had been the subject of a number of appeals, and a
preliminary investigation of one of these "revealed a lack of transparency, possible
'dominance,' and other irregularities in the Working Group".
In September 2006 the IEEE-SA Standards Board approved a plan to enable the
working group to continue under new conditions, and the standard is now expected
to be finalized by Q2 2008.
Internet-oriented systems
Early WirelessMAN standards, the European standard HIPERMAN and Korean
standard WiBro have been harmonized as part of WiMAX and are no longer seen as
competition but as complementary. All networks now being deployed in South Korea,
the home of the Wibro standard, are now WiMAX.
30
31. As a short-range mobile Internet solution, such as in cafes and at transportation
hubs like airports, the popular Wi-Fi 802.11b/g system is widely deployed, and
provides enough coverage for some users to feel subscription to a WiMAX service is
unnecessary.
Comparison
The following table should be treated with caution as it only shows peak rates which
are potentially very misleading. In addition the comparisons listed are not normalized
by physical channel size (i.e. spectrum used to achieve the listed peak rates); this
obfuscates spectral efficiency and net through-put capabilities of the different
wireless technologies listed below.
Competing technologies
Comparison of Mobile Internet Access methods
Uplin
Downli
Primary k
Standard Family Radio Tech nk Notes
Use (Mbit/
(Mbit/s)
s)
Quoted
speeds only
achievable at
Mobile MIMO- very short
802.16e WiMAX 70 70
Internet SOFDMA ranges, more
practically 10
Mbit/s at 10
km.
HIPERMA Mobile
HIPERMAN OFDM 56.9 56.9
N Internet
31
32. Mobile Inter Mobile range
WiBro WiBro OFDMA 50 50
net (900 m)
HC-
iBurst Mobile Inter
iBurst SDMA/TDD/MI 64 64 3–12 km
802.20 net
MO
EDGE Mobile Inter 3GPP
GSM TDMA/FDD 1.9 0.9
Evolution net Release 7
HSDPA
widely
deployed.
Typical
UMTS W-
CDMA/FDD downlink
CDMA 0.384 0.384
UMTS/3G Mobile rates today
HSDPA+HS 14.4 5.76
SM phone CDMA/FDD/MI 1–2 Mbit/s,
UPA 42 11.5
MO ~200 kbit/s
HSPA+
uplink; future
downlink up
to 28.8 Mbit/
s.
UMTS-TDD UMTS/3G Mobile CDMA/TDD 16 16 Reported
SM Internet speeds
according to
IPWireless
using
16QAM
modulation
similar to
HSDPA+HS
32
33. UPA
OFDMA/MIMO Still in
UMTS/4G
LTE UMTS General 4G /SC-FDMA >100 >50 development
SM
(HSOPA)
Succeeded
by EV-DO
CDMA200 Mobile
1xRTT CDMA 0.144 0.144
0 phone Rev B note:
N is the
EV-DO 1x R number of
ev. 0 1.25 MHz
2.45 0.15
EV-DO 1x R CDMA200 Mobile chunks of
CDMA/FDD 3.1 1.8
ev.A 0 Internet spectrum
4.9xN 1.8xN
EV-DO Rev. used.Not
B yetdeployed.
Notes: All speeds are theoretical maximums and will vary by a number of factors,
including the use of external antennae, distance from the tower and the ground
speed (e.g. communications on a train may be poorer than when standing still).
Usually the bandwidth is shared between several terminals. The performance of
each technology is determined by a number of constraints, including the spectral
efficiency of the technology, the cell sizes used, and the amount of spectrum
available. For more information.
Future development
Mobile WiMAX based upon 802.16e-2005 has been accepted as IP-OFDMA for
inclusion as the sixth wireless link system under IMT-2000. This can hasten
acceptance by regulatory authorities and operators for use in cellular spectrum.
WiMAX II, 802.16m will be proposed for IMT-Advanced 4G.
The goal for the long term evolution of both WiMAX and LTE is to achieve 100 Mbit/s
mobile and 1 Gbit/s fixed-nomadic bandwidth as set by ITU for 4G NGMN (Next
Generation Mobile Network) systems through the adaptive use of MIMO-AAS and
33
34. smart, granular network topologies. 3GPP LTE and WiMAX-m are concentrating
much effort on MIMO-AAS, mobile multi-hop relay networking and related
developments needed to deliver 10X and higher Co-Channel reuse multiples.
Since the evolution of core air-link technologies has approached the practical limits
imposed by Shannon's Theorem, the evolution of wireless has embarked on pursuit
of the 3X to 10X+ greater bandwidth and network efficiency by advances in the
spatial and smart wireless broadband networking technologies.
Interference
A field test conducted by SUIRG (Satellite Users Interference Reduction Group) with
support from the U.S. Navy, the Global VSAT Forum, and several member
organizations yielded conclusive results on the incompatibility of WiMAX systems
and satellites sharing the C-band.
The WiMAX Forum has not answered yet.
WI-FI
The purpose of Wi-Fi is simple: Hide complexity by enabling wireless access to
applications and data, media and streams. The main aims of Wi-Fi are:
enable access to information easily
ensure compatibility and coexistence
get rid of cabling and wiring
get rid of switches, adapters, plugs and connectors.
Uses
34
35. A Wi-Fi enabled device such as a PC, game console, cell phone, MP3 player or
PDA can connect to the Internet when within range of a wireless network connected
to the Internet. The coverage of one or more interconnected access points — called
a hotspot — can comprise an area as small as a single room with wireless-opaque
walls or as large as many square miles covered by overlapping access points. Wi-Fi
technology has served to set up mesh networks, for example, in London.[1] Both
architectures can operate in community networks.
In addition to restricted use in homes and offices, Wi-Fi can make access publicly
available at Wi-Fi hotspots provided either free of charge or to subscribers to various
providers. Organizations and businesses such as airports, hotels and restaurants
often provide free hotspots to attract or assist clients. Enthusiasts or authorities who
wish to provide services or even to promote business in a given area sometimes
provide free Wi-Fi access. Metropolitan-wide Wi-Fi (Muni-Fi) already has more than
300 projects in process.[2]
Wi-Fi also allows connectivity in peer-to-peer (wireless ad-hoc network)
mode, which enables devices to connect directly with each other. This connectivity
mode can prove useful in consumer electronics and gaming applications.
When wireless networking technology first entered the market many problems
ensued for consumers who could not rely on products from different vendors working
together. The Wi-Fi Alliance began as a community to solve this issue — aiming to
address the needs of the end-user and to allow the technology to mature. The
Alliance created the branding Wi-Fi CERTIFIED to reassure consumers that
products will interoperate with other products displaying the same branding.
Many consumer devices use Wi-Fi. Amongst others, personal computers can
network to each other and connect to the Internet, mobile computers can connect to
the Internet from any Wi-Fi hotspot, and digital cameras can transfer images
wirelessly. Routers which incorporate a DSL-modem or a cable-modem and a Wi-Fi
access point, often set up in homes and other premises, provide Internet-access and
internetworking to all devices connected (wirelessly or by cable) to them. One can
also connect Wi-Fi devices in ad-hoc mode for client-to-client connections without a
router.
35
36. As of 2007 Wi-Fi technology had spread widely within business and industrial
sites. In business environments, just like other environments, increasing the number
of Wi-Fi access-points provides redundancy, support for fast roaming and increased
overall network-capacity by using more channels or by defining smaller cells. Wi-Fi
enables wireless voice-applications (VoWLAN or WVOIP). Over the years, Wi-Fi
implementations have moved toward "thin" access-points, with more of the network
intelligence housed in a centralized network appliance, relegating individual access-
points to the role of mere "dumb" radios. Outdoor applications may utilize true mesh
topologies. As of 2007 Wi-Fi installations can provide a secure computer networking
gateway, firewall, DHCP server, intrusion detection system, and other functions.
Balancing effort, advantages and challenges
As in all aspects of life and technology arguing advantages and disadvantages is a
question of views and aspects. The baseline must be to balance cost and benefit.
There is no addressing of advantages without addressing the aspect and view on the
subject first.
Operational advantages
Wi-Fi allows LANs (Local Area Networks) to be deployed without cabling for client
devices, typically reducing the costs of network deployment and expansion. Spaces
where cables cannot be run, such as outdoor areas and historical buildings, can host
wireless LANs.
As of 2007 wireless network adapters are built into most modern laptops. The price
of chipsets for Wi-Fi continues to drop, making it an economical networking option
included in ever more devices. Wi-Fi has become widespread in corporate
infrastructures.
Different competitive brands of access points and client network interfaces are inter-
operable at a basic level of service. Products designated as "Wi-Fi Certified" by the
Wi-Fi Alliance are backwards inter-operable. Wi-Fi is a global set of standards.
Unlike mobile telephones, any standard Wi-Fi device will work anywhere in the
world.
Wi-Fi is widely available in more than 220,000 public hotspots and tens of millions of
homes and corporate and university campuses worldwide.[3] WPA is not easily
cracked if strong passwords are used and WPA2 encryption has no known
36
37. weaknesses. New protocols for Quality of Service (WMM) make Wi-Fi more suitable
for latency-sensitive applications (such as voice and video), and power saving
mechanisms (WMM Power Save) improve battery operation.
Limitations
Spectrum assignments and operational limitations are not consistent worldwide.
Most of Europe allows for an additional 2 channels beyond those permitted in the
U.S. for the 2.4 GHz band. (1–13 vs. 1–11); Japan has one more on top of that (1–
14). Europe, as of 2007, was essentially homogeneous in this respect. A very
confusing aspect is the fact that a Wi-Fi signal actually occupies five channels in the
2.4 GHz band resulting in only three non-overlapped channels in the U.S.: 1, 6, 11,
and three or four in Europe: 1, 5, 9, 13 can be used if all the equipment on a specific
area can be granted not to use 802.11b at all, even as fallback or beacon. Equivalent
isotropically radiated power (EIRP) in the EU is limited to 20 dBm (0.1 W).
Reach
Due to reach requirements for wireless LAN applications, power consumption is fairly
high compared to some other low-bandwidth standards. Especially Zigbee and
Bluetooth supporting wireless PAN applications refer to much lesser propagation
range of <10m (ref. e.g. IEEE Std. 802.15.4 section 1.2 scope). Range is always
making battery life a concern.
Wi-Fi networks have limited range. A typical Wi-Fi home router using 802.11b or
802.11g with a stock antenna might have a range of 32 m (120 ft) indoors and 95 m
(300 ft) outdoors. Range also varies with frequency band. Wi-Fi in the 2.4 GHz
frequency block has slightly better range than Wi-Fi in the 5 GHz frequency block.
Outdoor range with improved (directional) antennas can be several kilometres or
more with line-of-sight.
Wi-Fi performance decreases roughly quadratically as the range increases at
constant radiation levels.
Threats to security
The most common wireless encryption standard, Wired Equivalent Privacy or WEP,
has been shown to be easily breakable even when correctly configured. Wi-Fi
Protected Access (WPA and WPA2), which began shipping in 2003, aims to solve
37
38. this problem and is now available on most products. Wi-Fi Access Points typically
default to an "open" (encryption-free) mode. Novice users benefit from a zero-
configuration device that works out of the box, but this default is without any wireless
security enabled, providing open wireless access to their LAN. To turn security on
requires the user to configure the device, usually via a software graphical user
interface (GUI). Wi-Fi networks that are open (unencrypted) can be monitored and
used to read and copy data (including personal information) transmitted over the
network, unless another security method is used to secure the data, such as a VPN
or a secure web page. (See HTTPS/Secure Socket Layer.)
Population
Many 2.4 GHz 802.11b and 802.11g Access points default to the same channel on
initial startup, contributing to congestion on certain channels. To change the channel
of operation for an access point requires the user to configure the device. Yet, this
default use of channels 1, 6 and 11 gives better performance than "advanced" users
choosing channels 2, 5, 7 and 9 as "unused, free".
Pollution
Standardization is a process driven by market forces. Interoperability issues between
non-Wi-Fi brands or proprietary deviations from the standard can still disrupt
connections or lower throughput speeds on all user's devices that are within range,
to include the non-Wi-Fi or proprietary product. Moreover, the usage of the ISM band
in the 2.45 GHz range is also common to Bluetooth, WPAN-CSS, ZigBee and any
new system will take its share.
Wi-Fi pollution, or an excessive number of access points in the area, especially on
the same or neighboring channel, can prevent access and interfere with the use of
other access points by others, caused by overlapping channels in the 802.11g/b
spectrum, as well as with decreased signal-to-noise ratio (SNR) between access
points. This can be a problem in high-density areas, such as large apartment
complexes or office buildings with many Wi-Fi access points. Additionally, other
devices use the 2.4 GHz band: microwave ovens, security cameras, Bluetooth
devices and (in some countries) Amateur radio, video senders, cordless phones and
baby monitors can cause significant additional interference. General guidance to
those who suffer these forms of interference or network crowding is to migrate to a
38
39. Wi-Fi 5 GHz product, (802.11a, or the newer 802.11n if it has 5 GHz support) as the
5 GHz band is relatively unused and there are many more channels available. This
also requires users to set up the 5 GHz band to be the preferred network in the client
and to configure each network band to a different name (SSID). It is also an issue
when municipalities,[4] or other large entities such as universities, seek to provide
large area coverage. This openness is also important to the success and widespread
use of 2.4 GHz Wi-Fi.
3G
3G is the third generation of mobile phone standards and technology,
superseding 2G. It is based on the International Telecommunication Union (ITU)
family of standards under the International Mobile Telecommunications programme,
IMT-2000.
3G technologies enable network operators to offer users a wider range of more
advanced services while achieving greater network capacity through improved
spectral efficiency. Services include wide-area wireless voice telephony, video calls,
and broadband wireless data, all in a mobile environment. Additional features also
include HSPA data transmission capabilities able to deliver speeds up to 14.4Mbit/s
on the downlink and 5.8Mbit/s on the uplink.
Unlike IEEE 802.11 networks, 3G networks are wide area cellular telephone
networks which evolved to incorporate high-speed internet access and video
telephony. IEEE 802.11 (common names Wi-Fi or WLAN) networks are short range,
high-bandwidth networks primarily developed for data.
Implementation and history
The first pre-commercial 3G network was launched by NTT DoCoMo in Japan
branded FOMA, in May of 2001 on a pre-release of W-CDMA technology. The first
commercial launch of 3G was also by NTT DoCoMo in Japan on October 1, 2001.
The second network to go commercially live was by SK Telecom in South Korea on
the CDMA2000 1xEV-DO technology.
The first European pre-commercial network was at the Isle of Man by Manx
Telecom, the operator owned by British Telecom, and the first commercial network in
Europe was opened for business by Telenor in December 2001 with no commercial
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40. handsets and thus no paying customers. These were both on the W-CDMA
technology.
The first commercial United States 3G network was by Monet, on CDMA2000 1x EV-
DO technology, but this network provider later shut down operations. The first UMTS
3G network operator in the USA was Verizon.
The "first pre-commercial demonstration network" in the southern hemisphere was
built in Adelaide, South Australia by m.Net Corporation in February 2002 using
UMTS on 2100MHz. This was a demonstration network for the 2002 IT World
Congress. The first "commercial" 3G network was launched by Hutchison
Telecommunications branded as Three in April 2003. Australia's largest and fastest
3G UMTS/HSDPA network was launched by Telstra branded as "NextG(tm)" on the
850MHz band in October 2006, intended as a replacement of their cdmaOne
network Australia wide.
In December 2007, 190 3G networks were operating in 40 countries and 154
HSDPA networks were operating in 71 countries, according to the Global mobile
Suppliers Association. In Asia, Europe, Canada and the USA, telecommunication
companies use W-CDMA technology with the support of around 100 terminal
designs to operate 3G mobile networks.
In Europe, mass market commercial 3G services were introduced starting in March
2003 by 3 (Part of Hutchison Whampoa) in the UK and Italy. The European Union
Council suggested that the 3G operators should cover 80% of the European national
populations by the end of 2005.
Roll-out of 3G networks was delayed in some countries by the enormous costs of
additional spectrum licensing fees. (See Telecoms crash.) In many countries, 3G
networks do not use the same radio frequencies as 2G, so mobile operators must
build entirely new networks and license entirely new frequencies; an exception is the
United States where carriers operate 3G service in the same frequencies as other
services. The license fees in some European countries were particularly high,
bolstered by government auctions of a limited number of licenses and sealed bid
auctions, and initial excitement over 3G's potential. Other delays were due to the
expenses of upgrading equipment for the new systems.
By June 2007 the 200 millionth 3G subscriber had been connected. Out of 3 billion
mobile phone subscriptions worldwide this is only 6.7%. In the countries where 3G
was launched first - Japan and South Korea - over half of all subscribers use 3G. In
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41. Europe the leading country is Italy with a third of its subscribers migrated to 3G.
Other leading countries by 3G migration include UK, Austria, Australia and
Singapore at the 20% migration level. A confusing statistic is counting CDMA 2000
1x RTT customers as if they were 3G customers. If using this oft-disputed definition,
then the total 3G subscriber base would be 475 million at June 2007 and 15.8% of all
subscribers worldwide.
Still several major countries such as Turkey, China etc have not awarded 3G
licenses and customers await 3G services. China has been delaying its decisions on
3G for many years, partly hoping to have the Chinese 3G standard, TD-SCDMA, to
mature for commercial production.
The first African use of 3G technology was a 3G videocall made in Johannesburg on
the Vodacom network in November 2004. The first commercial launch of 3G in Africa
was by EMTEL in Mauritius on the W-CDMA standard. In north African Morocco in
late March 2006, a 3G service was provided by the new company Wana.
Rogers Wireless began implementing 3G HSDPA services in eastern Canada early
2007 in the form of Rogers Vision; expansion into western Canada is expected soon.
Phones and networks
3G technologies enable network operators to offer users a wider range of more
advanced services while achieving greater network capacity through improved
spectral efficiency.
UMTS terminals
The technical complexities of a 3G phone or handset depends on its need to
roam onto legacy 2G networks. In the first countries, Japan and South Korea, there
was no need to include roaming capabilities to older networks such as GSM, so 3G
phones were small and lightweight. In Europe and America, the manufacturers and
network operators wanted multi-mode 3G phones which would operate on 3G and
2G networks (e.g., W-CDMA and GSM), which added to the complexity, size, weight,
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42. and cost of the handset. As a result, early European W-CDMA phones were
significantly larger and heavier than comparable Japanese W-CDMA phones.
Japan's Vodafone KK experienced a great deal of trouble with these differences
when its UK-based parent, Vodafone, insisted the Japanese subsidiary use standard
Vodafone handsets. Japanese customers who were accustomed to smaller handsets
were suddenly required to switch to European handsets that were much bulkier and
considered unfashionable by Japanese consumers. During this conversion,
Vodafone KK lost 6 customers for every 4 that migrated to 3G. Soon thereafter,
Vodafone sold the subsidiary (now known as SoftBank Mobile).
The general trend to smaller and smaller phones seems to have paused, perhaps
even turned, with the capability of large-screen phones to provide more video,
gaming and internet use on the 3G networks.
Speed
The ITU has not provided a clear definition of the speeds users can expect
from 3G equipment or providers. Thus users sold 3G service may not be able to
point to a standard and say that the speeds it specifies are not being met. While
stating in commentary that "it is expected that IMT-2000 will provide higher
transmission rates: a minimum speed of 2Mbit/s for stationary or walking users, and
348 <sic> kbit/s in a moving vehicle,"[1] the ITU does not actually clearly specify
minimum or average speeds or what modes of the interfaces qualify as 3G, so
various speeds are sold as 3G intended to meet customers expectations of
broadband speed. It is often suggested by industry sources that 3G can be expected
to provide 384 Kbps at or below pedestrian speeds, but only 128 Kbps in a moving
car[2]. While EDGE is part of the 3G standard, some phones report EDGE and 3G
network availability as separate things.
Network standardization
The International Telecommunication Union (ITU) defined the demands for 3G
mobile networks with the IMT-2000 standard. An organization called 3rd Generation
Partnership Project (3GPP) has continued that work by defining a mobile system that
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43. fulfills the IMT-2000 standard. This system is called Universal Mobile
Telecommunications System (UMTS).
IMT-2000 standards and radio interfaces
International Telecommunications Union (ITU): IMT-2000 consists of six radio
interfaces
W-CDMA
CDMA2000
TD-CDMA / TD-SCDMA
UWC (often implemented with EDGE)
DECT
Mobile WiMAX
Advantages of a layered network architecture
Unlike GSM, UMTS is based on layered services. At the top is the services layer,
which provides fast deployment of services and centralized location. In the middle is
the control layer, which helps upgrading procedures and allows the capacity of the
network to be dynamically allocated. At the bottom is the connectivity layer where
any transmission technology can be used and the voice traffic will transfer over ATM/
AAL2 or IP/RTP.
3G evolution (pre-4G)
.
The standardization of 3G evolution is working in both 3GPP and 3GPP2. The
corresponding specifications of 3GPP and 3GPP2 evolutions are named as LTE and
UMB, respectively. 3G evolution uses partly beyond 3G technologies to enhance the
performance and to make a smooth migration path.
There are several different paths from 2G to 3G. In Europe the main path starts from
GSM when GPRS is added to a system. From this point it is possible to go to the
UMTS system. In North America the system evolution will start from Time division
multiple access (TDMA), change to Enhanced Data Rates for GSM Evolution
(EDGE) and then to UMTS.
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44. In Japan, two 3G standards are used: W-CDMA used by NTT DoCoMo (FOMA,
compatible with UMTS) and SoftBank Mobile (UMTS), and CDMA2000, used by
KDDI. Transition to 3G was completed in Japan in 2006.
Evolution from 2G to 3G
2G networks were built mainly for voice data and slow transmission. Due to rapid
changes in user expectation, they do not meet today's wireless needs.
Cellular mobile telecommunications networks are being upgraded to use 3G
technologies from 1999 to 2010. Japan was the first country to introduce 3G
nationally, and in Japan the transition to 3G was largely completed in 2006. Korea
then adopted 3G Networks soon after and the transition was made as early as 2004.
From 2G to 2.5G (GPRS)
"2.5G" (and even 2.75G) are technologies such as i-mode data services,
camera phones, high-speed circuit-switched data (HSCSD) and General packet
radio service (GPRS) were created to provide some functionality domains like 3G
networks, but without the full transition to 3G network. They were built to introduce
the possibilities of wireless application technology to the end consumers, and so
increase demand for 3G services.
When converting a GSM network to a UMTS network, the first new technology is
General Packet Radio Service (GPRS). It is the trigger to 3G services. The network
connection is always on, so the subscriber is online all the time. From the operator's
point of view, it is important that GPRS investments are re-used when going to
UMTS. Also capitalizing on GPRS business experience is very important.
From GPRS, operators could change the network directly to UMTS, or invest in an
EDGE system. One advantage of EDGE over UMTS is that it requires no new
licenses. The frequencies are also re-used and no new antennas are needed.
Migrating from GPRS to UMTS
From GPRS network, the following network elements can be reused:
Home location register (HLR)
Visitor location register (VLR)
Equipment identity register (EIR)
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45. Mobile switching centre (MSC) (vendor dependent)
Authentication centre (AUC)
Serving GPRS Support Node (SGSN) (vendor dependent)
Gateway GPRS Support Node (GGSN)
From Global Service for Mobile (GSM) communication radio network, the following
elements cannot be reused
Base station controller (BSC)
Base transceiver station (BTS)
They can remain in the network and be used in dual network operation where 2G
and 3G networks co-exist while network migration and new 3G terminals become
available for use in the network.
The UMTS network introduces new network elements that function as specified by
3GPP:
Node B (base station)
Radio Network Controller (RNC)
Media Gateway (MGW)
The functionality of MSC and SGSN changes when going to UMTS. In a GSM
system the MSC handles all the circuit switched operations like connecting A- and B-
subscriber through the network. SGSN handles all the packet switched operations
and transfers all the data in the network. In UMTS the Media gateway (MGW) take
care of all data transfer in both circuit and packet switched networks. MSC and
SGSN control MGW operations. The nodes are renamed to MSC-server and GSN-
server.
Issues
Although 3G was successfully introduced to users in Europe, Australia, Asia, South
America, North America and Africa, some issues are debated by 3G providers and
users:
Expensive input fees for the 3G service licenses
Numerous differences in the licensing terms
Large amount of debt currently sustained by many telecommunication
companies, which makes it a challenge to build the necessary infrastructure for 3G
Lack of member state support for financially troubled operators
Expense of 3G phones
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46. Lack of buy-in by 2G mobile users for the new 3G wireless services
Lack of coverage, because it is still a new service
High prices of 3G mobile services in some countries, including Internet access
(see flat rate)
Current lack of user need for 3G voice and data services in a hand-held
device
High power usage
VoD
VoD stands for Video on Demand. VoD permits a customer to browse an online
programme or film catalogue, to watch trailers and to then select a selected
recording for playback. The playout of the selected movie starts nearly
instantaneously on the customer's TV or PC.
Technically, when the customer selects the movie, a point-to-point unicast
connection is set up between the customer's decoder (SetTopBox or PC) and the
delivering streaming server. The signalling for the trick play functionality (pause,
slow-motion, wind/rewind etc.) is assured by RTSP (Real Time Streaming Protocol).
The most common codecs used for VoD are MPEG-2, MPEG-4 and VC-1.
In an attempt to avoid content piracy, the VoD content is usually encrypted. Whilst
encryption of satellite and cable TV broadcasts is an old practice, with IPTV
technology it can effectively be thought of as a form of Digital Rights Management. A
film that is chosen, for example, may be playable for 24 hours following payment,
after which time it becomes unavailable.
IPTV based Converged Services
Another advantage of an IP-based network is the opportunity for integration and
convergence. Converged services implies interaction of existing services in a
seamless manner to create new value added services. One good example is On-
Screen Caller ID, getting Caller ID on your TV and the ability to handle it (send it to
voice mail, etc). IP-based services will help to enable efforts to provide consumers
anytime-anywhere access to content over their televisions, PCs and cell phones, and
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47. to integrate services and content to tie them together. Within businesses and
institutions, IPTV eliminates the need to run a parallel infrastructure to deliver live
and stored video services.
Limitations
Because IPTV requires real-time data transmission and uses the Internet Protocol, it
is sensitive to packet loss and delays if the streamed data is unreliable. If the IPTV
connection is not fast enough, picture break-up or loss may occur. This problem has
proved particularly troublesome when attempting to stream IPTV across wireless
links. Improvements in wireless technology are now starting to provide equipment to
solve the problem
MP-3
MPEG-1 Audio Layer 3, more commonly referred to as MP3, is a digital audio
encoding format using a form of lossy data compression.
It is a common audio format for consumer audio storage, as well as a de facto
standard encoding for the transfer and playback of music on digital audio players.
MP3 is an audio-specific format that was co-designed by several teams of engineers
at Fraunhofer IIS in Erlangen, Germany, AT&T-Bell Labs in Murray Hill, NJ, USA,
Thomson-Brandt, and CCETT. It was approved as an ISO/IEC standard in 1991.
MP3's use of a lossy compression algorithm is designed to greatly reduce the
amount of data required to represent the audio recording and still sound like a faithful
reproduction of the original uncompressed audio for most listeners, but is not
considered high fidelity audio by most audiophiles. An MP3 file that is created using
the mid-range bitrate setting of 128 kbit/s will result in a file that is typically about
1/10th the size of the CD file created from the original audio source. An MP3 file can
also be constructed at higher or lower bitrates, with higher or lower resulting quality.
The compression works by reducing accuracy of certain parts of sound that are
deemed beyond the auditory resolution ability of most people. This method is
commonly referred to as Perceptual Coding. [1] It internally provides a
representation of sound within a short term time/frequency analysis window, by using
psychoacoustic models to discard or reduce precision of components less audible to
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48. human hearing, and recording the remaining information in an efficient manner. This
is relatively similar to the principles used by JPEG, an image compression format.
Internet
From the first half of 1995 through the late 1990s, MP3 files began to spread on the
Internet. MP3's popularity began to rise rapidly with the advent of Nullsoft's audio
player Winamp (released in 1997), and the Unix audio player mpg123. The small
size of MP3 files has enabled widespread peer-to-peer file sharing of music ripped
from compact discs, which would previously have been nearly impossible. The first
large peer-to-peer filesharing network, Napster, was released in 1999.
The ease of creating and sharing MP3s resulted in widespread copyright
infringement. Major record companies argue that this free sharing of music reduces
sales, and call it "music piracy". They reacted by pursuing lawsuits against Napster
(which was eventually shut down) and eventually against individual users who
engaged in file sharing.
Despite the popularity of MP3, online music retailers often use other proprietary
formats that are encrypted (known as Digital rights management) to prevent users
from using purchased music in ways not specifically authorized by the record
companies. The record companies argue that this is necessary to prevent the files
from being made available on peer-to-peer file sharing networks. However, this has
other side effects such as preventing users from playing back their purchased music
on different types of devices. The audio content of these files can be converted into
an unencrypted format, however, because often the user permissions include "burn
to audio CD". And even when that option is not available, many sound cards allow
the user to record anything they play. Unauthorized MP3 filesharing continues on
next-generation peer-to-peer networks, though some authorized services, such as
eMusic, and Amazon.com sell unrestricted music in the MP3 format.
Encoding audio
The MPEG-1 standard does not include a precise specification for an MP3 encoder.
Implementers of the standard were supposed to devise their own algorithms suitable
for removing parts of the information in the raw audio (or rather its MDCT
representation in the frequency domain). During encoding, 576 time domain samples
are taken and are transformed to 576 frequency domain samples. If there is a
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49. transient, 192 samples are taken instead of 576. This is done to limit the temporal
spread of quantization noise accompanying the transient.
As a result, there are many different MP3 encoders available, each producing files of
differing quality. Comparisons are widely available, so it is easy for a prospective
user of an encoder to research the best choice. It must be kept in mind that an
encoder that is proficient at encoding at higher bit rates (such as LAME) is not
necessarily as good at lower bit rates.
Decoding audio
Decoding, on the other hand, is carefully defined in the standard. Most decoders are
"bitstream compliant", which means that the decompressed output - that they
produce from a given MP3 file - will be the same (within a specified degree of
rounding tolerance) as the output specified mathematically in the ISO/IEC standard
document. The MP3 file has a standard format, which is a frame that consists of 384,
576, or 1152 samples (depends on MPEG version and layer), and all the frames
have associated header information (32 bits) and side information (9, 17, or 32
bytes, depending on MPEG version and stereo/mono). The header and side
information help the decoder to decode the associated Huffman encoded data
correctly.
Therefore, comparison of decoders is usually based on how computationally efficient
they are (i.e., how much memory or CPU time they use in the decoding process).
Audio quality
When performing lossy audio encoding, such as creating an MP3 file, there is a
trade-off between the amount of space used and the sound quality of the result.
Typically, the creator is allowed to set a bit rate, which specifies how many kilobits
the file may use per second of audio, for example, when ripping a compact disc to
this format. The lower the bit rate used, the lower the audio quality will be, but the
smaller the file size. Likewise, the higher the bit rate used, the higher the quality, and
therefore, larger the resulting file will be.
Files encoded with a lower bit rate will generally play back at a lower quality. With
too low a bit rate, "compression artifacts" (i.e., sounds that were not present in the
original recording) may be audible in the reproduction. Some audio is hard to
compress because of its randomness and sharp attacks. When this type of audio is
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50. compressed, artifacts such as ringing or pre-echo are usually heard. A sample of
applause compressed with a relatively low bitrate provides a good example of
compression artifacts.
Besides the bit rate of an encoded piece of audio, the quality of MP3 files also
depends on the quality of the encoder itself, and the difficulty of the signal being
encoded. As the MP3 standard allows quite a bit of freedom with encoding
algorithms, different encoders may feature quite different quality, even when
targeting similar bit rates. As an example, in a public listening test featuring two
different MP3 encoders at about 128 kbit/s, one scored 3.66 on a 1–5 scale, while
the other scored only 2.22.
Quality is heavily dependent on the choice of encoder and encoding
parameters. While quality around 128 kbit/s was somewhere between annoying and
acceptable with older encoders, modern MP3 encoders can provide adequate quality
at those bit rates (January 2006). However, in 1998, MP3 at 128 kbit/s was only
providing quality equivalent to AAC-LC at 96 kbit/s and MP2 at 192 kbit/s.
The transparency threshold of MP3 can be estimated to be at about 128 kbit/s with
good encoders on typical music as evidenced by its strong performance in the above
test, however some particularly difficult material, or music encoded for the use of
people with more sensitive hearing can require 192 kbit/s or higher. As with all lossy
formats, some samples cannot be encoded to be transparent for all users.
The simplest type of MP3 file uses one bit rate for the entire file — this is known as
Constant Bit Rate (CBR) encoding. Using a constant bit rate makes encoding
simpler and faster. However, it is also possible to create files where the bit rate
changes throughout the file. These are known as Variable Bit Rate (VBR) files. The
idea behind this is that, in any piece of audio, some parts will be much easier to
compress, such as silence or music containing only a few instruments, while others
will be more difficult to compress. So, the overall quality of the file may be increased
by using a lower bit rate for the less complex passages and a higher one for the
more complex parts. With some encoders, it is possible to specify a given quality,
and the encoder will vary the bit rate accordingly. Users who know a particular
"quality setting" that is transparent to their ears can use this value when encoding all
of their music, and not need to worry about performing personal listening tests on
each piece of music to determine the correct settings.
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