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ABSTRACT
Wi-MAX stands for worldwideinteroperabilityofmicrowaveaccess and is astandards-based wireless technology that provides high-throughput broadband
connections over long distances. Its applications, includes last mile broadband
connections, hotspot and cellular backhaul, and high-speed enterprise
connectivity for businesses.
An implementation of the IEEE 802.16 standard, Wi-Max provides
metropolitan area network connectivity at speeds up to 75 Mb/sec. It operates on
the synonymous general principles as Wi-Fi and consigns data from one
computer to another via radio signals.
Wi-Max systems first and foremost consist of a Wi-Max tower which
can provide coverage to a gargantuan area of 3,000 square miles (~8,000 square
km) by using an encrypted data keys to prevent unauthorized users from stealing
access and a Wi-Max receiver including a receiver and an antenna in a small box
or PCMCIA car.
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Introduction:-
The term WiMAX (Worldwide Interoperability for Microwave Access) has
become synonymous with the IEEE 802.16 Wireless Metropolitan Area Network
(MAN) air interface standard. In its original release the 802.16 standard addressed
applications in licensed bands in the 10 to 66 GHz frequency range. Subsequent
amendments have extended the 802.16 air interface standard to cover non-line of
sight (NLOS) applications in licensed and unlicensed bands in the sub 11 GHz
frequency range. Filling the gap between Wireless LANs and wide area networks,
WiMAX-compliant systems will provide a cost-effective fixed wireless alternative
to conventional wire-line DSL and cable in areas where those technologies are
readily available. And more importantly the WiMax technology can provide a cost-
effective broadband access solution in areas beyond the reach of DSL and cable.
The ongoing evolution of IEEE 802.16 will expand the standard to address mobile
applications thus enabling broadband access directly to WiMAX-enabled portable
devices ranging from smart phones and PDAs to notebook and laptop computers.
This paper will provide a detailed business case analysis for the WiMAX
technology in fixed wireless applications in the sub 11 GHz frequency range.
Mobile applications based on IEEE 802.16e will be addressed in a future
paper. This technology will be particularly beneficial to many rural areas and otherlocations where broadband access is not currently available. The current
infrastructure owned by cable providers provides coverage to only limited areas,
and much of it is suited only to cable television; upgrades to make it capable of
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delivering broadband data service are expensive, and therefore prohibitive in low-
density markets.
DSL has the limitation that end-users must be within approximately three
miles of the phone company's central office or a major secondary distribution point
called a Subscriber Loop Carrier. Thus, for many users, particularly those in rural
locations, DSL is not available.
WiMAX has the potential to do to broadband Internet access what cell
phones have done to phone access. In the same way that many people have given
up their "land lines" in favor of cell phones, WiMAX could replace cable and DSL
services, providing universal Internet access just about anywhere you go. WiMax
will also be as painless as WiFi -- turning your computer on will automatically
connect you to the closest available WiMAX antenna WiMAX is the wireless
solution for the next step up in scale, the metropolitan area network (MAN). A
MAN allows areas the size of cities to be connected.
Microwave
The term microwave refers to electromagnetic energy having a frequency higher
than 1 gigahertz (billions of cycles per second), corresponding to wavelength
shorter than 30 centimeters. Microwave signals propagate in straight lines and are
affected very little by the troposphere.They are not refracted or reflected by ionized
regions in the upper atmosphere. Microwave beams do not readily diffract around
barriers such as hills, mountains, and large human-made structures. Some
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attenuation occurs when microwave energy passes through trees and frame houses.
Radio-frequency (RF) energy at longer wavelengths is affected to a lesser degree
by such obstacles.
The microwave band is well suited for wireless transmission of signals
having large bandwidth . This portion of the RF electromagnetic radiation
spectrum encompasses many thousandsof megahertz. Compare this with the so-
called shortwave band that extends from 3 MHz to 30 MHz, and whose total
available bandwidth is only 27 MHz.
In communications, a large allowable bandwidth translates into high data
speed. The short wavelengths allow the use of dish antennas having manageable
diameters. These antennas produce high power gain in transmitting applications,
and have excellent sensitivity and directional characteristics for reception of
signals.
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WHAT ISWIMAX?
WiMAX is a standards-based technology enabling the delivery of last mile
wireless broadband access as an alternative to wired broadband like cable and
DSL. WiMAX provides fixed , nomadic, portable and, soon, mobile wireless
broadband connectivity without the need for direct line-of-sight with a base
station. In a typical cell radius deployment of three to ten kilometers, WiMAX
Forum Certified systems can be expected to deliver capacity of up to 40 Mbps
per channel, for fixed and portable access applications.
This is enough bandwidth to simultaneously support hundreds of businesses with
T-1 speed connectivity and thousands of residences with DSL speed connectivity.
Mobile network deployments are expected to provide up to 15 Mbps of capacity
within a typical cell radius deployment of up to three kilometers. It is expected thatWiMAX technology will be incorporated in notebook computers and PDAs by
2007, allowing for urban areas and cities to become "metro zones" for portable
outdoor broadband wireless access
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Standards AssociatedWithWimax
Fig-Wireless Standards
IEEE 802 refers to a family of IEEE standards dealing with local area networks
and metropolitan area networks. More specifically, the IEEE 802 standards are
restricted to networks carrying variable-size packets. (By contrast, in cell-based
networks data is transmitted in short, uniformly sized units called cells.
Isochronous networks, where data is transmitted as a steady stream of octets, or
groups of octets, at regular time intervals, are also out of the scope of this
standard.) The number 802 was simply the next free number IEEE could assign,
though 802 is sometimes associated with the date the first meeting was held
February 1980.
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IEEE 802.16 STANDARDS:
IEEE 802.16 refers to a family of IEEE standards about local area networks and
metropolitan area networks.
More specifically, the IEEE 802.16standards are restricted to networks carrying
variablesize packets. (By contrast, in cell-based networks data is transmitted in
short, uniformly sized units called cells. Isochronous networks, where data is
transmitted as a steady stream of octets, or groups of octets, at regular time
intervals, are also out of the scope of this standard.)
The services and protocols specified in IEEE 802 map to the lower two
layers (Data Link and Physical) of the seven-layer OSI networking reference
model. In fact, IEEE 802 splits the OSI Data Link Layer into two sub-layers named
Logical link control (LLC) and Media Access Control, so that the layers can be
listed like this:
yData link layerylogical link control Sub layer/yMedia Access Control MAC Sub layer/yPhysical layer
The LLC Sub layer of this architecture can optionally be replaced by an Ethernet
sublayer. (Alternatively the ethernet frames may be encapsulated into LLC frames
as described by RFC 1042, RFC 1390 and the IEEE 802.1H standard.)
The IEEE 802 LAN/MAN Standards Committee (LMSC) maintains the IEEE 802
family of standards. The most widely used standards are for the Ethernet family,
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Token Ring, Wireless LAN, Bridging and Virtual Bridged LANs. An individual
Working Group provides the focus for India.
WheredidtheideaofWiMAX comefrom?
Much of the credit for the formation of the WiMAX Forum" and the notion of the
WiMAX initiative must go the founding members of the Forum, which committed
themselves early to the process of creating a collaborative standards body.
Once Intel came aboard it recognized that for the broadband wireless industry
(both fixed and mobile broadband wireless) to gain traction and wide acceptance
that both hardware prices must decline and a consistent operating environment
must be cemented into place.
The key point of launch however, had to begin with the silicon chip manufacturers
whose chip products would form the core of WiMAX technology value and
capability. Intel deserves a great deal of credit for helping drive this process.
Other technology standards for digital subscriber line (DSL) service and the Cable
broadband industry (the DOCSIS standard) have been responsible for driving those
respective technologies to wide acceptance.
WiMAX itself is commonly mentioned in conjunction with the Institute for
Electrical and Electronics Engineers (IEEE) IEEE 802.16 working group, which is
tasked with defining the technological aspects and features that will be
incorporated into WiMAX.The WiMAX Forum" is a collaborative body geared to
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ensure compliance with the IEEE 802.16 standards and certified interoperability
between radio vendors.
WhywerequireWiMax:-
Think about how you access the Internet today. There are basically three different
options:
yBroadbandaccess - In your home, you have either a DSL or cable modem.At the office, your company may be using a T1 or a T3 line.
yWiFiaccess - In your home, you may have set up a WiFi router that lets yousurf the Web while you lounge on the deck with your laptop. On the road,
you can find WiFi hot spots in restaurants, hotels, coffee shops and libraries.
Dial-upaccess If you are still using dial-up, chances are that either
yBroadband access is not availableyYou think that broadband access is too expensive.
The main problems with broadband access are that it is pretty expensive and it
doesn't reach all areas. The main problem with WiFi access is that hot spots are
very small, so coverage is sparse.
What if there was a new technology that solved all of these problems? This
new technology would provide
yThe high speed of broadband serviceyWireless rather than wired access, so it would be a lot less expensive than
cable or DSL and much easier to extend to suburban and rural areas
yBroad coverage like the cell phone network instead of the tiny little hotspotsof WiFi
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WiMAX may become the only wireless technology because Wi-Fi and cellular
have not penetrated areas that can be reached with WiMAX technology.
Range The wide range of the WiMAX technology depends on the height of the
antennas, if they are installed at the suitable position from where there is no
barrier between the transmitter and receiver, and then we can get better range and
service from it. Even though the frequency for operation of WiMAX is not
definite, the most likely band at 3.5GHz is higher in frequency than the 3G bands
at around 2.1 GHz. Range will, as a result, be lower, perhaps somewhere between
50% and 75% of the range of 3G. WiMAX can therefore support 30 to 50
kilometres distance with Line-of-Sight (LOS) links. As far as Non-line-of-sight
(NLOS) links in concerned WiMAX can support the broad range from 3 to 10
kilometres using advanced modulation algorithm that can overcome many
interfering objects that Wi-Fi systems cannot pass through.
Data Rates The technology used for WiMAX is Orthogonal Frequency
Division Multiplexing (OFDM), it is not appreciably more supernaturally efficient
then the technology commonly used for 3G that is Wideband Code Division
Multiple Access (WCDMA). However OFDM is coupled with a high channel
bandwidth, that allows greater data rates. So, on average, for an equivalent
spectrum allocation, users will see similar data rates. In specific simulations,
where there are few users it is possible that WiMAX will provide a higher data
rate than 3G. However, in commercial systems, such simulations are likely rare.
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Fig-DATA RATES
Timing:-
It is normally believed that WiMAX will enter into the market some five years
after 3G is well established. This drawback in time is likely to be important since
without a convincing advantage only a few service providers will choose to move
from 3G to WiMAX. However, those yet to deploy a system may find the choice
balanced between the two technologies.
Cost
The network costs of WiMAX will be likely to be higher than for 3G because of
the reduced range and hence the necessity to build more cells. The subscriber
subsidy costs may be lower if WiMAX is built into processor chips, although this
may not apply if users wish to have WiMAX handsets.
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HowWiMAXWorks:-
In practical terms, WiMAX would operate similar to WiFi but at higher speeds,
over greater distances and for a greater number of users. WiMAX could potentially
erase the suburban and rural blackout areas that currently have no broadband
Internet access because phone and cable companies have not yet run the necessary
wires to those remote locations.
A WiMAX system consists of two parts:
yA WiMAX tower, similar in concept to a cell-phone tower - A singleWiMAX tower can provide coverage to a very large area -- as big as 3,000
square miles (~8,000 square km).
yA WiMAX receiver - The receiver and antenna could be a small box orPCMCIAcard, or they could be built into a laptop the way WiFi access is
today.A WiMAX tower station can connect directly to the Internet using a high
bandwidth, wired connection (for example, a T3 line). It can also connect to
another WiMAX tower using a line-of-sight, microwave link. This connection to a
second tower (often referred to as a backhaul), along with the ability of a single
tower to cover up to 3,000 square miles, is what allows WiMAX to provide
coverage to remote rural areas.
What this points out is that WiMAX actually can provide two forms of wireless
service:
yThere is the non-line-of-sight, WiFi sort of service, where a small antennaon your computer connects to the tower. In this mode, WiMAX uses a lower
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frequency range -- 2 GHz to 11 GHz (similar to WiFi). Lower-wavelength
transmissions are not as easily disrupted by physical obstructions -- they are
better able to diffract, or bend, around obstacles.
yThere is line-of-sight service, where a fixed dish antenna points straight atthe WiMAX tower from a rooftop or pole. The line-of-sight connection is
stronger and more stable, so it's able to send a lot of data with fewer errors.
Line-of-sight transmissions use higher frequencies, with ranges reaching a
possible 66 GHz. At higher frequencies, there is less interference and lotsmore bandwidth.
WiFi-style access will be limited to a 4-to-6 mile radius (perhaps 25 square miles
or 65 square km of coverage, which is similar in range to a cell-phone zone).
Through the stronger line-of-sight antennas, the WiMAX transmitting station
would send data to WiMAX-enabled computers or routers set up within the
transmitter's 30-mile radius (3,600 square miles or 9,300 square km of coverage).
This is what allows WiMAX to achieve its maximum range.
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Technology:WiMAX Design
The design of the WiMAX is ideal for challenges related with earlier versions of
wired and wireless access networks. At the same time the backhaul connects the
WiMAX system to the network, it is not an integrated part of WiMAX system.
Normally a WiMAX network consists of two parts, a WiMAX Base Station (BS)
and a WiMAX receiver also referred as Customer Premise Equipment (CPE).
Backhaul
Backhaul is actually a connection system from the Access Point (AP) back to the
provider and to the connection from the provider to the network. A backhaul can
set out any technology and media provided; it connects the system to the backbone.
In most of the WiMAX deployments circumstances, it is also possible to connect
several base stations with one another by use of high speed backhaul microware
links. This would also allow for roaming by a WiMAX subscriber from one base
station coverage area to another, similar to roaming enabled by cellular phone
Receiver
A WiMAX receiver, which is also referred as Customer Premise Equipment
(CPE), may have a separate antenna or could be a stand-alone box or a PCMCIA
card that inserted in a laptop or a desktop computer. Access to a WiMAX base
station is similar to accessing a wireless access point (AP) in a Wi-Fi network,
but the coverage is more.
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So far one of the biggest restrictions to the widespread acceptance of WiMAX has
been the cost of CPE. This is not only the cost of CPE itself, but also that of
installation. In the past, Broadband Wireless Access (BWA) have been
predominantly Line Of Sight (LOS), requiring highly skilled labour and a truck
role to install and provide a service to customer. The concept of a self-installed
CPE has been difficult for BWA from the beginning, but with the advent of
WiMAX, this issue seems to be getting resolvedBase Station (BS)
A WiMAX base station comprises of internal devices and a WiMAX tower. A base
station can normally covers the area of about 50 kilometres or 30 miles radius, but
some other and environmental issues bound the limits of WiMAX range to 10 km
or 6 miles. Any wireless user within the coverage area would be able to access the
WiMAX services (Fig: 2). The WiMAX base stations would use the media access
control layer defines in the standard and would allocate uplink and downlink
bandwidth to subscribers according to their requirements on real time basis.
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TypesofWiMAX
The WiMAX families of standards concentrate on two types of usage models a
fixed usage model and a mobile usage model. The basic element that differentiates
these systems is the ground speed at which the systems are designed to manage.
Based on mobility, wireless access systems are designed to operate on the move
without any disruption of service; wireless access can be divided into three
classes; stationary, pedestrian and vehicular.
A mobile wireless access system is one that can address the vehicular class,
whereas the fixed serves the stationary and pedestrian classes. This raises a
question about the nomadic wireless access system, which is referred to as a
system that works as a fixed wireless access system but can change its location
FixedWiMAX
Service and consumer usage of WiMAX for fixed access is expected to reflect that
of fixed wire-line service, with many of the standards-based requirements being
confined to the air interface. Because communications takes place via wireless
links from Customer Premise Equipment (CPE) to a remote Non Line-of-sight
(NLOS) base station, requirements for link security are greater than those needed
for a wireless service. The security mechanisms within the IEEE 802.16 standards
are sufficient for fixed access service.
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Another challenge for the fixed access air interface is the need to set up high
performance radio links capable of data rates comparable to wired broadband
service, using equipment that can be self installed indoors by users, as is the case
for Digital Subscriber Line (DSL) and cable modems. IEEE 802.16 standards
provide advanced physical (PHY) layer techniques to achieve link margins
capable of supporting high throughput in NLOS environments.
MobileWiMAX
The 802.16a extension, refined in January 2003, uses a lower frequency of 2 to 11
GHz, enabling NLOS connections. The latest 802.16e task group is capitalizing on
the new capabilities this provides by working on developing a specification to
enable mobile WiMAX clients. These clients will be able to hand off between
WiMAX base stations, enabling users to roam between service areas.
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RELATIONSHIPWITH DIFFERENTWIRELESS
TECHNOLOGIES
3G Wi-Fi 802.11 WiMax
802.16
Max Speed 2 Mbps 54 Mbps 100 Mbps
Coverage Several miles 300 feet 50 miles
Airwave Licensed Unlicensed Either
Advantage Range,
mobility
Speed ,price Speed ,range
Disadvantages Slow
expensive
Short range Interference
issues
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USES FORWIMAX
WiMAX is a wireless metropolitan area network (MAN) technology that can
connect IEEE 802.11(Wi-Fi) hotspots with each other and to other parts of the
Internet and provide a wireless alternative to cable and DSL for last mile (last km)
broadband access. IEEE 802.16 provides up to 50 km (31 miles) of linear service
area range and allows connectivity between users without a direct line of sight.
Note that this should not be taken to mean that users 50 km (31 miles) away
without line of sight will have connectivity and practical limits from real world
tests seem to be around "3 to 5 miles" (5 to 8 kilometers). The technology has been
claimed to provide shared data rates up to 70Mbit/s, which, according to WiMAX
proponents, is enough bandwidth to simultaneously support more than 60
businesses with T1-type connectivity and well over a thousand homes at 1Mbit/s
DSL-level connectivity. Real world tests, however, show practical maximum data
rates between 500kbit/s and 2 Mbit/s, depending on conditions at a given site.
It is also anticipated that WiMAX will allow interpenetration for broadband
service provision of VoIP, video, and Internet accesssimultaneously. Most cable
and traditional telephone companies are closely examining or actively trial-testing
the potential of WiMAX for "last mile" connectivity. This should result in better
pricepoints for both home and business customers as competition results from the
elimination of the "captive" customer bases both telephone and cable networks
traditionally enjoyed. Even in areas without preexisting physical cable or telephone
networks, WiMAX could allow access between anyone within range of each other;
home units the size of a paperback book that provide both phone and network
connection points are already available and easy to install.
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TheFuturewithwimax
The technology has been a long time coming but advancements combined with
international standards such as 802.11.16 has made it feasible. Add to this the slice
of licensed spectrum that will become available in 2007 when the broadcasting
companies have to give up these frequencies due to a FCC mandate to digitize TV
transmissions. The decisive factor here will be for the FCC to enforce the mandate
rather than succumbing to political pressures to extend the deadline.
There are already a few pioneers offering High Speed Broadband via WiMAX.
One example is Tower Stream. The company currently offers up to 1000MB
broadband service in seven major markets that include New York City, Chicago,
and Los Angeles. AT&T has recently announced plans to test the waters in this
market, and Bell South has deployed this technology in Athens GA, a university
town just northeast of Atlanta.
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APPLICATION:-
The WiMax will provide solutions to the following multiple broadband segments:
Cellularbackhaul:
The robust bandwidth of technology makes it an excellent choice for the
backhaul for commercial enterprises, such as those providing hotspots, as well as
for point to point backhaul applications.
Broadbandtoundeservedandremoteareas:
WiMax is a natural choice for under serviced rural and outlying areas withy a
low population density.
Broadbandon-demand:
It can help to accelerate the deployment of Wi-Fi hotspots and SOHO wireless
LANs, especially in those areas not served by cabel, DSL or in areas where the
local telephone company may have a long lead time for providing a broadband
service.Broadband Residential:-
This fills the gaps is cable and DSL coverage.
Best-connectedwirelessservice:-
WiMAX has monadic capabilities, which allow users to connect to a WISP
(wireless ISP) Even when they roam outside their home or business, or go to
another city that also has a WISP
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CONCLUSION:-
WiMAX promises to expand the availability of broadband service to residences
and businesses that are currently under-served, including low-density rural
locations in developed countries, as well as in emerging markets. It will also
provide a flexible solution to end users for whom current provisioning timeframes
are prohibitive, or for whom wired infrastructure is not available.
WiMAX technology represents an expanding opportunity for service
providers, equipment manufacturers, and chipset suppliers operating in both
licensed and license exempt bands. Initially, WiMAX solutions will be based on
the IEEE 802.16-2004 specification, allowing fixed access for point-to point and
point-to-multipoint use. A robust technology ecosystem, based on worldwide
standards, is expected to evolve over time, ultimately yielding the dual benefits of
interoperability and volume economics.
As with any new and evolving technology, numerous factor must be
understood to ensure a successful deployment. This paper has focused on several
specific issues related to license-exempt deployments, including RF interference
and infrastructure placement.
RF interference results in a complex and ever changing environment. It
should be respected and understood by service providers, but not feared. Solutions
for dealing with rf interference include proper network design, use of advanced
antenna technologies, point-to-point deployments identification of appropriate
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markets for WiMAX technology, filtering, shielding, frequency reuse, and
synchronization with other providers. These solutions will help address some
RFinterference issues.
A robust network design is based on site surveys, statistics gathering, and
coordination of RF use with neighboring providers to directly address interference
issues. WiMAX license-exempt solutions based on robust network design are
poised to becomea dependable and resilient solution for specialized markets.
Business class WiMAX services can and will soon be deployed in both licensed
and license-exempt bands.
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REFERENCE
www.howstuffworks.com
www.intelmagazine.com
www.wimaxforum.corn
www.wikimedia.Corn
www.wimax.com
www.gd-decisionsystems.com/satelliteservices
www.etsi.fr
www.futron. Com