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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