Wimax

ABSTRACT

Imagine a single wireless technology that can:
• make portable Internet a reality by extending public WLAN hotspots to
metropolitan area coverage for mobile data-centric service delivery,
• connect enterprises and residential users in urban and suburban
environments where access to copper plant is difficult,
• bridge the digital divide by delivering broadband in low-density areas.

Thanks to its innovative technology, WiMAX will offer broadband wireless
access at data rates of multiple Mbit/s to the end-user and within a range of
several kilometers. The same radio technology will also offer high-speed
data services to all nomadic terminals (laptops, PDAs, etc.) with an
optimized trade off between throughput and coverage. Ultimately it will
enable the "Portable Internet" usage replicating on the move the same user
experience as at home or at the office.
Given its huge benefits, WiMAX will develop as a powerful radio access
solution with many integration synergies in mobile or fixed network
architecture. WiMAX will also enable end-users to benefit from an "Always
Best Connected" experience when accessing their applications via the best
available network, at home, on the pause, or on the move. WiMAX
particularly fits in Alcatel's vision for a User-Centric Broadband World in
full complementarity with the other broadband access technologies: from
ADSL to UMTS and their evolutions towards higher speed and data
efficiency

ii

Table of Contents

Chapter Title Page
No. No.
1 Introduction 1
2 What is Wimax? 2
2.1 Standards associated with Wimax 3
3 Why Wimax? 8
4 Wimax Technology 9
4.1 Technological Features 9
4.2 Technology Wimax Design 11
4.3 Types of Wimax 13
5 Wimax Technology Challenge 15
6 Enhancements in Wimax 18
7 Wimax a complement to fixed and mobile access 22
8 Wimax spectrum and regulation issues 26
9 Wimax services 31
10 Relationship with different wireless technolies 34
11 Wimax in INDIA 35
12 Conclusion 39
13 References 40

List of figures
Sl. Images Page
No. No.

2.1 Wireless Standards 3
2.2 Types of 802.16 4
3.1 Data Rates 7
4.1 Radio Access Requirements 9
4.2 Wimax Tower 13
6.1 OFDM 18
9.1 Services 1 31
9.2 Services 2 33

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CHAPTER 1

INTRODUCTION

Broadband Wireless Access (BWA) has been serving enterprises and operators for
years, to the great satisfaction of its users. However, the new IP-based standard
developed by the IEEE 802.16 is likely to accelerate adoption of the technology. It
will expand the scope of usage thanks to: the possibility of operating in licensed and
unlicensed frequency bands, unique performance under Non-Line-of-Sight (NLOS)
conditions, Quality of Service (QoS) awareness, extension to nomadicity, and more.
In parallel, the WiMAX forum, backed by industry leaders, will encourage the
widespread adoption of broadband wireless access by establishing a brand forthe
technology and pushing interoperability between products.

The purpose of this White Paper is to highlight and assess the value of WiMAX as
the right solution to:

• extend the currently limited coverage of public WLAN (hotspots) to citywide
coverage (hot zones)

- the same technology being usable at home and on the move,

• blanket metropolitan areas for mobile data-centric service delivery,

• offer fixed broadband access in urban and suburban areas where copper quality is
poor or unbundling difficult,

• bridge the digital divide in low-density areas where technical and economic factors
make broadband deployment very challenging. In addition to these uses, this paper
will highlight other potential applications, such as telephony or an effective point-to
multipoint backhauling solution for operators or enterprises.

Division of Computer Engineering 1

WIMAX

CHAPTER 2

WHAT IS WIMAX?

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 that WiMAX
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.

USES:

The bandwidth and range of WiMAX make it suitable for the following potential
applications:

x Connecting Wi-Fi hotspots with other parts of the Int

x Providing a wireless alternative to cable and DSL for "last mile” broadband
access.

x Providing data and telecommunications services.


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x Providing a source of Internet connectivity as part of a business continuity
plan. That is, if a business has a fixed and a wireless Internet connection, especially
from unrelated providers, they are unlikely to be affected by the same service
outage.


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2.1 Standards Associated With Wimax

2.1 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.

IEEE 802.16 : The IEEE 802.16 Working Group on Broadband Wireless
Access Standards, which was established by IEEE Standards Board in 1999, aims
to prepare formal specifications for the global deployment of broadband Wireless
Metropolitan Area Networks. The Workgroup is a unit of the IEEE 802 LAN/MAN


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Standards Committee. A related future technology Mobile Broadband Wireless
Access (MBWA) is under development in IEEE 802.20.

Although the 802.16 family of standards is officially
called Wireless MAN, it has been dubbed “WiMAX” (from "Worldwide
Interoperability for Microwave Access") by an industry group called the WiMAX
Forum. The mission of the Forum is to promote and certify compatibility and
interoperability of broadband wireless products.

2.2Types of 802.16

x In January 2003, the IEEE approved 802.16a as an amendment to IEEE
802.16-2001, defining (Near) Line-Of- Sight capability.

x In July 2004, IEEE 802.16REVd, now published under the name IEEE
802.16-2004,introduces support for indoor CPE (NLOS) through additional
radio capabilities such as antenna beam forming and OFDM sub-channeling.

x Early 2005, an IEEE 802.16e variant will introduce support for mobility.


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See Figure 2.2 for the applications associated with each of these standards The
WiMAX Forum intends to do for 802.16 what the Wi-Fi Alliance did for 802.11:

x harmonize standards and certify interoperability between equipment from
different vendors. Standardized interoperable solutions will result in mass
mass volume and bring down cost

x promote and establish a brand for the technology

WiMAX, the reality beyond the hype

As mentioned above, WiMAX can offer very high data rates and extended coverage.
However,

•75 Mbit/s capacity for the base station is achievable with a 20 MHz channel in
bestpropagation conditions. But regulators will often allow only smaller channels
(10 MHz orless) reducing the maximum bandwidth.

• Even though 50 km is achievable under optimal conditions and with a reduced data
rate (a few Mbit/s), the typical coverage will be around 5 km with indoor CPE
(NLOS) and around 15 km with a CPE connected to an external antenna(LOS).


WIMAX

CHAPTER 3

WHY WIMAX?

WiMAX stands for wireless interoperatibility for microwave access. WiMAX is
expected to do more for Metropolitan Area Networks (MANs) and what Wi-Fi has
done for local area networks (LANs)? WiMAX is not projected to replace Wi-Fi, but
to complement it by connecting Wi-Fi networks to each other or the Internet through
high-speed wireless links. You can therefore use WiMAX technology to extend the
power and range of Wi-Fi and cellular networks. However, in developing countries,
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


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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.

3.1 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


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costs may be lower if WiMAX is built into processor chips, although this may not
apply if users wish to have WiMAX handsets.

Quality of Service (QoS)

Excellent Quality Of service management donates from variety of WiMAX features.
Just as on a Wi-Fi network, WiMAX users share a data pipe and QoS can degrade as
more users are added to the network. Using the QoS features of WiMAX service
providers can guarantee certain users specific bandwidth amounts by limiting the
bandwidth consumption of other users.

Grant request mechanism for accessing to network is the first aspect of Quality of
Service. The WiMAX functioning of disagreement allocates only a fixed amount of
time to be given to these grant requests. Disagreement refers to the act of competing
for access to the network. Because of the limited amount of time available,
bandwidth cannot be consumed by contention requests. When a disagreement
request comes into the network, the system compares the request with a service
level agreement for the user making the request, and they are granted, or denied,
access accordingly.

Link by link modulation schemes is another benefit of WiMAX Quality of
Service. In other words, the base station can use different modulation schemes for
different links. The modulation scheme used is related directly to the distance of the
link. Rather than all users' links being downgraded by the user farthest away, link by
link modulation enables closer users to use higher data-rate modulation schemes


WIMAX

CHAPTER 4

WiMAX technology

4.1 Technological features

Various advanced technologies will be developed to meet services above and
consequently WiMAX will support seamless mobility and technologies such as the
technique for minimized power consumption of the terminal, fast link adaptation,
and efficient MAC for broadband services will be developed for high data rate
transmission in mobile environments.

4.1 RADIO ACCESS REQUIREMENS

For the phase I standardization, PG302 decided several system parameters and
Radio access requirements. Major system parameters include duplex scheme (TDD)
and multiple access (OFDMA) and Channel bandwidth (10MHz) as well. Any


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detailed contents could be shown in Table 2. For the radio access requirements,
some parameters have been determined as follows:

x Frequency reuse factor is set as 1.

x Maximum guaranteed speed of user is 60 Km/h.

x Radius of service coverage can be a few Km.

x Maximum of spectral efficiency should be 6 bits/Hz/cell for downlink and 2
bits/Hz/cell for uplink, but the averages are 2 bits/Hz/cell for downlink and 1
bits/Hz/cell for uplink.

x Handoff latency should be less than 150 ms.

x Throughout per user should be 0.512 to 3 Mbps for downlink and 0.128 to 1
Mbps for uplink.

Table 4.1 shows the development contents in association with system requirement.
Requirements could be induced by consideration on radio access requirements

Table 4.1

Deployment contents corresponding with system requirements

System Requirements Deployment contents

TDD to minimize required guard band
High spectrum efficiency
10 MHz broadband/OFDMA


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To use AMC(Adaptive Modulation and Coding) supporting 64
QAM modulation with turbo code

Supporting frequency reuse factor ‘1’

Using Reed Solomon sequence based subchannel to minimize
other RASs interference

Supporting wide coverage
In the cell edge with band SINR area, the operation guaranteed
with low rate FEC

Supporting safety channel in order to reduce interference of the
cell edge area

Employing H-ARQ to enhanced link performance

Guaranteeing mobility up to 60 km/h speed

Supporting mobility
Short OFDM symbol length can minimize the degradation due to
the mobility.

The pilot structure supporting channel estimation under mobility.

Employing variable duty rates of TDD DL/UL

1:1, 2:1, 5:1 DL/UL ratios are available
Flexible resource allocation
for multiple subscriber
To support multiple subscriber scheduling algorithm,
management of the status of individual terminals and packet
scheduling algorithm are considered


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Supporting various QoS Best effort/Real-time polling/Non-real-time polling

Handheld support Supporting sleep mode to reduce terminal power consumption

TDD Smart Antenna
To apply the Smart Antenna for low mobility user
(optional feature)

4.2 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


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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.

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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4.2 WIMAX TOWER

4.3 Types of WiMAX

The WiMAX family 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


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Fixed WiMAX

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.

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.

Mobile WiMAX

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.


WIMAX

CHAPTER 5

WIMAX TECHNOLOGIES CHALLENGE

WiMAX, more flexibility and security

Unlike WLAN, WiMAX provides a media access control (MAC) layer that uses a
grant-request mechanism to authorize the exchange of data. This feature allows
better exploitation of the radio resources, in particular with smart antennas, and
independent management of the traffic of every user. This simplifies the support of
real-time and voice applications. One of the inhibitors to widespread deployment of
WLAN was the poor security feature of the first releases. WiMAX proposes the full
range of security features to ensure secured data exchange:

• terminal authentication by exchanging certificates to prevent rogue devices,

• user authentication using the Extensible Authentication Protocol (EAP),

• data encryption using the Data Encryption Standard (DES) or Advanced
Encryption Standard (AES), both much more robust than the Wireless Equivalent
Privacy (WEP) initially used by WLAN. Furthermore, each service is encrypted
with its own security association and private keys.

WiMAX, a very efficient radio solution

WiMAX must be able to provide a reliable service over long distances to customers
using indoor terminals or PC cards (like today's WLAN cards). These requirements,
with limited transmit power to comply with health requirements, will limit the link
budget. Subchannelling in uplink and smart antennas at the base station has to
overcome these constraints. The WiMAX system relies on a new radio physical


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(PHY) layer and appropriate MAC layer to support all demands driven by the target
applications. The PHY layer modulation is based on OFDMA, in combination with a
centralized MAC layer for optimized resource allocation and support of QoS for
different types of services (VoIP, real-time and non real-time services, best effort).
The OFDMA PHY layer is well adapted to the NLOS propagation environment in
the 2 - 11 GHz frequency range. It isinherently robust when it comes to handling the
significant delay spread caused by the typical NLOS reflections. Together with
adaptive modulation, which is applied to each subscriber individually according to
the radio channel capability, OFDMA can provide a high spectral efficiency of about
3 - 4 bit/s/Hz. However, in contrast to single carrier modulation, the OFDMA signal
has an increased peak: average ratio and increased frequency accuracy requirements.
Therefore, selection of appropriate power amplifiers and frequency recovery
concepts are crucial. WiMAX provides flexibility in terms of channelization, carrier
frequency, and duplex mode (TDD and FDD) to meet a variety of requirements for
available spectrum resources and targeted services. An important and very
challenging function of the WiMAX system is the support of various
advancedantenna techniques, which are essential to provide high spectral efficiency,
capacity, system performance, and reliability:

• beam forming using smart antennas provides additional gain to bridge long
distances or to increase indoor coverage; it reduces inter-cell interference and
improves frequency reuse,

• transmit diversity and MIMO techniques using multiple antennas take advantage
of multipath reflections to improve reliability and capacity.

WiMAX technology can provide coverage in both LOS and NLOS conditions.
NLOS has many implementation advantages that enable operators to deliver
broadband data to a wide range of customers. WiMAX technology has many
advantages that allow it to provide NLOS solutions, with essential features such as
OFDM technology, adaptive modulation and error correction. Furthermore,
WiMAX has many optional features, such as ARQ, sub-channeling, diversity, and


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space-time coding that will prove invaluable to operators wishing to provide quality
and performance that rivals wireline technology. For the first time, broadband
wireless operators will be able to deploy standardized equipment with the right
balance of cost and performance; choosing the appropriate set of features for their
particular business model.

System performance

Table 5.1 gives typical cell size and throughput at 3.5 GHz in various configuration
and environments.

Environment Typical cell size Sector throughput

Urban indoor (NLOS) 1 km (5/8 miles) 21 Mbit/s w.10MHz
channel
Suburban indoor (NLOS) 2.5 km (1.5 miles) 22 Mbit/s w.10 MHz
channel
Suburban outdoor (LOS) 7 km (4 miles) 22 Mbit/s w. 10 MHz
channel
Rural indoor (NLOS) 5 km (3 miles) 4.5Mbit/s w.3.5 MHz
channel
Rural outdoor (LOS) 15 km (9 miles) 4.5Mbit/s w.3.5MHz
channel

5.1 Typical Cell Size and Throughput


WIMAX

6 ENHANCEMENTS IN WIMAX

OFDM

OFDM stands for Orthogonal Frequency Division Multiplexing; it’s a technology
that provides the operator to beat the challenges of Non-Line-of-Sight (NLOS)
transmission in the more efficient manner. OFDM waveform put forward the
advantage of functioning with the larger delay spread of the NLOS background.
With the excellent quality of OFDM functionality, time and use of a cyclic prefix
and its also removes the Inter Symbol Interference (ISI) complications of adaptive
equalization. Multiple narrowband orthogonal carriers composed because of OFDM
waveform, localizing selective fading to a subset of carriers that are comparatively
simple to equalize. A comparison between an OFDM signal and a single carrier
signal, with the information being sent in parallel for OFDM and in series for single
carrier are shown in Fig: 6.1 (WiMAX Forum)

6.1 OFDM


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The facility to remove delay spread, Inter Symbol Interference (ISI) and multi-path
in a proficient manner allows for higher data rate throughput. It is simpler to
equalize the individual OFDM carriers than it is to equalize the broader single
carrier signal. For these entire reasons modern international standard such as those
set by IEEE 802.16, have created OFDM as the ideal technology.

Antennas For Fixed WiMAX Applications

Directional antennas enhance the fade margin by adding together extra gain. This
increases the link accessibility comparisons between directional and Omni-
directional antennas. Delay spread is further reduced by directional antennas at both
the Base Station and Customer Premise Equipment (CPE). The antenna pattern
restrains any multi-path signals that appear in the side lobes and back lobes. The
efficiency of these methods has been verified and demonstrated in booming
deployments, in which the service operates under considerable NLOS fading.

Adaptive Modulation

WiMAX system supports adaptive modulation to regulate the Signal Modulation
Scheme (SMC) depending on the Signal to Noise Ratio (SNR) state of the radio
link. When the radio link is soaring in quality, the peak modulation scheme is used,
offering the system additional capacity. During a signal fade, the WiMAX system
can move to a lower modulation scheme to keep the connection quality and link
permanence. This element allows the system to overcome time-selective fading. The
key element of adaptive modulation is that it enhances the range that a higher
modulation scheme can be used over, because the system can bend to the actual
fading circumstances, as opposed to having a fixed scheme that is planned for the
worst case situations.


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WiMAX & IMT-Advanced

IMT-Advanced, also known as “systems beyond IMT-2000” is expected to offer
constant higher data rates with high mobility to assure likely growing need for
mobile WiMAX services that goes beyond what IMT-2000 can afford to provide.
IMT- Advanced is awaiting technology that will require 3 to 5 years in the future
with target maximum data rates, for research and examination, of up to 100
Mbits/sec in high mobility applications and up to 1 Gbit/sec in low mobility or
nomadic applications. The capacity expected by IMT-Advanced is often referred to
as 4G. It is commonly acknowledged that Orthogonal Frequency Division Multiple
Access (OFDMA) technology will be integrated in IMT-Advanced in near future to
get more the maximum benefits from the WiMAX.

“IMT-Advanced is a continuing effort. The full criteria, being extended within ITU-
R Working Party 8F, are not expected until 2008. The specification of IMT-
Advanced technologies will probably not be completed until at least 2010. In
preparation for IMT-Advanced, the IEEE 802.16 Working Group has moved to
initiate a new project designated as “802.16m” with the intent of developing
enhancements to IEEE STD 802.16 to ensure suitability as an IMT-Advanced
proposal”.

Power Control

Algorithms of power control are applied to enhance the general performance of the
system, it is deployed by the base station sending power control information to
every Customer Premise Equipments (CPEs) to control the transmit power level so
that the level inward bound at the base station is at a fixed level. In a dynamical
changing fading environment this pre-determined performance level indicates that
the CPE only broadcasts sufficient power to meet this constraint. The
communication would be that the CPE broadcast level is supported on worst case
circumstances. The power control decreases the general power consumption of the
CPE and the possible interference with other base stations. For Line-of-Sight (LOS)


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the transmission power of the CPE is approximately comparative to its distance
from the base station, for Non-Line-Of-Sight (NLOS) it is also closely dependant on
the clearance and barriers.

Error Detection Techniques

WiMAX have built-in error detection techniques to reduce the system Signal to
Noise Ratio (SNR) obligations. Convolutional Encoding, Strong Reed Solomon
FEC, and interleaving algorithms are used to identify and correct errors to enhance
throughput. These strong error correction techniques assist to recover corrupted
frames that may have been missing due to frequency selective fading or burst errors.
To remove the errors, Automatic Repeat Request (ARQ) is used that cannot be
corrected by the FEC by resending the error-ed information again. This notably
improves the Bit Error Rate (BER) performance for a similar maximum level.


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CHAPTER 7

WIMAX A COMPLEMENT TO A FIXED & MOBILE ACCESS

WiMAX integrates perfectly into existing fixed and mobile networks,
complementing them when needed. This section gives a more detailed analysis of
WiMAX integration into fixed and the mobile markets.

WiMAX for fixed wireless access

Nationwide broadband access has become a priority in many countries. In most
developed countries, the average broadband coverage will reach 90% in the coming
years. Still, in some rural areas of such countries, broadband coverage will not
exceed 50%.The service gap can be categorized by two characteristics: the type of
area (rural or urban) and the level of national development (see Table 1). In
developed countries, DSL service deployment has been massive in urban and sub-
urban deployments, whereas coverage of remote areas - smaller towns and rural
areas - is lagging behind.

Hurdles to overcome are the poor line quality of the installed copper base, the large
distances to the central offices or cabinets, or the low population density. In this
context, WiMAX, with its QoS support, longer reach, and data rates similar to DSL,
is naturally positioned as a viable first mile option to offer broadband access to
residential users.

In emerging countries, the main focus of broadband deployment is on urban and
suburbanareas, and will remain so in the near future. The low POTS penetration and
the low quality of the copper pair prevent mass scale DSL deployment and foster the
need for alternate broadband technologies. In this context, WiMAX is positioned as
an excellent option. Moreover, the possibility of offering broadband services in
combination with voice services will gradually lead to narrowband WLL


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substitution. Parameters such as availability of the copper, distance to the remote
unit/central office, backhauling costs, and teledensity will drive the choice for one
or other of these solutions. For further details, refer to the article "Providing
Always-on

Broadband Access to Under-served Areas" in the Alcatel Telecommunication
Review(Q4 2003).

WiMax is of interest for large enterprises with several locations in the same
metropolitan area. WiMax will permit Operator's bypass under license conditions:
building a metropolitan private network of IP lines at a very low cost (no civil
works). The comparison to leased lines rental fee is in favor of Wimax even for two
sites only.

Deployment topologies

Several topology and backhauling options are to be supported on the WiMAX base
stations: wireline backhauling (typically over Ethernet), microwave Point-to-Point
connection, as well as WiMAX backhaul. See Figure 3. With the latter option,
thebase station has the capability to backhaul itself. This can be achieved by
reserving part of the bandwidth normally used for the end-user traffic and using it
for backhauling purposes.

WiMAX for Portable Internet

WiMAX, the natural complement to mobile and Wi-Fi networks

Mobile networks offer full mobility, nation-wide coverage voice support and
moderate data rates. WiMAX can then be positioned as a complementary solution
by offering higher bandwidth when required, in particular in dense urban areas.
Public WLAN, while offering clear benefits, is limited in coverage and mobility


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capabilities. WiMAX by-passes these limitations and offers broadband connectivity
in larger areas (hotzones). Wi-Fi and WiMAX solutions are also complementary,
with Wi-Fi being more adapted for short-range, indoor connections (in particular in
the enterprise and at home) and WiMAX for long- range outdoor connections.

From nomadicity to Portable Internet

While nomadicity offers connectivity within the coverage area of a single base
station, Portable Internet implies session continuity throughout the network. In
addition a new generation of networks with multi-access (3G, Wi-Fi, WiMAX,
DSL, FTTU, etc.) enable end-users to enjoy an "Always Best Connected"
experience when accessing their applications via the best available network at home,
on the pause, or on the move. See Figure 4. WiMAX becomes an additional radio
access solution in the global network architecture.

The WiMAX CPE

In most case, a simple plug and play terminal, similar to a DSL modem, provides
connectivity. For customers located several kilometers from the WiMAX base
station, a self-install outdoor antenna may be required to improve transmission
quality. To serve isolated customers, a directive antenna pointing to the WiMAX
base station may be required. For customers requesting voice in addition to
broadband services, specific CPE will allow the connection of standard or VoIP
phones. Ultimately, WiMAX chipset will be embedded in data-centric devices.

Operator's business case

WiMAX is of interest for incumbent, alternate, and mobile operators. Some
business cases are possible.


WIMAX

• The incumbent operators can use the wireless technology as a complement to DSL,
allowing them to offer DSL-like services in remote, lowdensity areas that cannot be
served with DSL.

• For alternate operators, the wireless technology is the solution for a competitive
high-speed Internet with applicability in urban or sub-urban areas.

• The larger opportunity will come with the Portable Internet usage, complementing
fixed and mobile solution in urban and suburban areas. Therefore it will enhance the
business case by giving access to a large potential of end users.

WiMAX, the obvious choice for operators

By integrating WiMAX into their networks, mobile operators can boost their service
with high bandwidth, when necessary, the same applications (messaging, agenda,
location-based services, …) being offered on both networks with a single billing and
subscriber profile. Mobile operators can also reuse existing radio sites and
backhauling equipment to facilitate the deployment of WiMAX. Fixed operators,
incumbent or alternate, will offer nomadic and Portable Internet usage as an addition
to their fixed access offering to complement their DSL and Wi-Fi bundle. For those
having deployed WiMAX for fixed access, this is also a natural evolution of their
offering.


WIMAX

CHAPTER 8

WIMAX SPECTRUM AND REGULATION ISSUES

WiMAX-compliant equipment will be allowed to operate in both licensed and
unlicensed bands. The minimum channel bandwidth for WiMAX usage is 1.75 MHz
per channel, while 10 MHz is considered as an optimum. Although 2.4 GHz and 5
GHz non-licensed bands are largely available, their usage could be limited to trials
because of the risks of interference preventing QoS commitments. The 2.5 and 3.5
GHz licensed bands will be the most common bands for WiMAX applications. It
should be noted that the 5 GHz band is also partially licensed in some countries.
Most countries have already allocated licensed spectrum, generally to alternate
operators. Nevertheless large quantities of spectrum are still in process of allocation,
and some countries have not even defined any WiMAX licensed bands yet. WiMAX
is designed to accommodate either Frequency Division Duplexing (FDD), which is
more suited to enterprise traffic, or Time Division

Duplexing (TDD), which is more adapted to asymmetrical traffic. Cohabitation of
FDD and TDD techniques is possible within the same bands, provided guard bands
are implemented.

Throughput, Scalability, QoS, and Security

Throughput

By using a robust modulation scheme, IEEE 802.16 delivers high throughput at long
ranges with a highlevel of spectral efficiency that is also tolerant of signal
reflections. Dynamic adaptive modulation allows the base station to tradeoff
throughput for range. For example, if the base station cannot establish a robust link
to a distant subscriber using the highest order modulation scheme, 64 QAM
(Quadrature Amplitude Modulation), the modulation order is reduced to 16 QAM or


WIMAX

QPSK (Quadrature Phase Shift Keying), which reduces throughput and increases
effective range.

Scalability

To accommodate easy cell planning in both licensed and license-exempt spectrum
worldwide, 802.16 supports flexible channel bandwidths. For example, if an
operator is assigned 20 MHz of spectrum, that operator could divide it into two
sectors of 10 MHz each, or 4 sectors of 5 MHz each. By focusing power on
increasingly narrow sectors, the operator can increase the number of users while
maintaining good range and throughput. To scale coverage even further, the
operator can re-use the same spectrum in two or more sectors by creating proper
isolation between base station antennas.

Coverage

In addition to supporting a robust and dynamic modulation scheme, the IEEE
802.16 standard also supports technologies that increase coverage, including mesh
topology and “smart antenna” techniques. As radio technology improves and costs
drop, the ability to increase coverage and throughput by using multiple antennas to
create “transmit” and/or “receive diversity” will greatly enhance coverage in
extreme environments.

Quality of Service

Voice capability is extremely important, especially in underserved international
markets. For this reason the IEEE 802.16a standard includes Quality of Service
features that enable services including voice and video that require a low-latency
network. The grant/request characteristics of the 802.16 Media Access Controller
(MAC) enables an operator to simultaneously provide premium guaranteed levels of
service to businesses, such as T1-level service, and high-volume “best-effort”


WIMAX

service to homes, similar to cable-level service, all within the same base station
service area cell.

Security

Privacy and encryption features are included in the 802.16 standard to support
secure transmissions and provide authentication and data encryption.

Benefits of Standards

Standards are important for the wireless industry because they enable economies of
scale that can bring down the cost of equipment, ensure interoperability, and reduce
investment risk for operators. Without industry-wide standards, equipment
manufacturers must provide all the hardware and software building blocks and
platforms for themselves, including the fundamental silicon, the subscriber station,
the base station, and the network management software that is used to provision
services and remotely manage the subscriber station. With the 802.16 standard in
place, suppliers can amortize their research and development costs over much higher
product volume. For example, a volume silicon supplier can supply the same
standard component to many equipment makers at a far lower cost than would be
possible if the device manufacturers were required to develop proprietary silicon for
use only by their equipment. Standards also specify minimum performance criteria
for equipment, enabling a common broadband wireless access baseline platform that
equipment manufacturers can use as the foundation for ongoing innovations and
faster time to market. With its broad industry support, the 802.16 standard lets device
manufacturers and solutions vendors do what they do best, achieving overall
price/performance improvements and opening mass-market opportunities that cannot
be equaled by proprietary approaches.


WIMAX

WiMAX Focuses on Interoperability

WiMAX (the Worldwide Interoperability for Microwave Access Forum) is a non-
profit corporation formed by equipment and component suppliers, including Intel
Corporation, to promote the adoption of IEEE 802.16 compliant equipment by
operators of broadband wireless access systems. The organization is working to
facilitate the deployment of broadband wireless networks based on the IEEE 802.16
standard by helping to ensure the compatibility and interoperability of broadband
wireless access equipment. In this regard, the philosophy of WiMAX for the
wireless MAN is comparable to that of the Wi-Fi* Alliance in promoting the IEEE
802.11 standard for wireless LANs. In an effort to bring interoperability to
Broadband Wireless Access, WiMAX is focusing its efforts on establishing a unique
subset of baseline features grouped in what is referred to as “System Profiles” that
all compliant equipment must satisfy. These profiles will establish a baseline
protocol that allows equipment from multiple vendors to interoperate, and that also
provides system integrators and service providers with the ability to purchase
equipment from more than one supplier. System Profiles can address the regulatory
spectrum constraints faced by operators in different geographies. For example, a
service provider in Europe1 operating in the 3.5 GHz band who has been allocated
14 MHz of spectrum is likely to want equipment that supports 3.5 and/or 7 MHz
channel bandwidths and TDD (time-division duplex) or FDD (frequency-division
duplex) operation. Similarly, a WISP in the U.S. using licenseexempt spectrum in
the 5.8 GHz UNII band may desire equipment that supports TDD and a 10 MHz
bandwidth. WiMAX will establish a structured compliance procedure based upon
the proven test methodology specified by ISO/IEC 96462. The process starts with
standardized Test Purposes written in English, which are then translated into
Standardized Abstract Test Suites in a language called TTCN3. In parallel, the Test
Purposes are also used as input to generate test tables referred to as the PICS
(Protocol Implementation Conformance Statement) pro forma. The end result is a
complete set of test tools that WiMAX will make available to equipment developers


WIMAX

so they can design in conformance and interoperability during the earliest possible
phase of product development. Typically, this activity will begin when the first
integrated prototype becomes available. Ultimately, the WiMAX suite of
conformance tests, in conjunction with interoperability events, will enable service
providers to choose from multiple vendors of broadband wireless access equipment
that conforms to the IEEE 802.16a standard and that is optimized for their unique
operating environment. Internationally, WiMAX will work with ETSI, the European
Telecommunications Standards Institute, to develop similar test suites for the ETSI
HIPERMAN standard for European broadband wireless metropolitan area access.
WiMAX has key benefits for operators. By choosing interoperable, standards-based
equipment, the operator reduces the risk of deploying broadband wireless access
systems.

x Economies of scale enabled by the standard help reduce monetary risk.

x Operators are not locked in to a single vendor because base stations will
interoperate with subscriber stations from different manufacturers

x .Ultimately, operators will benefit from lower-cost and higher-performance
equipment, as equipment manufacturers rapidly create product innovations based on
a common, standards-based platform.


WIMAX

CHAPTER 9

WIMAX SERVICES

Potential services

WiMAX services can have potential applications in various fields. Different
applications can demand different QoS, which can be classified as follows

1. INTERACTIVE SERVICES : Web Browsing, Game interface,etc

2. STREAMING SERVICES : VoD ,MPEG ,etc.

3. BACK GROUND SERVICES: FTP,E-Mail, SMS, Multicast/Broadcast
,MMS, PUSH TO TALK

9.1 SERVICES 1


WIMAX

Possible services provided by WiMAX are widespread over various data
communication services including entertainment, information and commerce
services. The first round of WiMAX technology is expected to be nomadic, meaning
that CPEs will be portable, but not truly mobile. But with Samsung’s new
developments on hand-over, the technology may become truly mobile, offering the
20 Mb/s to 30 Mb/s at speeds up to 120 km/h WiMAX enthusiasts are touting. For
entertainment services, WiMAX will provide high quality VoD/MoD/AoD, real-
time streaming broadcasting, 3G network games and MMS. Web Browsing, file
downloading and interactive information services will be provided as information
services by WiMAX. Commerce services such as m-commerce, mobile banking,
trading will be also provided by WiMAX as well. Table 1 summarizes possible
services to be provided by WiMAX. Example of WiMAX Services

Application Service type QoS class

VoD/MoD/AoD Streaming

Realtime-Broadcasting Real Time
Entertainment service
Network Game Interactive

MMS Background

Web Browsing Interactive

FTP Information service Background

Interactive information Interactive

m-Commerce Interactive

Mobile banking Commerce service Interactive
Stock trading Interactive


WIMAX

Current Service

KT offers 18.4Mbit/s/4Mbit/s for $22 a month with unlimited data usage. WiMAX
seems faster than HSDPA. There are similar service in U.S. operated by wireless
company but much more expensive and slower. Hanaro Telecom have announced a
partnership to roll out WiMAX nationwide in Korea, excluding Seoul and six
provincial cities, where independent networks will be rolled out.In November 2004,
Intel and LG Electronics executives agreed to ensure compatibility between
WiMAX and WiMAX technology In September 2005, Samsung Electronics signed
a deal with Sprint Nextel Corporation to provide equipment for a WiMAX trial. In
November 2005, KT Corporation(aka Korea Telecom) showed off WiMAX trial
services during the Asia-Pacific Economic Cooperation (APEC) summit in Busan.

9.2 SERVICES2

February 10th 2006: Telecom Italia, the dominant telephony and internet service
provider in Italy, together with Korean Samsung Electronics, has demonstrated to
the public a WiMAX network service on the occasion of the 2006 Winter Olympics,
held in Turin, with downspeed of 10 Mbit/s and upspeed of some hundreds of kbit/s
even in movement up to 120 km/h.


WIMAX

In the same event Samsung tlc div. president Kitae Lee assured a future of 20-30
Mbit/s by the end of this year (2006) and 100+ Mbit/s down / 1+ Mbit/s up in 2008
KT Corporation launched commercial WiMAX service in mid-2006 as reported
Sprint (US), BT (UK), KDDI (JP), and TVA (BR) have or are trialing WiMAX. KT
Corporation and SK Telecom launched WiMAX around Seoul on June 30, 2006.
More about the KT launch.On April 3, 2007, KT launched WiMAX coverage for all
areas of Seoul including all subway lines.


WIMAX

CHAPTER 10

RELATIONSHIP WITH DIFFERENT WIRELESS
TECHNOLOGIES

3G Wi-Fi WiMax Mobile-Fi
802.11 802.16 802.20

Max Speed 2 Mbps 54 Mbps 100 Mbps 16 Mbps

Coverage Several miles 300 feet 50 miles Several miles

Airwave Licensed Unlicensed Either Licensed

Advantage Range Speed Speed Speed
,mobility ,price ,range ,mobility

Disadvantagges Slow Short range Interference High price
,expensive issues?


WIMAX

CHAPTER 11

WIMAX IN INDIA

Overview: Widespread, Affordable Connectivity

Connectivity is vital to Indian business and society. Globalization and the Internet
have created rapid growth in information technology-related businesses in India.
Although only half a percent of the Indian population has residential Internet access
(4.7 million out of 1 billion people), India’s more than 9,000 Internet cafes can be
seen bustling with people everywhere in the Indian cities.These Internet services
provide a means for people to stay connected with their friends and family through e-
mail, audio or video chat, and to browse the Internet for job and academic
opportunities. While Indians are enthusiastic about the Internet, the lack of physical
connectivity or telecommunications infrastructure and the cost and lack of broadband
technologies are a big hindrance to more widespread adoption of the Internet. In fact,
14 percent of India’s 0.6 million villages still do not have a single public telephone.
But wireless technologies are beginning to offer reliable alternatives to fixed-line
access, offering the potential for widespread, affordable connectivity to every region,
village, and person in India.

The Promise of Wireless Internet Access

India is increasingly embracing wireless technologies. Cellular phones based on
various wireless technologies have revolutionized telecommunications in India. As
the growth of fixed-line subscribers has slowed over the past several years, cellular
usage has skyrocketed, nearly doubling in 2003 and growing by 159 percent so far in
2004, with 1.4 million new subscribers every month. But these cellular technologies
have not delivered broadband data connectivity to the households, due to both cost
and complexity. Yet India needs a way to provide widespread Internet access, access
that can usher in economic growth, better education and healthcare and improved


WIMAX

entertainment services as it has done elsewhere in the world. And the solution must
be wireless, to avoid the overwhelming cost and resources that would be required to
deploy countrywide fixed-line broadband Internet infrastructure.With widespread
wireless broadband facilities, the Indian information technology (IT) industry could
grow beyond a few cities, students in rural areas could videoconference with
educators across the country, and entertainment programs could be telecast to remote
areas along with Internet telephony services, using technologies like Voice over
Internet Protocol (VoIP). Improved communications could bring remote villages into
the world economy, information access could speed worker productivity, and faster
communication between producers and suppliers could fuel demand for Indian
products.

Improved Education, Health Care and Entertainment

With higher bandwidth and faster speeds, broadband Internet can make education
more accessible by delivering interactive distance education at a low cost. TRAI
reports that in Korea, the government provided training on PC and Internet usage for
low-income and disabled households with children. They also launched programs to
provide these families with heavily subsidized and sometimes free PCs. Over 55
percent of all educational documents are electronic at this point. Teachers in schools
have access to their own PCs with Internet connections, and are required to leverage
information and communication technologies as an integral part of their curriculum.5
In India, schools and libraries in rural or remote areas without wired infrastructure or
broadband services can be costeffectively connected to broadband using WiMAX.
Video conferencing tools can help students to study a variety of subjects with
educators who may not be able to commute to remote areas. Lecture classes from
urban schools and top universities can be broadcast to rural students, and the students
could use the broadband facilities of WiMAX for communicating with teachers and
with their remote classmates. The Indira Gandhi National Open University (IGNOU)
is already encouraging state governments and conventional universities to establish
distance learning programs, providing financial support and grants for programs and


WIMAX

facilitating development of multimedia materials for delivery through distance
learning programs,6 Other premier institutions such as the Birla Institute of

Technology and Science (BITS), Pilani, are already offering distance learning
programs through relationships with industry and development agencies. BITS
conducts off-campus degree programs as a means of continuing education for
employed professionals as part of the human resource development programs of
specific organizations at various off-campus centers.” BITS offerings include degree
programs in math, science and engineering, computer science, medical and
healthcare and other fields.

7 Extensive and reliable broadband Internet can help these Internet-based quality
distance education reach more people across the nation. Agriculture and health care
can also benefit from broadband services. High-resolution pictures or real-time
images of crop diseases can be transmitted to agricultural experts in a different
geographic location for immediate expert advice, thus containing the crop diseases
faster. Similarly, doctors can use real-time video conferencing to discuss patient
symptoms with faraway experts, thus providing faster and better care to the patients.

802.16 Driving Down Costs

LaBrecque estimates that there are over 2,400 wireless Internet service providers
(ISPs) in the United States, serving over 6,000 markets (ISP-Market, LLC
Broadband Wireless Access 2002). But they use expensive, proprietary equipment
that's not interoperable with equipment from other vendors. A lack of standards has
also limited the usefulness of the technology and made it hard for wireless broadband
access providers to be competitive and profitable. To combat these issues the 802.16
standard was conceived. 802.16 will provide definitive standards for a carrier-class
solution that can scale to support thousands of users with a single base station and
provide differentiated service levels. For example, a single base station sector can
provide enough data rate to simultaneously support more than 60 businesses with T1-
type connectivity and hundreds of homes with DSL-type connectivity.


WIMAX

The benefits of 802.16 are many: by enabling standards-based products with fewer
variants and larger volume production, it will drive the cost of equipment down, and
having standardized equipment will also encourage competition, making it possible
to buy from many sources. For areas poorly served by a wired infrastructure,
including many developing countries, 802.16 will be important both for its ease of
implementation and its low cost

The Future of WiMAX

The IEEE 802.16 standard body members are working toward incremental
evolution, from fixed operation to portability and mobility. The IEEE 802.16e
amendment will amend the base specification to enable not just fixed, but also
portable and mobile operation. IEEE 802.16f and IEEE 802.16g task groups are
addressing the management interfaces for fixed and mobile operation. Clients will
be able to hand-off between 802.16 base stations, enabling users to roam between
service areas. In a fully mobile scenario users may be moving while simultaneously
engaging in a broadband data access or multimedia streaming session. All of these
improvements will help make WiMAX an even better Internet access solution for
growing economies like that of India.


WIMAX

CHAPTER 12

CONCLUSION

The latest developments in the IEEE 802.16 group are driving a broadband wireless
access (r) evolution thanks to a standard with unique technical characteristics. In
parallel, the WiMAX forum, backed by industry leaders, helps the widespread
adoption of broadband wireless access by establishing a brand for the technology.
Initially, WiMAX will bridge the digital divide and thanks to competitive equipment
prices, the scope of WiMAX deployment will broaden to cover markets where the
low POTS penetration, high DSL unbundling costs, or poor copper quality have
acted as a brake on extensive high-speed Internet and voice over broadband.
WiMAX will reach its peak by making Portable Internet a reality. When WiMAX
chipsets are integrated into laptops and other portable devices, it will provide high-
speed data services on the move, extending today's limited coverage of public
WLAN to metropolitan areas. Integrated into new generation networks with seamless
roaming between various accesses, it will enable end users to enjoy an "Always Best
Connected" experience. The combination of these capabilities makes WiMAX
attractive for a wide diversity of people: fixed operators, mobile operators and
wireless ISPs, but also for many vertical markets and local authorities. Alcatel, the
worldwide broadband market leader with a market share in excess of 37%, is
committed to offer complete support across the entire investment and operational
cycle required for successful deployment of WiMAX services


WIMAX

CHAPTER 13

REFERENCES

1) www.ewh.ieee.org/r4/chicago/Yu-WiMAX.pdf

2) http://computer.howstuffworks.com/wimax.htm

3) www.wimaxforum.org

4) http://standards.ieee.org/catalog/olis/lanman.html


Wimax

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