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Wi-Max

IEEE 802.16

4/14/2013

Zankhit Desai

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ABSTRACT

The new era of communication, currently employed in some parts of the world, is

Worldwide Interoperability for Microwave Access (WIMAX). Imagine a technology that canreach even into the remote areas or the suburbs where the access to power plants is even difficult.

This innovation technology will provide transfer rates of multiple Megabits to the users within a

range of several kilometers. It is the latest technology which is approved by IEEE 802.16 group ,

which is a standard for point-to-multipoint wireless networking. Wimax vision is to deliver last

mile broadband connectivity to home or business locations, also its data rates are comparable

with Cable and Digital Subscriber Line (DSL) rates. It has the capability which connects to the

ISP (Internet Service Provider) even when you are roaming outside home or office. The Wimax

technology is becoming the way to avert the impending crisis of rural connectivity i.e. it will be

accessible till the last mile.

This Seminar explains about the purpose of Wimax, the study of Wimax systems, its

implications and applications and its capabilities.

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CHAPTER 1

INTRODUCTION

1.1 Introduction of Wimax

Worldwide Interoperability for Microwave Access, or WIMAX for short, is a next generation

open standard that seeks to serve users' increasing demands for high data throughput (broadband)

services such as streaming media on the internet, live video conferencing, and mobile TV on

computers as well as handsets and PDAs. Wimax is expected to be integrated into the next

generation mass market consumer devices and to offer something that does not exist today that is

speeds similar to cable and metropolitan area coverage while on the move, all for a much lower

cost than we are used to today. Wimax already offers broadband services in many emerging and

rural markets which are not supported by wireline-based technologies and started its first

deployment in developed countries replacing both commonly used Wi-Fi on one hand and

traditional cellular standards such as 3G.

IEEE 802.16 is the standard to state the radio frequency of fixed Broadband Wireless Access.

Wimax is the trade name of IEEE 802.16 Standard. IEEE 802.16 was first planned to offer the

last mile for Wireless Metropolitan Area Network (WMAN) with the line of sight (LOS) of 30

50 km. Basically the goal of WIMAX is to provide high speed internet access to home and

business subscribers without wires. It supports legacy voice systems, voice over IP, TCP/IP, and

Application with different QOS requirements. 802.16 consist of the access point, base station and

subscriber station. During a communication, all the information coming from a subscriber station

go to the base station and retransmitted back to subscriber station. Base station can handle

multiple of subscriber station. Two types of links are defined in this:

The downlink: From base station to the subscriber station. The uplink: From subscriber station to the base station.A Wimax tower is similar in concept to cell phone tower. A single Wimax tower can provide

coverage to very large area. A Wimax receiver and antenna could be a small box or a PCMCIA

card, or could be built into a laptop. Wimax combines the familiarity of Wi-Fi with the mobility

of cellular that will deliver personal mobile broadband that moves with you. It will let you get

connected to the Internet, miles from the nearest Wi-Fi hotspot. Soon, Mobile Wimax will

blanket large areas metropolitan, suburban, or ruraldelivering mobile broadband Internet

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access at speeds similar to existing broadband. WiMAX is built for the future with advanced,

efficient wireless technology that provides higher speeds than todays wide area wireless

technologies. It will be able to completely transform your mobile Internet lifestyle, enabling you

to connect in ways youve only dreamed about. The speed of Wimax is faster than broadband

service. Being a a wireless service, cable cost is reduced and is easier to extend to suburban and

rural areas. It also has wider coverage than WiFi hotspots. The service provider delivers high

output throughput broadband based services like VoIP, high speed Internet and video reducing

the capital expenditure required for network expansion, providing improved performance and

extended range. For the customers, DSL-like services are available at DSL prices but with

portability and rapidly declining fixed broadband prices and no installation fees. Wimax provides

a wireless portable connectivity alternative to cable and DSL for last mile broadband access,

making it a source of Internet connectivity as a part of a business continuity plan. It also reduces

the capital expenditures required for network expansion.

Figure 1.1 Uses of Wimax

The figure 1.1 shows the uses of Wimax indicating its mobility and widespread coverage in

various areas.

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CHAPTER 2

LITERATURE SURVEY

A Wi-Fi hotspot is like an oasis in the desert. As you travel, your notebook connects to one Wi-

Fi oasis after another to replenish your Internet thirst. In between and beyond these Wi-Fi

watering holes are vast expanses of dead air where your notebook is unconnected. Wimax will

make these deserts come alive with the crackle of broadband Internet access.

Figure 2.1 Wimax System

2.1 Literature Review

Historically, the main usage of wireless data-transfer was voice communication. As wireless

communication standards evolved to become digital (Wi-Fi or GSM), voice has become one

among several more bandwidth consuming (broadband) applications such as high definition

video or games. Many wireless IP (internet protocol) network standards try to satisfy the

increasing demand for more bandwidth in more locations while on the move.

Wi-Fi is the most popular and successful broadband wireless IP network standard to date.

Popular Wi-Fi standards like 802.11b and 802.11g are used in many homes and businesses

and enable internet access with high data throughput for computer notebooks, PCs, and more

recently, for Smartphone users. 802.11n, the upcoming Wi-Fi standard, (currently in draft state)

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coverage to a very large area as big as 3,000 square miles (~8,000 square km). A WiMAX

receiver - The receiver and antenna could be a small box or Personal Computer Memory card, or

they could be built into a laptop the way WiFi access is today. .Figure 2.2 shows WiMax

transmitter and receiver.

Figure 2.2 WiMAX transmitter and receiver

2.3 WiMax Facilities

Broadband that travels with you across town or across the nation makes all things Internet

available on your terms. WiMAX enables the freedom and convenience that comes from having

your Internet standing by where and when you need itstaying connected on the go to the

people, communities, and resources that make up our lives. Broadband on the go is your front

row seat to all the rich multimedia Internet applications you already use, and exciting future

possibilities enabled by Mobile WiMAX. WiMax can be used in real time by playing multiplayer

3-D games, view YouTube videos, and listen to radio broadcasts its all there waiting to

entertain you on the go. WiMAX pulls productivity out of thin air. Capture lost time by doing

things in areas previously unavailable. Working on the go changes the rules of competition by

allowing you to be more productive. Broadband on the go is about keeping in touch with family,

friends, and your communities using all the typical tools like e-mail and IM, but WiMAX adds

face-to-face video conferencing and voice to your connections. WiMAX enables a spontaneous

lifestyle. Location-based services creates a new paradigm in accessing real-time information

where and when you need it. . There are just more streams of data available with WiMAX, so

why not pipe broadcast television and radio into a Mobile WiMAX device? Radio stations

already co-broadcast over the Internet. Mobile Internet-based TV transmissions also set the stage

for content-on-demand services like movies and sporting events.

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The Indira Gandhi National Open University (IGNOU), Birla Institute of Technology and

Science (BITS), Pilani are already encouraging state governments and conventional universities

to establish distance learning programs, providing financial support and grants for programs and

facilitating development of multimedia materials for delivery through distance learning

programs.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.

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CHAPTER 3

WIMAX SYSTEM

3.1 Concept

Wimax refers to interoperable implementations of the IEEE 802.16 wireless-networks standard,

in similarity with Wi-Fi, which refers to interoperable implementations of the IEEE 802.11

Wireless LAN standard. Wimax is the commercial name of products compliant with the IEEE

802.16 standard. Effectively replicating the successful history of IEEE 802.11 and Wi-Fi, an

industrial organization, the WiMAX Forum has been set up to promote the adoption of such

technology and to ensure interoperability among equipment of different vendors.

3.2 Working of WiMAX

Think of WiMAX as taking the best part of cellular network accessthe part that allows you toeasily connect anywhere within your service providers wide coverage area and taking the best

part of your Wi-Fi experience: the fast speeds and a familiar broadband Internet experience, and

combining them into a new wireless standard. WiMAX is a Wide Area Network (WAN)

technology. Service providers will deploy a network of towers that will enable access over many

miles. Internet access is instantly available anywhere within coverage areas. And like Wi-Fi,

WiMAX is a standards-based technology that will unleash the benefits of open markets and

global economies of scale to deliver the devices and services that consumers want. The figure 3.1

shows basic working of WiMax.

Figure 3.1 Working of WiMAX

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The WiMAX network uses an approach that is similar to that of cell phones. A user sends data

from a subscriber device to a base station mounted on a tower or tall building to broadcast the

wireless signal in a channel called an uplink, and the base station transmits to the same or other

user in a channel called a downlink. Unlike the user, who traditionally has limited resources, i.e.

very limited transmission power, limited number of antennas, and limited computation

capabilities, the base station can use higher transmission power, more antennas, and enhanced

computation algorithms. WiMAX service providers deploy a network of towers that enable

access over many miles and the WiMAX broadband service will be available anywhere within

coverage areas. Coverage for a geographical area is divided into a series of overlapping areas

called cells. When the user travels from one cell to another, the wireless connection is transferred

from one cell to another.

The signal transmitted from the base station to the user or from the user to the base station

through wireless channel faces attenuation in space, fraction, refraction, reflection from objects

on the propagation path, and shadowing from walls or other barriers. As a result, the transmitted

signal is distorted and sometimes splits into different replicas called multi-paths. The transmitted

signal is commonly described by its structure in time, frequency (its frequencies and its

bandwidth), and space. The receiver's target at both uplink and downlink is to combat the signal's

distortion in order to perfectly recover the transmitted signal and enable reliable data

transmission.

Figure 3.2: Transmitted signal in multipaths and in space, time and frequency domain

At the heart of WiMAX technology stands several comprehensive concepts that can improve

spectral efficiency (the number of information bits transmitted over a given spectrum resource)

compared to other technologies. The first important relatively new transmission technique used

by WiMAX is orthogonal frequency division multiplexed access (OFDMA), applied in order to

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efficiently exploit the frequency bands. The WiMAX Forum has defined three licensed spectrum

profiles (transmission frequencies) of 2.3 GHz, 2.5 GHz, and 3.5 GHz to decrease the cost for

manufacturers, as each spectrum profile may require different hardware infrastructures.

Additionally, there is more unlicensed spectrum that is less frequently used by most telecom

companies that prefer to control the entire available spectrum. Each spectrum profile has a

related bandwidth profile which determines the channel's bandwidth. The signal bandwidth is

divided in OFDMA to small narrowband, equally and closely-spaced signal carriers used to

carry data called sub-carriers. The transmitted data is then divided into several parallel

independent data streams where each is allocated to another sub-carrier and all are transmitted at

the same transmission interval. In the downlink path, the base station can transmit the data

streams for different subscribers efficiently over consecutive sub-carriers. The independency of

data streams is an important feature of OFDMA that prohibits several users' data from interfering

with each other and be multiplexed (transmitted in parallel simultaneously). It is obtained by

orthogonality of the different sub-carriers carrying the data at different bandwidths.

Orthogonality is achieved when the peak of each signal sub carrier (in frequency) coincides with

the nulls of other signals (due to the certain equal bandwidth of each sub-carrier) so that they do

not interfere with each other.

3.3 Technical specifications of IEEE 802.16

Range- 30 miles from base station Speed- 70 Megabits per second Frequency bands- 2 to 11 and 10 to 66(licensed and unlicensed bands respectively) Defines both MAC and PHY layer and allows multiple PHY layer specifications.

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3.3.1 IEEE 802.16 Specifications

Type Use

802.16a Uses the licensed frequencies from 2 to 11 GHz.Supports Mesh network

802.16b Increase spectrum to 5 and 6 GHz.Provides QoS(for real time voice and video service)

802.16c Represents a 10 to 66GHz

802.16d Improvement and fixes for 802.16a

802.16e Addresses on Mobile.Enable high-speed signal handoffs necessary for

communications with users moving at vehicular speeds

Table 2: IEEE Specification

Figure 3.1 IEEE 802.16 Specifications

3.3.2 Protocol architecture of the IEEE 802.16 standard

A common media access control (MAC) is provided to work on top of different physical layers

(PHY). The interface between the different PHYs and the MAC is accomodated as a separate

sublayer, the transmission convergence sublayer. A Convergence Sublayer (CS) is provided on

top of the MAC, to accomodate both IP as well as ATM-based network technologies. A basic

privacy support is provided at the MAC layer.

3.3.2.1 MAC (Data Link) Layer

In Wi-Fi the media access controller (MAC) uses contention accessall subscriber stations that

wish to pass data through a wireless access point (AP) are competing for the AP's attention on a

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random interrupt basis. This can cause subscriber stations distant from the AP to be repeatedly

interrupted by closer stations, greatly reducing their throughput.

In contrast, the 802.16 MAC uses a scheduling algorithm for which the subscriber station needs

to compete only once (for initial entry into the network). After that it is allocated an access slot

by the base station. The time slot can enlarge and contract, but remains assigned to the subscriber

station, which means that other subscribers cannot use it. In addition to being stable under

overload and over-subscription, the 802.16 scheduling algorithm can also be more bandwidth

efficient. The scheduling algorithm also allows the base station to control QOS parameters by

balancing the time-slot assignments among the application needs of the subscriber stations.

MAC layer consists of three sub layers.

Service Specific Convergence Sublayer (MAC CS)

The MAC Common Part Sublayer (MAC CPS) and The privacy sublayer.

MAC CS sublayer is to converse with higher layers and transforms upper level data services to

MAC layer flows and associations.MAC CS has two types of sub layers, One is ATM

convergence sublayer for ATM networks & services while the other one is Packet Convergence

sublayer for packet data services.

For example: Ethernet, PPP, IP etc. The basic function of CS Layer is that it receives data from

higher layers, classifies data as ATM cell or packet and forwards frames to CPS layer.

The core part of the IEEE 802.16 MAC is the MAC CPS, which defines all methods for

connection management, bandwidth distribution, request & grant, system access procedure,

uplink scheduling, connection control, and automatic repeat request (ARQ). Communication

between the CS (Convergence Sublayer) and the MAC CPS are maintained by MAC Service

Access Point (MAC SAP). Creation, modification, deletion of connection and transportation of

data over the channel are four the basic functions occuring in this communication process.

The Privacy Sublayer is accountable for the encryption and decryption of data that is coming and

leaving the Physical layer. It is also used for authentication and secure key exchange.

From a security point of view, MAC CPS (Common Part Sublayer) and MAC PS (Privacy

Sublayer) have wide responsibility.

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3.3.2.2 Physical Layer

The original version of the standard on which WiMAX is based (IEEE 802.16) specified a

physical layer operating in the 10 to 66 GHz range. 802.16a, updated in 2004 to 802.16-2004,

added specifications for the 2 to 11 GHz range. 802.16-2004 was updated by 802.16e-2005 in

2005 and uses scalable orthogonal frequency-division multiple access (SOFDMA) as opposed to

the orthogonal frequency-division multiplexing (OFDM) version with 256 sub-carriers (of which

200 are used) in 802.16d. More advanced versions, including 802.16e, also bring multiple

antenna support through MIMO. This brings potential benefits in terms of coverage, self

installation, power consumption, frequency re-use and bandwidth efficiency. 802.16e also adds a

capability for full mobility support. The WiMAX certification allows vendors with 802.16d

products to sell their equipment as WiMAX certified, thus ensuring a level of interoperability

with other certified products, as long as they fit the same profile.

Most commercial interest is in the 802.16d and 802.16e standards, since the lower frequencies

used in these variants suffer less from inherent signal attenuation and therefore give improved

range and in-building penetration. Already today, a number of networks throughout the world are

in commercial operation using certified WiMAX equipment compliant with the 802.16d

standard.

In IEEE 802.16 standard, Privacy Sublayer resides on the top of Physical layer. Therefore,

802.16 networks are vulnerable to physical layer attacks for example, jamming and scrambling.

Jamming is done by instigating a source of strong noise to significantly lessen the capacity of the

channel, thus denying services (DOS) to all parties. However, jamming is detectable with radio

analyzer devices. Scrambling is another kind of jamming, but it takes place for a short interval of

time aimed at specific frames. Control or management messages could be scrambled, but it is not

possible with delay sensitive message i.e., scrambling Uplink slots are relatively difficult,

because attacker has to interpret control information and to send noise during a particular

interval.

3.4 Deployment

As a standard intended to satisfy needs of next-generation data networks (4G), 802.16e is

distinguished by its dynamic burst algorithm modulation adaptive to the physical environment

the RF signal travels through. Modulation is chosen to be spectroscopically more efficient (more

bits per OFDM/SOFDMA symbol). That is, when the bursts have high signal strength and a

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carrier to noise plus interference ratio (CINR), they can be more easily decoded using digital

signal processing (DSP). In contrast, operating in less favorable environments for RF

communication, the system automatically steps down to a more robust mode (burst profile)

which means fewer bits per OFDM/SOFDMA symbol; with the advantage that power per bit is

higher and therefore simpler accurate signal processing can be performed.

Burst profiles are used inverse (algorithmically dynamic) to low signal attenuation; meaning

throughput between clients and the base station is determined largely by distance. Maximum

distance is achieved by the use of the most robust burst setting; that is, the profile with the largest

MAC frame allocation trade-off requiring more symbols (a larger portion of the MAC frame) to

be allocated in transmitting a given amount of data than if the client was closer to the base

station.

The client's MAC frame and their individual burst profiles are defined as well as the specific

time allocation. However, even if this is done automatically then the practical deployment should

avoid high interference and multipath environments. The reason for which is obviously that too

much interference causes the network function poorly and can also misrepresent the capability of

the network.

The system is complex to deploy as it is necessary to track not only the signal strength and CINR

(as in systems like GSM) but also how the available frequencies will be dynamically assigned

(resulting in dynamic changes to the available bandwidth.) This could lead to cluttered

frequencies with slow response times or lost frames.

As a result the system has to be initially designed in consensus with the base station product

team to accurately project frequency use, interference, and general product functionality.

3.5 Features of WiMAX

Scalability - The 802.16 standard supports flexible radio frequency (RF) channelbandwidths.The standard supports hundreds or even thousands of users within one RF

channel. As the number of subscribers grow the spectrum can be reallocated

with process of sectoring.

Quality of Service - Primary purpose of QOS feature is to define transmission orderingand scheduling on the air interface.These features often need to work in conjunction with

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mechanisms beyond the air interface in order to provide end to end QoS or to police the

behaviour or SS.

Range It is Optimized for up to 50 Km and designed to handle many users spread outover kilometres. Also it has been designed to tolerate greater multi-path delay spread

(signal reflections) up to 10.0 seconds. PHY and MAC designed with multi-mile range

in mind.

Coverage - Standard supports mesh network topology and optimized for outdoor NLOSperformance.Also standard supports advanced antenna techniques.

3.6 Comparison with Wi-Fi

Comparisons and confusion between WiMAX and Wi-Fi are frequent because both are related to

wireless connectivity and Internet access.

.Both 802.11 and 802.16 define Peer-to-Peer (P2P) and ad hoc networks, where an end user

communicates to users or servers on another Local Area Network (LAN) using its access point

or base station. The table 3 compares various services given by the providers.

3G Wi-Fi: 802.11 WiMax

Maximum Speed 2 Mbps 54 Mbps 100 Mbps

Coverage Several Miles 300 Feet 50 Miles

Airwave Licensed Unlicensed Either

Advantages Range, Mobility Speed, Price Speed, Range,

Mobility, Price

Disadvantages Slow, Expensive Short Range Interference Issues

Table 3: Comparison between 3G, Wi-Fi, WiMAX

The smallest-scale network is a personal area network (PAN). A PAN allows devices to

communicate with each other over short distances. Bluetooth is the best example of a PAN.

The next step up is a local area network (LAN). A LAN allows devices to share information, but

is limited to a fairly small central area, such as a company's headquarters, a coffee shop or

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yourhouse. Many LANs use WiFi to connect the network wirelessly. WiMAX is the wireless

solution

3.7 Spectrum Allocation Issues

The 802.16 specification applies across a wide area of the RF spectrum, and WiMAX could

function on any frequency below 66 GHz, (higher frequencies would decrease the range of a

Base Station to a few hundred meters in an urban environment).

There is no uniform global licensed spectrum for WiMAX, although the WiMAX Forum has

published three licensed spectrum profiles: 2.3 GHz, 2.5 GHz and 3.5 GHz, in an effort to

decrease cost: economies of scale dictate that the more WiMAX embedded devices (such as

mobile phones and WiMAX-embedded laptops) are produced, the lower the unit cost. (The two

highest cost components of producing a mobile phone are the silicon and the extra radio needed

for each band.) Similar economy of scale benefits apply to the production of Base Stations.

In the unlicensed band, 5.x GHz is the approved profile. Telecommunication companies are

unlikely to use this spectrum widely other than for backhaul, since they do not own and control

the spectrum.

In the USA, the biggest segment available is around 2.5 GHz, and is already assigned, primarily

to Sprint Nextel and Clearwire. Elsewhere in the world, the most-likely bands used will be the

Forum approved ones, with 2.3 GHz probably being most important in Asia. Some countries in

Asia like India and Indonesia will use a mix of 2.5 GHz, 3.3 GHz and other frequencies.Pakistan's Wateen Telecom uses 3.5 GHz.

Analog TV bands (700 MHz) may become available for WiMAX usage, but await the complete

roll out of digital TV, and there will be other uses suggested for that spectrum. In the USA the

FCC auction for this spectrum began in January 2008 and, as a result, the biggest share of the

spectrum went to Verizon Wireless and the next biggest to AT&T. Both of these companies have

stated their intention of supporting LTE, a technology which competes directly with WiMAX.

EU commissioner Viviane Reding has suggested re-allocation of 500800 MHz spectrum for

wireless communication, including WiMAX.

WiMAX profiles define channel size, TDD/FDD and other necessary attributes in order to have

inter-operating products. The current fixed profiles are defined for both TDD and FDD profiles.

At this point, all of the mobile profiles are TDD only. The fixed profiles have channel sizes of

3.5 MHz, 5 MHz, 7 MHz and 10 MHz. The mobile profiles are 5 MHz, 8.75 MHz and 10 MHz.

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3.8 Spectral Efficiency

One of the significant advantages of advanced wireless systems such as WiMAX is spectral

efficiency. For example, 802.16-2004 (fixed) has a spectral efficiency of 3.7 (bit/s)/Hertz, and

other 3.54G wireless systems offer spectral efficiencies that are similar to within a few tenths of

a percent. The notable advantage of WiMAX comes from combining SOFDMA with smart

antenna technologies. This multiplies the effective spectral efficiency through multiple reuse and

smart network deployment topologies. The direct use of frequency domain organization

simplifies designs using MIMO-AAS compared to CDMA/WCDMA methods, resulting in more

effective systems.

3.9 Limitations of WiMax

A commonly-held misconception is that WiMAX will deliver 70 Mbit/s over 50 kilometers. In

reality, WiMAX can either operate at higher bitrates or over longer distances but not both:

operating at the maximum range of 50 km (31 miles) increases bit error rate and thus results in a

much lower bitrate. Conversely, reducing the range (to under 1 km) allows a device to operate at

higher bitrates. There are no known examples of WiMAX services being delivered at bit rates

over around 40 Mbit/s.

Typically, fixed WiMAX networks have a higher-gain directional antenna installed near the

client (customer) which results in greatly increased range and throughput. Mobile WiMAX

networks are usually made of indoor "customer-premises equipment" (CPE) such as desktop

modems, laptops with integrated Mobile WiMAX or other Mobile WiMAX devices. Mobile

WiMAX devices typically have omni directional antennae which are of lower-gain compared to

directional antennas but are more portable. In current deployments, the throughput may reach

2 Mbit/s symmetric at 10 km with fixed WiMAX and a high gain antenna. It is also important to

consider that a throughput of 2 Mbit/s can mean 2 Mbit/s symmetric simultaneously, 1 Mbit/s

symmetric or some asymmetric mix (e.g. 0.5 Mbit/s downlink and 1.5 Mbit/s uplink or

1.5 Mbit/s downlink and 0.5 Mbit/s uplink), each of which required slightly different network

equipment and configurations. Higher-gain directional antennas can be used with a WiMAX

network with range and throughput benefits but the obvious loss of practical mobility.

Like most wireless systems, available bandwidth is shared between users in a given radio sector,

so performance could deteriorate in the case of many active users in a single sector. In practice,

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Figure 3.2 OFDMA in multipath environment

In multipath, frequency selective fading affects certain frequencies of a transmission and can

result in deep fading at certain frequencies. One reason this occurs is because of the wideband nature of the signals. When a signal is reflected off a surface, different frequencies will

reflect in different ways. In Figure below, both CDMA (left) and OFDMA (right) experience

selective fading near the center of the band. With optimal channel coding and interleaving,

these errors can be corrected. CDMA tries to overcome this by spreading the signal out and

then equalizing the whole signal. OFDMA is therefore much more resilient to frequency

selective fading when compared to CDMA.

Figure 3.3 Comarison between CDMA and OFDMA

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Figure 3.4 OFDMA signal

3.12 Standards

The current WiMAX incarnation, Mobile WiMAX, is based upon IEEE Std 802.16e-2005,

approved in December 2005. It is a supplement to the IEEE Std 802.16-2004 and so the actual

standard is 802.16-2004 as amended by 802.16e-2005 the specifications need to be read

together to understand them.

IEEE Standard 802.16-2004 addresses only fixed systems. It replaced IEEE Standards 802.16-

2001, 802.16c-2002, and 802.16a-2003. IEEE 802.16e-2005 improves upon IEEE 802.16-2004

by adding support for mobility (soft and hard handover between base stations). This is seen as

one of the most important aspects of 802.16e-2005, and is the very basis of 'Mobile WiMAX'.

It does scaling of the Fast Fourier transform (FFT) to the channel bandwidth in order to keep the

carrier spacing constant across different channel bandwidths (typically 1.25 MHz, 5 MHz,

10 MHz or 20 MHz). Constant carrier spacing results in higher spectrum efficiency in wide

channels, and a cost reduction in narrow channels. It is also known as Scalable OFDMA

(SOFDMA). Other bands not multiples of 1.25 MHz are defined in the standard, but because the

allowed FFT sub carrier numbers are only 128, 512, 1024 and 2048, other frequency bands will

not have exactly the same carrier spacing, which might not be optimal for implementations.

802.16d vendors point out that fixed WiMAX offers the benefit of available commercialproducts and implementations optimized for fixed access. It is a popular standard among

alternative service providers and operators in developing areas due to its low cost of deployment

and advanced performance in a fixed environment. Fixed WiMAX is also seen as a potential

standard for backhaul of wireless base stations such as cellular, or Wi-Fi.

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SOFDMA (used in 802.16e-2005) and OFDM256 (802.16d) are not compatible thus equipment

will have to be replaced if an operator is to move to the later standard. Intel provides a dual-

mode 802.16-2004 802.16-2005 chipset for subscriber units which can be used in the production

of dual-mode CPE's for network operators which have an existing OFDM256 investment.

3.13 Conformance testing

TTCN-3 test specification language is used for the purposes of specifying conformance tests for

WiMAX implementations. The WiMAX test suite is being developed by a Specialist Task Force

at ETSI (STF 252).

TTCN-3 (Testing and Test Control Notation version 3) is a strongly typed test scripting language

used in conformance testing of communicating systems and a specification of test infrastructure

interfaces that glue abstract test scripts with concrete communication environments. TTCN-3 has

been developed by ETSI and its predecessor is TTCN-2. Despite sharing same fundamental

concepts, TTCN-2 and TTCN-3 are essentially two different languages, the latter having simpler

syntax and standardized adapter interfaces. TTCN-3 scripts can be combined with ASN.1 type

definitions. ASN.1 is natively supported by major TTCN-3 tool vendors.

The European Telecommunications Standards Institute (ETSI) is an independent, non-profit,

standardization organization in the telecommunications industry. ETSI has been successful in

standardizing the GSM cell phone system.

3.14 ChallengesUnlike WLAN, WiMAX provides a medium 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 Sta ndard

(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.

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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 (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 is inherently 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 advanced antenna

techniques, which are essential to provide high spectral efficiency, capacity, system

performance, and reliability:

WiMAX has many optional features, such as ARQ, sub-channeling, diversity, and space-time coding that

will prove invaluable to operators wishing to provide quality and performance that rivals wire line

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. The table 4 given below sows the potential solution against some

challenges.

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Challenge Potential Solution

Interference Adaptive Antennas,

Security Encryption, access control

Portability Power Efficient Modulation

Mobility Seamless Handover

Low Cost IP based protocols

Table 4: Potential Solution for various Challenges

3.15 ADVANTGES

1. Single station can serve hundreds of users.2. Much faster deployment of new users comparing to wired networks.3. Speed of 10 Mbps at 10 kilometers with line-of-site.4. It is standardized, and same frequency equipment should work together.5. It has the capacity to offer different types of services in one platform6. Many think that the tower becomes overloaded due to high number of requests

from users but wimax has an inner built algorithm which transfer the user to

another wimax tower

7. WiMax is a globally accepted, technically capable, and industry-wide supported standard.8.

The emergence of WiMax has opened up the solution to many of the problems faced byWi-Fi because, WiMax cover tens of miles unlike Wi-Fi that is restrictive to the

surroundings and resources.

9. Through WiMax wireless networking is possible through longer distances.10.WiMax can run in licensed and non licensed frequencies. 11.It has the capacity to offer different types of services in one platform

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CHAPTER 4

WIMAX SERVICES & APPLICATIONS

4.1 Potential ServicesWiMAX 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,etc2. Streaming Services: VoD ,MPEG ,etc.3. Background Services: FTP,E-Mail, SMS, Multicast/Broadcast ,MMS, PUSH TO TALK

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 Samsungs 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 downloadingand 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.

Further the table 4.1 summarizes possible services to be provided by WiMAX. Example of

WiMAX Services

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Application Service type QOS class

VoD/MoD/AoD Entertainment service Streaming

Real time-Broadcasting ------ Real Time

Network Game ------ Interactive

MMS ------ Background

Web Browsing Information service Interactive

FTP ----- Background

Interactive information ----- Interactive

m-Commerce Commerce service Interactive

Mobile banking ------ Interactive

Stock trading ------ Interactive

Table 4.1 Types of WiMAX Services and QOS of different applications

4.2 Current Service

KT (Korea Telecom) offers 18.4Mbit/s/4Mbit/s for $22 a month with unlimited data usage.

WiMAX seems faster than HSDPA. There are similar services in U.S. operated by wireless

company but much more expensive and slower. Hanaro Telecom has 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 (Korea Telecom) showed off WiMAX trial

services during the Asia-Pacific Economic Cooperation (APEC) summit in Bussan. 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 down speed of 10 Mbit/s and up

speed of some hundreds of kbit/s even in movement up to 120 km/h.In the same event Samsung telecom division president Kitae Lee assured a future of 20-30

Mbit/s by the end of this year (2006) and 100+ Mbit/s down speed and 1+ Mbit/s up speed 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

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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.

Figure 4.1 Korean Telecom WiMAX Trial

4.3 Overview of Wimax Applications

Broadband is becoming a necessity for many residential and business subscribers worldwide.

According to analysts, broadband services will see rapid growth from their current starting point.

There were close to 450 million broadband subscribers worldwide at the end of 2009, up from

300 million at the end of 2007 and 130 million at the end of 2004. WiMAX as a leading

broadband technology is starting to make its niche in this market. At the end of 2009, there were

1,650,000 WiMAX subscribers; currently WiMAX subscribers are estimated at 1.9 million

according to the WiMAX Maravedis Telecom research company. Only a little over half were

using WiMAX Certified technology (WiMAX Forum Certified means that a product or service

based on the WiMAX standard from different companies will work together). 64% of the

customers are residential and 36% businesses. Operators are competing progressively more head

to head with DSL in suburban and urban areas. The WiMAX Forum is to certify 100 productsand more than 100 mobile certified productsacross all profilesby the end of 2009, rising to

more than 1,000 by the end of 2011..The WiMAX silicon market is expected by to grow from

$34 million in 2006 to over $1 billion in 2011.

In Asia, Taiwan is considered a leader in the development and deployment of WiMAX

operability with six commercial WiMAX licenses awarded in July 2007 to six separate

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Taiwanese wireless communication providers. In regions like Taiwan, where users are spread out

and the wireless traffic has to traverse a long distance, WiMAX technology provides a reliable,

inexpensive solution for constant wireless broadband connectivity.

In India, the newly announced changes to the 3G auction policy and the WiMAX spectrum

auctions now prove that WiMAX is not simply a way to extend wireless but an entirely viable

and complete technology in itself. WiMAX Forum estimated recently that Indias WiMAX

market potential, including devices, to be worth $13 billion by 2012 with a base of 27.5 million

WiMAX users. In the Pacific, in countries like Australia, WiMAX technology is perfectly suited

for regional and rural areas with geography challenges and limited wireline footprints. In Africa,

which has many developing countries, WiMAX technology provides the opportunity to connect

the African people with internet and VOIP services faster and more affordable than wireline. In

many European countries the first WiMAX deployments are taking place. Russia is the leading

WiMAX market in Europe and the Russian WIMAX company Scartel LLC, along

with Samsung Electronics, is about to begin trials of mobile WiMAX services in Moscow and St.

Petersburg. In the United States, Intel, Google, Comcast, Time Warner Cable, and Bright House

Networks recently joined forces to form a new venture, to be called Clearwire, to establish a

nationwide WiMAX network. This venture gives WiMAX a better footing as a next-generation

4G wireless network. The first laptops with built-in mobile WiMax wireless broadband are now

available in the U.S. and Nokia is about to sell the new pocket size Nokia N810 internet tablet

WiMAX edition, with a widescreen display and small keyboard, at select independent retailers in

Baltimore. WiMAX-enabled notebooks will be available in the U.S. for connections to Sprint

and Clearwire networks in 2009. Sprint is the first and only wireless carrier to launch a dual-

mode 3G/4G access device, in the fourth quarter of 2008. The figure 4.2 shows some practical

applications.

Figure 4.2 Nokia N810 with WiMAX edition

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CHAPTER 5

FUTURE SCOPE & CONCLUSION

5.1 CONCLUSION

The latest developments in the IEEE 802.16 group are driving a broadband wireless access

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.

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.

5.2 FUTURE SCOPE

This system can be used to serve the internet network to the public covering the large amount of

area. One can easily access the network at any place any time. It got its easily and efficient

accessibility in the basement.

Built for the future, WiMAX technology will allow one to connect in more places, more often,

without being restricted to hotspots. When built into notebooks and mobile devices, one will be

able to extend their connected experience beyond Wi-Fi.

Intel is providing advancements in wireless mobile technology for the future of notebooks and a

wide range of consumer devices. Its wireless products provide great coverage and reliable

connectivity while consuming minimal power.

The IEEE 802.16 standard body members are working toward incremental evolution,from fixed operation to portability and mobility.

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IEEE 802.16f and IEEE 802.16g task groups are addressing the management interfacesfor fixed and mobile operation.

In a fully mobile scenario users may be moving while simultaneously engaging in abroadband 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.

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REFERENCES

[1] K. Fazel and S. Kaiser Multi-Carrier and Spread Spectrum Systems: From OFDM and

MC-CDMA to LTE and WiMAX,2nd Edition, John Wiley & Sons, 2008[2] M. Ergen, Mobile Broadband - Including WiMAX and LTESpringer, NY, 2009

[3] http://www.wimax.com/commentary/spotlight/spotlight9-16-2006mw1

[4] http://www.wimax.com/commentary/blog/blog-2009/september-2009/india-upcoming-

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[5] http://www.tutorialreports.com/wireless/wimax/introduction.php?PHPSESSID=102eb0af

52a9e697e693385ee03903b5

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[10] http://www.networkworld.com/topics/wimax.html

[11] http://www.intel.com/technology/wimax/

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