CHAPTER 1

INTRODUCTION OF WIMAX

1.1 Introduction

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 – 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, 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.

1.2 Infrastructure of WiMAX

• A wimax tower: It is similar in concept to cell phone tower. A single wimax tower can provide coverage to very large area.
• A wimax receiver: The receiver and antenna could be a small box or a PCMCIA card, or could be built into a laptop.

1.3 Background

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) can double the data throughput of Wi-Fi for heavy demanding applications. A number of cities around the world are in the process of building city-wide Wi-Fi networks to allow citizens to enjoy wireless data transfer across the city (also known as a metropolitan area network). While Wi-Fi operates over a free unlicensed spectrum and is simple to install and operate, it has some major disadvantages. One of the main drawbacks is poor signal coverage; only 30 meters indoors and 200 meters outdoors. Wi-Fi as a fixed broadband standard cannot support broadband services while on the move and does not support continuous connectivity between Wi-Fi hotspots which could enable, for instance, a person going from his office to a cafe while having a continuous wireless conversation, Wi-Fi is exposed to other interferers on the same band since it runs over an unlicensed spectrum, is considered relatively insecure since it does not use enhanced encryption, is very power inefficient, and does not guarantee quality of service.

1.4 Benefits Of WiMAX

• Speed - Faster than broadband service
• Wireless - Not having to lay cables reduces cost. Easier to extend to suburban and rural areas.        
• Broad Coverage- Much wider coverage than WiFi hotspot.

1.4.1 Benefits to Service Providers

• Allow service providers to deliver high throughput broadband based services like VoIP, high-speed Internet and Video
• Facilitate equipment compatibility
• Reduce the capital expenditures required for network expansion
• Provide improved performance and extended range

1.4.2  Benefits to Customers

• Range of technology and service level choices from both fixed and wireless broadband operators
• DSL-like services at DSL prices but with portability
• Rapidly declining fixed broadband prices
• No more DSL “installation” fees from incumbent.

1.5   Uses

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

• Connecting Wi-Fi hotspots to the Internet.
• Providing a wireless alternative to cable and DSL for "last mile" broadband access.
• Providing data and telecommunications services.
• 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.
• Providing portable connectivity
• Allow service providers to deliver high throughput broadband based services like VoIP, high-speed Internet and Video
• Reduce the capital expenditures required for network expansion

Fig 1.1 Uses of WiMAX

CHAPTER 2

MOBILIZING YOUR INTERNET

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.

              Fig 2.1 WiMAX System

2.1 What is WiMAX?

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 rural—delivering mobile broadband Internet access at speeds similar to existing broadband. WiMAX is built for the future with advanced, efficient wireless technology that provides higher speeds than today’s wide area wireless technologies. It will be able to completely transform your mobile Internet lifestyle, enabling you to connect in ways you’ve only dreamed about.

2.2 Specifications of WiMAX

Table 2.1 WiMAX Specifications

Think of Internet, There are three possible ways to access internet.

• Broadband access: Uses DSL or cable modem at home and T1 or T3 line at office
• WIFI: Uses WIFI routers at home and hotspots on the road
• Dial Up Connection

Broadband access is too expensive and WiFi coverage is very sparse. So, WIMAX gives a very good option replacement for the all above internet access. It promises

• High speed of broadband service
• Wireless rather than wired access.
• Broad Coverage

A WIMAX system consists of A WiMAX tower, similar in concept to a cell-phone tower - A single WiMAX tower can provide 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. .

Fig 2.2 WiMAX transmitter and receiver

2.3 Imagine Broadband on the Go

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 it—staying 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.

• Playing in Real-Time.  Play multiplayer 3-D games, view YouTube videos, and listen to radio broadcasts— it’s all there waiting to entertain you on the go.

• Working Smarter. 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.

• Staying in Touch. 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.

• Locating People and Places. WiMAX enables a spontaneous lifestyle. Location-based services creates a new paradigm in        accessing real-time information where and when you need it.

• Receiving TV and Radio on the Go. 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.

2.4 WiMAX/Wi-Fi Synergies

WiMAX takes your wireless Internet further, but you don’t have to burn any Wi-Fi bridges. WiMAX and Wi-Fi are perfectly compatible companions. Together, they give you an always-best connected experience whether you are in a Wi-Fi or WiMAX coverage area. 

Fig 2.3 WiMAX/Wi-Fi Synergies

Figure: WiMAX/Wi-Fi synergies enable integration of both wireless technologies into notebooks and mobile devices.

CHAPTER 3

MAKING WiMAX FLY

A huge ecosystem of companies have coalesced around WiMAX to deliver on the promise of open, standards-based, interoperable wireless broadband built for the Internet.

3.1 Why WiMAX?

WiMAX success stems from a robust vision incorporating four key strengths:

• Open standards-based, interoperable technology built from the ground up for the Internet fosters innovation and competition.

• Vibrant, growing ecosystem of industry leaders such as Intel, Sprint, Clearwire, Motorola, Samsung, Nokia, Cisco, and hundreds of other companies.

• Global economies of scale and more attractive intellectual property environment that enable lower costs compared to other wireless technologies.

• Advanced wireless technology that enables a faster wireless broadband solution for doing more on the go.

• Connect in more places, more often.

• Connecting notebooks of the future with WiMAX: Intel is providing advancements in wireless mobile technology for the future of notebooks and a wide range of consumer devices.

3.2 The Joy of Open Wireless

WiMAX is a robust standard designed for the Internet. It’s born from the same open-standards approach that made Wi-Fi so successful. Nurturing WiMAX deployment in the real world is the WiMAX Forum, a large industry-wide collaboration that works to ensure that WiMAX service and products work together seamlessly.

3.3 Certified WiMAX

WiMAX Forum Certified means anyone can buy a product or service based on the IEEE 802.16 standard from different companies and be confident that everything will work together. This method follows the

successful approach that 802.11-based Wi-Fi networks used. The IEEE 802.11 standard set the requirements, and the Wi-Fi Alliance ensured product compliance for interoperability.

Fig 3.1  The WiMAX Forum Certified logo on WiMAX products

3.4 Built for the Internet

WiMAX is built from the ground up for Internet applications, services, and security, with architecture specifically designed to seamlessly extend the Internet to mobile users. Because WiMAX is built on Internet protocol (IP) networking, it supports all the latest IP security and quality of service (QOS) standards. WiMAX support of QOS standards enables real-time media like Voice over IP (VoIP) and streaming video.

3.5 A Wireless for All Reasons

The WiMAX standard supports mobile, portable, and fixed service options. This enables wireless providers to offer broadband Internet access to areas underserved by telephone and cable companies. For fixed WiMAX deployments, service providers supply Customer Premises Equipment (CPE) that acts as a wireless “modem” to provide the interface to the WiMAX network for a specific location, such as a home, cafe, or office. WiMAX is also well suited for emerging markets as a cost-effective way to deliver high-speed Internet.

3.6 How Does WiMAX Work?

Think of WiMAX as taking the best part of cellular network access– the part that allows you to easily connect anywhere within your service provider’s 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.

Fig 3.2 Working of WiMAX

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.

Fig 3.3: 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 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.

Fig 3.4 OFDMA signal

CHAPTER 4

TECHNICAL INFORMATION

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 stan-

dard. 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 adop-

tion of such technology and to ensure interoperability among equipment of different

vendors.

4.1 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.

4.1.1  IEEE 802.16 Specifications 

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.

Fig 4.1 IEEE 802.16 Specifications

4.1.2 Protocol architecture of the IEEE 802.16 standard

Fig 4.2 IEEE 802.16 protocol architecture.

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.

4.1.2.1 MAC (Data Link) Layer

In Wi-Fi the media access controller (MAC) uses contention access — all subscriber stations that wish to pass data through a wireless access point (AP) are competing for the AP's attention on a random interrupt basis. This can cause subscriber stations distant from the AP to be repeatedly interrupted by closer stations, greatly reducing their throughput.

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.

                                                                                                                                              The 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 sublayers:

One is ATM convergence sublayer for ATM networks & services and

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.

4.1.2.2 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.

4.2 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 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.

4.3  Features Of WiMAX

• Scalability - The 802.16 standard supports flexible radio frequency (RF) channel bandwidths.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 ordering and scheduling on the air interface.These features often need to work in conjunction with 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 out over kilometres. Also it has been designed to tolerate greater multi-path delay spread (signal reflections) up to 10.0μ  seconds. PHY and MAC designed with multi-mile range in mind.
• Coverage - Standard supports mesh network topology and optimized for outdoor NLOS performance.Also standard supports advanced antenna techniques.

4.4 Comparison with Wi-Fi

Comparisons and confusion between WiMAX and Wi-Fi are frequent because both are related to wireless connectivity and Internet access.

WiMAX is a long range system, covering many kilometers, that uses licensed or unlicensed spectrum to deliver a point-to-point connection to the Internet.

Different 802.16 standards provide different types of access, from portable (similar to a cordless phone) to fixed (an alternative to wired access, where the end user's wireless termination point is fixed in location.)

Wi-Fi uses unlicensed spectrum to provide access to a network.

Wi-Fi is more popular in end user devices.

WiMAX and Wi-Fi have quite different quality of service (QOS) mechanisms:

WiMAX uses a QOS mechanism based on connections between the base station and the user device. Each connection is based on specific scheduling algorithms.

Wi-Fi has a QOS mechanism similar to fixed Ethernet, where packets can receive different priorities based on their tags. For example VoIP traffic may be given priority over web browsing.

Wi-Fi runs on the Media Access Control's CSMA/CA protocol, which is connectionless and contention based, whereas WiMAX runs a connection-oriented MAC.

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.

Table 4.1  Comparison between 3G, Wi-Fi, WiMAX

4.5  Network scale

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 your house. Many LANs use WiFi to connect the network wirelessly. WiMAX is the wireless solution for the next step up in scale, the metropolitan area network (MAN). A MAN allows areas the size of cities to be connected.

Fig 4.3 Network Scale

4.6 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 500–800 MHz spectrum for wireless communication, including WiMAX.

WiMAX profiles define channel size, TDD/FDD and other necessary attributes in order to have inter-operating products. The current fixed profiles are defined for both TDD and FDD profiles. At this point, all of the mobile profiles are TDD only. The fixed profiles have channel sizes of 3.5 MHz, 5 MHz, 7 MHz and 10 MHz. The mobile profiles are 5 MHz, 8.75 MHz and 10 MHz. (Note: the 802.16 standard allows a far wider variety of channels, but only the above subsets are supported as WiMAX profiles.)

Since October 2007, the Radio communication Sector of the International Telecommunication Union (ITU-R) has decided to include WiMAX technology in the IMT-2000 set of standards. This enables spectrum owners (specifically in the 2.5-2.69 GHz band at this stage) to use Mobile WiMAX equipment in any country that recognizes the IMT-2000.

4.7 Spectral Efficiency

One of the significant advantages of advanced wireless systems such as WiMAX is spectral efficiency. For example, 802.16-2004 (fixed) has a spectral efficiency of 3.7 (bit/s)/Hertz, and other 3.5–4G wireless systems offer spectral efficiencies that are similar to within a few tenths of a percent. The notable advantage of WiMAX comes from combining SOFDMA with smart antenna technologies. This multiplies the effective spectral efficiency through multiple reuse and smart network deployment topologies. The direct use of frequency domain organization simplifies designs using MIMO-AAS compared to CDMA/WCDMA methods, resulting in more effective systems.

4.8 Limitations

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, most users will have a range of 2-3 Mbit/s services and additional radio cards will be added to the base station to increase the number of users that may be served as required.

Because of these limitations, the general consensus is that WiMAX requires various granular and distributed network architectures to be incorporated within the IEEE 802.16 task groups. This includes wireless mesh, grids, network remote station repeaters which can extend networks and connect to backhaul.

4.9 Silicon Implementations

A critical requirement for the success of a new technology is the availability of low-cost chipsets and silicon implementations.

Mobile WiMAX has a strong silicon ecosystem with a number of specialized companies producing baseband ICs and integrated RFICs for implementing full-featured Mobile WiMAX Subscriber Stations based on the IEEE 802.16e standard. It is notable that most of the major semiconductor companies have not developed WiMAX chipsets of their own and have instead chosen to invest in and/or utilise the well developed products from smaller specialists or start-up suppliers. These companies include but not limited to Beceem, Sequans and PicoChip. The chipsets from these companies are used in the majority of Mobile WiMAX devices.

Intel Corporation is a leader in promoting WiMAX, but has limited its WiMAX chipset development and instead chosen to invest in these specialized companies producing silicon compatible with the various WiMAX deployments throughout the globe.

4.10 Role of ‘OFDMA’ In Multipath Environment

Technologies using DSSS (802.11b, CDMA) and other wide band technologies are very susceptible to multipath fading, since the delay time can easily exceed the symbol duration, which causes the symbols to completely overlap (ISI). The use of several parallel sub-carriers for OFDMA enables much longer symbol duration, which makes the signal more robust to multipath time dispersion

Fig 4.4 OFDMA in multipath environment

(a). Multipath: Frequency Selective Fading

This type of fading affects certain frequencies of a transmission and can result in deep fading at certain frequencies. One reason this occurs is because of the wide band 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.

Fig 4.5 Comarison between CDMA and OFDMA

4.11 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'.

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. 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 commercial products and implementations optimized for fixed access. It is a popular standard among alternative service providers and operators in developing areas due to its low cost of deployment and advanced performance in a fixed environment. Fixed WiMAX is also seen as a potential standard for backhaul of wireless base stations such as cellular, or Wi-Fi.

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.

4.12 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.

4.13 Associations

4.13.1 WiMAX Forum

The WiMAX Forum is a non profit organization formed to promote the adoption of WiMAX compatible products and services.

A major role for the organization is to certify the interoperability of WiMAX products. Those that pass conformance and interoperability testing achieve the "WiMAX Forum Certified" designation, and can display this mark on their products and marketing materials. Some vendors claim that their equipment is "WiMAX-ready", "WiMAX-compliant", or "pre-WiMAX", if they are not officially WiMAX Forum Certified.

Another role of the WiMAX Forum is to promote the spread of knowledge about WiMAX. In order to do so, it has a certified training program that is currently offered in English and French. It also offers a series of member events and endorses some industry events.

4.13.2 WiMAX Spectrum Owners Alliance

WiSOA was the first global organization composed exclusively of owners of WiMAX spectrum with plans to deploy WiMAX technology in those bands. WiSOA focussed on the regulation, commercialization, and deployment of WiMAX spectrum in the 2.3–2.5 GHz and the 3.4–3.5 GHz ranges. WiSOA merged with the Wireless Broadband Alliance in April 2008.

CHAPTER 5

                                                            WIMAX SERVICES

5.1 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

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

Table 5.1 Types of WiMAX Services and QOS of different applications

5.2 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.

Fig 5.1 Korean Telecom WiMAX Trial

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 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.

CHAPTER 6

WIMAX:FIXED & MOBILE ACCESS

WiMAX integrates perfectly into existing fixed and mobile networks, complementing them when needed.

6.1 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. 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 suburban areas, and will remain so in the near future. The low 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 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.

6.2 WiMAX for Portable Internet

6.2.1 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 capabilities. WiMAX by-passes these limitations and offers broadband connectivity in larger areas. 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.

6.2.2 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.

6.3 Operator's business case

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

• The incumbent operators can use the wireless technology as a complement to DSL, allowing them to offer DSL-like services in remote, low density 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.

6.4 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.  

                                                      Fig 6.1 WiMAX Tower

The Wimax tower is shown in the above diagram which serves multiple users for their multiple uses at a particular instance of time.

CHAPTER 7

WIMAX IN INDIA

7.1 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.

7.2 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 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.

7.3 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 cost effectively 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 facilitating development of multimedia materials for delivery through distance learning programs.

 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 conduct 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.

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. 

                                  CHAPTER 8

WiMAX TODAY

8.1 Overview

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 products and more than 100 mobile certified products – across all profiles – by 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 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 India’s 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. Sprint adopted WiMAX as their next generation broadband service. Sprint expects to complete the anticipated combination of its XOHM (Sprint’s 4G business unit) WiMAX business assets with Clearwire to form a new company in the fourth quarter. On August 10, 2008 XOHM, Intel, and WiMAX partners celebrated a new 4G broadband era with WiMAX service in Baltimore, and the slated next cities to be Chicago, Illinois and Washington, D.C. XOHM USB WiMax dongles by ZTE have also recently become available. 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.

                 Fig 8.1  Nokia N810 with WiMAX edition

CHAPTER 9                                                                    CHALLANGES  

 9.1 WiMAX, more flexibility and security

Unlike 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 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.

9.2 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 (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: 

• 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 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.

Challenge                                                             Potential Solution

Interference                                                          Adaptive Antennas,                                 

Security                                                              Encryption, access control

Portability                                                        Power Efficient Modulation

Mobility                                                                 Seamless Handover

Low Cost                                                          IP based protocols  

CHAPTER 10

ISSUES

It seems that India (home to over 1 billion people) is having problems with deploying WiMAX. This is in part due to the government taking its time in allocating spectrum to system integrators and ISP's. According to a news source, the globally used band for WiMAX is 2.5 GHz - 2.7 GHZ, but in India this band is locked for satellite based mobile and broadcast applications such as national emergencies and natural disasters.

What is available is the 2.3 GHz- 2.4 GHz and 5.8 GHz that has been allocated to several IPS's. According to the ISP's, these bands are good for trials only, but not for city wide and commercial deployment. The key players of WiMAX and even 3G have asked the Indian government to release higher band frequencies so that deployment can be made, but government officials are confused as to how much and at what price they should let go of the spectrum. On the other hand, the department of Defense has certain frequency bands under its belt, which it is unwilling to give up for any price.

The problem in India is a common one. A scarce resource like spectrum, which is held by both, the government as well as the military will be allocated slowly over a short period of time. Due to India's highly regulated spectrum market people should not expect WiMAX to mushroom all over the country anytime soon.

CHAPTER 11

ADVANTGES AND DISADVANTAGES

Advantages

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 platform
6. 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 by Wi-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

Disadvantages

i) Line of site is needed for longer connections.
ii) Weather conditions like rain could interrupt the signal.
iii) Other wireless equipment could cause interference.
iv) Multiplied frequencies are used.
v) WiMAX is very power intensive technology and requires strong electrical support.
vi) Big installation and operational coast.

CHAPTER 12

FUTURE ASPECTS

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 it’s 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.

• IEEE 802.16f and IEEE 802.16g task groups are addressing the management interfaces for fixed and mobile operation.

• 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.

CHAPTER 13

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.

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 LTE” Springer, NY, 2009 

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

[3]http://www.wimax.com/commentary/blog/blog-2009/september-2009/india-upcoming-wimax-auction-0901

[4]http://www.tutorialreports.com/wireless/wimax/introduction.php?PHPSESSID=102eb0af52a9e697e693385ee03903b5

[5]http://download.intel.com/network/connectivity/products/wireless/welcome-to-your-internet-future.pdf

[6]http://www.4gwirelessjobs.com/pdf/WIMAX.pdf

[7]http://www.frost.com/prod/servlet/market-insight-top.pag?docid=36644731

[8]http://gigaom.com/2010/02/10/wimax-global-deployments/

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

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