Wimax(wi-fi)wireless Communications

AB STRA CT : Wireless LAN technology is gaining broad acceptance and being adopted world-wide in organizations that clamor for competitive advantage of an increasingly mobile and highly productive workforce. The WAP 2000 series access point, which sets the enterprise standard for secure, manageable and reliable wireless LANs while also providing a smooth migration path to future high-speed wireless LAN technologies. This innovative, state-of-the art wireless infrastructure platform features dual-band functionality that simultaneously supports current and emerging wireless standards. One of the most innovative aspects of the WAP 2000 series access point is that it is both software and hardware upgrade their software to take advantage of new features that DAX will develop in the future, but they also will be able to upgrade the radios in the field to take advantage of new high-speed wireless standards. WIMAX (world-wide interoperability for microwave access) is the IEEE 802.16 standards based wireless technology that provides MAN (metropolitan area network) broad band connectivity. WIMAX can offer a solution to what is normally called the “last-mile” problem by connecting individual homes and business offices Communications. It is to be less expensive than their wired counterparts, such as digital subscriber lines (DSL). This will now be able to enjoy high-speed internet access since distance up to 30miles (50km) are supported “No wires, No rules”. Zooming down the highway, you will be able to use a laptop or PDA to check the weather or traffic a few miles ahead. From physical issues up to applications aspects, Mobile Ad hoc networking in Wi-Fi (wireless-fidelity) comprehensively covers all areas of the technology including protocols and models with an emphasis on the most current research and development. To understand wireless technology trends and to see why non infrastructure-based Mobile Ad hoc networks are poised to play an Important role in the evolution of future wireless networks. It helps in the evolution path of different generations

IN TR OD UC TIO N :

Wireless technology for computer users is nothing new. The first connections were established two decades ago . Adoption, though, has proceeded very slowly, mostly limited to a few specialized vertical markets, such as warehousing, education and retail. Implementation has been slow for three reasons. First, the original wireless data rates were too slow to serve mainstream users on a shared LAN. Although throughput did gradually increase, network speeds still drastically lagged those of wired LANs. Second, proprietary, nonstandard solutions dominated the marketplace, providing little interoperability among devices, or the peace of mind for users that come from having multiple vendor options. Third, these low speed proprietary solutions were very expensive compared to wired solutions. In recent years, the situation has changed dramatically. In 1999, institute of Electrical and Electronics Engineers(IEEE) ratified the 802.11b standard, offering data rates up to 11 megabits per second (mbps),similar to the 10 mbps connections that are common for many Ethernet-based workgroups. For the first time, wireless LANs became truly usable for most work environments and office applications. Multiple vendors quickly came to support the 802.11b standard. This rapidly drove down costs, leading to increased demand and even greater vendor support. In addition, the 802.11bstandard assured users of device interoperability. The Wireless Ethernet Compatibility of wireless LAN products based on the IEEE 802.11b specification and to promote the use of the standard across all Market segments. With the rapid adoptions of the 802.11b standard, users began to have a choice of a wide variety of interoperable, low-cost, high –performance wireless equipment. Perhaps most importantly, much type of organizations today sees tremendous value by adding wireless on to the corporate LAN. For years, laptop and notebook computers have Promised anytime, any where computing. But, with access to the LAN and the internet becoming such an integral part of business, a wireless connection is needed to make true the Promise of anytime, anywhere computing. Wireless devices enable users to be constantly connected from virtually anywhere: a desk, a conference room, the coffee shop, or another Building on a corporate or academic campus. This ability provides users with maximum flexibility, productivity and efficiency, while dramatically boosting collaboration and cooperation with colleagues, business partners and customers. In addition, wireless can bring LAN access to location where laying cable is difficult or expensive.

W iMax_ Standar ds: This figure shows how 802.16 broadband wireless systems have evolved over time. This diagram shows that the original 802.16 specification defined fixed broadband wireless service that operates in the 10-66 GHz frequency band. To provide wireless broadband service in lower frequency range, the 802.16A specification was created that operates in the 2-11 GHz frequency band. To provide both fixed and mobile service, the 802.16E specification was developed. Both 802.11a and 802.11g offer substantial improvements over the current 802.11b standard, Because higher data rates deliver far greater performance and usability for devices on the wireless LAN. The one disadvantage is that the 802.11a and 802.11g standards are not compatible because they use different frequency bands.futher more, 802.11a is not compatible with the exiting installed base of 802.11b devices. So, what should organizations do? This decision is critical as look a head to the future of their wireless infrastructure. it will guide their product choices and infrastructure capabilities for years to come.

W imax : Broadband wireless access technology Wimax is a wireless standards developed by working group of institute of electrical And electronics engineers (IEEE). The first version, IEEE 802.16 activities were initiated by the national wireless electronics systems tested (N-WEST) of the u.s national institute of standards and technology. The WIMAX from is a non-profit group that promotes 802.16 technology and certificates compatibility and interoperability of broadband wireless access equipment that conforms to IEEE802.16&ETSIHIPERMAN standards. That standard offers an alternative [1] to cabled access networks, such as fiber optic links, coaxial system using cable modems, and digital subscriber line (DSL) links or t1 links. This technology provides fast services, flexible, cost effective filling of the existing gaps of wired network and facility to create new services. The IEEE has established many wireless standards as IEEE 802.15 for personal Area

network (PAN), IEEE802.11 for local area network (LAN), IEEE802.16 for local area network (LAN), IEEE802.16 for metropolitan Area network (MAN). Each standards represents the optimized technology for usage model.

802 .16 BROAD BR AN D WIR ELESS SY STEM TY PICAL WL AN ROAMIN G: The topology of roaming cells may take on many forms but the essential building block is a collection of wireless devices with overlapping BSS. The overlapping wireless roaming cells mainly constitute an Access Point to Access Point (AP-to-AP) signal, Access Point-to-Wireless Client (AP-to-WC) linkage, or Wireless Client-to-Wireless Client (WC-to-WC) association.

In a typical WLAN topology, the WC does not communicate directly with each other; they communicate with the access point. If a single BSS doe not provide enough coverage, a number of wireless cells can be added to

extend the range(ESS). One form of Wi-Fi™ Mesh comprise of a collection Root-AP overlapping to create wireless roaming cells. An AP attached directly to a wired network provides a centralized point for wireless end users to remain attached to a wired Internet. If more than one AP is connected to the wired network, users can roam from one area (or wireless cell) of a facility to another cell without losing their connection to the network in a large facility (Figure 3). As users

move out of range of one AP, they automatically connect to the network through another AP; consequently, the roaming process is seamless and transport to the user.LC-WLAN Repeater Roaming

Another Wi-Fi™ Mesh comprise of a Root-AP and a collection of adjacent Repeater-APs Another wireless roaming configuration is attaching a principal AP to a wired network and arranging other access points as a repeater or central router for mobile end users. The WLAN repeater-roaming configuration is a chain of repeaters overlapping be neighboring wireless cells and maintain an indirection association to the wired AP. Similar to a teacher leading a group of children, by the hand, across a street intersection. The AP wired to the backbone network is designated as a Root Access Point (Root-AP) and the wireless APs not attached to the wired network are called Repeater Accesss Points (Repeater-APs). The IEEE 802.16 standard, WIMAX is a broadband wireless access to link homes and business to core telecommunications networks worldwide. The wireless MAN technology bringing the network to a building, users inside the building will connect to it with conventional in-building networks. This technology allows for the efficient extension of the individual users laptop computer in a home. The working group’s initial interest was the 10to 66 GHZ range which is developed for a point-to-multipoint broadband wireless access over 30 miles. The standards covers both

the media access control (MAC) and the physical (PHY) layers. Task groups a and b are jointly producing an amendment to extend the specification to cover both the licensed and unlicensed bands in the 2 to 11GHZ range [2]. The data rate is of 70 mbps over 30 miles (50Kms).WIMAX is speed broadband network.

The WIMAX network is as shown in figure . A WIMAX system consists of two parts.

(1) A WI MAX TOWER : A single WIMAX tower can provide coverage to Avery large area [5].

(2) A WI MAX REA CEI VER : The receiver and antenna could be a small box or PCMCIA card,or they could be built into a laptop. A WIMAX tower station can connect directly to the internet using a highbandwidth, wired connection (for example, a T3 line). It can also connect to another WIMAX tower using a line-of-sight, microwave link. This connection to a second tower (often referred to as a backhaul). A long with the ability of a single tower to cover up to 3,000 square miles is what allows WIMAX to provide coverage to remote rural areas. WIMAX is capable of delivering flexible and affordable last-mile broadband access for millions of subscribers in homes and business throughout the world.

WIMA X RA DIO

CH ANN ELS :

This figure shows the key components of a basic WiMax radio system. This diagram shows that the major component of a WiMax system include subscriber station (SS), a base station (BS) and interconnection gateways to datacom (e.g. Internet) and telecom (e.g. PSTN). An antenna and receiver (subscriber station) in the home or business converts the microwave radio signals into broadband data signals for distribution in the home. In this example, a WiMax system is being used to provide telephone and broadband data communication services. When used for telephone services, the WiMax system converts broadcast signals to an audio format (such as VoIP) for distribution to IP telephones or analog telephone adapter (ATA) boxes. When WiMax is used for broadband data, the WiMax system also connects the Internet through a gateway to the Internet. This example also shows that the WiMax system can reach distances of up to 50 km when operating at lower frequencies (2-11 GHz).

WIMA X BR OADB AND C ONN EC TIVIT Y : RESIDENTIAL BROADBAND

For residential broadband WIMAX can be used to fill the gaps in cable and DSL coverage. Practical limitations prevent cable and DSL technologies from reaching many potential broadband customers. Due to the absence a line of sight requirement, high bandwidth and the inherent flexibility and low cost, IMAX helps to overcome the limitations of traditional wired and proprietary wireless technologies.

PRA CTIC AL A PPLICA TIO N OF ME SH

NE TW OR KS:

A Wireless Mesh Network has two practical applications in the Wi-Fi community: Static Wireless Mesh and Dynamic Wireless Mesh. With a Static Wireless Mesh, the permanent IP address is assigned to a centralized or specific wireless device, like a wireless router, as it rarely change in physical location. Adjacent wireless routers can overlap in RF coverage to produce a roaming effect or extend the range via a repeater configuration as well as several pockets of mobile wireless end-users. Users or wireless devices wishing to communicate without any infrastructure or vital administration primarily form the Dynamic Wireless Mesh. Each node is free to enter or leave the network area at any time; however, a very complex IP layer is required to assign or de-assign IP addresses because of an every changing mobile environment.

Static Wireless Mesh: Wireless Bridge delivers Internet access to Homes and roaming can occur between neighboring home.

“Las t mi le ” br oadband acce

ss s ol ution :

Metropolitan-Area networks (MAN) connections to home and business office, especially in those areas that were not served by cable or DSL or in areas where the local telephone company may need a long time to deploy broadband service WIMAX is useful. The WIMAX –based wireless solution makes it possible for the service provider to scale-up or scale-down service levels in short times with the client request.

cel lul ar ba ckhaul : The networks for cellular base stations by passing the public switched telephone network (PSTN); the cellular service providers can look to wireless backhaul as a more cost effective alternative. The robust WIMAX technology makes it a nice choice fir backhaul for enterprises such as hotspots as well as point-point backhaul solution WIMAX helps backhaul enterprise connections to the internet for WIFI hotspots. It will allow users to connect to the wireless internet service provider even when they roam outside their home or business office. A variety of new business services by wireless internet service provider are possible.

WIMA X Usa ge Scenar io s: Extending Ser vices

the

Reac h

of

Communica tion

and

Go ver nment

In Indian cities, house holds with internet access use it to keep in touch with their families and friends or in other parts of the country or abroad. But dial-up connection, currently the most prevalent method of internet access does not provide the service quality or reliability for applications like video chat. Low bandwidth results in video frames being dropped and in poor audio quality, and makes the telephone unavailable for the duration of the internet connection

Broadband facilities solve these problems and extend the reach and variety of personal communication to include the efficient VOIP, video conferencing, instant messaging and quick access to e-mail. Broadband access can increase the effectiveness of e-governance initiatives Egovernance can reduce wait times for service and increase productivity in government offices. India is already testing the e-governance idea in pilot programs aimed at bringing local government services to people through internet access. E-seva is one such initiative, created by the Andhra Pradesh government to provide its citizens with online services such as obtaining birth certificates and various licenses, payment of utility bills and taxes, tickets reservations for transportation services and listings of government pay orders and policies. Gramdoot is a similar initiative by Rajasthan government. The states of Karnataka, Madhya Pradesh and Kerala also have several internet-based services and literacy programs. Broader internet adoption driven by cost-effective technologies like WIMAX can speed-up and extend the reach of government services at a reduced cost to both the people and government.

Impr oved Educ ation , Hea lth Car e and Ente r tain ment With higher bandwidth and faster speeds broadband internet can make education more accessible by delivering interactive distance education at low cost. 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 conducts off-campus degree programs as a means of continuing education for the employed professionals as part of the human restores. Development programs of specific organizations at various off-campus centers. BITS offering include degree programs in math’s, science and engineering, computer sciences, medical and health care and other fields. Extensive and reliable broadband internet can help this 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 far away experts, thus providing faster and better care to the patients. Videos of this and similar scenarios are available at the Intel web site. The many social advantages of broadband internet also include telecasting of entertainment programs, as “on-demand” movie and infotainment service business models evolve. Entertainment delivered via broadband could be an event for social gatherings in isolated villages.

Bac khau l f or M eshed W i- Fi : Local Area Network India has one of the fastest-growing IT industries in the world, and this growth is expected to continue. Broadband internet connectivity is critical for many business, so ITdependant industry concentrates in areas where broadband service is available. Wireless last-mile broadband could accelerate the development of meshed office wireless LANs (like wi-fi), and business could than backhaul the LAN traffic to the WIMAX network. Service providers will be able to quickly provide on-demand high-speed connectivity to businesses anywhere within their base station range.

W i- Fi Me sh Ne tw or ks , Hoc Makings of a

T he

Path

to

Mob il e

Ad

Wi-fi Mesh Network: Wireless Roaming Cells (WC) by combining at least two P-to-P or P-to-Mp wireless cells create a roaming effect and thus is the start of a Wi-Fi™ Mesh Network. Roaming is the ability to maintain network connectivity while moving from one access point to another. The basic service set (BSS) is the area of RF coverage provided by an access point, also referred to as a wireless cell. The AP is the master for the wireless cell and controls traffic flow to and from the network for its given RF circle. The RF coverage of a wireless cell is limited and each county has its own set of rules of cell coverage. To extend the BSS or to simply add wireless devices and increase the range of an existing wired system, an Access Point can be added, hints this unit is the point at which wireless end users can access the network. Because the wireless end users ranges from PDAs, Laptops, tabletops, PCs, these wireless accessible devices are called Wireless Clients most manufactures.

Normally, Wireless Local Area Networks (Wireless LANs) are configured using a peer-tomultipoint network, which has one access point (AP) that controls communications with other wireless devices accessing the network. Signals in peer-to-multipoint networks

converge at a single access point. The reliability of these networks is set by the quality of the RF linkage between the central AP and the endpoints. In a real-world application, it can be problematical to find an ideal location for an access point that provides dependable communication with each end point, especially if two or more floors exist or due to a home’s physical structure. Moving an access point to improve communications with one node will often degrade communications with other end points. The status of a communication link between wireless devices, at any given time, is a function of their positions, transmission power levels, antenna patterns, interference levels, and many other minor phenomena.

WIMA X Benefit s: Cost and investment risks • • •

Interoperable equipment lets operators purchase WIMAX-Certified equipment from more than one vendor [4]. A stable, standards-based platform improves Op ex by sparking innovation at the network management layer, antenna layers and elsewhere in the protocol stack. Better bits per second per Hz at longer ranges.

Scalable System Capacity • •

Easy addition of channels maximizes cell capacity. Flexible channel bandwidths accommodate allocations for both licensed and unlicensed spectrums.

.

Toda y’ s wir eles s a ppl ica tion s: Wireless access at LAN speeds: Workers today need secure access to an organizations network, whether they are at the office, at a branch location, at home, or at the airport. with wireless connection, they can enjoy full access to their applications and data, enabling them to work from a wide variety of locations within range of an access point. Therefore, workers can stay connected and be fully productive from almost anywhere.

Internet/intranet access: Today, workers require continual access to the internet and to the company intranet. wireless technology lets employees take advantage of these capabilities constantly, conducting research and communicating with co workers and business partners through email and instant messaging .Without the physical restriction of wired connection.

Highly mobile computing: Currently, most wireless computing is conducted with laptop computers. However, that scenario is rapidly changing and broadening. More and more, wireless vendors are offering silicon solutions that dramatically power consumption and cost of wireless solutions. As a result wireless capabilities increasingly will be featured in smaller devices, such as very small laptops, PDAs and phones .these devices when connected wirelessly to the company network, will become critical productivity tools for workers who do not spend their entire day at a desk

Conc lu si on: The IEEE 802.16 wireless MANTM air interface standard provides the wireless alternative to cable and DSL. The WIMAX can offer a solution to what is normally called the “lastmile” problem by connecting individual homes and business offices communications. It’s high throughout , scalability, and QOS features, are combined with techniques for coverage extension. IMAX provides world-wide broadband connectively. The standard is intended to allow for multiple venders to produce interoperable equipment.

Refer ences : 1. IEEE 802.16-2001,”IEEE standard for local and metropolitan Area networkspart 16: Air later face for fixed broadband wireless access system”, apr.8, 2002. 2. www.wimaxforum.org

3. http://computer.howstufffworks.com 4. www.wi-fitechnology.com