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ABSTRACT
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 technology generations.
1.0 INTRODUCTION:
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.
1.1 WiMax Standards
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.
2. Wimax:
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.
2.1 - Typical WLAN Roaming
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 does
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 transparent to the user. 1c- WLAN Repeater Roaming