A person with a Wi-Fi enabled device such as a computer, cell phone or PDA can connect to the Internet when in proximity of an access point. The region covered by one or several access points is called a hotspot. Hotspots can range from a single room to many square  kilometres of  overlapping hotspots. Wi-Fi can also be used to create a mesh network and allows connectivity in peer- to- peer mode. Both architectures are used in community networks.

Discovery:

Despite the similarity between the terms ‘Wi-Fi’ and ‘Hi-Fi’, statements reportedly made by Phil Belanger of the Wi-Fi Alliance contradict the popular conclusion  that ‘Wi-Fi’ stands for ‘Wireless Fidelity. The precursor to Wi-Fi was invented in 1991 by NCR Corporation/AT&T (later Lucent & Agere Systems) in Nieuwegein, the Netherlands.   Vic Hayes, who was the primary inventor of Wi-Fi and has been named the  ‘father of  Wi-Fi,’ was involved in designing standards such as IEEE 802.11b, 802.11a and 802.11g.

Types:

Wi-Fi infrastructure devices typically fall into 3 categores as per it’s Application, with wireless being only one of many features.

1. Wi-Fi At Home
Home Wi-Fi clients come in many shapes and sizes, from stationary PCs to digital cameras. The trend today and into the future will be to enable wireless into every devices where mobility is prudent.

Wi-Fi devices are often used in home or consumer-type environments in the following manner:

• Termination of a broad band connection into a single router which services both wired and wireless clients, where cable connection can not be hooked up.
• Ad-hoc mode for client to client connections ,
• Built into non-computer devices to enable simple wireless connectivity to other devices or the Internet.

2. Wi-Fi in Business
In Business and Industry  current Technology of  Wi-Fi  is  moving toward ‘thin’ Access Points, with all of the intelligence housed in a centralized network appliance; relegating individual Access Points to be simply ‘dumb’ radios   utilizing true mesh topologies.

3.Wi-Fi in gaming
Some gaming consoles and hand helds make use of Wi-Fi technology to enhance the gaming experience   in local multiplayer as well as connecting to wireless networks for online game play or with separate adapter.

Technical information

Wi-Fi: How it Works

A typical Wi-Fi setup contains one or more Access Points (APs) and one or more clients. An AP broadcasts its SSID (Service Set Identifier, “Network name”) via packets that are called beacons, which are usually broadcast every 100 ms. The beacons are transmitted at 1 Mbit/s, and are of relatively might use signal strength to decide which of the two APs to make a connection to. The Wi-Fi standard leaves connection criteria and roaming totally open to the client. Since Wi-Fi transmits in the air, it has the same properties as a non-switched wired Ethernet network, and therefore collisions can occur  , which can not be   detected, and instead uses a packet exchange (RTS/CTS used for Collision Avoidance or CA) to try to avoid collisions.

Channels:
Wi-Fi uses the spectrum near 2.4 GHz, which is standardized, although the exact frequency allocations vary slightly in different parts of the world, as does maximum permitted power, except for 802.11a,which operates at 5 GHz.. However, channel numbers are standardized by frequency throughout the world, so authorized frequencies can be identified by channel numbers. The maximum number of available channels for Wi-Fi enabled devices are:

• 13 for Europe
• 11 for North America. Only channels 1, 6, and 11 are recommended for 802.11b/g to minimize interference from adjacent channels.
• 14 for Japan.

Standard Devices

A wireless access point connects a group of wireless devices to an adjacent wired LAN. An access point is similar to an ethernet  hub, relaying data between connected wireless devices in addition to a (usually) single connected wired device, most often an ethernet hub or switch, allowing wireless devices to communicate with other wired devices.

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• offers cheap voice calls and high speed internet
• ensures  a boost for government security
• extend the currently limited coverage of public LAN    (hotspots) to citywide coverage (hot zones) the same technology being usable at home and on the move,
• blanket metropolitan areas for mobile data-centric service delivery,
• offer fixed broadband access in urban and suburban areas where copper quality is poor or unbundling difficult,
• bridge the digital divide in low-density areas where technical and economic factors make broadband deployment very challenging.

In addition to these uses, this paper will highlight other potential applications, such as telephony or an effective point-to-multipoint backhauling solution for operators or enterprises

1. INTRODUCTION

WiMAX is an acronym that stands for Worldwide Interoperability for Microwave Access, a  certification mark for products that pass conformity and interoperability tests for the IEEE 802.16 standards.  Products that pass the conformity tests for WiMAX are capable of forming wireless connections between them to permit the carrying of internet packet data. It is similar to   Wi-Fi in concept, but has   certain improvements that are aimed at improving performance and should permit usage over much greater distances. the WiMAX forum, backed by industry leaders, will encourage the widespread   adoption of   broadband  wireless access by establishing a brand for the technology and pushing.

2.  TECHNICAL ADVANTAGES OVER WIFI

Because IEEE 802.16 networks use the  same  Logical    Link   Controller (standardized by IEEE 802.2) as other LANs and WANs, it can be both bridged and routed to them.

An important aspect of the IEEE 802.16 is that it defines a MAC layer that supports multiple physical layer (PHY) specifications. This is crucial to allow equipment makers to differentiate their offerings. This is also an important aspect of why WiMAX can be described as a “framework for the evolution of wireless broadband” rather than a static implementation of wireless technologies. Enhancements   to   current   and   new technologies and potentially new   basic technologies incorporated into the PHY (physical layer) can be used. A converging trend is the use of multi-mode and multi-radio SoCs and system designs that are harmonized through the use of common MAC, system management, roaming, IMS and other levels of the system. WiMAX may be described as a bold attempt at forging many technologies to serve many needs across many spectrums.

The MAC is significantly different from that of Wi-Fi (and ethernet from which Wi-Fi is derived). In Wi-Fi, the MAC uses contention access—all subscriber stations wishing to pass data through an access point are competing for the AP’s attention on random basis. This can cause distant nodes from the AP to be repeatedly interrupted by less sensitive, closer nodes, greatly  reducing their throughput. By contrast, the 802.16 MAC is a scheduling   MAC   where   the subscriber station only has to compete once (for initial entry into the network).  After that it is allocated a time slot by the base station.  The time slot can enlarge and constrict, but it remains assigned to the subscriber station meaning that other subscribers are not supposed to use it but take their turn. This scheduling algorithm is stable under overload and oversubscription (unlike 802.11). It is also much more bandwidth efficient. The scheduling algorithm also allows the base station to control Quality of Service by balancing the assignments among the needs of the subscriber stations. A recent addition to the WiMAX standard is underway which will add full capability by enabling WiMAX nodes to simultaneously operate in “subscriber station” and “base station” mode. This will blur that initial distinction and allow for widespread adoption of WiMAX based mesh networks and promises widespread WiMAX adoption. The original WiMAX standard, IEEE 802.16, specifies WiMAX in the 10 to 66 GHz range. 802.16a added support for the 2 to 11 GHz range, of which most parts are already unlicensed internationally and only very few still require domestic licenses. Most business interest will probably be in the 802.16a standard, as opposed to licensed frequencies. The WiMAX specification improves upon many of the limitations of the Wi-Fi standard by providing increased bandwidth and stronger encryption. It also aims to provide connectivity between network endpoints without direct line of sight in some circumstances. The details of performance under non-line of sight (NLOS) circumstances are unclear as they have yet to be demonstrated. It is commonly considered that spectrum under 5-6 GHz is needed to provide reasonable NLOS performance and cost effectiveness for PtM (point to multi-point) deployments.

3. HOW WIMAX WORKS

In practical terms, WiMAX would operate similar to WiFi but at higher speeds, over greater distances and for a greater number of users. WiMAX could potentially erase the suburban and rural blackout areas that currently have no broadband Internet access because phone and cable companies have not yet run the necessary wires to those remote locations.

A WiMAX system consists of two parts:

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 PCMCIA card, or they could be built into a laptop the way WiFi access is today.

A WiMAX tower station can connect directly to the Internet using a high-bandwidth, 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), along 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.  What this points out is that WiMAX actually can provide two forms of wireless service:

There is the non-line-of-sight, WiFi sort of service, where a small antenna on your computer connects to the tower. In this mode, WiMAX uses a lower frequency range — 2 GHz to 11 GHz (similar to WiFi). Lower-wavelength transmissions are not as easily disrupted by physical obstructions — they are better able to diffract, or bend, around obstacles

There is line-of-sight service, where a fixed dish antenna points straight at the WiMAX tower from a rooftop or pole. The line-of-sight connection is stronger and more stable, so it’s able to send a lot of data with fewer errors. Line-of-sight transmissions use higher frequencies, with ranges reaching a possible 66 GHz. At higher frequencies, there is less interference and lots more bandwidth.  WiFi-style access will be limited to a 4-to-6 mile radius (perhaps 25 square miles or 65 square km of    coverage, which is similar in range to a cell-phone zone). Through the stronger line-of-sight antennas, the WiMAX transmitting station would send data to WiMAX-enabled computers or routers set up within the transmitter’s 30-mile radius (2,800 square miles or 9,300 square km of coverage.

4. GLOBAL AREA NETWORK

The final step in the area network scale is the global area network (GAN). The proposal for GAN is IEEE 802.20. A true GAN would work a lot like today’s cell phone networks, with users able to travel across the country and still have access to the network the whole time. This network would have enough bandwidth to offer Internet access comparable to cable modem service, but it would be accessible to mobile, always-connected devices like laptops or next-generation cell phones). This is what allows WiMAX to achieve its maximum range.

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