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Prepared by:-Jiten Patel

Maharashtra Academy Of Engineering

Basic three different options for Internet access are available today

• Dial-up access

• Broadband access

• WiFi access

Problems The main problems with broadband access are that it is pretty expensive and it doesn't reach all areas. The main problem with WiFi access is that .

Solution - A new technology that provides The high speed of broadband service.

Wireless rather than wired access, so it would be a lot less expensive than cable or DSL and much easier to extend to suburban and rural areas.

Broad coverage like the cell phone network instead of small WiFi hotspots.

What is WiMAX ?

Defined as Worldwide Interoperability for Microwave Access by the WiMAX Forum, formed in June 2001.

It also goes by the IEEE name 802.16.

The Forum describes WiMAX as "a standards-based technology enabling the delivery of last mile wireless broadband access as an alternative to cable and DSL".

WiMAX is not a technology, but rather a certification mark, or 'stamp of approval' given to equipment that meets certain conformity and interoperability tests for the IEEE 802.16 family of standards.

How WiMAX works?

A WiMAX system consists of two parts:

A WiMAX tower:

It is 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 (equivalent to 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.

IEEE 802.16 Specifications

Range - 30-mile (50-km) radius from base station.

Speed - 70 megabits per second.

Line-of-sight not needed between user and base station.

Frequency bands - 2 to 11 GHz and 10 to 66 GHz (licensed and unlicensed bands).

Operation

Sends data from one computer to another via radio signals.

A computer equipped with WiMAX would receive data from the WiMAX transmitting station, probably using encrypted data keys to prevent unauthorized users from stealing access.

WiMAX can provide two types of wireless service:

Non line-of-sight service

A small antenna on the computer connects to the tower.

In this mode, WiMAX uses a lower frequency range of 2 GHz to 11 GHz (similar to WiFi).

Lower-wavelength transmissions are not easily disrupted by physical obstructions because they are better able to diffract, or bend, around obstacles.

Line-of-sight service:

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.

Installation WiMAX subscriber units are available in both indoor and outdoor versions from several manufacturers.

Self install indoor units are convenient, but the subscriber must be significantly closer to the WiMAX base station.

Indoor units require a much higher infrastructure investment as well as operational cost (site lease, backhaul, maintenance) due to the high number of base stations required to cover a given area.

Indoor units are comparable in size to a cable modem or DSL modem.

Outdoor units allow for the subscriber to be much further away from the WiMAX base station, but usually require professional installation.

Outdoor units are roughly the size of a textbook, and their installation is comparable to a residential satellite dish.

Technical Information The 802.16 MAC(Media Access Controller) uses a scheduling algorithm for which the subscriber station need compete once for initial entry into the network.

After that it is allocated an access time slot by the base station which can enlarge and contract, but remains assigned to the subscriber station which means that other subscribers cannot use it.

The 802.16 scheduling algorithm is stable under overload and over-subscription and it can also be more bandwidth efficient.

The scheduling algorithm also allows the base station to control QoS(Quality of Service) parameters by balancing the time-slot assignments among the application needs of the subscriber stations.

Uses Connecting Wi-Fi hotspots with each other and to other parts of the Internet.

Providing a wireless alternative to cable and DSL for last mile (last km) broadband access.

Providing high-speed mobile data and telecommunications services (4G) through Voice Over Internet Protocol (VoIP).

VoIP allows people to make local, long-distance and even international calls through a broadband Internet connection.

Providing a diverse 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.

Advantages over WiFi

The WiMAX specification provides symmetrical bandwidth over many kilometers and range with stronger encryption and typically less interference.

Wi-Fi is short range (approximately 10's of meters) and suffers from interference as in metropolitan areas where there are many users.

Wi-Fi Hotspots are typically backhauled over ADSL in most places therefore Wi-Fi access is typically highly contended and has poor upload speeds between the router and the internet.

Limitation A commonly held misconception is that WiMAX will deliver 70 Mbit/s, over 70 miles (112.6 kilometers).

Each of these is true individually, given ideal circumstances, but they are not simultaneously true.

In Line of sight environments it could deliver symmetrical speeds of 10Mbps at 10Km but in Urban Environments it is more likely that 30% of installations may be Non Line of sight and therefore Users may only receive 10Mbps over 2Km.

WiMAX has some similarities to DSL in this respect, where one can either have high bandwidth or long reach, but not both simultaneously.

The other feature to consider with WiMAX is that available bandwidth is shared between users in a given radio sector, so if there are many active users in a single sector, each will get reduced bandwidth.

Real time Applications for boosting security In an emergency, communication is crucial for government officials as they try to determine the cause of the problem, find out who may be injured and coordinate rescue efforts or cleanup operations.

A gas-line explosion or terrorist attack could damage the cables that connect leaders and officials with their vital information networks.

WiMAX could be used to set up a back-up (or even primary) communications system that would be difficult to destroy with a single, pinpoint attack.

A cluster of WiMAX transmitters would be set up in range of a key command center but as far from each other as possible. Each transmitter would be in a bunker hardened against bombs and other attacks. No single attack could destroy all of the transmitters, so the officials in the command center would remain in communication at all times.

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