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INTRODUCTION : 

INTRODUCTION Wireless network Wireless network refers to any type of computer network that is wireless, and is commonly associated with a telecomunication network whose interconnections between nodes is implemented without the use of wires. Wireless telecommunications networks are generally implemented with some type of remote information transmission system that uses electromagnatic waves such as radio waves for the carriers and this implementation usually takes place at the physical level or "layer" of the network.

802.11 Wireless Networks : 

802.11 Wireless Networks 802.11 wireless networks operate in one of two modes- ad-hoc or infrastructure mode In ad hoc mode, each client communicates directly with the other clients within the network In infrastructure mode, each client sends all of it’s communications to a central station, or access point (AP).

USES : 

USES Through the use of wireless networks, information could be sent overseas or behind enemy lines easily, efficiently and more reliably. People use these phones daily to communicate with one another. Sending information overseas is possible through wireless network systems using satellites and other signals to communicate across the world Another important use for wireless networks is as an inexpensive and rapid way to be connected to the internet in countries and regions where the telecom infrastructure is poor or there is a lack of resources, as in most developing countries.

802.11 Wireless Standards : 

802.11 Wireless Standards 802.11a 802.11b 802.11g 802.11a is an established IEEE standard for wireless networking that improves on the performance limitations of 802.11b. 802.11a is a relatively high cost solution found in some business networks

802.11 Wireless Standards : 

802.11 Wireless Standards 802.11a 802.11b 802.11g 802.11b is an industry-standard technology for wireless communication via Ethernet. Because of its low cost and established history, 802.11b is commonly found in home networks.

802.11 Wireless Standards : 

802.11 Wireless Standards 802.11a 802.11b 802.11g IEEE 802.11g-2003 or 802.11g, is an amendment to the IEEE 802.11 specification that extended throughput to up to 54 Mbits/s using the same 2.4 GHz band as 802.11b This specification under the marketing name of Wi-fi has been implemented all over the world. The 802.11g protocol is now Clause 19 of the published IEEE 802.11 2007 standard.

DESCRIPTION802.11a : 

DESCRIPTION802.11a The 802.11a standard uses the same core protocol as the original standard operates in 5 GHz band uses a 52-subcarrier orthogonal frequency-division multiplexing (OFDM) with a maximum raw data rate of 54 Mbit/s The effective overall range of 802.11a is slightly less than that of 802.11b/g; 802.11a signals cannot penetrate as far as those for 802.11b because they are absorbed more readily by walls and other solid objects in their path

Technical description802.11a : 

Technical description802.11a Of the 52 OFDM sub carriers, 48 are for data and 4 are pilot subcarriers with a carrier separation of 0.3125 MHz (20 MHz/64). Each of these subcarriers can be a BPSK, QPSK 16-QAM or 64-QAM The total bandwidth is 20 MHz with an occupied bandwidth of 16.6 MHz. Symbol duration is 4 microseconds

DESCRIPTION802.11b : 

DESCRIPTION802.11b 802.11b has a maximum raw data rate of 11 Mbit/s and uses the same CSMA/CA media access method defined in the original standard Due to the CSMA/CA protocol overhead, in practice the maximum 802.11b throughput that an application can achieve is about 5.9 Mbit/s using TCP and 7.1 Mbit/s using UDP

RANG : 

RANG 802.11b is used in a point-to-multipoint configuration, wherein an access point communicates via an omni-directional antenna with one or more nomadic or mobile clients that are located in a coverage area around the access point Typical indoor range is 30 m (100 ft) at 11 Mbit/s and 90 m (300 ft) at 1 Mbit/s With high-gain external antennas, the protocol can also be used in fixed point-to-point arrangements, typically at ranges up to 8 kilometers (5 miles) although some report success at ranges up to 80–120 km (50–75 miles) where line of sight can be established

DESCRIPTION802.11g : 

DESCRIPTION802.11g 802.11g was the third modulation standard for Wireless LAN It works in the 2.4 GHz band (like 802.11b) but operates at a maximum raw data rate of 54 Mbit/s The modulation scheme used in 802.11g is orthogonal frequency-division multiplexing (OFDM) copied from 802.11a with data rates of 6, 9, 12, 18, 24, 36, 48, and 54 Mbit/s, 802.11g operates in the same frequency band as 802.11b, it can achieve higher data rates because of its heritage to 802.11a.

Adoption802.11g : 

Adoption802.11g The 802.11g standard was rapidly adopted by consumers starting in January 2003, well before ratification, due to the desire for higher speeds, and reductions in manufacturing costs. By summer 2003, most dual-band 802.11a/b products became dual-band/tri-mode, supporting a and b/g in a single mobile adapter card or access point

Frames802.11 : 

Frames802.11 Current 802.11 standards define "frame" types for use in transmission of data Each frame has a 2-byte frame control field that provides detailed information on the wireless link This field is segmented 11 ways and will be presented in order, with the first two bits reserved for identification of the protocol being used (e.g., 802.11g, 802.11b, etc.). These respectively two and four bit fields are used for identification of which frame type is used The next two segments are reserved for type and subtype The next two bits are the To DS and From DS fields. They indicate whether a frame is headed for a distributed system

802.11 Standard Security Mechanisms : 

802.11 Standard Security Mechanisms Three Mechanism Wired Equivalent Privacy protocol Open System Authentication Shared Key Authentication