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PRESENTATION ON IEEE 802.11

Learn about the introduction, physical layer, architecture, frame format, different protocols, and media access control (MAC) of IEEE 802.11. Understand how this technology is used to implement wireless local area networks (WLAN) in various frequency bands. Discover the features and benefits of different versions like 802.11a, 802.11b, 802.11g, 802.11n, 802.11ac, and more.

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PRESENTATION ON IEEE 802.11

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  1. PRESENTATION ONIEEE 802.11

  2. Slides Includes • Introduction • Physical Layer • Architecture • Frame format • Different Protocols • Media Access Control (MAC)

  3. Introduction • Created and maintained by IEEE • Set of media control(MAC) and physical layer • Used to implement wireless local area network(WLAN) • In the frequency band 2.4,3.6,5 and 60 GHz • Wi-fi refers to the IEEE 802.11 communication for WLAN The Linksys WRT54G contains a router with an 802.11b/g radio and two antennas

  4. Introduction cntd. • Adopted in 1997 • Family of 802 • Origins in a 1985 ruling by the U.S. Federal Communications commission • Consist of series of half duplex over the air modulation • Uses same basic protocols • It uses two spread spectrum technology • Frequency Hopping Spread Spectrum (FHSS) • Direct Sequence Spread Spectrum (DSSS)

  5. 802.11 Physical Layer (PHY) • The 802.11 physical layer (PHY) is the interface between the MAC and the wireless media where frames are transmitted and received. • The PHY provides three functions. • First, the PHY provides an interface to exchange frames with the upper MAC layer for transmission and reception of data. • Secondly, the PHY uses signal carrier and spread spectrum modulation to transmit data frames over the media. • Thirdly, the PHY provides a carrier sense indication back to the MAC to verify activity on the media.

  6. Architectures Station (STA) Architecture: • It contains IEEE 802.11 conformant MAC and PHY interface to the wireless medium, but does not provide access to a distribution system Access-Point Architecture: • Device that contains IEEE802.11 conformant MAC and PHY interface to the wireless medium, and provide access to a distribution system for associated stations • Implemented in infra-structure products that connect to wired backbones

  7. General terminologies • BSS (basic service set): • Group of stations that communicate each other • IBSS(independent basic service set): • It is a BSS without access point • Extended Service Set (ESS): • A set of one or more Basic Service Sets inter connected by a distribution System (DS)

  8. BSS IBSS

  9. General terminologies cntd • Service Set Identifier (SSID): • It is network name similar to domain id • One network (ESS or IBSS) has one SSID • Basic Service Set Identifier (BSSID) • It is cell identifier and is 6 octets long • Similar to NW ID in pre-IEEE Wave LAN systems

  10. Frame format 802.11 MAC header Frame control Field

  11. protocols 802.11 legacy • Release in Jun 1997 • Original version of 802.11 • Specifies two net bit rate 1or 2 mbits per sec • It has forward error correction code • Three alternatives physical layer • Diffuse infrared • Frequency hopping spread spectrum • Direct sequence spread spectrum

  12. 802.11a(ofdm waveform) • Release in sep 1999 • Data rates 1.5 to 54 mbit/s • First widely accepted 802 family • Operates at 5GHz frequency band • Less range

  13. 802.11b • Release on the market in 2000 • Maximum raw data rate of 11mbit/s • High throughput • Low cost • Interference problem

  14. 802.11g • Release on june 2003 • Operates in the 2.4 GHz band • Uses OFDM based transmission scheme • Operates at the average bit rate of 22 Mbit/s or maximum 54 Mbit/s • Its hardware are full back compatible with 802.11b hardware

  15. 802.11n • Release on October 2009 • It is the improvement over previous 802.11 standard • It has MIMO antennas • Operates at the 2.4 GHz or less than 5GHz bands • Data rates from 54 Mbit/s to 600 Mbit/s

  16. 802.11ac • Release in December 2013 • It is an amendment to IEEE 802.11 • It has wider channels(80 or 160 MHz) • Operates at 5GHz band • It supports multi-user MIMO • Data rates up to 1300 Mbit/s

  17. 802.11ad • Release in Dec 2012 • It defines new physical layer for 802.11 n/w • Operates in the 60GHz millimeter wave spectrum • Product implementing this standard are being brought under the name of wigig brand • Peak transmission rate 7 Gbit/s

  18. Other Protocols • 802.11 AH • Estimated to release 2016 • Bandwidth 900MHz • 802.11 AJ • Estimated to release 2016 • Bandwidth 24/60 • 802.11 AX • Estimated to release 2019 • Bandwidth 2.4/5

  19. 802.11 Media Access Control • The 802.11 MAC layer provides functionality to allow reliable data delivery for the upper layers over the wireless PHY media. • The data delivery itself is based on an asynchronous, best-effort, connectionless delivery of MAC layer data. • There is no guarantee that the frames will be delivered successfully. • The 802.11 MAC provides a controlled access method to the shared wireless media called Carrier-Sense Multiple Access with Collision Avoidance (CSMA/CA). • CSMA/CA is similar to the collision detection access method deployed by 802.3 Ethernet LANs.

  20. 802.11 Media Access Control cntd • Another function of the 802.11 MAC is to protect the data being delivered by providing security and privacy services. • Security is provided by the authentication services and by Wireless Equivalent Privacy (WEP), which is an encryption service for data delivered on the WLAN.

  21. Security • For security 802.11 specifies two Authentication modes: • OSA(Opens Systems Authentication) • Device that request to access the network is granted without any security check • Shared Key Authentication • Device that request to access the network is granted with security check • WEP: wired equivalent privacy • ESSID offers casual separation of traffic

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