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wireless network IEEE 802.11

wireless network IEEE 802.11

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wireless network IEEE 802.11

  1. 1. PRESENTATION ON IEEE 802.11 Prepared By: Shreejan Acharya BEX 68114
  2. 2. Slides Includes Introduction Physical Layer Architecture Frame format Different Protocols Media Access Control (MAC)
  3. 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. 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. 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. 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. 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. 8. BSS IBSS
  9. 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. 10. Frame format Bytes 2 22 6 6 6 66 2 6 0- 2312 4 Frame control Durati on ID A1 A2 A3 seq.ctr l A4 Frame body CRC 802.11 MAC header Bits :2 2 2 4 1 1 1 1 1 1 1 Protocol version type Sub type To DS From DS More flag Retry Pwr Mgt More data wep rsvd Frame control Field
  11. 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. 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. 13. 802.11b Release on the market in 2000 Maximum raw data rate of 11mbit/s High throughput Low cost Interference problem
  14. 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. 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. 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. 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. 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. 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. 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. 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
  22. 22. THANK YOU

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