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Unit – II Wireless LAN’s (IEEE 802.11x)

Unit – II Wireless LAN’s (IEEE 802.11x). Introduction to IEEE 802.11x Technologies Evolution of Wireless LAN’s IEEE 802.11 Design Issues IEEE 802.11 Services – Overview IEEE 802.11 MAC Layer Operations IEEE 802.11a/b/g – Higher-Rate Standards IEEE 802.11 – Wireless LAN Security

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Unit – II Wireless LAN’s (IEEE 802.11x)

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  1. Unit – II Wireless LAN’s (IEEE 802.11x)

  2. Introduction to IEEE 802.11x Technologies • Evolution of Wireless LAN’s • IEEE 802.11 Design Issues • IEEE 802.11 Services – Overview • IEEE 802.11 MAC Layer Operations • IEEE 802.11a/b/g – Higher-Rate Standards • IEEE 802.11 – Wireless LAN Security • Competing Wireless Technologies

  3. Introduction to IEEE 802.11x Technologies • IEEE 802.11x (high perf. wireless comm. networks) • - over-the –air protocols for wireless LAN • - extension of wired LAN • Goals – seamless roaming / message forwarding / • greatest range of operations / large number of users • Initial standard • - ISM band – Operating Frequency(2.4 Ghz) • speed- 1,2 mbps (FHSS, DSSS, IR) • Applications: Wi-Fi hot spots deployment

  4. Evolution of Wireless LAN’s • Due to the development of wired computer network ,the expansion and increased use of the Internet & large no. of network computers to the network , introduce wireless LANs • The Beginning – ALOHA Net • - 1971 – Network & radio Technology brought together for the1st time during implementation of research project called ALOHA-Net (Hawaii Islands) • This system allows computers at seven campuses out over four islands to communicate with a central computer without using expensive & sometimes unreliable telephone lines. • This system uses Star topology between the central computer and the remote stations.

  5. Extensions to 802.11 • - 802.11 – 2 mbps (wired 10/100 mbps) • - 1999 – 802.11b – 11 mbps(2.4 GHz band)  DSSS • – 802.11a – 54 mbps (5 GHz band) Orthogonal FDMA • - 802.11d – Operation in Other countries • - 802.11e – enhance MAC & PHY (voice, video, audio) • - 802.11f – Multi-vendor AP interoperability • - 802.11h – MAC & PHY (energy management – measurement, reporting, power control) • - 802.11i – Security & Authentication

  6. Extensions to 802.11 • - 802.11j – Operation in Japan (4.9 & 5.0 GHz) • - 802.11k – Radio Resource measurement & Mobility mgmt. • - 802.11ma – Editorial & Technical corrections • - 802.11n – data rates (100 mbps) • - 802.11p – Mobility (200 km/h upto 1000m – 5.8,5.9 GHz) • - 802.11r – enhance BSS & ESS • - 802.11s – Auto-configuration & Multi-hop technologies • - 802.11u – Internetwork with external networks • - 802.11v – Wireless Network mgmt.

  7. Layer 1 : Overview • - WLAN radio cards • - WLAN access points • - Ad hoc or peer-to-peer connection • - WLAN radio link

  8. IEEE 802.11 Design Issues • Wired vs Wireless • - Wired (reliable, predictable transmission) • - Wireless (unreliable, changing topologies, interference) • (multipath propagation, mobility, • battery powered devices, portability) • Services Set’s • Independent Basic Service Set Networks • Distributed System Concepts • Extended Service Set Networks • Integration of Wired & Wireless LAN’s

  9. Independent Basic Service Set Networks • - Fundamental structure of IEEE 802.11x • - peer-to-peer OR ad-hoc • - IBSS = 2 or more wireless stations

  10. Distributed System Concepts • - station-station distance – RF power + propagation condition • - DS – mobility support • – multiple BSS • - Access Point

  11. Extended Service Set Networks (ESS) • - ESS = multiple BSS + multiple DS • - Mobile stations move from 1 BSS to other BSS in same ESS

  12. Integration of Wired & Wireless LAN’s • - Portal (AP) – integration wired LAN + wireless LAN

  13. IEEE 802.11 Services – Overview • Overview of Services – Distribution • Association, Reassociation, Disassociation • Access & Security Control Services • Relationship between Services

  14. Overview of Services – Distribution • - IEEE 802.11 – 9 services • (6 – support MSDU + 3 – control WLAN Access) • - MAC messages – control, data, management • - Distribution Service (STA in Same BSS & Different BSS) • - Integration Service (wired to wireless data delivery) • - Mobility of User • No Transition, BSS Transition & ESS Transition

  15. Association, Re-association, Disassociation • - Association (One to Many & Many to One) • STA associate with AP • many to one mapping of many STA to one AP • No transition mobility • - Re-association • BSS transition mobility within ESS • Initiated by WLAN station • - Disassociation • Termination of Association

  16. Access & Security Control Services • - Authentication between 2 STA • - IEEE 802.11 – open system & shared key • - De-authentication • termination of authentication • - Privacy – encryption of message contents • - WEP (Wired Equivalent Privacy) Algorithm • data frames & authentication msgs.

  17. Relationship between Services • Class 1 Frames (control, management, restricted data frames) • Class 2 Frames (association, re-association, disassociation) • Class 3 Frames (above 3 + restricted data frames)

  18. IEEE 802.11 MAC Layer Operations • MAC Services • LLC/MAC Layer Services Primitives • MAC Basic Frame Structure • MAC Layer Operations – Accessing & Joining Wireless Network

  19. MAC Services • - Accessing the wireless medium, joining a network, authentication & privacy  MAC frames • - MAC frames – control, management, data • - Asynchronous data service • - best effort delivery of MSDU by unicast, multicast, broadcast • - Security – authentication service & WEP encryption • - MSDU – Ordered or Re-orderable multicast

  20. LLC/MAC Layer Services Primitives • - used for comm. between 2 layers • - request, confirm, indication & response • - 3 service primitives • - MA–UNITDATA request • – request transfer of MSDU from local LLC to peer LLC or group of peers • - MA–UNITDATA indication • – transfer MSDU from local MAC to peer LLC • - MA–UNITDATA–STATUS indication • – MAC sublayer to LLC sublayer

  21. MAC Basic Frame Structure • - MAC frame = MAC header + Frame Body + FCS • – header (frame control, duration, address, sequence) • – FCS (32 bit CRC) • - Address (48 bit) – (SA, DA, TA, RA)= BSSID • ~Sequence Field- (16 bit)- 12 bit for sequence no. for each MSDU & 4 bit for MSDU fragment no.

  22. IEEE 802.11a/b/g – Higher-Rate Standards • IEEE 802.11 b • IEEE 802.11 a • IEEE 802.11 g

  23. IEEE 802.11 b • - high speed physical layer extension in 2.4 GHz band • - data rate – 5.5 & 11 mbps • - Modulation – 8 chip CCK (Complementary Code Keying) • - CCK or HR/DSSS

  24. - Modulation – PBCC (Packet Binary Convolutional Coding) - higher data rates - shorter PLCP preamble - limited frequency hopping

  25. IEEE 802.11 a • - high speed physical layer at 5 GHz band using OFDMA • - Data rate – 6, 9, 12, 18, 24, 36, 48, 54 mbps

  26. IEEE 802.11 g • - adopted June 2003 in 2.4 GHz band • - Modulation – PBCC(packet binary convolutional coding) & OFDMA • - Data rate – 6, 9, 12, 18, 24, 36, 48, 54 mbps • - Backward Compliant – 1, 2, 5.5, 6, 11, 12, 24 mbps • - ERP (Extended Rate Physical) Layer • - ERP-DSSS/CCK only mode • - ERP-DSSS/CCK mixed mode • - ERP-DSSS-OFDM & ERP-DSSS/CCK non-ERP mode

  27. IEEE 802.11 – Wireless LAN Security • Types of Wireless LAN Security Problems • Initial IEEE 802.11 Security

  28. Types of Wireless LAN Security Problems • - Eavesdropping • - MAC Spoofing • - Dictionary Attack • - Man-in-Middle Attack • - Theft of Service • - Session Hijacking

  29. Initial IEEE 802.11 Security • - Authentication Details • - IEEE 802.11 User Authentication •  Traffic only from authorized MAC •  Compare MAC address of STA with AP database • or RADIUS Server for authentication • - Drawbacks • - MAC address spoofing • - Authentication tied to h/w instead of user

  30. Initial IEEE 802.11 Security • - WEP Encryption Details

  31. Competing Wireless Technologies • Hiper LAN 1 & Hiper LAN 2 • Home RF & MMAC

  32. Hiper LAN 1 & Hiper LAN 2 • - 1996 – ETSI – BRAN (broadband radio access network) • - 5.2 GHz / 24 mbps / GMSK modulation • - 1998 – HiperLAN2 (25mbps / indoor, local mobility) - high performance, next gen LAN • – HiperAccess (25 mbps / outdoor, fixed operation) • – HiperLink (155 mbps / fixed backbone) • Home RF & MMAC • - Home RF – SWAP (shared wireless access protocol) • - 2.4 GHz, FHSS, 1/2 mbps, disbanded Jan 2003 • - Multimedia Mobile Access Comm. – operation in Japan

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