802.11 Wireless LANsContentsReferencesIEEE 802 Standards & OSI ModelRelated Standards802.11 Standards and SpectrumBasic Service Sets (BSSs)Extended Service Set (ESS)Network ServicesSeamless Transition802.11b: HR/DSSS* PHY802.11b: HR/DSSS PHY - 2802.11b: HR/DSSS PHY - 3802.11a: 5 GHz OFDM PHY802.11a: 5 GHz OFDM PHY - 2802.11a: 5 GHz OFDM PHY - 3802.11a: 5 GHz OFDM PHY - 4802.11a: 5 GHz OFDM PHY - 5MAC: Access ModesMain Ideas of MAC: CSMA/CAMain Ideas of MAC: CSMA/CA - 2Interframe SpacingContention WindowError RecoveryWLAN ProblemsRTS/CTS ClearingVirtual Carrier SensingFragmentation BurstFraming Details: FormatFraming Details: Frame TypesBroadcast/MulticastPower Save (PS)-PollData Frames and AddressesIllustrations of use of AddressesRTS/CTS Control FramesAck and PS-Poll Control FramesManagement FramesFixed-Length Management FieldsFixed-Length Management Fields - 2Management Information ElementsMain Management FramesMain Management Frames - 2Management Operations: ScanningManagement Operations: Authentication and AssociationManagement Operations: Buffered Frame RetrievalPCF: MechanismPCF FramesPCF Frames - 2QoS: Shortcomings of PCFEnhanced DCF of 802.11eIntra-station Virtual Backoff (802.11e)Hybrid Coordination Function of 802.11eSecurity GoalsSecurity: States of Mobile StationsWired Equivalent Privacy (WEP)WEP EnciphermentWEP DeciphermentWEP based AuthenticationWEP Flaws802.1x Authentication802.1x ArchitectureFlaws of 802.1x802.11 Wireless LANs802.11 Wireless LANsEECS 228A, Spring 2006EECS 228A, Spring 2006Shyam ParekhShyam ParekhContentsContentsReferencesReferencesStandardsStandardsBasicsBasicsPhysical LayerPhysical Layer–802.11b802.11b–802.11a802.11aMACMACFraming DetailsFraming DetailsManagementManagementPCFPCFQoS (802.11e)QoS (802.11e)SecuritySecurityReferencesReferences802.11 Wireless Networks: The Definitive Guide, 802.11 Wireless Networks: The Definitive Guide, M. Gast, O’Reilly, 2002*M. Gast, O’Reilly, 2002*IEEE Std 802.11, 1999 EditionIEEE Std 802.11, 1999 EditionIEEE Std 802.11b-1999IEEE Std 802.11b-1999IEEE Std 802.11a-1999IEEE Std 802.11a-1999IEEE 802.11e-2005IEEE 802.11e-2005*Many drawings used in this lecture are from here *Many drawings used in this lecture are from hereIEEE 802 Standards & OSI ModelIEEE 802 Standards & OSI ModelObserve 802.11 MAC is common to all 802.11 Physical Layer Observe 802.11 MAC is common to all 802.11 Physical Layer (PHY) standards(PHY) standards802.11 PHY is split into Physical Layer Convergence Procedure 802.11 PHY is split into Physical Layer Convergence Procedure (PLCP) and Physical Medium Dependent (PMD) sublayers(PLCP) and Physical Medium Dependent (PMD) sublayersRelated StandardsRelated StandardsBluetoothBluetooth–Originally intended for interconnecting computing and Originally intended for interconnecting computing and communication devicescommunication devicesHIPERLANHIPERLAN–European standard for Wireless LANsEuropean standard for Wireless LANsIEEE 802.16 Broadband WirelessIEEE 802.16 Broadband Wireless–802.16-2004 addresses needs of fixed broadband 802.16-2004 addresses needs of fixed broadband wireless access replacing fibers, cables, etc.wireless access replacing fibers, cables, etc.–802.16-2005 (approved in Dec 2005) provides 802.16-2005 (approved in Dec 2005) provides broadband access at vehicular speedbroadband access at vehicular speed802.11 Standards and Spectrum802.11 Standards and SpectrumKey StandardsKey StandardsMax RateMax RateSpectrum (U.S.)Spectrum (U.S.)YearYear802.11802.112 Mbps2 Mbps2.4 GHz2.4 GHz19971997802.11a802.11a54 Mbps54 Mbps5 GHz5 GHz19991999802.11b802.11b11 Mbps11 Mbps2.4 GHz2.4 GHz19991999802.11g802.11g54 Mbps54 Mbps2.4 GHz2.4 GHz20032003802.11e802.11eN/AN/AN/AN/A200520052.4-2.5 GHz spectrum is referred to as S-Band Industrial, Scientific, and 2.4-2.5 GHz spectrum is referred to as S-Band Industrial, Scientific, and Medical (ISM)Medical (ISM)–Microwave ovens and some cordless phones operate in the same bandMicrowave ovens and some cordless phones operate in the same band802.11a uses Unlicensed National Information Infrastructure bands802.11a uses Unlicensed National Information Infrastructure bands–5.15 – 5.25 GHz5.15 – 5.25 GHz–5.25 – 5.35 GHz5.25 – 5.35 GHz–5.725 – 5.825 GHz5.725 – 5.825 GHz802.11e provides QoS enhancements at the MAC layer802.11e provides QoS enhancements at the MAC layer802.11n has a draft specification approved in Jan 2006802.11n has a draft specification approved in Jan 2006–Based on MIMO technologyBased on MIMO technology–Claims to support rate up to 600 MbpsClaims to support rate up to 600 MbpsBasic Service Sets (BSSs)Basic Service Sets (BSSs)Independent BSSs are also referred to as Ad Hoc BSSsIndependent BSSs are also referred to as Ad Hoc BSSsObserve that the AP in an Infrastructure BSS is the centralized Observe that the AP in an Infrastructure BSS is the centralized coordinator and could be a bottleneckcoordinator and could be a bottleneckExtended Service Set (ESS)Extended Service Set (ESS)BSSs in an ESS communicate via Distribution SystemBSSs in an ESS communicate via Distribution SystemA DS has to keep track of stations within an ESSA DS has to keep track of stations within an ESSInter Access Point protocol (IAPP) is standardized by 802.11f-2003Inter Access Point protocol (IAPP) is standardized by 802.11f-2003Network ServicesNetwork ServicesDistributionDistributionIntegrationIntegrationAssociationAssociationReassociationReassociationDisassociationDisassociationAuthenticationAuthenticationDeauthenticationDeauthenticationPrivacyPrivacyMAC Service Data Unit (MSDU) deliveryMAC Service Data Unit (MSDU) deliverySeamless TransitionSeamless TransitionSeamless transition Seamless transition between two BSSs between two BSSs within an ESSwithin an ESSBetween ESSs, Between ESSs, transitions are not transitions are not supportedsupported802.11b: HR/DSSS802.11b: HR/DSSS** PHY PHYUse Complementary Code Keying (CCK) instead Use Complementary Code Keying (CCK) instead of Differential Quadrature Phase Shift Keying of Differential Quadrature Phase Shift Keying (DQPSK) used at lower rates(DQPSK) used at lower rates4-bit (for 5.5 Mbps) or 8-bit (for 11 Mbps) symbols 4-bit (for 5.5 Mbps) or 8-bit (for 11 Mbps) symbols form MAC layer arrive at 1.375 million symbols form MAC layer arrive at 1.375 million symbols per secondper
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