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Ieee 802.11 wlan


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Ieee 802.11 wlan

  1. 1. IEEE 802.11 WLAN PART 1 IEEE Standards 802.11a 802.11b 802.11g 802.11n Maximum Throughput 54 Mbps 11 Mbps 54 Mbps 300 Mbps Frequency 5 GHz 2.4 GHz 2.4 GHz 2.4/5 GHz Modulation OFDM DSSS DSSS/OFDM OFDM Channels (FCC/ETSI) 21/19 11/13 11/13 32/32 Ratified 1999 1999 2003 2009 WLAN Types WLAN ComponentsAd Hoc ESSA WLAN between isolated stations with IBSS BSS BSSno central point of control; an IBSSInfrastructureA WLAN attached to a wired network viaan access point; a BSS or ESS DS Frame TypesType ClassAssociation ManagementAuthentication Management Basic Service Area (BSA) The physical area covered by the wireless signal of a BSSProbe Management Basic Service Set (BSS)Beacon Management A set of stations and/or access points which can directlyRequest to Send (RTS) Control communicate via a wireless medium Distribution System (DS)Clear to Send (CTS) Control The wired infrastructure connecting multiple BSSs to form an ESSAcknowledgment (ACK) Control Extended Service Set (ESS)Data Data A set of multiple BSSs connected by a DS which appear to wireless stations as a single BSS Client Association Independent BSS (IBSS) An isolated BSS with no connection to a DS; an ad hoc WLAN Measuring RF Signal Strength Probe Request Decibel (dB) Probe Response An expression of signal strength as compared to a reference signal; Authentication Request calculated as 10log10(signal/reference) Authentication Response dBm Signal strength compared to a 1 milliwatt signal Association Request dBw Signal strength compared to a 1 watt signal Association Response dBi Compares forward antenna gain to that of an isotropic antenna ModulationsScheme Modulation Throughput Terminology DBPSK 1 Mbps Basic Service Set Identifier (BSSID) A MAC address which serves to uniquely identify a BSS DSSS DQPSK 2 Mbps Service Set Identifier (SSID) CCK 5.5/11 Mbps A human-friendly text string which identifies a BSS; 1-32 characters BPSK 6/9 Mbps Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) QPSK 12/18 Mbps The mechanism which facilitates efficient communication across aOFDM shared wireless medium (provided by DCF or PCF) 16-QAM 24/36 Mbps Effective Isotropic Radiated Power (EIRP) 64-QAM 48/54 Mbps Net signal strength (transmitter power + antenna gain - cable loss)by Jeremy Stretch v2.2
  2. 2. IEEE 802.11 WLAN PART 2 Distributed Coordination Function (DCF) DIFS DIFS DIFS DIFS A Frame B Deferral Period C Random Backoff D Contention Window Interframe Spacing Client AuthenticationShort IFS (SIFS) Open No authentication is usedUsed to provide minimal spacing delay between Pre-shared Encryption Keyscontrol frames or data fragments Keys are manually distributed among clients and APsDCF IFS (DIFS) Lightweight EAP (LEAP)Normal spacing enforced under DCF for management Cisco-proprietary EAP method introduced to provideand non-fragment data frames dynamic keying for WEP (deprecated)Arbitrated IFS (AIFS) EAP-TLSVariable spacing calculated to accommodate differing Employs Transport Layer Security (TLS); PKIqualities of service (QoS) certificates are required on the AP and clientsExtended IFS (EIFS) EAP-TTLSExtended delay imposed after errors are detected in a Clients authenticate the AP via PKI, then form a securereceived frame tunnel inside which the client authentication takes Encryption Schemes place (clients do not need PKI certificates)Wired Equivalent Privacy (WEP) Protected EAP (PEAP)Flawed RC4 implementation using a 40- or 104-bit A proposal by Cisco, Microsoft, and RSA which employspre-shared encryption key (deprecated) a secure tunnel for client authentication like EAP-TTLSWi-Fi Protected Access (WPA) EAP-FASTImplements the improved RC4-based encryption Developed by Cisco to replace LEAP; establishes aTemporal Key Integrity Protocol (TKIP) which can secure tunnel using a Protected Access Credentialoperate on WEP-capable hardware (PAC) in the absence of PKI certificatesIEEE 802.11i (WPA2) RF Signal InterferenceIEEE standard developed to replace WPA; requires anew generation of hardware to implement significantly Reflection Scattering Absorptionstronger AES-based CCMP encryption Quality of Service MarkingsWMM 802.11e 802.1pPlatinum 7/6 6/5 Refraction DiffractionGold 5/4 4/3Silver 3/0 0Bronze 2/1 2/1Wi-Fi Multimedia (WMM)A Wi-Fi Alliance certification for QoS; a subset of Antenna Types802.11e QoS Directional Radiates power in one focused directionIEEE 802.11eOfficial IEEE WLAN QoS standard ratified in 2005; Omnidirectionalreplaces WMM Radiates power uniformly across a plane IsotropicIEEE 802.1p A theoretical antenna referenced when measuringQoS markings in the 802.1Q header on wired Ethernet effective radiated powerby Jeremy Stretch v2.2