IEEE Wireless Standards PDF

IEEE Standards Dr. R.Radha, VIT Chennai Outline ▪ Wireless ▪ IEEE 802.11 ▪ IEEE 802.15.1 Dr. R. Radha, VIT Chennai  IEEE 802.11 Basics ▪ Standard for Wireless Local Area Network (WLAN) ▪ Commonly known as WiFi ▪ Data transmission using Electromagnetic Sp...

IEEE Standards Dr. R.Radha, VIT Chennai Outline ▪ Wireless ▪ IEEE 802.11 ▪ IEEE 802.15.1 Dr. R. Radha, VIT Chennai  IEEE 802.11 Basics ▪ Standard for Wireless Local Area Network (WLAN) ▪ Commonly known as WiFi ▪ Data transmission using Electromagnetic Spectrum: ▪ Radio Waves, Infrarred ▪ License free –ISM band 2.4 GHz ▪ Only a support to wired network – not a replacement Dr. R. Radha, VIT Chennai Architecture – Basic Service Set (BSS) Infrastructure Ad-hoc Access Point (AP) Station Dr. R. Radha, VIT Chennai  Architecture – Extended Service Set (ESS) Distribution System Source: Behrouz A Forouzan, “Data Communications and Networking”, 4th Edition Dr. R. Radha, VIT Chennai Station types ▪ Based on the mobility ▪ No transition station ▪ BSS transition station ▪ ESS transition station Connection not guaranteed during movement Dr. R. Radha, VIT Chennai  Association Active Scanning Passive Scanning Probe request Probe request Beacon Beacon frame frame frame frame Probe response Probe response frame frame Association request frame Association request frame Association response frame Association response frame Dr. R.Radha VIT Chennai IEEE 802.11 ▪ Physical Layer – various amendments available based on ▪ Bandwidth ▪ Encoding scheme ▪ Frequency Hopping Spread Spectrum (FHSS) ▪ Direct Sequence Spread Spectrum (DSSS) ▪ Orthogonal Frequency Division Multiplexing (OFDM) ▪ Speed : 1 , 2, 5.5, 11, 54 Mbps ▪ Range 250 METERS Dr. R.Radha VIT Chennai IEEE 802.11 (contd.) ▪ Data Linked Layer ▪ MAC sublayer ▪ Distributed Coordination Function (DCF) ▪ Contention-based service ▪ Mandatory ▪ Point Coordination Function (PCF) ▪ Contention-free service ▪ Optional Dr. R.Radha VIT Chennai Distributed Coordination Function (DCF) ▪ Multiple stations contend with each other to access carrier ▪ CSMA/CA (Carrier Sense Multiple Access Collision Avoidance) ▪ Reasons for not using Collision Detection: ▪ Stations are half duplex ▪ Signal strength is very low ▪ Hidden station problem Dr. R.Radha VIT Chennai  CSMA/CA Carrier Sender Receiver Other Station Other Station Check if free Wait for DIFS Request to Send (RTS) Wait for SIFS Clear to Send (CTS) Wait for NAV (Network Allocation Vector) Wait for SIFS Data Wait for SIFS Acknowledgement DIFS – Distributed Interframe space Source: Behrouz A Forouzan, “TCP/IP Protocol Suite”, 4th Edition SIFS – Short Interframe space Dr. R.Radha VIT Chennai Problems Solved by CSMA/CA Hidden Station Problem Exposed Station Problem Send data Send data Currently sending data Waiting to send data S1 R1 S2 R1 S1 S2 R2 S1 R1 R1 S1 S2 S2 R2 Dr. R.Radha VIT Chennai  Point Coordination Function (PCF) Access Station requiring Other Other Point contention free service Station Station Wait for PIFS Beacon Frame Wait for SIFS Poll Frame Wait for SIFS Wait for NAV (Network Allocation Vector) Acknowledgement Data Wait for SIFS Acknowledgement Contention free frame Dr. R.Radha VIT Chennai IEEE 802.15 Dr. S. Kirthica, VIT Chennai IEEE 802.15.1 - Bluetooth ▪ WLAN technology to connect devices of different functions ▪ Ad-hoc network ▪ License free band of 2.45 Ghz ▪ Bandwidth: 1-3 Mbps ▪ Range: ~10 metres ▪ Low power consumption Dr. S. Kirthica, VIT Chennai Architecture Piconet Scatternet ▪ 1 master & upto 7 slaves ▪ Communication only between master and slave ▪ State of a slave: ▪ Active ▪ Parked Dr. R.Radha VIT Chennai