Wireless Local Area Network ดร. อน นต ผลเพ ม Anan Phonphoem, Ph.D. anan@cpe.ku.ac.th http://www.cpe.ku.ac.th/~anan Computer Engineering Department Kasetsart University, Bangkok, Thailand iwing Lab CPE - Kasetsart University 1 Outline Wireless World (2G, 3G, ) ) Basic Wireless Knowledge Wireless Local Area Network (WLAN) WLAN Standards Where are we heading to? iwing Lab CPE - Kasetsart University 2 1
Wireless World Mobile (telephony) On the move GSM 9.6 kbps 40 kbps Nomadic Within a building (low mobility) Wireless LAN 2 mbps 25 mbps Satellite iwing Lab CPE - Kasetsart University 3 1G (First Generation) Analog Circuit-switched Network Low voice quality No security Low capacity AMPS (Advanced Mobile Phone System 800-900MHz) iwing Lab CPE - Kasetsart University 4 2
2G (Second Generation) Digital encoding High bit rate voice Limited data communications (tens Kbps) GSM, D-AMPS (TDMA) and CDMA Auxiliary services (data, fax and SMS) Some levels of encryption iwing Lab CPE - Kasetsart University 5 2.5G Extend 2G systems (GSM) Packet-switched connection (GPRS) Higher data rate (up to hundred Kbps) iwing Lab CPE - Kasetsart University 6 3
3G (Third Generation) Higher data rates (Mbps) More than voice... Support bandwidth-hungry applications Full-motion video Video-conferencing Full Internet access (IP) 3G & WLAN: complementary relationship IMT-2000 W-CDMA iwing Lab CPE - Kasetsart University 7 4G NTT DoCoMo of Japan Beyond IMT-2000 iwing Lab CPE - Kasetsart University 8 4
Evolution of the system Source: Mobile Communications International iwing Lab CPE - Kasetsart University 9 Wireless System Path Source: Mobile Communications International iwing Lab CPE - Kasetsart University 10 5
Outline Wireless World (2G, 3G, ) Basic Wireless Knowledge Wireless Local Area Network (WLAN) WLAN Standards Where are we heading to? iwing Lab CPE - Kasetsart University 11 Communication Principle How can the information be transmitted? Information Signals (Electromagnetic Energy) Visible light 430-750 THz Power, Voice Radio communication Radio, microwave, satellite Infrared Light Ultra- Violet Light X, gamma, Cosmic rays 0 3000 Hz 300 GHz iwing Lab CPE - Kasetsart University 12 6
Wireless Applications Mobility needs (Inventory) Physical media is not feasible (Factory) Eliminate paperwork (Car Rental) Decrease errors (Health care) Reduce process cost (Automatic Reading) Improve efficiency (Mobile Office) iwing Lab CPE - Kasetsart University 13 Wireless Network Concerns Radio signal interference (Noise) Power management (Battery) System interoperability (Standards) Network security and Privacy (Encryption) Connection problems (Loss, Timeout) Installation issues (Barrier) Health risks (Brain Damage?) iwing Lab CPE - Kasetsart University 14 7
PWR 10M100M ACTACT 123456789101112 COLCOL SWITCH 131415161718192021222324 1 2 3 4 13 14 15 16 5 6 7 8 17 18 19 20 9 10 11 12 21 22 23 24 UPLINK Wireless Network Configurations Wireless LANs (WLAN) Radio Waves Infrared Light Carrier currents ( no new wire ) Wireless Point-to-Point Networks Wireless WANs iwing Lab CPE - Kasetsart University 15 Radio Based Wireless LANs Advantages No line of sights Propagate through obstacles Disadvantages Interference Security Radio Based WLAN iwing Lab CPE - Kasetsart University 16 8
Infrared Light LAN Categories Ceiling Diffused Infrared LAN Point-to-point Infrared LAN iwing Lab CPE - Kasetsart University 17 Infrared Light Based WLAN Invisible to the naked eye Advantages over Radio Waves: More Secure Less susceptible to common noises (e.g.oven) Better performance High data rate Disadvantage: Limited Coverage iwing Lab CPE - Kasetsart University 18 9
Carrier Current LANs Powerline network Phoneline network No new wire LAN Home networks Office Living Room Bed Room 2 Residential Gateway Kitchen Bed Room 1 iwing Lab CPE - Kasetsart University 19 Wireless Point-to-point Similar to WLAN technologies: Radio waves Laser beam Applications Building links Links for traffic control lights Leased line backup iwing Lab CPE - Kasetsart University 20 10
Wireless WANs Packet Radio WAN Analog cellular WAN Cellular Digital Packet Data WAN Satellite Meteor burst (Ionosphere) GPS & Wireless WANs iwing Lab CPE - Kasetsart University 21 Outline Wireless World (2G, 3G, ) Basic Wireless Knowledge Wireless Local Area Network (WLAN) WLAN Standards Where are we heading to? iwing Lab CPE - Kasetsart University 22 11
WLAN Topology Architecture iwing Lab CPE - Kasetsart University 23 WLAN Topologies Physical (Single & Multiple Cells) Logical (Ad-hoc & Infrastructure) Connectivity (Standalone & Wired Network Interface) MAC (Distributed & Centralized) iwing Lab CPE - Kasetsart University 24 12
Single Cell VS. Multiple Cells AP AP AP Single Cell Multiple Cells iwing Lab CPE - Kasetsart University 25 Ad-hoc VS. Infrastructure AP Ah-hoc Infrastructure iwing Lab CPE - Kasetsart University 26 13
Standalone VS. Wired Network Interface AP Standalone Wired Network Interface iwing Lab CPE - Kasetsart University 27 Distributed VS. Centralized Distributed Centralized iwing Lab CPE - Kasetsart University 28 14
WLAN Topology Architecture iwing Lab CPE - Kasetsart University 29 Outline Wireless World (2G, 3G, ) Basic Wireless Knowledge Wireless Local Area Network (WLAN) WLAN Standards Where are we heading to? iwing Lab CPE - Kasetsart University 30 15
Why Wireless LAN not so popular in last ten years? Low data rate High price Lack of standard Proprietary products Active Standards / Organizations IEEE 802.11 Bluetooth HIPERLAN iwing Lab CPE - Kasetsart University 31 16