Wireless LANs: 802.11 and Mobile IP docx

Wireless LANs: 802.11 and Mobile IP Sridhar Iyer Leena Chandran-Wadia K R School of Information Technology IIT Bombay {sri, leena}@it.iitb.ac.in http://www.it.iitb.ac.in/ IIT Bombay ICPWC'02 2 Outline  Overview of wireless networks – Single-hop wireless: Cellular, Wireless LANs (WLANs) – multiple wireless hops – Mobile ad hoc networks (MANETS)  Challenges of wireless communications  IEEE 802.11 – spread spectrum and physical layer specification – MAC functional specification: DCF mode • role in WLANs – infrastructure networks • role in MANETs – MAC functional specification: PCF mode  Mobile IPv4  Mobile IPv6 IIT Bombay ICPWC'02 3 References  http://standards.ieee.org/getieee802/802.11.html IEEE Computer Society 1999, Wireless LAN MAC and PHY layer specification  J. Schiller, “Mobile Communications”, Addison Wesley, 1999. – several figures  Short tutorials on 802.11 and spread spectrum by J.Zyren, A.Petrick, C.Andren http://www.intersil.com  Mobile IPv4 – RFC 3344 (main)  IPv6 and Mobile IPv6 – many RFCs, Internet drafts – http://www.iprg.nokia.com/~charliep/ IIT Bombay ICPWC'02 4 Overview of wireless networks IIT Bombay ICPWC'02 5 Wireless networks  Access computing/communication services, on the move  Cellular Networks – traditional base station infrastructure systems  Wireless LANs – infrastructure as well as ad-hoc networks possible – very flexible within the reception area – low bandwidth compared to wired networks (1-10 Mbit/s)  Multihop Ad hoc Networks – useful when infrastructure not available, impractical, or expensive – military applications, rescue, home networking IIT Bombay ICPWC'02 6 Cellular Wireless  Single hop wireless connectivity to the wired world – Space divided into cells, and hosts assigned to a cell – A base station is responsible for communicating with hosts/nodes in its cell – Mobile hosts can change cells while communicating – Hand-off occurs when a mobile host starts communicating via a new base station IIT Bombay ICPWC'02 7 Evolution of cellular networks  First-generation: Analog cellular systems (450-900 MHz) – Frequency shift keying; FDMA for spectrum sharing – NMT (Europe), AMPS (US)  Second-generation: Digital cellular systems (900, 1800 MHz) – TDMA/CDMA for spectrum sharing; Circuit switching – GSM (Europe), IS-136 (US), PDC (Japan) – <9.6kbps data rates  2.5G: Packet switching extensions – Digital: GSM to GPRS; Analog: AMPS to CDPD – <115kbps data rates  3G: Full-fledged data services – High speed, data and Internet services – IMT-2000, UMTS – <2Mbps data rates IIT Bombay ICPWC'02 8 Wireless LANs  Infrared (IrDA) or radio links (Wavelan)  Advantages – very flexible within the reception area – Ad-hoc networks possible – (almost) no wiring difficulties  Disadvantages – low bandwidth compared to wired networks – many proprietary solutions • Bluetooth, HiperLAN and IEEE 802.11 IIT Bombay ICPWC'02 9 Wireless LANs vs. Wired LANs  Destination address does not equal destination location  The media impact the design – wireless LANs intended to cover reasonable geographic distances must be built from basic coverage blocks  Impact of handling mobile (and portable) stations – Propagation effects – Mobility management – Power management IIT Bombay ICPWC'02 10 Infrastructure vs. Ad hoc WLANs infrastructure network ad-hoc network AP AP AP wired network AP: Access Point Source: Schiller [...]... A and C are “exposed” terminals IIT Bombay ICPWC'02 25 Effect of mobility on protocol stack  Application – new applications and adaptations  Transport – congestion and flow control  Network – addressing and routing  Link – media access and handoff  Physical – transmission errors and interference IIT Bombay ICPWC'02 26 802.11- based Wireless LANs Architecture and Physical Layer IEEE 802.11  Wireless. .. Wireless LAN standard defined in the unlicensed spectrum (2.4 GHz and 5 GHz U-NII bands) λ 12cm 33cm 26 MHz 902 MHz 83.5 MHz 2.4 GHz 928 MHz 5cm 200 MHz 5.15 GHz 2.4835 GHz 5.35 GHz  Standards covers the MAC sublayer and PHY layers  Three different physical layers in the 2.4 GHz band – FHSS, DSSS and IR  OFDM based Phys layer in the 5 GHz band (802.11a) IIT Bombay ICPWC'02 28 802.11- in the TCP /IP stack... search -and- rescue, police and firefighters  Sensor networks  Taxicabs and other closed communities  airports, sports stadiums etc where two or more people meet and want to exchange documents  Presently MANET applications use 802.11 hardware  Personal area networks - Bluetooth IIT Bombay ICPWC'02 13 Wireless Technology Landscape 72 Mbps 72 Mbps Turbo 11a 54 Mbps 802.11{ a,b} 54 Mbps 5-11 Mbps 802.11b... GHz band (802.11a) IIT Bombay ICPWC'02 28 802.11- in the TCP /IP stack fixed terminal mobile terminal server infrastructure network access point application application TCP TCP IP IP LLC LLC LLC 802.11 MAC 802.11 MAC 802.3 MAC 802.3 MAC 802.11 PHY 802.11 PHY 802.3 PHY 802.3 PHY IIT Bombay ICPWC'02 29 802.11 - Layers and functions  MAC  PLCP Physical Layer Convergence Protocol – access mechanisms, fragmentation,... multiple BSSs  802.11 standard logically separates the wireless medium from the distribution system – it does not preclude, nor demand, that the multiple media be same or different  An Access Point (AP) is a STA that provides access to the DS by providing DS services in addition to acting as a STA  Data moves between BSS and the DS via an AP  The DS and BSSs allow 802.11 to create a wireless network... Enterprise 802.11 Network Wireless Carrier Public 802.11     IIT Bombay ICPWC'02 Market consolidation Entry of Wireless Carriers Entry of new players Footprint growth 16 Source: Pravin Bhagwat Spectrum War: Steady State Enterprise 802.11 Network Wireless Carrier Public 802.11 Virtual Carrier   IIT Bombay ICPWC'02 Emergence of virtual carriers Roaming agreements 17 Source: Pravin Bhagwat 802.11 Market... limited range – Station (STA): terminal with access mechanisms to the wireless medium – Basic Service Set (BSS): group of stations using the same radio frequency 802.11 LAN ICPWC'02 32 Source: Schiller 802.11 - infrastructure network Station (STA) 802.11 LAN STA1 802.x LAN – terminal with access mechanisms to the wireless medium and radio contact to the access point Basic Service Set (BSS) BSS1 Portal... everyone Fake base stations can attract calls from mobile phones secure access mechanisms important IIT Bombay ICPWC'02 22 Difference Between Wired and Wireless Ethernet LAN Wireless LAN B A B C A C  If both A and C sense the channel to be idle at the same time, they send at the same time  Collision can be detected at sender in Ethernet  Half-duplex radios in wireless cannot detect collision at sender IIT... – have time varying and asymmetric propagation properties IIT Bombay ICPWC'02 20 Limitations of the mobile environment • Limitations of the Wireless Network • limited communication bandwidth • frequent disconnections • heterogeneity of fragmented networks • Limitations Imposed by Mobility • route breakages • lack of mobility awareness by system/applications • Limitations of the Mobile Device • short... Challenges of Wireless Communications Wireless Media  Physical layers used in wireless networks – have neither absolute nor readily observable boundaries outside which stations are unable to receive frames – are unprotected from outside signals – communicate over a medium significantly less reliable than the cable of a wired network – have dynamic topologies – lack full connectivity and therefore . tutorials on 802. 11 and spread spectrum by J.Zyren, A.Petrick, C.Andren http://www.intersil.com  Mobile IPv4 – RFC 3344 (main)  IPv6 and Mobile IPv6 – many RFCs, Internet drafts – http://www.iprg.nokia.com/~charliep/ IIT. 2 Outline  Overview of wireless networks – Single-hop wireless: Cellular, Wireless LANs (WLANs) – multiple wireless hops – Mobile ad hoc networks (MANETS)  Challenges of wireless communications  IEEE 802. 11 – spread. IPv4  Mobile IPv6 IIT Bombay ICPWC'02 3 References  http://standards.ieee.org/getieee802 /802. 11. html IEEE Computer Society 1999, Wireless LAN MAC and PHY layer specification  J. Schiller, “Mobile