INTRODUCTIONINTRODUCTIONTo To Wireless NetworksWireless Networks

Wireless Comes of AgeWireless Comes of Age

• Guglielmo Marconi invented the wireless telegraph in Guglielmo Marconi invented the wireless telegraph in 18961896– Communication by encoding alphanumeric characters in Communication by encoding alphanumeric characters in

analog signalanalog signal– Sent telegraphic signals across the Atlantic OceanSent telegraphic signals across the Atlantic Ocean

• Communications satellites launched in 1960sCommunications satellites launched in 1960s• Advances in wireless technologyAdvances in wireless technology

– Radio, television, mobile telephone, communication Radio, television, mobile telephone, communication satellitessatellites

• More recentlyMore recently– Broadband wireless networking, cellular technologyBroadband wireless networking, cellular technology

Broadband Wireless TechnologyBroadband Wireless Technology

• Higher data rates obtainable with broadband wireless Higher data rates obtainable with broadband wireless technologytechnology– Graphics, video, audioGraphics, video, audio

• Shares same advantages of all wireless services: Shares same advantages of all wireless services: convenience and reduced costconvenience and reduced cost– Service can be deployed faster than fixed serviceService can be deployed faster than fixed service

– No cost of cable plantNo cost of cable plant

– Service is mobile, deployed almost anywhereService is mobile, deployed almost anywhere

Limitations and Difficulties of Limitations and Difficulties of Wireless TechnologiesWireless Technologies

• Wireless is convenient and less expensive Wireless is convenient and less expensive • Limitations and political and technical difficulties Limitations and political and technical difficulties

inhibit wireless technologiesinhibit wireless technologies• Lack of an industry-wide standardLack of an industry-wide standard• Device limitationsDevice limitations

– E.g., small LCD on a mobile telephone can only displaying E.g., small LCD on a mobile telephone can only displaying a few lines of texta few lines of text

– E.g., browsers of most mobile wireless devices use wireless E.g., browsers of most mobile wireless devices use wireless markup language (WML) instead of HTMLmarkup language (WML) instead of HTML

A Wireless NetworkA Wireless Network

Definition: Definition:

A Group of interconnected nodes A Group of interconnected nodes that exchange information and share that exchange information and share resources through a wireless resources through a wireless transmission mediumtransmission medium

TYPES OF WIRELESS TYPES OF WIRELESS NETWORKSNETWORKS

• Wireless PAN Wireless PAN • Wireless LANWireless LAN• Wireless Broadband Wireless Broadband • Wireless WAN (satellite , Wireless WAN (satellite ,

Microwave ,..etc)Microwave ,..etc)• Cellular Networks Cellular Networks

Characteristics of Characteristics of WirelessWireless WANs WANs

• Covers large geographical areasCovers large geographical areas• Circuits provided by a common carrierCircuits provided by a common carrier• Consists of interconnected switching nodesConsists of interconnected switching nodes• Traditional WANs provide modest capacityTraditional WANs provide modest capacity

– 64000 bps common64000 bps common

– Business subscribers using T-1 service – 1.544 Mbps Business subscribers using T-1 service – 1.544 Mbps commoncommon

• Higher-speed Higher-speed WirelessWireless W WANANss use use satellitesatellite , , and 10s of Mbps commonand 10s of Mbps common

Characteristics of Characteristics of WirelessWireless LANsLANs

• LLike WAN, ike WAN, WirelessWireless LAN interconnects a LAN interconnects a variety of devices and provides a means for variety of devices and provides a means for information exchange among theminformation exchange among them

• Traditional Traditional WirelessWireless LANs LANs– Provide data rates of 1 to 20 MbpsProvide data rates of 1 to 20 Mbps

• High-speed High-speed WirelessWireless LANS LANS– Provide data rates of 100 MbpsProvide data rates of 100 Mbps

• Standards for Wireless LANS is WI-FIStandards for Wireless LANS is WI-FI

Characteristics of Characteristics of WirelessWireless LANsLANs

• Used to be a network with Used to be a network with high high prices, low data rates, occupational prices, low data rates, occupational safety concerns, and licensing safety concerns, and licensing requirementsrequirements

• Problems Problems have been addressedhave been addressed and and popularitypopularity of wireless LANs has of wireless LANs has grown rapidlygrown rapidly

Differences between Differences between WirelessWireless LANs and WANsLANs and WANs

• Scope of a LAN is smallerScope of a LAN is smaller– LAN interconnects devices within a single LAN interconnects devices within a single

building or cluster of buildingsbuilding or cluster of buildings

• LAN usually owned by organization that owns LAN usually owned by organization that owns the attached devicesthe attached devices– For WANs, most of network assets are not owned For WANs, most of network assets are not owned

by same organizationby same organization

• Internal data rate of LAN is much greaterInternal data rate of LAN is much greater

The Need for The Need for WirelessWireless MANs MANs

• TTraditional point-to-point and switched network raditional point-to-point and switched network techniques used in WANs are inadequate for growing techniques used in WANs are inadequate for growing needs of organizationsneeds of organizations

• Need for high capacity and low costs over large areaNeed for high capacity and low costs over large area• MAN provides:MAN provides:

– Service to customers in metropolitan areasService to customers in metropolitan areas– Required capacityRequired capacity– Lower cost and greater efficiency than equivalent service Lower cost and greater efficiency than equivalent service

from telephone companyfrom telephone company

• Standards for Wireless MANS is WI-MAX Standards for Wireless MANS is WI-MAX

Wireless StandardsWireless Standards

• PAN , LAN and MAN standards were PAN , LAN and MAN standards were defined by IEEE and Industrial forumsdefined by IEEE and Industrial forums

• A LAN standard define media, coding A LAN standard define media, coding scheme, frame form at , MAC protocol and scheme, frame form at , MAC protocol and other data link layer protocols :other data link layer protocols :

• Examples of standards : Examples of standards : – Wireless PAN: Bluetooth , IEEE 802.15 Wireless PAN: Bluetooth , IEEE 802.15 – Wireless LAN : IEEE 802.11 (a ,b , g )Wireless LAN : IEEE 802.11 (a ,b , g )– Broadband Wireless Networks : IEEE 803.16Broadband Wireless Networks : IEEE 803.16

Wireless LAN Wireless LAN Configurations Configurations

• AA wireless LAN use wireless LAN usess wireless wireless transmission medium in a local Area transmission medium in a local Area in : in : – Single Cell Configuration - Multi-cell Single Cell Configuration - Multi-cell

ConfigurationConfiguration– Infrastructure Wireless LAN Infrastructure Wireless LAN – - Add Hoc LAN- Add Hoc LAN

Single Cell Wireless LAN Single Cell Wireless LAN ConfigurationConfiguration

Multi-Cell Wireless LAN Multi-Cell Wireless LAN ConfigurationConfiguration

Infrastructure Wireless Infrastructure Wireless LANLAN

Add Hoc LANAdd Hoc LAN

Factors To Consider: Factors To Consider: For Wireless LANFor Wireless LAN

• Same as Same as any LANany LAN– HighHigh capacity, short distances, full connectivity, broadcast capacity, short distances, full connectivity, broadcast

capabilitycapability

• Throughput: efficient use wireless mediumThroughput: efficient use wireless medium• Number of nodes:Number of nodes:Hundreds Hundreds of nodes across multiple cellsof nodes across multiple cells• Connection to backbone LAN:Connection to backbone LAN: Use Use control modules control modules to to

connect to both types of LANsconnect to both types of LANs• Service area: 100 to 300 mService area: 100 to 300 m• Low Low power consumption:power consumption:Need Need long battery life long battery life on mobile on mobile

stationsstations– Mustn'tMustn't require nodes to monitor access points or frequent require nodes to monitor access points or frequent

handshakeshandshakes

• Transmission robustness and security:Transmission robustness and security:InterferenceInterference prone prone and easily eavesdroppedand easily eavesdropped

Factors To Consider: Factors To Consider: For Wireless LANFor Wireless LAN

• Collocated network operation:Collocated network operation:TwoTwo or more wireless LANs in same areaor more wireless LANs in same area

• License-free operationLicense-free operation• Handoff/roaming: Handoff/roaming: MoveMove from one from one

cell to anothercell to another• Dynamic configuration: Dynamic configuration: AdditionAddition, ,

deletion, and relocation of end deletion, and relocation of end systems without disruption to userssystems without disruption to users

Wireless LAN Wireless LAN ApplicationsApplications

• LAN ExtensionLAN Extension• Cross-Building InterconnectCross-Building Interconnect• Nomadic AccessNomadic Access• Ad Hoc NetworkingAd Hoc Networking

Applications - Applications - LAN LAN ExtensionExtension

• SavesSaves installation of LAN cabling installation of LAN cabling• EasesEases relocation and other modifications to relocation and other modifications to

network structurenetwork structure• Wireless Wireless LAN to replace wired LANs has not LAN to replace wired LANs has not

happenedhappened• In someIn some environments, role for the wireless LAN environments, role for the wireless LAN

– BuildingsBuildings with large open areas with large open areas• ManufacturingManufacturing plants, stock exchange trading floors, plants, stock exchange trading floors,

warehouseswarehouses• HistoricalHistorical buildings buildings• SmallSmall offices where wired LANs not economical offices where wired LANs not economical

• May alsoMay also have wired LAN have wired LAN– Servers Servers and stationary workstationsand stationary workstations

Applications – Applications – Cross-Building Cross-Building InterconnectInterconnect

• ConnectConnect LANs in nearby buildings LANs in nearby buildings• PointPoint-to-point wireless link-to-point wireless link• ConnectConnect bridges or routers bridges or routers• NotNot a LAN per se a LAN per se

– UsualUsual to include this application under to include this application under heading of wireless LANheading of wireless LAN

•   

Applications - Applications - Nomadic Nomadic AccessAccess

• LinkLink between LAN hub and mobile data between LAN hub and mobile data terminal terminal – LaptopLaptop or notepad computer or notepad computer– Enable Enable employee returning from trip to employee returning from trip to

transfer data from portable computer to transfer data from portable computer to serverserver

• Also Also useful in extended environment useful in extended environment such as campus or cluster of buildingssuch as campus or cluster of buildings– UsersUsers move around with portable computers move around with portable computers– MayMay wish access to servers on wired LAN wish access to servers on wired LAN

Applications – Applications – Ad Hoc NetworkingAd Hoc Networking

• PeerPeer-to-peer network-to-peer network• Set Set up temporarily to meet some up temporarily to meet some

immediate needimmediate need• E.g.E.g. group of employees, each with group of employees, each with

laptop or palmtop, in business or laptop or palmtop, in business or classroom meetingclassroom meeting

• NetworkNetwork for duration of meeting for duration of meeting