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Wireless Networks(CSC-7602)Lecture 1 (27 Aug 2007)

Seung-Jong Park (Jay)http://www.csc.lsu.edu/~sjpark

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HandoutsClass informationSchedule (check online frequently)

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GoalsPrinciples on Wireless Networks

TopicsArchitectureTechnologiesProtocols

MACRoutingTransport

Simulation & Performance Evaluation

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Requirements for SimulationProgramming

C/C++Linux (just need to know how to use it and compile C)

Linux server account ?Passion

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Administrative InformationSeung-Jong Park

Room 289, Coates HallEmail : sjpark at csc.lsu.eduOffice hours: Mon. 5:10pm-8:00pm

Class websitehttp://www.csc.lsu.edu/~sjpark

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PoliciesLecture slides will be available on website before the day of classLecture slides are NOT comprehensive – students are expected to attend classes to “fill in” informationMiss classes at your own risk. Professor will NOT be responsible for any information you might not have because of a missed classZero tolerance policy toward cheating

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TextbookTextbook

NOJust Slides

Additional reading list will be available on website

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GradingExam

1 final (1 x 30% = 35%)Paper Presentation

1 x 20% = 20%Project (Ns2 Simulation)

2 Projects1st project (20%)2nd project (20%)

Class pointsInteraction in class (1 x 5% = 5%)

GradesA if above 85 out of 100B if above 70 out of 100C if above 50 out of 100F if below 50 or miss class more than 4 times

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Introduction of Networks

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Communication NetworksBroadcast networks

Each station can hear every other station in the network (fully connected network)

Switched networksStations interconnected through a (non-fully) connected meshPacket switched vs. Circuit switched

What kind of a network is the Internet?

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Communication ProtocolsRules used in communicationMonolithic vs. LayeredProtocol data units – used to exchange information between peer layers of protocol stackExamples of communication protocols?

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OSIOpen Systems Interconnection: ISO (International Standards Organization)’s standard for communication protocolsAlso referred to as the OSI reference model or simply the OSI model7 layer protocol stack

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OSI Protocol StackPhysicalData linkNetworkTransportSessionPresentationApplication

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OSI (contd.)Physical: mechanical/electrical rules for transferring bitsData link:

flow controlerror detectionerror recovery

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OSI (contd.)Network

RoutingCongestion controlQuality of service

TransportEnd-to-end communication of dataReliabilitySequencingFlow controlCongestion control

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OSI (contd.)Session

Application specific functionalityStill, generic to multiple applications (e.g. security)

PresentationData formatting

Application

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TCP/IP Protocol SuiteDifferences between OSI and TCP/IP?5 layers:

PhysicalData link/MAC (ARP, SLIP)Network (IP, ICMP, IGMP)Transport (TCP, UDP)Application (http, ftp, telnet, smtp)

Introduction of Wireless Communications

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How Radio WorksElectricity vs. Magnetic Field

Sine Wave

Frequency

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How Communication WorksAM (Amplititute Modulation)

FM (Frequency Modulation)

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Wireless Transmission

• The Electromagnetic Spectrum• Radio Transmission• Microwave Transmission• Infrared and Millimeter Waves• Lightwave Transmission

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The Electromagnetic SpectrumThe electromagnetic spectrum and its uses for communication.

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Politics of the Electromagnetic Spectrum

The ISM bands in the United States.

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Voice Communication

n

nx

Sampling & Quantization

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Voice vs. Data CommunicationPast: analog voice communication which is the 1st application of wireless networks, such as radioCurrent: digital voice communication (4 or 8 Kbps) and low speeddigital data communicationFuture: high speed data communication for speech, video, and data

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Wireless Networks from System Perspective

Cellular networks

WLAN networks

Ad-hoc networks

Sensor networks

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Architecture of Cellular Networks

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Evolution of Cellular Networks

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Issues at Cellular Networks

Multiple access technologyIncrease # of users in finite amount of frequency bandwidth

Resource managementReduce redundant usage of resourceHandoff

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Multiple Access TechnologiesFDMA (Frequency Division Multiple Access)

Each user has a private frequencyAMPS

TDMA (Time Division Multiple Access)Each user has a private time on a private frequencyGSM, IS-54

CDMA (Code Division Multiple Access)Users share time and frequency with a private codeIS-95

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Frequency Division Multiplexing

(a) The original bandwidths.(b) The bandwidths raised in frequency.(b) The multiplexed channel.

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Advanced Mobile Phone System

(a) Frequencies are not reused in adjacent cells.(b) To add more users, smaller cells can be used.

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Time Division MultiplexingMultiplexing T1 streams into higher carriers.

01234

Large BW

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HandoffHow to find neighboring base stationsHow to connect BSs

Hard handoff between different service providers or different systemsSoft handoff between CDMA base stations

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Wireless Local Area Networks

IEEE 802.11LAN

WLAN

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Ad-hoc NetworksMulti-hop wireless networksNo Infrastructure

Typically used in military applications (where there is no infrastructure), or disaster relief (where infrastructure has been destroyed)

Mobile stations double-up as forwarders/routersCan use existing WLAN technology (e.g. IEEE 802.11 supports a Distributed Coordination Function (DCF) mode of operation)Study on network layer and transport layers

How to know paths between two remote nodes without coordination

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Sink Sensors Field

MedicalMonitoring

IndoorControl

Wireless Sensor NetworkElements

Sink : sends queries to collect data from sensorsSensor : monitors phenomenon and reports to sink

Application

EnvironmentMonitoring

Object Tracking

Issues in 7602 course

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Protocol PerspectiveProtocol: Rules used in communicationMonolithic vs. LayeredProtocol data units – used to exchange information between peer layers of protocol stack7 layers Open Systems Interconnection: ISO (International Standards Organization)’s standard for communication protocols

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Problems for Each Protocol

Physical Layer

Link (MAC) Layer

Network Layer

Transport Layer

Application Layer

Ethernet (IEEE 802.3)WLAN (IEEE 802.11b)

Physical Layer

Mobile IP

Variants of TCP

HTTP, FTP

How to share a common media

How to connect two nodes physically

How to reach toa destination

How to deliver data

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Problems at MAC LayerBasic

How to fairly share a mediumHidden Terminal Problem

A talks to BC senses the channelC does not hear A’s transmission (out of range)C talks to BSignals from A and B collide

A B C

Collision

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Problems at Network LayerMobile IP Problem

The IP address associated with a mobile host is network dependent!When user connects to another network, IP address needs to changePackets belonging to ongoing connections somehow need to be delivered to the mobile host

Post Office SolutionLeave a forwarding address with your old post-office!The old post-office forwards mails to your new post-office, which then forwards them to you

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Problems at Transport LayerTCP over wireless networks

TCP uses losses as indication of congestionReduces congestion window by half (LIMD) when it experiences

congestionEven when no congestion, if packets are dropped due to

random losses, TCP will cut down its rate (is this right?)TCP will interpret hand-offs related losses also as congestion based lossesHence, it will reduce the congestion window every time hand-

offs related losses occurSplit Connection Approach divide a path into two sub-paths

WTCP: Use inter-packet delay (as opposed to losses) as indication of congestion