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CSE 453: Wireless Networks

Lecture 1: Introduction

Fall 2014

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Why Use Wireless Communication?

Provides mobility A user can send or receive a message no matter where he

or she is located

Added convenience/reduced cost

Enables communication without installing an expensiveinfrastructure

Can easily set-up temporary LANs Disaster situations

Office moves

Developing nations utilize cellular telephony rather thanlaying twisted-pair wires to each home

Only use resources when sending or receiving a signal

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What Makes Wireless Different?

Higher loss-rates

Restrictive spectrum regulations

Lower transmission rates

Higher delays, higher jitter

Signal attenuation Broadcast medium

Easier to snoop on, or tamper with, wireless transmissions

Mobility

change of point of attachment to network how to find a user / device

Limitations of access devices battery power

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History Of Wireless Communication

Many people in history used light for communication

Discovery of electromagnetic waves 1831: Faraday demonstrates electromagnetic induction

1864: J. Maxwell theory of electromagnetic fields, wave equations

1886: H. Hertz demonstration of the wave character of electrical

transmission 1895: Guglielmo Marconi, first demonstration of wireless

telegraphy (long wave)

1907: Commercial transatlantic connections

1915: Wireless voice transmission New York - San Francisco

1920: Marconi, discovery of short waves 1928: many TV broadcast trials (across Atlantic, color TV, TV news)

1933: Frequency modulation (E. H. Armstrong)

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History Of Wireless Communication

1956: First mobile phone system in Sweden

1972: B-Netz in Germany

1979: NMT at 450MHz (Scandinavian countries)

1982: Start of GSM-specification goal: pan-European digital mobile phone system with roaming

1992: Start of GSM

1997: Wireless LAN - IEEE802.11

1998: Specification of UMTS(Universal Mobile

Telecommunication System) 1998: Iridium: portable satellite telephony

1999: IEEE Standard 802.11b, 2.4 GHz, 11 Mbit/sBluetooth, 2.4 GHz, < 1 Mbit/s

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History Of Wireless Communication

2001 Start of 3G (Japan)

UMTS trials in Europe

2002: Start of UMTS in Europe

IEEE 802.11g

mobile subscribers overtake fixed-line subscribers worldwide

1 billion cellular subscribers

2004: UMTS launch in Netherlands

2007: Introduction of iPhone

2009: IEEE 802.11n standard

2012: 6 billion cellular subscribers

2013: LTE launch in Netherlands (KPN, February, Amsterdam)

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Current Wireless Technologies

Telecommunication Systems initial / primary service: mobile voice telephony

large coverage per access point (100s of meters - 10s of kilometers)

low - moderate data rate (10s of kbit/s 10s of Mbits/s)

Examples: GSM, UMTS, LTE

WLAN initial service: wireless ethernet extension

moderate coverage per access point(10s of meters - 100s of meters)

moderate - high data rate (Mbits/s - 100s of Mbits/s)

Examples: IEEE 802.11b, a, g, n.

Short-range Other systems

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Current Wireless Technologies Short-range

direct connection between devices (< 10s of meters)

typical low power usage

examples: Bluetooth, ZigBee

Other systems Satellite systems

global coverage,

Applications audio/TV broadcast; positioning

personal communications

Broadcast systems satellite/terrestrial

DVB, DAB (Support of high speeds for mobiles)

Fixed wireless access several technologies (DECT, WLAN, IEEE802.16 (11-60GHz))

DECT Digital Enhanced Cordless Telecommunication

TETRA Terrestrial Trunked Radio

Netherlands: C2000 system

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Standardization

3GPP (3G partnership project) GSM

UMTS

LTE

Specifications: http://www.3gpp.org/-specificationsq

IEEE (Institute of Electrical and Electronics Engineers) 802.11 (Wireless LAN: WiFi)

802.15 (Wireless PAN: Bluetooth, Zigbee)

802.16 (Broadband Wireless Access: WiMAX))

Standards: http://standards.ieee.org/about/get/802/802.html

IETF (Internet Engineering Task Force) Mobile IP

TCP

AODV

Requests for Comments (RFCs): http://www.ietf.org/rfc.html

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Why Is Wireless Networking

Challenging?

Wireless network: Getting the data without the

pipes

Speed of light

Shared infrastructure

Things break

Dynamic range Security

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Fundamental Challenge: Speed of Light

How long does it take light to travel from X to2,935 km distant away Y?

Answer:

Distance X > Y is 2,935 km

Traveling 300,000 km/s: 9.78ms

Note: Dependent on transmission medium

3.0 x 108 meters/second in a vacuum

2.3 x 108 meters/second in a cable

2.0 x 108 meters/second in a fiber

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Fundamental Challenge: Shared

infrastructure

Different parties must work together

Multiple parties with different agendas must

agree how to divide the task between them

Working together requires

Protocols (defining who does what)

These generally need to be standardized

Agreements regarding how different types of

activity are treated (policy)

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Fundamental Challenge: Shared

infrastructure

Links and switches must be shared among manyusers

Common multiplexing strategies

Time-division multiplexing (TDM) Frequency-division multiplexing (FDM)

Code-division multiplexing (CDM)

Statistical Multiplexing (SM)

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Fundamental Challenge: Enormous

dynamic range

Challenge: enormous dynamic range

Round trip times (latency): 10 ss to secs

Data rates (bandwidth): kbps to 10 Gbps

Queuing delays in the network: 0 to secs

Packet loss 0 to 90+%

End system (host) capabilities: cell phones to

clusters

Application needs: size of transfers,

bidirectionality, reliability, tolerance of jitter

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Fundamental Challenge: Security

Challenge: there are Bad Guys out there!

Early days Vandals

Hackers

Crazies Researchers

As network population grows, it becomes more andmore attractive to crooks

As size of and dependence on the network grows,becomes more attractive to spies, governments, andmilitaries

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Fundamental Challenge: Security

Attackers seek ways to misuse the network

towards their gain

Carefully crafted bogus traffic to manipulate the

networks operation Torrents of traffic to overwhelm a service (denial-of-

service) for purposes of extortion/competition

Passively recording network traffic in transit (sniffing)

Exploit flaws in clients and servers using the network

to trick into executing the attackers code

(compromise)

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How Do We Design a Network?

Need to deal with Complexity

Many parties involved

Very long life time Key is modularity

Natural solution to deal with complexity

Independent parties can develop components that

can interoperate Different pieces of the system can evolve

independently, at different paces

Need well-defined protocols and interfaces

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Network Protocols

A protocol is an abstract object that makes up thelayers of a network system

A protocol provides a communication service thathigher-layer objects use to exchange messages Service interface

To objects on the same computer that want to use itscommunication services

Peer interface To its counterpart on a different machine

Peers communicate using the services of lower-levelprotocols

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OSI Protocol Stack

Application: Application specificprotocols

Presentation: Format of

exchanged data Session: Name space for

connection mgmt

Transport: Process-to-processchannel

Network: Host-to-host packetdelivery

Data Link: Framing of data bits

Physical: Transmission of rawbits

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OSI Model

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OSI vs. Internet

OSI: conceptually define: service, interface, protocol

Internet: provide a successful implementation