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8/10/2019 CSE 453 Lecture-1
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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