Topic 4: Telecommunications

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The Edge of IT ITEC-200 Fall 2006

• Topic 4 Telecommunications Networks
• Professor J. Alberto Espinosa

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Agenda

• Learn the basics about telecommunications
• Introduction to networking concepts

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Roadmap
Decision SupportDistributed CollaborationEnterpr
ise CollaborationFinancial Managementetc.
Information
BusinessApplications
Transaction Processing
Client Appl
ServerAppl
ITInfrastructure
DB
DB
Database
IT Infrastrucure - HW SW - Database -
Telecom
IT Business
Business Applications
IT Business
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• Telecom Basics

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Telecom

• Any sufficiently advanced technology
  isindistinguishable from magic Arthur C.
  Clarke (a famous scientist)
• 2 worlds
• Digital signal (what computers understand e.g.,
  00111001)
• Analog signal (what humans sense)

1 0
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Data and Transmission Signals

• Data is what you want to transmit
• Data is transmitted with signals through a
  communication medium
• Data can be analog (sine waves) i.e., what
  humans understand (e.g., voice, video)
• Or it can be digital (square signals representing
  0s and 1s) i.e. what computers understand
  (e.g., bit and bytes)
• Analog and digital data can both be transmitted
  using either analog or digital signals

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Examples of Data and Signals

• Internal computer bus
• Local area networks
• Computer data over digital phone lines (DSL)

• Computer data over regular phone line dial-up
  connection (via modem)

Digital Data
Original Data Form

• Video-conferencing
• Digital cable TV
• Music CDs
• MP3/media players

• Regular telephone (voice transmission)
• Regular TV
• Analog cable TV
• Radio transmission

Analog Data
Digital Signal
Analog Signal
Transmission Mode
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Example How Modems Work
Computers send digital signals, but regular
telephone lines only transmit analog signals. A
modem (modulator/demodulator) converts the
digital signals to analog (fast audible beeps) so
that the message can be transmitted through
telephone lines
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Transmission Medium

• physical medium through which data signals
  travel
• All signals travel as electromagnetic waves
  i.e., pulses (of voltage, light, etc.) at a given
  frequency (e.g., 1000 pulses per second or 1000
  hertz, or 1 kilohertz)
• Examples of transmission media
• Twisted wire ? inexpensive, available in most
  buildings
• Coaxial cable ? faster, thick, hard to wire
• Fiber optic cable ? expensive, faster, lighter,
  durable
• Wireless ? slower, flexible (microwave, radio,
  cellular, infrared)

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Transmission Channels

• A channel is the link between a sending and
  receiving point
• A medium is usually broken into several channels,
  depending on the mediums capacity, so that data
  can be transmitted simultaneously through various
  channelse.g., cable TV signal, cell phone
  signals

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Characteristics of Channels

• Transmission speed or capacity
• How much data you can send per second
• Kilo/Mega/Gigabits per second (Kbps/Mps/Gps)
• Affected by medium bandwidth, network traffic,
  noise, transmission errors
• Transmission Frequency
• Cycles per second of the electromagnetic signal
• Not necessarily related to transmission speed
• It is just the nature of how the signal travels
  through a medium
• Measured in hertz (cycles per second), kilohertz,
  etc.
• Bandwidth (see next slide)

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Bandwidth

• Every data transmission medium (e.g., cables,
  airwaves, etc.) and each of its channels, have a
  bandwidth that affect the data transmission
  capacity of that medium or channel More
  bandwidth ? more channels ? more capacity to
  transmit dataMetaphor wider highway ? more
  lanes ? more traffic capacity
• Bandwidth (of a medium or channel) is defined as
  the difference between the highest and lowest
  frequencies that can be transmitted (through that
  medium or channel)
• e.g., if a channel or medium can transmit from
  300Mz to 800Mz, the bandwidth is 800 - 300 500Mz

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Splitting the Medium into Channels

• A useful physics principle about electromagnetic
  waves waves of different frequencies dont mix!!
  (sound check)
• Therefore, we can send more than one signal
  through a medium, provided that each signal uses
  a different frequency
• Ex. You 100 TV channels through one channel
• Ex. Your cell phone signals dont mix with those
  of your neighbor
• Ex. Signal from radio station doesnt mix with
  another station
• But if the frequencies of two channels are too
  close to one another, there may be some
  interference (noise, etc.)

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Bandwidth
Animation
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Medium and Channel Bandwidth Illustration
800 MHz 700 MHz 600 MHz 500 MHz 400 MHz 300
MHz
Channel Bandwidth 400 MHz 300 MHz 100 MHz
Medium Bandwidth 800 MHz 300 MHz 500
MHz Number of Channels 5 500 MHz / 100 MHz
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Electromagnetic Wave Frequencies
Example WiFi -- 2.4 GHz 2.4x109 (unregulated
frequency) (chart) Kilohertz (KHz) 103
Megahertz (MHz) 106 Gigahertz (GHz) 109
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Switching

• How does data travel over distance from point A
  to point B?
• It travels from the source (the sending point),
  to the destination (the receiving point)
• Going through switching points widely distributed
  throughout the country (and the world)
• Every switching point has equipment (i.e.,
  hardware and software) called switches that
  take care of making the necessary connections and
  finding the best routes
• There are two general types of switching
  methodsCircuit Switching and Packet
  Switching

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Circuit Switching
San Francisco
Washington, DC
Circuit Switches

• Dedicated path (circuit) between communication
  points
• Connected through switching nodes
• Good for continuous transmissions
• e.g., voice and video (e.g., telephone networks)
• Inefficient otherwise (idle circuit connection
  ties up the circuit)

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Packet Switchinge.g. ATM, Frame Relay

• Data is broken into packets
• Each packet contains destination and re-assembly
  info (packet , msg )
• Each packet is sent separately
• And reassembled at the receiving end
• Good for data transmissions

Miami
Atlanta
Packet Switches
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• Introduction to Networking

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A Network

• Is a number (2 or more) of interconnected
  computer devices
• The connecting devices are called nodes

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Protocols

• A Protocol A set of rules and procedures
  that govern data transmissions between components
  in a network
• For two entities (e.g., computers, persons,
  radios) to communicate, there needs to be a
  protocol
• Implemented in software and/or hardware
• Examples of protocols TCP, IP, FTP, HTTP

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The Network Layer Architecture

• Networks are very complex
• Because there are too many HW and SW components
  communicating with each other
• So, ensuring reliable/fast data communications
  requires numerous networking steps and functions
• No single networking component can do this alone
• Thus, different networking functions are carried
  out by different specialized components
• These components are arranged in layers.
• Each layer function is performed by specific HW
  and/or SW
• Each layer needs to follow the standard
  communication protocols agreed upon for that layer

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Physical Analogy Postal Service
Actual Communication
Application write a letter
Application read the letter
Mail Person
Mail Person
Local Post Office(for zip code)
Local Post Office(for zip code)
Mail Sorting Facility
Mail Sorting Facility
Trucks, Airplanes,Trains, etc.
Trucks, Airplanes,Trains, etc.
Physical Infrastructure Highways, Sky, Railways,
etc.
Data Flow
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Another Analogy A Telephone Network
ActualCommunication
Applicationmake a phone call
Applicationreceive a phone call
Telephone
Telephone
End Office or PBX
End Office or PBX
Circuit Switch
Circuit Switch
Telephone Network
Telephone Network
Physical Media
Physical Media
Cables, Airwaves, etc.
Data Flow
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A Generic 5-Layer Networking Model(each layer
has its own set of protocols)
Data Communication
ApplicationsE-Mail, Web, Chat, etc.
Applications E-Mail, Web, Chat, etc.
Each layer is HW and/or SW performing a distinct
function
Application Layer
Application Layer
Transport Layer
Transport Layer
Network Layer
Network Layer
Data Link Layer
Data Link Layer
The data flows from layer to layer and through
the network 00100010010
Physical Layer
Physical Layer
Network
Data Flow
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Network Layer Architecture An ExampleFYI Only
no need to study this

• Application Layer
• (SW) Communicates with the software applications
  (e.g., e-mail, web pages) and break data into
  small packets and passes the packets to the
  Transport Layer (and reassembles incoming packets
  into original data)
• Transport Layer
• (Usually SW) Communicates with the Application
  Layer, adds some digits for error checking and
  flow control to each packet, and passes these
  larger data packets to the Network Layer (and the
  other way around)
• Network Layer
• (HW and/or SW) Communicates with the Transport
  Layer, gets each packet, adds network address
  information necessary to route the packets
  through the network, and passes these packets to
  the Data Link Layer (and picks up packets routed
  from other layers).
• Data Link Layer
• (Usually HW) Communicates with the Network Layer
  and manage the traffic flow of data packets from
  the computer to Physical Layer (and acknowledges
  receipt of incoming packets from other networks).
• Physical Layer
• (HW) Communicates with the Data Link Layer, gets
  the packets and converts them into (analog or
  digital) signals that can be transmitted over
  that particular network physical medium (cable,
  fiber optics, airwaves) (and converts incoming
  signals into data packets)

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Networking

• Network
• A facility that interconnects a number of devices
• To transmit data from one attached device to
  another
• Networks are classified by their GEOGRAPHIC
  SCOPE
• 1. Local Area Networks (LANs)
• typically within a single building (e.g. Kogod)
  or small area (AU)
• Metropolitan Area Networks (MANs) are like LANs
  but for multiple buildings throughout a city.
• 2. Wide Area Networks (WANs)
• over larger geographical areas (e.g., across
  states, countries)
• 3. Inter-Networks internets networks of
  networks
• INTERconnected NETworks

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1. Local Area Networks (LANs)

• Small scope network
• Typically within a single building (e.g. Kogod)
• Or within a small group of nearby buildings
  (e.g., AU Campus)
• If the network spans several buildings throughout
  a city it is often called a Metropolitan Area
  Network (MAN)
• High data rates

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Key Implementation Decisions for LANs

• Physical Layout
• Physical configuration of network cables (i.e.,
  the medium) in buildings
• Structured Cabling
• A standard for wiring commercial buildings
• Horizontal wires connected vertically via
  telecom closets
• Telecom closets connected vertically to closets
  in other floors
• Via a backbone cable
• Entry point into the building is through the
  equipment room
• Transmission Medium (physical layer)
• Medium used to connect hardware nodes
• Twisted pair, co-axial, fiber optics, wireless,
  etc.
• Network Topology
• Configuration of hardware nodes in the network
• Bus (i.e. linear) topology most predominant
  today

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Bus (linear) Topology w/Hubs

• Very popular ? network is easily scalable via
  hubs
• Passive Hubs ? to connect nodes to the network
• Active Hubs ? to connect other hubs (to amplify
  signal)
• Physically, it looks like star topology, but it
  is bus topology
• Every hub extends the bus
• Predominant with Ethernet networks (AUs Novell
  LAN)

Wireless
Transceiver
Passive Hub
Active Hub
Terminator
Terminator
PassiveHub
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Wide Area Networks (WANs)

• Cover large geographical areas (e.g., across
  states, countries)
• Wired, wireless or both
• A companys WAN is generally implemented by
  interconnecting all the LANs in the companys
  multiple office locations
• Each locations LAN has a ROUTER that connects
  the LAN to a WAN service providers access point
• The connection from the router to the WAN service
  access is called point-to-point connection

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Point to Point Connections in WANsNeeded to
connect your home or office to a network service
provider

• DSL digital subscriber line, fast
  dedicated(ADSL is asymmetric DSL ? same as DSL
  but receive speed is higher than send speed)
• ISDN dial up digital telephone lines, fast
• T1, T3, etc. fastest (1.5 Mbps ), dedicated
  digital lines, which is always connected (no need
  to dialup)
• Note two or more LANs in a city can also be
  interconnected with point-to-point connections
  (forming a MAN). For example, you can connect two
  office LANs using a T1 line the cost depends on
  the distance between the two offices

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Connection Through Network Services in
WANsthrough Packet Switching Nodes

• There are many types of wide area network
  services, which vary according to the type of
  packet switching technology they use. The main
  kinds of switching technologies are
• Frame Relay
• Variable transfer speed
• You pay more for faster speeds
• Speeds 64 Kilobytes per second (Kbps) to 45 Mbps
• Asynchronous Transfer Mode (ATM)
• NOT THE SAME AS A BANKS ATM
• Really fast networks
• Very fast data packet switching at fixed speeds
• Speed up to 1 Gbps

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Wide Area NetworksGeneral Configuration
Frame Relay Network Service
LAN 2e.g.New York
LAN 1e.g. Dallas
T1, T3, or ISDN(point to point)
WAN Service access points
Server
Server
ATMNetwork Service
ATM Router
Frame RelayRouter
T1, T3or ISDN(point to point)
Client
Client
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• Introduction to Inter-Networks The Internet,
  Intranets and Extranets

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3. Inter-Networking

• An internet (in lower case)
• a network of networks (i.e., INTERconnected
  NETworks)
• Connected through routers and packet switching
  nodes (Frame Relay, ATM, etc.)
• The Internet (capitalized)
• the most popular public internet
• All nodes connected to The Internet
  communicated using the same widely adopted
  supported protocol TCP/IP

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The TCP/IP Reference Model (Internet
INTERconnected NETworks)
Ex Mail Server, Web Server, etc.
Application 1
Related Application
Application Layer
Application Layer
TCP
TCP
IP
IP
Network Access Layer
Network Access Layer
Physical Layer
Physical Layer
The Internet
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Routers
The Internet is a network of networks. A
router connects two networks (similar or
dissimilar) e.g., your companys LAN and its
Internet service providers network. It routes
IP packets from one network to another through
its IP layer
Application Layer
Application Layer
TCP
TCP
IP
IP
Network Access Layer (protocol 1)
Network Access Layer (protocol 2)
Physical Layer 1
Physical Layer 2
Network 1
Network 2
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Intranets and Extranets

• An Intranet
• A companys internal network
• Spanning multiple geographic locations
• Interconnected via the Internet instead of a WAN
• Usually protected by Firewalls
• Usually secured with Virtual Private Networks
  (VPNs)
• An Extranet
• Similar to an intranet, but external with other
  companies

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Firewalls and VPNs

• Firewalls
• Hardware and/or software that restrict access
  into and out of a the companys internal networks
  or intranets
• They protect your internal network from outsiders
• They dont protect your communications outside
• Virtual private networks (VPNs)
• Provide secure internal networks or intranets
• Protect your internal communications on the
  outside
• Uses Tunneling (encrypt transmissions betw
  points)

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Intranets, Extranets,Firewalls VPNs (contd.)
T1, T3, or ISDN(point to point)
Internet ServiceAccess Points
IPRouter
Firewall
VPN
LAN Company A
VPN (Tunnelling)
LAN Company B
Internet
Firewall
IPRouter
T1, T3or ISDN(point to point)
IPRouter
VPN
Extranet
Intranet
Firewall
LAN Company A
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Network Configuration Example (1) thru the
Internet (no WAN)
T1, T3, ISDN(point to point)
Internet ServiceAccess Points
IP Router w/Firewall and VPN
LAN Company A
LAN Company B
IP Router w/Firewall and VPN
Internet
T1, T3ISDN(point to point)
Most commercial routers have built in firewall
and VPN functions
IP Router w/Firewall and VPN
Intranet
Extranet
LAN Company A
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Network Configuration Example (2) thru WAN
Internet
T1, T3, or ISDN
WAN ServiceAccess Points
IP Router w/Firewall and VPN
LAN 1 Company A
LAN Company B
ATM, Frame Relay or other Router
WAN
Internet ServiceAccess Points
Router w/IP, ATM, Frame Relay, Firewall and VPN
support
Internet
T1, T3ISDN
WAN
Extranet
LAN 2 Company A
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Client-Server Architecture

• A key technological development in the 90s
• A form of distributed computing
• Most predominant computing architecture today
• Software application (i.e., processing) is split
  into tasks
• These tasks are distributed among computers
• Depending where it is more efficient to do the
  processing

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Clients and Servers

• Clients
• Request specialized services from servers, and
• Perform other tasks for users (e.g., screen
  displays)
• Servers
• Acknowledge service requests from clients, and
• Provide requested services (i.e., tasks,
  processes)
• Via responses to clients
• Servers and clients connect via networks
• Client and servers dont work in isolation, but
  they are designed to work together (i.e. there is
  no client without a server, there is no server
  without a client)

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Client-Server Computing (contd.)
Client
Client
Server
Network
Client
Server
Client
Server
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Examples of Servers

• A server can be hardware, software or both
• File Server ? central file storage, process file
  requests(ex. Novells NetWare, Windows NT)
• Database Server ? back-end DBMS functions (ex.
  MS SQL Server, Oracle Server, Lotus Notes Server)
• Web Server ? store and fetch web files on
  request(ex. Apache, Microsoft IIS)
• Print Server ? print job queuing for central
  printers
• Mail Server ? routes mail to users and other mail
  servers

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Examples of Clients

• A client can be hardware, software or both
• Networked PCs ? request files and other services
  from file servers (Windows 2000, XP)
• Database Clients ? request records from database
  server, process data locally, screen formatting,
  etc. (Lotus Notes client, MS Access)
• Web Browsers ? request web files from web
  servers, translate HTML code into formatted
  screen displays(Internet Explorer, Netscape)
• Mail Client ? Send/retrieve mail to/from mail
  servers, organize and display user mail(Outlook
  Express Lotus Notes mail client)

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Generic Client-Server ArchitectureThere are many
variants of this architecture as presented in
the next few slides
Client
Server
To format and display information to end users
Presentation Software
Request
Client ApplicationSoftware
Server ApplicationSoftware
Response
Client Communication Software
Server Communication Software
Client Operating System
Server Operating System
Client Hardware
Server Hardware
Network
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Example Client-Server Database Management
Systems (DBMS)
Client Workstation
Presentation Software
Database Application
Server
Request
Client Front-End DBMS
Server Back-End DBMS
Response
Client Communication Software
Server Communication Software
Databases
Client Operating System
Server Operating System
Hardware Platform
Hardware Platform
Network
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Ex. Web Client-Server
Client
Server
Web pages (HTML and other files)
Browser
Web Server
HTTP
HTTP
TCP/IP
TCP/IP
Client Communication Software
Server Communication Software
Client Operating System
Server Operating System
Hardware Platform
Hardware Platform
Network
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Ex. Web Client-Server Database Server
HTML Response
Server
HTML Form
Client
Web pages (HTML and other files)
Web Server
SQL Queries
Browser
DBMS Server
HTTP
HTTP
Databases
TCP/IP
TCP/IP
Client Communication Software
Server Communication Software
Client Operating System
Server Operating System
Hardware Platform
Hardware Platform
Network
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Ex. Thin Client or Fat Server model Most of
the processing is done by the server
Thin Client
Fat Server

• Example
• Web Server-Browser Applications
• The trend these days
• Easy to support and upgrade applications for
  distributed use

Presentation Software
Application Software
DBMS
Client Communication Software
Server Communication Software
Client Operating System
Server Operating System
Hardware Platform
Hardware Platform
Network
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Ex. Fat Client or Thin Server model Most of
the processing is done by the client
Thin Server
Fat Client

• Example
• File Servers (Novells NetWareyour G drive,
  Windows NT)

Presentation Software
Application Software
Server Communication Software
Client Communication Software
Server Operating System(incl. file management)
Client Operating System
Hardware Platform
Hardware Platform
Network
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Examples of Very Thin Servers Embeddable Web
Servers
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• Introduction to Wireless Communications and
  Networks

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Wireless Communications

• One of the fastest growing areas of IT
• There are many types of wireless technologies
  available these days. The only similarity is that
  they dont use wires. Otherwise they are all very
  different.
• Some key concepts to help you distinguish these
  technologies
• Line-of-sight when physical objects in between
  devices block communications (e.g. your TV remote
  control)
• Frequencies
• Lower frequencies longer distance, less
  line-of-sight required (e.g., radio waves, cell
  phone signals)
• Higher frequencies shorter distances,
  line-of-sight required (e.g., visible light,
  infrared)

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Wireless Technologies

• Examples
• Wireless Telephony
• Wireless Ethernet and WiFi
• Microwave Antennas
• Bluetooth
• Infrared
• Radio Frequency Identifiers (RFID)

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Wireless Telephony

• Mobile units communicate with ground antennas
• Ground antennas are connected with each other
  with ground wires
• And with the PSTN (public service telephone
  network), also known as POTS (plain old telephone
  systems)
• Your telephone signal travels from your mobile
  cell phone, to a ground antenna, to the regular
  telephone system

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Evolution of Wireless Telephony

• 1st. Generation (1G) Wireless analog service
• 2nd. Generation (2G) Wireless digital service
  (PCS in the US, GSM in Europe) ? compression
  (more channels), encryption and data transmission
  are enabled with digital communication
• 2.5 G provide packet switching services for more
  efficient transmission of data (e-mail, minimal
  web access, PDAs, etc.)
• 3G high speed multi-media transmission and
  better Internet access
• (see http//www.devx.com/wireless/Door/11259 for
  terminology)

62
Wireless Telephony Networks (Cellular)
1st Generation to analog2nd Generation to
digital 3rd Generation to IP net
To Landline Telephone Networks
Radio FrequencyChannels
Handover
MS
4,8,12
1,5,9
3,7,11
3,7,11
2,6,10
Radio FrequencyChannelReuse
1,5,9
4,8,12
BS Base Station MS Mobile Station MSC
Main Switching Center
Land Links
Radio Links
63
Wireless Ethernet WiFi

• Wireless Ethernet Wireless Fidelity (WiFi) are
  standards for wireless local area networks
• Standards 802.11a, b, g, etc. different
  speeds, frequencies, capacities and ranges (see
  http//www.devx.com/wireless/Door/11259 for
  terminology)
• Short range (up to 250 ft) communication between
  devices (note this is changing with new
  technologies like WiMax)
• Large office LANs have wireless transceivers
  (i.e., transmitters/receivers) attached to the
  wired network, so that wireless devices (e.g.,
  network cards on your laptops) can connect to the
  wired network over the airwaves
• Small LANs and home networks have a wireless
  router attached to the wired Internet service
  access (e.g., DSL, cable modem) with which all
  wireless devices communicate
• Wireless access points are called hot spots
• Great for mobility and when wiring buildings is
  difficult

64
Wireless LANs
Wireless
Transceiver
Wired Office LAN
Transceiver
Wired connection to DSL, Cable Modem or other
Internet Access Service
Wireless Router
Home Wireless LAN
65
Other Wireless Technologies

• Microwave Antennas
• Low frequency antennas to interconnect, for
  example, two nearby buildings (with roof
  microwave antennas) without wires
• Bluetooth (named for a Danish King)
• Wireless technology developed by a group of
  companies (IBM, Nokia, Intel, Lucent, etc.) to
  connect small devices wirelessly from short
  distances (30-50 ft)
• Ideal for wireless speakers, keyboards, printers
• Less line-of-sight required than infrared
• Infrared
• High frequency signals to send signals from one
  device to another at very short distances and
  line-of-sight
• Ex. TV remote controls, printer infrared ports

66
Other Wireless Technologies (contd)

• Radio Frequency Identifiers (RFIDs)
• Devices (small chips, tags, etc.) that contain
  small amounts of data that can be transmitted to
  an RFID sensor wirelessly
• The tags can be passive (RFID tag has no power,
  the reader reads the RFID) or active (the RFID
  tag has a power source and can beam its own
  signals to the sensor)
• The RFID readers are connected to networks that
  transmit the data (e.g., EZ Pass)

Submit RFID tag code, toll location and time
stamp to EZ Pass central system
RFID Sensor
EZ PassDatabasein remotecentrallocation
Beam signal
Bounce signal with RFID tag code
RFID Tag