Telecommunications is the movement of information between two devices over a distance

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Chapter 6Information Technology in
BusinessTelecommunications and Networks

• Telecommunications is the movement of information
  between two devices over a distance
• Information includes data, audio, video, graphics
• Networks are collections of devices (nodes) that
  can engage in telecommunications

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1. Four Basic Improvements Telecommunications
brought to Business

• Telecommunications has improved business in four
  main ways
• Better communication
• Higher efficiency
• Better distribution of data
• Instant transactions
• Modern business could not be conducted without
  telecommunications

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2. Home Networks

• Connecting to the Internet from home
• Dialup connection with a modem
• Digital Subscriber Line (DSL)
• Cable connection from a cable TV company
• Satellite connection
• Fixed wireless
• The middle three connections are referred to as
  broadband connections because of their high speed
  and ability to carry multiple channels
  simultaneously (e.g., voice and data)

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Dialup Modem Connection

• Requires a telephone modem, network software, and
  Internet service provider (ISP)
• Uses the phone line to connect to the Internet
• Ties up the phone line while on the Internet no
  incoming or outgoing calls
• Slowest type of connection (56 KBPS)

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DSL Connection

• Requires a DSL modem, network software, and
  within a specified distance from a phone company
  installation
• Often the phone company is the ISP (BellSouth)
• Internet access is through the telephone line
• Information traveling over the phone line can be
  split so that voice communication is not
  disrupted (you dont need a separate phone line
  for your Internet connection)
• Speeds range from 128 KBPS 1500 KBPS
• Line is not shared (security) and always on
• Various forms of DSL

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Cable Connection

• Requires a cable modem, software, and access to
  cable TV provider
• Receive information from the cable connection
  send information via phone line Newer systems
  use cable for both directions
• Cable modem separates TV signals from Internet
  data
• Speeds are comparable to DSL speeds
• Always-on connection
• Not private since information is shared over the
  cable connection into your neighborhood
  transmission speeds diminish with many users

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Satellite Connection

• Requires a satellite modem, software, satellite
  dish, and satellite provider
• Receive information from the satellite
  connection, sends information via phone line
  Newer systems use satellite for both directions
• Receiving speeds 200 KBPS-400 KBPS
• Same company that offers DirectTV offers DirectPC

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Fixed Wireless

• Alternative where cable or DSL is not available
• Customer must install a microwave transceiver on
  roof (no wiring required)
• Repeaters (from the telecom provider) pick up
  signals and transmit them to a base station
• Transmission rates range from 2 Mbps to 100 Mbps
• Growing market

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3. Business Networks

• Why network? Sharing
• Hardware, software, and files
• Communication and collaboration applications
• Client/Server networks are networks in which one
  or more computers are servers and provide
  services to other computers called clients.
• Servers are usually powerful computers with large
  storage systems (high end PC or minicomputer)
• Clients are usually PCs or laptops
• Print servers, file servers, Web servers

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Client-Server Applications

• Client-server networks are examples of
  distributed processing because the processing for
  a given application is split between the server
  and client
• Types of processing in an application
• Processing for presentation of information (user
  interface)
• Processing of logic or business rules
  (calculations)
• Processing related to data management (storing
  and retrieving data)
• Several ways that this processing is split

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4. Telecommunications Systems Components

• Computers to process information
• Terminals that send or receive data
• Communications channels that carry the data
  between the devices in the network (channels use
  different media)
• Communications processors that perform specific
  tasks in the transmission process
• Communications software which controls input and
  output activities and other functions

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(1) Computers and Channels

• Channels are the links over which data are
  transmitted from one node to another
• Data moves through the channel in the form of
  electromagnetic signals or pulses of light
• Computer signals are digital
• Parts of the telephone network require analog
  signals
• Conversion of the signals (modems)
• Media that provide channels
• wire
• wireless (electromagnetic spectrum)

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(2) Mediums for Channels

• Wire mediums
• twisted pair
• coaxial cable
• fiber optic (each strand carries one signal)
• Next generation optical networks (multiple data
  streams over a single strand)
• Wireless transmissions
• terrestrial microwave
• satellite microwave (GEO)
• low-orbit satellites (LEO)

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Characteristics of Communication Channels

• Transmission speed through a medium is measured
  in bits per second (BPS)
• The frequency of a signal is the number of times
  a signal makes a complete cycle in a given time
  period. If the time period is one second, then
  the frequency is measured in Hertz (Hz).
• The greater the frequency of a signal the higher
  the transmission speed. Conversely high
  transmission speeds require higher frequencies.

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Channels and Media
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Bandwidth and Media
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Transmission Speed
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Sample Calculations

• Suppose you wanted to download the movie Jurassic
  Park. In compressed form it would contain about
  4109 bytes or 32109 bits. If you had a
  typical 28.8 Kbps modem, how long would it take
  to download the movie?
• Answer 32109 bits/ 28.8103 bits/sec
• 1.11106 sec or
• 1.11106 sec/3.6 103 sec/hour
• 926 hours or
• 926 hours/ 24 hours/day
• 12.86 days

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(3) Components Special Communication Processors

• Front-end processor - a special computer that
  manages the communications tasks for the host
• Controller - a device that supervises
  communications between the CPU and other
  peripheral devices (terminals and printers) in a
  network
• Multiplexor - a device that enables a single
  communications channel to carry data signals from
  multiple sources simultaneously
• All of these devices can be considered special
  purpose computers

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Location of a Multiplexor
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Other Networking Hardware

• Network Interface Card - a circuit board required
  by any device that will connect to a network
  (wired or wireless)
• Hub device used to connect several devices to a
  network
• Switch a more intelligent hub
• Bridge a device for connecting two dissimilar
  networks (a LAN to the Internet)
• Router a more intelligent bridge

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(4) Components Communications Software

• Special software is required for
  telecommunications it resides in the host,
  front-end processor, or other special processors
• Communications software for the PC at home
• Systems software (for networks)
• network operating systems (NOS)
• security software
• Network management software
• Application software for networks
• Email software
• Client/server applications (FrontPage)

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5. Types of Networks (Topology)

• Star -central host, all communication must pass
  through the host
• Ring - all computers are linked by a closed loop
  data passes from one node to the next in one
  direction no central host
• Bus - a single circuit links a number of devices
  data is broadcast to the entire network if one
  machine fails none of the other machines are
  effected
• Tree consists of several stars connected to
  form a tree

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Network Topology
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Types of Network (Geographic Scope)

• Local networks
• PBX
• LANs
• Large networks
• WANs
• VANs

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Local Networks PBX

• A PBX (Private Branch Exchange) is special
  purpose computer designed to do the switching for
  a firms internal phone network
• Modern PBX can carry both voice and data
• Advantages - no special wiring, expandable,
  vendor support
• Disadvantages - limited geographic scope, cannot
  handle high volumes of data (e.g., video)

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Local Networks LANs

• Local area network - a network that requires its
  own cabling and encompasses a limited distance
  (one or two buildings) nodes are usually PCs
  and peripherals
• Advantages
• handle high volumes of data
• sharing of hardware, software, files, and data
• unique application (email, video conferencing,
  on-line applications)
• Disadvantages
• expandability
• vendor support or internal expertise

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Large Networks WAN

• Wide area networks nodes
• Corporations can build their own or using
  communications service providers
• Switched and dedicated lines
• Individual firm assumes significant role in
  telecommunications management

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Large Networks VANs

• Value-added networks are private data-only
  networks that provide economies in service cost
  and network management because they are used by
  many firms
• Value-added means that customers do not have to
  invest in network equipment and management
• Disadvantage
• loss of control/expertise
• Security
• General Electric is a company that provides a VAN
• An example of a Web based EDI product

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Virtual Private Network

• A combination of private and public lines offered
  by a telecom provider to allow customers,
  employees, and suppliers to access a firms
  private network (intranet) via the Internet. Use
  of a VPN creates an extranet.
• The link between the private network and the
  Internet is often referred to as a tunnel
• Virtual refers to the illusion that the use is
  accessing a private network directly.
• Heavily used in supply chain management

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6. Protocols

• Protocols are rules and procedures (virtually
  languages) that govern the transmissions between
  components (devices) in a single network or
  between two networks
• Important protocols
• TCP/IP (Internet protocols)
• HTTP (Internet protocol)
• Ethernet (LAN protocol)
• Token passing (LAN protocol)
• ANSI X12 and EDIFACT (EDI protocols)
• Open systems interconnection or OSI (WAN protocol)

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7. Characteristics of Telecommunication Signals
and Network Capabilities

• Serial versus parallel
• Directions of signals (simplex, half-duplex, full
  duplex)
• Types of signals (analog versus digital)
• Timing of signal transmissions (asynchronous
  versus synchronous)
• Switching techniques (circuit and packet
  switching)

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Serial Versus Parallel Transmissions

• In serial transmissions one bit is transmitted
  after another in a stream of bits over a single
  line
• On PCs modems and mice use serial transmission
• Serial ports
• In parallel transmissions more than one bit is
  transmitted simultaneously (usually an entire
  byte is transmitted along a bundle of parallel
  lines)
• On PCs information sent to your printer employs
  parallel transmissions
• Parallel ports

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Data Communications (Cont.)
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Three Modes of Communication Between Devices

• Simplex
• One-way in one direction
• Radio and television
• Half-Duplex
• One-way in two directions
• Walkie-Talkie, CB radio
• Older connections between terminals and computers
• Full-Duplex
• Both device can transmit and receive
  simultaneously
• Telephones
• Communication between modern computers

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Analog vs. Digital Signals

• Analog signals
• A continuous series of waves
• Like a sine curve
• Digital signals
• A series of discrete bits
• Modulation is the transformation of digital
  signal to an analog signal
• Demodulation is the transformation of an analog
  signal to a digital signal
• Role of a modem

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Timing of Communication Between Devices

• In asynchronous communication data is transmitted
  in a serial manner without concern of a special
  timing aid (clock). Most communication between
  computers and devices is asynchronous -- it can
  occur at any time and at irregular intervals.
• Overhead bits start, stop, and parity bits
• In synchronous communication, transmissions
  between devices are governed by a timing device.
  Large blocks of bits can be transmitted at
  regular time intervals. Communications within
  the CPU and memory are usually synchronous.
• Much lower overhead but requires expensive timing
  devices

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Communication Modes
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8. Switching Techniques

• Circuit switching sets up a dedicated path
  between two points in a network. For the
  duration of the communication no other
  transmissions may use this circuit and all
  transmissions follow the dedicated path.
• The telephone system links together media
  segments to create a single unbroken line for
  each telephone call.
• Not very efficient for large volumes of data
• In packet switching all data are packaged into
  fixed-sized packets that make their way to the
  destination over many different paths.
• The Internet uses packet switching
• Very efficient for sending large amounts of data
• New Internet protocols will make the Internet
  viable for telephone calls

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9. Wireless Technologies

• Wireless technologies are of interest to business
  because they eliminate the need for expensive
  cables and enable mobility
• Wireless standards (or Wi-Fi) apply to mobile
  devices (laptops, PDA, cell phones)
• Family of standards IEEE 802.11 (the 11 stands
  for the max bit rate supported, 11 Mpbs)
• Most popular is 802.11b which operates in the
  2.4-2.5 GHz range
• Enables spread spectrum communication (the
  transmitting device transmits over several
  frequencies so that if one degrades you can
  switch to another
• Transmission range is about 300 ft (distance is
  likely to increase)
• To make a device wireless requires that the
  device contain a wireless card

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Wireless Networks

• In order to communicate with a network using a
  wireless device, you must be close enough to an
  access point (AP). The access point is a device
  that is connected to a wired network.
• If a household has a wired connection to the
  Internet (cable or DSL) then wireless devices can
  access the Internet by acquiring a wireless
  router (an AP) that is connected to your cable or
  DSL modem. This enables all your wireless
  devices to link to the Internet.
• Public access points are often called hotspots.
  Winthrop has several hotspots on campus
• Cell phones with dual circuitry

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Other Wireless Issues

• Wi-Fi networks are much cheaper to install than
  stationary LANS
• Wi-Fi networks can be extended by adding
  additional access points
• Wi-Fi networks are susceptible to interference
  from other devices
• Bluetooth is another wireless networking standard
  for creating small private networks
• The Wi-Fi standard (802.11b) is easily penetrated
  by outsiders with appropriate hardware and
  software