Laudon

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Laudon Laudon, Chapter 8Telecommunications
Networks
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Agenda

• Basic Definitions
• Basic Types of Signals
• Technology Overview
• Basic Network Types
• Wireless Communication
• Applications

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MIS in Action Page 264

• Dial-up 56 Kbps 40 per month for
  internet 35 phone line
  per month
• ISDN 128 Kbps 100 per month 300
  install
• Cable Modem 1-2 Mbps 75 per month
  125 install
• DSL 1.5 Mbps (512 Kbps) 100 for modem
  175 per month
• T1 line 1.5 Mbps 1200 per month

7.5 Mbps
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Cable Modem
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DSL
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Telecommunications

• Communication by electronic means
• Can be text, graphic images, voice, or video
• Functions
• establishes interface between sender and receiver
• converts messages
• directs traffic along most efficient path
• transmits information
• performs error checking and reformatting

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Types of Signals

• Analog
• continuous sine wave over a certain frequency
  range Example
• positive voltage 1
• negative voltage 0
• Carrier Wave Sample
• Digital
• discrete burst of electric energy
• on 1
• off 0
• Most phone line use analog signaling (why??)

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Converting Signals

• Computers can only process digital signals
• If data is transmitted using analog signaling,
  it must be converted into a digital signal before
  the computer can process it

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Modems

• MOdulation - converting digital signals into
  analog form
• DEModulation - converting analog signals back
  into digital form

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Telecommunication Components

• interconnected hardware and software components
• computers to process the data
• telecommunications processors
• telecommunications software
• channels to transmit the data

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Communications Processors

• Front end processor
• dedicated to communications management
• error checking, editing, controlling, routing,
  signal conversion
• Multiplexer
• device which enables a single communications
  channel to carry data from multiple sources
  simultaneously. Sample T-1
• Concentrator
• temporary storage buffer
• Controller
• supervises traffic between CPU and peripherals

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Channels for Transmitting the Data (Land)

• twisted wire
• coaxial cable
• fiber optics

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Channels for Transmitting the Data (Wireless)

• Microwave
• Satellites
• Pagers
• Mobile phones
• Sky phones
• PCS (personal communications services)
• PDA (personal data assistant)
• Mobile data networks

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Telecommunications Software

• network control
• access control
• transmission control
• error detection/correction
• Metrics needed
• security
• ISP e.g, AOL flat rate surcharge

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http//www.gvu.gatech.edu/user_surveys/
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Protocol

• common set of rules that allow different
  components in a network to talk to each other
• handshaking protocol
• identify each device
• secure attention of other device
• transmission protocol
• verify correct receipt of message
• send re-transmit message if necessary
• recover error and re-transmit

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Measuring Transmission

• Transmission speed
• measured in bits per second (BPS)
• Faster units purchases ? more cost
• Transmission capacity
• function of the frequency (cycles per second)
• bandwidth the range of frequencies that can be
  accommodated on that channel

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Networks

• Other side of the transmission
• NETWORKS
• Networks can by classified by topology
• What is the configuration?
• Can be classified by geography
• What area does it cover
• Can be classified by services offered

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Network Topology

• Star
• central host is connected to several other
  computers
• all communications must pass through the host

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Network Topology

• Bus
• computers are linked by a single loop circuit
• all messages transmitted over entire network
• data pass in either direction

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Network Topology

• Token Ring
• number of computers are linked by a closed loop
• data passes in a single direction

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Geography

• PBX (private branch exchange)
• originally for voice, now can do data
• Limited distance
• Uses regular phone lines for voice and data
• LAN (local area network)
• limited distance, wireless or hardwired
• Data only, uses cables
• totally controlled by end-users
• WAN (wide area network)
• broad geographic distance, uses public switched
  network, end-user responsible for software,
  hardware

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Network Services

• VAN (value added network)
• not over public switched network
• provider manages network and equipment
• Integrated Services Digital Network (ISDN)
• Digital Subscriber Line (DSL)
• Cable Modems
• T1 line dedicated phone line