TELECOMMUNICATION AND NETWORK

• Telecommunication


  The hardware and software that transmits information from one location to another
• Computer network


  Two or more objects sharing resources and information<|>Computers, terminals, and servers interconnected by communication channels share data and program resources

  
• Network


  • Communication devices, media, and software needed to connect two or more computer systems

  
• Major geographic categories in Network

  • Local area networks (LANs)
  • Wide area networks (WANs)
• Local Area Network (LAN)

  A small area network with a series of cables or wireless access points that allow computers to share information and devices on the same network

  
• LANs


  • Connect computers and other devices enabling resource sharing
  • Variety of topologies can be used, each with performance strengths and weaknesses
  • Several LANs can be connected via bridges
  • LANs can be connected to external networks via gateways

  
• Alternative LAN Topologies


  • Star
  • Bus
  • Ring
  • Mesh
• LANs


  • Least expensive to install
  • Much faster than WANs due to their smaller size
  • Has the fastest communication technology due to less equipment and fewer resources needed to complete the network
  • PACS workstation in the radiology read room is considered as a LAN
• Wide Area Network (WAN)


  A network that spans a large geographic distance
• WANs


  • Service provided by common carriers
  • Internet is a public WAN
  • Value-added networks (VAN) - private, data-only networks managed by third party; accessed via subscription
  • Virtual private network (VPN) - secure gateway between corporate systems and the Internet
• Components of the Telecommunications System

  • Hardware
  • Media
  • Networks
  • Software
  • Data comm providers
  • Protocols
  • Applications

  
• Analog signals


  Continuous waves; Information conveyed by changing wave characteristics (amplitude and frequency)
• Digital signals


  Discrete pulses; Information conveyed in binary form (on or off pulses); Easily understood by computer
• Communication Processors


  • Modem
  • Multiplexor
  • Front-end processor
• Modem


  • Device that converts analogue signals to digital (and vice versa); enables signal transmission over the telephone system
• Wire-based Communication Channels


  • Twisted-pair wire (telephone wire)
  • Coaxial cable
  • Fiber-optic cable
• Twisted-pair wire


  • Cheap and easy to work with
  • Slow
  • Subject to interference
  • Low security
• Coaxial cable


  • Carries more data
  • Shielded from interference
  • More expensive
  • Harder to work with
  • Low security

  
• Fiber-optic cable


  • Transmit information as light waves through glass fiber
  • Fast
  • High-capacity
  • Secure
  • Not subject to interference
  • Hard to work with
• Wireless Communication Channels


  • Microwave
  • Satellite
  • Radio
  • Infrared
• Microwave


  • High capacity
  • Inexpensive relative to wire
  • Requires line-of-sight transmission towers
  • Subject to environmental interference
• Satellite


  • Very high capacity
  • Large coverage area
  • Expensive
  • Propagation delay
  • Requires encryption for security
• Radio


  • Suitable for short distance communication
  • Inexpensive
  • Easy to install
  • High speed
  • Interference problems; insecure
• Telecomm Carriers and Services


  • Common carriers
  • Value-added carriers
• Common carriers


  Long-distance phone companies
• Value-added carriers


  Provide private telecom systems and services for a fee
• Network Communication Software


  • Network Operating System
  • Network Management Software
  • Protocols
• Network Operating System


  Enables all devices on network to communicate
• Network Management Software


  Simplifies human network management tasks
• Protocols


  Specify rules that govern device communication over the network
• Types of Protocols


  • Ethernet
  • Transmission Control Protocol/Internet Protocol (TCP-IP)
• Ethernet


  • Most common protocol
  • May be 10BaseT (10 Mbps); Fast Ethernet 100BaseT (100Mbps); Gigabit Ethernet (1Gbps)
• Transmission Control Protocol/Internet Protocol (TCP-IP)


  Sends large files accurately over different systems<|>Standard of the Internet
• Network Processing Strategies


  • Distributed processing
  • Terminal-to-host processing
  • File server processing
  • Client/server architecture and processing
• Telecomm Applications


  • Electronic Mail
  • Videoconferencing
  • Electronic Data Interchange
  • Electronic Funds Transfer
  • Facsimiles
  • Telecommuting
  • Distance Learning
  • Telematics