istn 101

• Telecommunications


  The electronic transmission of signals for communications, by such means as telephone, radio, and television

  
• Telecommunications


  • It lessens the barriers of time and distance
  • As networks are connected with one another and transmit information more freely, a competitive marketplace demands excellent quality and service from all organizations
• General model of telecommunications


  1. Sending unit sends message signal to telecommunications device

  2. Telecommunications device processes signal

  3. Telecommunications device sends signal through medium

  4. Receiving telecommunications device receives signal

  5. Receiving unit can send another message to original sending unit
• Synchronous communication


  The receiver gets the message almost instantaneously, when it is sent. Examples are a phone call, and instant messaging services
• Asynchronous communication


  There is a measurable delay between the sending and receiving of the message, sometimes hours or even days. Examples are sending a letter through the post office and e-mail
• Both synchronous and asynchronous communications are important in business
• Types of Guided Transmission Media


  • Twisted-pair wire
  • Coaxial cable
  • Fiber-optic cable
  • Broadband over power lines

  
• Telecommunication media types


  • Twisted-pair wire
  • Coaxial cable
  • Fiber-optic cable
  • Broadband over power lines

  
• Microwave Transmission


  • Microwave is a high-frequency (300 MHz–300 GHz) signal sent through the air
  • Terrestrial (Earth-bound) microwaves are transmitted by line-of-sight devices, so that the line of sight between the transmitter and receiver must be unobstructed
  • Microwave signals can carry thousands of channels at the same time

  
• Satellite Transmission


  • A very small aperture terminal (VSAT) is a two-way satellite ground station with a dish antenna smaller than three meters in diameter
  • Many retail chains employ this technology to support point-of-sale transactions, including credit cards
• Generations of Wireless Communication


  • 1G (first generation) - analogue communications
  • 2G (second generation) - fully digital networks
  • 3G (third generation) - wireless communication supports voice and broadband data communications in a mobile environment at speeds of 2–4 Mbps
  • 4G (fourth generation) - delivers access speeds in the range 5–20 Mbps, ten times the speed of 3G
  • 5G (fifth generation) - enables a new kind of network that is designed to connect virtually everyone and everything together including machines, objects, and devices
• WiFi


  • A medium-range wireless telecommunications technology brand owned by the Wi-Fi Alliance
  • A wireless access point (WAP) receives the signal, decodes it and sends the information to the Internet over a wired connection
  • When receiving data, the wireless access point takes the information from the Internet, translates it into a radio signal and sends it to the device's wireless adapter
• Near Field Communication (NFC)


  • A very short range wireless connectivity technology designed for consumer electronics, smartphones and credit cards
  • Once two NFC-enabled devices are a few centimetres apart, they exchange communications parameters and passwords to enable Bluetooth or other wireless communications between the devices
  • Because only two devices participate, NFC establishes a peer-to-peer network
• Bluetooth


  • A wireless communications specification that describes how smartphones, computers, printers and other electronic devices can be interconnected over distances of a few meters at a rate of about 2 Mbps
  • One important application of Bluetooth is in hands free use of mobile phones when driving, using a Bluetooth headset to connect to a phone
• Ultra Wideband (UWB)


  • Involves the transmission of extremely short electromagnetic pulses lasting just 50 to 1000 picoseconds
  • Offers a high throughput rate, the ability to transmit virtually undetected and impervious to interception or jamming, and a lack of interference with current communications services
• Infrared Transmission


  • Sends signals through the air via light waves at a frequency of 300 GHz and above
  • Requires line-of-sight transmission and short distances – under a few hundred metres
  • Can be used to connect a display screen, a printer and a mouse to a computer, meaning there are no wires to clutter up the desk
• Telecommunications Hardware


  • Modems
  • Multiplexer
  • Front end processor
  • Private branch exchange
  • Switches, bridges, routers and gateways
• Modems

  • Converts (modulates and demodulates) communications signals so they can be transmitted over the communication media
  • Translates data from digital to analogue (modulation) and from analogue to digital (demodulation)
• Multiplexers


  Encodes data from two or more data sources onto a single communications channel, reducing the number of communications channels needed and therefore lowering telecommunications cost
• Front-end Processors


  • Special-purpose computers that manage communications to and from a computer system serving hundreds or even thousands of users
  • They poll user devices to see if they have messages to send and facilitate efficient, error-free communications
• Private Branch Exchange (PBX)


  • A telephone switching exchange that serves a single organization
  • Enables users to share a certain number of outside lines for making telephone calls
• Multiplexer


  A device that encodes data from two or more data sources onto a single communications channel, reducing the number of communications channels needed and lowering telecommunications cost
• Front-end processors


  • Special-purpose computers that manage communications to and from a computer system serving hundreds or even thousands of users
  • They poll user devices to see if they have messages to send and facilitate efficient, error-free communications
• Private branch exchange (PBX)


  • A telephone switching exchange that serves a single organization
  • It enables users to share a certain number of outside lines (trunk lines) to make telephone calls to people outside the organization
  • It enables the routing of calls between individuals within the organizations
• Switch


  • Uses the physical device address in each incoming message on the network to determine to which output port it should forward the message to reach another device on the same network
• Bridge


  • Connects one local area network (LAN) to another LAN that uses the same telecommunications protocol
• Router


  • Forwards data packets across two or more distinct networks towards their destinations through a process known as 'routing'
• Gateway


  • A network device that serves as an entrance to another network
• A computer network consists of communications media, devices, and software needed to connect two or more computer systems or devices
• Nodes can share data, information, and processing jobs
• Organizations can use networks to share hardware, programs, and databases
• Businesses are linking computers in networks to streamline work processes and allow employees to collaborate on projects and grow into an agile, powerful, and creative organization
• Networks enable geographically separated workgroups to share information, which fosters teamwork, innovative ideas, and new business strategies
• Network types


  • Personal Area Network (PAN)
  • Local Area Network (LAN)
  • Metropolitan Area Network (MAN)
  • Wide Area Network (WAN)
  • International networks
  • Mesh networking
• Personal area network (PAN)


  A wireless network that connects information technology devices within a range of ten metres or so
• Local area network (LAN)


  A network that connects computer systems and devices within a small area, such as an office, home or several floors in a building
• Metropolitan area network (MAN)


  A telecommunications network that connects users and their computers in a geographical area that spans a campus or city
• Wide area network (WAN)


  A telecommunications network that connects large geographic regions
• Mesh networking


  A way to route communications between network nodes (computers or other devices) by allowing for continuous connections and reconfiguration around blocked paths by 'hopping' from node to node until a connection can be established
• Partial Mesh Network