ch1

• Communication system

  A system model that describes a communication exchange between two stations, transmitter, and receiver

  
• Signals/information


  Passes from source to destination through a channel, which represents a way that signal use it to move from source toward destination
• Data transmission process


  Refers to data communication, and deployed physical environment (hardware / software / protocols / channel ) is network
• Communication system provides


  • Electronic exchange of multimedia data
  • Voice
  • Data
  • Video
  • Music
  • Email
  • Web pages
• Components of data communication

  • Sender
  • Receiver
  • Message
  • Transmission Medium
  • Protocol

  
• Message (Resource)


  All sharable / accessible items over network, which may physical / virtual, knows as resource
• Sender

  A computer / device from which data / files are send to specific destination
• Receiver


  The device which receives the data messages/files/resources
• Transmission Medium


  • Physical channel like; network cable, fiber optic, electrical wire, twisted-pair wire
  • Logical or virtual channel like; wireless, radio frequency, Wi-Fi, Wi-Max, and Bluetooth

  
• Protocol


  Regulates the following characteristics of a network: access method, allowed physical topologies, types of cabling, and speed of data transfer. May include signaling, authentication, error detection method, and network policies
• Types of communication systems


  • Analog
  • Digital

  
• Analog technology

  Communicates data as electronic signals of varying frequency or amplitude

  
• Digital technology


  Generates and processes data in two states: High (represented as 1) and Low (represented as 0). Stores and transmits data in the form of 1s and 0s

  
• Wired (Line) communication systems

  • Parallel wire communication
  • Twisted wire communication
  • Coaxial cable communication
  • Optical fiber communication
• Wireless (Space) communication systems

  • Ground wave communication
  • Skywave communication
  • Space wave communication
  • Satellite communication

  
• Communication systems


  • Public Switched Telephone network
  • Television and radio
  • Cellular communication
  • Internet
• Wireless communications


  A type of data communication that is performed and delivered wirelessly. Incorporates all procedures and forms of connecting and communicating between two or more devices using a wireless signal through wireless communication technologies and devices

  
• Wireless communication


  A method of transmitting information from one point to other, without using any connection like wires, cables or any physical medium. Generally works through electromagnetic signals that are broadcast by an enabled device within the air, physical environment or atmosphere

  
• Benefits of wireless communication

  • Mobility
  • Flexibility and ease of use
  • High throughput performance
  • Easy and low-cost infrastructure setup
  • Viable option for emergency situations and remote locations
• Guglielmo Marconi invented the wireless telegraph


  1896
• Advances in wireless technology

  • Radio
  • Television
  • Mobile telephone
  • Communication satellites
• Mobile


  The ability to be on the move. A mobile device is anything that can be used on the move, ranging from laptops to mobile phones. As long as location is not fixed, it is considered mobile
• User mobility

  Users communicate anytime, anywhere, with anyone
• Device portability


  Devices can be connected anytime, anywhere to the network
• Wireless


  Transmission of voice and data over radio waves. Allows workers to communicate with enterprise data without requiring a physical connection to the network

  
• In most cases, wireless is a subset of mobile; but in many cases, an application can be mobile without being wireless
• For an application to be considered mobile or wireless, it must be tailored to the characteristics of the device that it runs on. Limited resources, low network bandwidth, and intermittent connectivity all factor into the proper design of these applications

  
• Wireless applications that are not mobile use fixed wireless networks. These are wireless networks that provide network access in a fixed environment
• There are mobile applications that are not wireless. Any application that can be used on the move and that does not have wireless connectivity fits into this category
• Wireless transmission


  Operates via transmission through space, other than through physical connections. Without the use of wires or electronic conductors, allows for information to be transmitted by using electromagnetic waves

  
• Types of wireless communication

  • Radio broadcast (RF)
  • Infrared (IR)
  • Satellite
  • Microwave
  • Bluetooth

  
• Issues in wireless communication

  • Communication channel often varies with time and frequency
  • Interference between multiple service users
• Electromagnetic spectrum

  The entire range of electromagnetic radiation according to the wavelength or frequencies. The differing behaviors of different groups in the electromagnetic spectrum make them suitable for a range of uses

  
• Broad groups of wireless transmission waves

  • Radio waves
  • Microwaves
  • Infrared waves

  
• Radio waves


  Electromagnetic waves ranging in frequencies between 3 kHz and 1 GHz. Transmitted by an antenna. Omnidirectional - propagated in all directions

  
• Characteristics of radio waves


  • Useful for multicast communications
  • Can travel long distances
  • Can penetrate walls

  
• Microwaves


  Electromagnetic waves having frequencies between 1 and 300 GHz. Transmitted in a straight line through the air. Unidirectional - can be narrowly focused

  
• Advantages of microwaves


  • Can penetrate haze, light rain and snow, clouds, and smoke
  • Sending and receiving antennas need to be aligned
• Radio waves

  • Good for long-distance broadcasting
  • Can penetrate walls

  
• Examples of multicasting using radio waves

  • AM and FM radio
  • Television
  • Maritime radio
  • Cordless phones
  • Paging