Data+Transmission

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= = = = = = = = = = =A short video about how data is transmitted via the Internet. = = = media type="youtube" key="qv0XCaUkfNk" height="405" width="500"

|| * Broadcast (radio & TV) ** || The way data is encoded in order for a network to transmit information from one computer to another * Also known as computer representation || || * Digital : information is encoded as a set of binary values || These allow data to circulate in the form of electromagnetic, electrical, light, or acoustic waves. * || A connection between 2 machines * || The elements that allow information to flow between transmission devices || * Direct link- Signal goes from transmitter to receiver with no intermediate devices || * Describes the computers within our schools
 * ** Types of Data Transmission **** Technologies **
 * Cable (TV & modems)
 * Recording (digital & video)
 * Wired telephony
 * Mobile communications systems (PCS, cellular, etc.)
 * Analog (telephone) networks
 * Digital (data) networks (ISDN, Ethernet, etc.)
 * Fiber optics
 * Satellite ||
 * **Data Transmission
 * **Types of Data** || * Audio
 * Text
 * Graphical
 * Video ||
 * **2 Categories of Data Representation**
 * Analogue : data will be represented by the variation in a continuous physical quantity ||
 * **Transmission Channels**
 * Simple (serial) - when there are only two machines communicating, or if only a single piece of data is sent.
 * Multiplexing (parallel) - when it is necessary to install several transmission lines or to share the line among several different communications. ||
 * **Transmission Channel**
 * transmitter - the machine that sends the data
 * receiver - the machine that receives the data ||
 * **Physical Media**
 * 3 Categories of Physical Media
 * Wire media allow an electrical quantity to circulate on a cable that is generally metallic
 * Aerial media refers to the air which allow the circulation of electromagnetic waves and various types of radio-electric waves
 * Optical media allow information to be sent in the form of light ||
 * **Media** || * Guided media - Waves are guided along a physical path; twisted pair, optical fiber, coaxial cable
 * Unguided media - Waves are not guided; air waves, radio ||
 * **Links**
 * Point-to-point link - Guided media with direct link between two devices
 * Multipoint guided configuration -More than two devices sharing the same medium ||
 * **Protocols and Handshaking** [[image:handshaking.png width="240" height="155"]] || * Protocol – the agreed-upon format for transmitting data between two devices
 * (ex. computer and printer)
 * Handshaking - the process by which two devices initiate communications - must occur before data transmission as it allows the protocol to be agreed ||
 * **Analog Transmission** || Uses signals that carry sound waves or pictures. These forms of information are then carried via either wires or wireless tools to receiving units. The signal strength varies based on frequency or amplitude. ||
 * **Digital Transmission** || Utilizes binary code to transmit data (1/0) ||
 * **Local Area Transmission**
 * Works well over short distances
 * Greater reliability
 * Ethernet cables are the main source of connection within school buildings ||
 * **Wide Area Transmission** || * Connected computers can be several miles away
 * The major problem is speed of transmission which decreases over distance
 * Fiber optic cable is most reliable and the preferred method of data delivery ||
 * **Types of Cable**

|| * Coaxial
 * Fiber optic ||
 * **Optical Fiber Cable**

|| * Light-weight || The peripherals determine the most effective device for the transfer of information - enables a smooth and efficient dissemination of information || (Universal Serial Bus)** || * has been the industry standard for 13 years || For wireless data transmission to occur you need three things * > The higher the frequency of the channel the more information it can transfer ||
 * Immune to noise
 * Low attenuation
 * Tolerates data rates on the order of 100 Mbps
 * Bandwidth from tens of megahertz to several gigahertz
 * Particularly suited to links between distributors (central link between several buildings, known as backbone ) as it allows connections over long distances.
 * Very secure as it is extremely difficult to tap in to such a cable.
 * Not suitable for local network connections ||
 * **Fire Wire**
 * **Hi-Speed USB 2.0
 * serves as one of the most vital data transmission device
 * offers internal power options
 * transmits data at 480 Mbps ||
 * **Uploads** || Data transfer from your computer to the server ||
 * **Downloads** || Data transfer from the server to your computer ||
 * **Wireless Data Transmission**
 * A transmitter
 * A receiver
 * A wireless channel
 * **Bluetooth**

|| * Range is up to 10 feet and in some cases reach up to 100 meters || * Wireless fidelity
 * Small Bluetooth chip inserted into the device along with software to run it
 * Invented in 1994 by engineers at Ericsson
 * In 1998 a group of companies joined forces to add it into their technology so no company ‘owns’ the rights to it
 * Meant to be a collaborative tool between various types of technology ||
 * **Wi-Fi**
 * Small Hotspots
 * Accessible with a router
 * Transmit at frequencies of 2.4 GHz or 5 GHz
 * WiFi radios can transmit on any of three frequency bands
 * They can also hop between the frequencies so that more devices can be in the network ||
 * **Types of Wifi Networks** || * Open - Open for anyone to use. Anyone can connect.
 * WEP - Wired Equivalent Privacy - Can be accessed with a password
 * WPA Wi-Fi Protected Access - Uses TKIP - Provides more security
 * WPA2 Wi-Fi Protected Access 2 - Uses a pre-shared key -Most secure ||
 * **WiMAX** [[image:wimax.jpg width="298" height="195"]] || * Worldwide Interoperability for Microwave Access
 * Range - 30-mile (50-km) radius from base station
 * Speed - 70 megabits per second
 * Line-of-sight not needed between user and base station
 * Frequency bands - 2 to 11 GHz and 10 to 66 GHz (licensed and unlicensed bands) ||
 * **Satellite** || * receive (download) at a speed of about 1 Mbps
 * send (upload) at a speed of about 200 kbps.
 * Cell Phone 3G and 4G Services
 * Slower than Broadband but accessible anywhere there is cell phone service ||