A Level Key Terminology-Communications.pdf

Note: Terms written in red italic font are part of the FULL A Level specification only. Students undertaking the AS Level exams will not be expected to know these terms. Serial transmission “Serial communication is the method of transferring...

Note: Terms written in red italic font are part of the FULL A Level specification only. Students undertaking the AS Level exams will not be expected to know these terms. Serial transmission “Serial communication is the method of transferring one bit at a time through a medium.” Parallel transmission “Parallel communication is the method of transferring blocks of data at the same time.” Synchronous “Data transfer method characterised by a continuous stream of data in the form of signals accompanied by transmission regular timing signals. These signals are generated by an external clocking mechanism to ensure both the sender and receiver are synchronised with each other.” Asynchronous “The transmission of data in which each character is a self-contained unit with its own start and stop bits transmission and an uneven interval between them.” Start and stop bits “In asynchronous transmission, a start bit alerts the receiving computer of the arrival of a character. A stop bit (or sometimes two) signals the end of the character.” Baud rate “A number related to the speed of data transmission in a system. The rate indicates the number of electrical oscillations per second that occurs within a data transmission. The higher the baud rate, the more bits per second that are transferred.” Bit rate “The number of bits per second that can be transmitted along a digital network.” Bandwidth “A range of frequencies within a given band, particularly those used for transmitting a signal.” Latency “The delay before a transfer of data begins following an instruction for its transfer.” Protocol “A set of rules that allow two devices to communicate.” Physical star topology “A topology for a Local Area Network (LAN) in which all nodes are individually connected to a central connection point, like a hub or a switch. A star takes more cable than a bus, but the benefit is that if a cable fails, only one node will be brought down.” Logical bus network “A network physically wired in star topology can behave logically as a bus network by using a bus protocol topology and appropriate physical switching.” Peer-to-peer “A method of network organisation in which network stations can share resources on other network stations, so one station can use a printer on another station or save data on another station’s local storage.” Client-server “A method of network organisation in which network stations make use of resources available at one or more servers.” Wi-Fi “A facility that allows computers, smartphones or other devices to connect to the internet or communicate with one another wirelessly within a particular area.” CSMA/CA Carrier Sense Multiple Access with Collision Avoidance: “A network multiple access method in which carrier sensing is used, but nodes attempt to avoid collisions by transmitting only when the channel is sensed to be ‘idle’.” RTS/CTS Request to Send/Clear to Send: “An optional mechanism used by many wireless networking protocols to reduce frame collisions introduced by the hidden node problem.” SSID Service Set Identifier: “The name assigned to a Wi-Fi (wireless) network. All devices in the network must use this case-sensitive name to communicate over Wi-Fi, which is a text string up to 32 bytes long.”