communication

• In serial data transmission, each bit is sent one after another along a single wire (one bit at a time)
• In parallel data transmission multiple bits are sent simultaneously over multiple wires
• What are the two types of data transmission?

  Serial and parallel
• Cons of parallel:

  cross talk

  data skew
• cross talk: when a signal in one wire causes interference with signals on neighboring wires meaning data can be corrupted
• Data skew: due to each wire being slightly different, the data can arrive in a random order due to travelling at different speeds which can cause problems
• Series vs parallel:

  In theory parallel is quicker

  However parallel is bad over long distances

  parallel is harder to set up therefore more expensive than series

  Therefore series is more commonly used
• In synchronous data transmission, both sender and receiver must be in sync meaning their clock speeds must be synchronised
• In asynchornous data, there is no common clock therefore a start and stop bit must be used
• A start bit indicates the beginning of a transmission which then synchronises the clocks and must differ from the stop bit
• A stop bit indicates the end of transmission and must differ from the start bit
• There are 4 different measures of performance:

  baud rate, bit rate, bandwidth and latency
• baud rate: the number of signal changes per second measured in hertz (Hz)
• bit rate: the number of bits that can be transferred per second
• bandwidth: the range of possible signals that can be transmitted, the bandwidth is directly proportional to the bitrate
• latency: The delay between sending and receiving
• Protocol: A set of rules or standard used by devices to communicate with each other