Comm Methods

• Serial communication: data is sent one bit after another along the same line.
• Parallel communication: Several bits are sent at the same time along multiple wires
• Advantages of using serial:

  • Smaller
  • Cheaper
• Advantages of parallel:

  • Faster
• Problems with skew are caused by the cables having slightly different properties.

  This means that the time taken for one bit to be transferred will differ slightly between cables.

  This results in the bits being received at slightly different times.
• Skew is worsened when increasing cable length.
• When the communication lines are tightly packed, signals from one line can corrupt data in other lines because of electromagnetic forces.
• When data is transmitted using synchronous transmission, a clock is used to time when signals are sent.
• Synchronous transmission means that data is sent at regular intervals and received in the same order that they were sent.
• In asynchronous transmission, there is no clock, instead start and stop bits are used to indicate the length of transmission. (example of parity bits)

  The start bit can be either a 0 or a 1 and the stop bit is always the opposite of the start bit.
• A symbol is a particular pattern of bits represented by a signal
• Baud rate is the number of signal changes per second
• Bit rate is the number of bits transferred per second
• Bit rate = baud rate x num of bits per signal
• Bandwidth is the range of frequencies that can be transmitted. This has a direct relationship with bit rate
• Latency is the difference in time between an action and its result being registered.
• Protocol is a set of rules or instructions relating to communication between devices.