Describe serial and parallel transmission
Definitions
Serial data transmission – bits are sent one after another along the same data line.
Parallel data transmission – several bits (e.g. 8 bits for one byte of data) are sent simultaneously along separate lines/channels.
Problems with parallel data transmission
Skew – each individual wire would have slightly different properties, meaning bits travel at slightly different speeds along each wire, meaning they arrive at slightly different times. This problem worsens the longer the wire, meaning that parallel cables are typically only used for short distances.
Crosstalk – electromagnetic interference can occur between adjacent lines, and the problem gets worse as the frequency/speed of transmission increases.
Parallel vs serial summary
Parallel transmission can only be used over very short distances. They are, for instance, used for connecting parts of a computer together. Parallel cables are fairly difficult and expensive to manufacture and are quite bulky due to the number of wires.
Serial transmission is very reliable at high frequencies over very long distances. Serial cables/connectors are small and cheap. USB, meaning universal serial bus, is a very widespread serial connector.