A-level Computing/AQA/Paper 2/Fundamentals of communication and networking/Communication methods



Key definitions
Serial data transmission is when bits are sent one bit at a time over a single wire when transmitting data.

Parallel data transmission is when bits are sent concurrently over a number of parallel wires. This is specifically used in integrated circuits with RAM.

Synchronous transmission is where data is sent at regular intervals that are timed by a clock signal to allow for a more reliable transfer of data.

Asynchronous transmission is where data is sent one byte at a time with each character starting with a start bit and ending with a stop and parity bit.

Advantages of serial over parallel transmissions

 * There is a huge reduction in size and complexity, allowing the cost to be less.
 * The "crosstalk" between parallel lines creates corrupted data transmissions easily. As the signal frequency increases, the worse the communication link becomes.
 * Serial is more reliable over distances, as the "crosstalk" worsens over distances with parallel.
 * Signal frequencies have the potential to be higher due to lack of interference.

The importance of start and stop bits
By using a start and stop bit, the receiver is able to discern when the next set of data is sent and ends, allowing for only one byte of data to be sent at a time.

