Communication Methods Flashcards
What is Serial Data Transmission?
Data bits are sent in a sequence, one after the other, over a single line
What is Parallel Data transmission?
Several bits are sent at the same time over a set of parallel lines
What is a problem with Parallel Data transmission?
Only reliable over short distances, with lower bit rates.
Due to skew and crosstalk
What are the advantages of serial over parallel data transmission?
- Less crosstalk (electromagnetic interference between wires in proximity, resulting in corrupted data)
- No skew (when bits transmitted across parallel links travel at different speeds, data can fall out of sync and be read incorrectly)
What is the bit rate? (No it is NOT bandwidth) What unit is it measured in?
The number of bits transmitted over a channel each second, measured in bits per second (bps)
What is the baud rate? What unit is it measured in?
The number of times a signal (symbol) changes per second, measured in Bauds (Bd).
Each symbol can encode a certain number of bits
What is the relationship between bit rate and baud rate?
bit rate = baud rate x number of bits encoded per symbol
What is bandwidth? What unit is it measured in?
The maximum rate of data transfer of a communication channel.
What is latency?
The delay from the time that a signal is sent to the time that it is received
What is synchronous transmission?
Streams of bits are transferred over a communication channel at a constant rate. Transmitter and receiver are synchronised using a common clock signal
What is asynchronous transmission?
No clock signal, so start and stop bits are used to control the communication. Data is transmitted when it is available, not at specific intervals.
How are start and stop bits used in asynchronous transmission?
A start bit is sent at the beginning of the transmission so the receiver can prepare for incoming data, and the stop bit marks the end of transmission.
Stop bit must be opposite to the start bit so the receiver can recognise the next set of bits.
Why do you need both start and stop bits in asynchronous transmission?
If you only used one of them, the receiver would never know when one transmission ends and the next one begins
What is a parity bit?
A single bit added to the data to ensure the sum of the total bits is either even or odd - used for error checking
