4.9.1 Communication Flashcards
What is the difference between parallel and serial transmission?
In serial transmission, bits are sent sequentially (one after the other) down the same wire (channel).
In parallel data transmission, multiple bits are sent simultaneously down different wires (channels) within the same cable.
What are the advantages of serial transmission over parallel transmission?
Serial transmission is better for long distance as there are no synchronisation issues.
When is a serial transmission used?
Transmission to another computer or to external devices
Medium to long distances
Universal Serial Bus (USB)
When is a parallel transmission used?
Fast transmission within a computer system
Short distances
Integrated Circuits (IC), Busses
What is asynchronous data transmission?
Data is transmitted in discrete packets (usually 1 byte)
Each packet of data is sent with control bits
The control bits allow the receiver to know when the data starts and ends
The control bits prevent the packets of data getting mixed up
Packets are sent intermittently (they have uneven time intervals between them)
Slower than synchronous
What is synchronous data transmission?
A continuous stream of data
The data is accompanied by timing signals (generated by an internal clock)
The clock ensures the sender and receiver are in step with each other
The receiver counts how many bits were sent over a period of time then reassembles them into bytes (multiple bytes sent at once)
Timings have to be accurate as there are no control bits
Faster than asynchronous
Examples of asynchronous data transmission
Emails, Forums, Letters
What is the purpose of the start and stop bits in asynchronous data transmission?
The start and stop bits are used to identify the beginning and end of the data transmission.
Define baud rate
Baud rate is a measurement of the number of signal changes in a second
Define bit rate
The number of bits being processed or transmitted every second
Can baud rate be higher than bit rate?
No, bit rate is usually higher than baud rate as multiple bits can be sent in each signal. If the baud rate is 1200 and 8 bits are being sent per signal then the bit rate is 9600
Define bandwidth
A measure of information or carrying capacity of a signal, expressed as the width of the spectrum of that signal in Hertz
Define latency
Latency is the amount of time a message takes to traverse a system
Define protocol
A protocol is a set of rules which computers use to allow them to communicate
What is the relationship between bit rate and bandwidth?
Bit rate is directly proportional to bandwidth
