Define symbol.
A particular pattern of bits represented by a signal.
Define Baud rate.
The number of signal changes in the medium per second(1Bd = 1 symbol change per second).
Define Bit rate.
The number of bits which are transmitted over a medium per second (bps).
State the formula used to calculate bit rate.
Bit rate = baud rate * bits per signal.
State the case where bit rate is equal to baud rate, greater than baud rate and less than baud rate.
Bit rate = baud rate * bits per signal
- Bit rate > baud rate if there is more than 1 bit sent per signal.
- Bit rate = baud rate if there is 1 bit sent per signal.
Define bandwidth.
The range of frequencies that a communication medium is capable of transmitting (Hz).
Describe the relationship between bandwidth and bitrate.
A higher bandwidth is directly proportional with an increase bit rate.However, there is not a causal relationship.
Define latency.
The difference in time (milliseconds) between an action (signal sent) being initiated and its effect being noticed (signal received).
Describe the relationship between latency and distance.
The greater the distance, the greater the latency.
Define protocol.
A set of rules defining methods of communication, agreed upon by manufacturers to enable seamless communication.
Define serial data transmission.
Data is sent one bit at a time over a single communication line.
Define parallel data transmission.
Multiples bits are sent simultaneously over many parallel wires.
Define skew.
Due to tiny differences in the electrical properties of parallel wires, during parallel transmission the time taken for each bit to transferred not be the same.
Define crosstalk.
Electrical interference between tightly packed adjacent wires causes signal data to change, which leads to corruption.
Describe the relationship between skew, crosstalk and distance in parallel transmission.
The greater the distance, data to be corrupted because...
- Over long distances different signals may overlap due to skew.
- Over long distances there is more opportunity for crosstalk.
State and Explain the type of transmission best suited for long distance communication.
Serial data transmission because...
- At long distances data is susceptible to corruption due to skew and crosstalk with parallel transmission.
- At long distances cabling is cheaper with serial transmission as many more wires are required at the same distance for parallel transmission.
Define synchronous transmission.
- A clock signal, which is share by both the sender and recipient, is used to time when signals are sent.
- This means data will be sent at regular intervals and received in the same order they were sent.
Define asynchronous transmission.
- No clock signal required.
- Replaced by stop and start bit system.
- Where sender and receiver must use the same baud rate for the duration of the transmission.
State the purpose of start and stop bits within asynchronous transmission.
Use to synchronise only for the period of transmission, so that the recipient systems will understand when a character ends and another begins.