Communication 4.9.1 Flashcards
What is a symbol?
A symbol is a particular pattern of bits represented by a signal.
What is the baud rate?
Number of signal changes in the medium per second.
• 1 baud is equal to 1 symbol change person second
What is a bit rate?
- A communication medium’s bit rate refers to the number of bits that are transmitted over the medium per second.
- This is often measured in bits per second.
How is the bit rate worked out?
A communication system’s bit rate is equal to the baud rate multiplied by the number of bits per signal in the communication medium.
What is the formula for the bit rate?
Bit rate = baud rate x no of bits per signal.
What is the correlation between the bit rate and baud rate?
A communication medium’s bit rate will be higher than its baud rate if there is more than one bit sent per signal
What is bandwidth?
- Expressed in Hertz, relates to the range of frequencies that a communication medium is capable of transmitting.
- There is a direct relationship between bandwidth and bit rate, higher bandwidth results in a higher bit rate.
What is latency?
The difference in time between an action being initiated and its and its effected being noticed.
How is latency affected by distance?
Latency usually increases with distance
What is a protocol?
A protocol is a set of rules relating to communication between devices.
What is the purpose of protocols?
Allow for devices made by different manufacturers in opposite ends of the world to communicate seamlessly
What are the two means of transmission between different components?
- Serial
* Parallel
What is serial data transmission?
Data is sent one bit at a time over one communication line, usually a metal wire, but could also be an optical fibre or a wireless channel.
What is serial data transmission used for?
Serial data transmission is frequently used for transmitting data over medium to long distances ( computationally speaking ) such as from wired peripherals to your computer
How does parallel data transmission work?
Parallel data transmission uses numerous parallel communication lines in order to send multiple bits between components in a computer simultaneously.
How does the number of lines a communication medium uses affect data transmission?
The more lines a parallel communication medium uses, the more data that can be transferred simultaneously.
What is the skew problem caused by?
Each of the communication lines that forms part of the parallel communication medium will have slightly different properties, meaning that the time taken for one bit to be transferred will differ slightly from line to line.
What is the skew problem?
Bits sent together may not be received together.
What is skew worsened by?
Long distances
What may skew lead to?
Bits from different pulses overlapping, causing corruption of data.
What is a disadvantage of parallel communication mediums?
They are more expensive than their serial counterparts because of their use of multiple lines.
Where is parallel communication used and why?
Parallel data transmission is most often used over short distances such as between prats of the processor and within RAM.
Parallel communication mediums are more expensive than their serial counterparts.
What is crosstalk?
When communication lines are tightly packed, signals from one can leak into another, causing data corruption.
What are the advantages of serial over parallel?
- Serial data transmission doesn’t suffer from skew or crosstalk, making it a more reliable communication method, especially over long distances.
- Serial communication mediums which use just one line are cheaper to install than parallel mediums which use more than one line.
What is synchronous transmission?
When data is transmitted using synchronous transmission, a clock signal ( which is shared by both the sender and the receiver ) is used to time when the signals are sent.
Where is synchronous data transmission used?
Within the busses of a computer’s processor in the fetch execute cycle.
Why is synchronous transmission suitable for transmitting information in real time systems?
Signals which are sent at regular intervals will be received in the same order that they were sent, this makes synchronous data transmission suitable for transmitting information in real time systems.
What is asynchronous transmission?
The requirement for a shared clock signal is done away with by using start and stop bits to indicate the duration of a transmission
• The start bit can be either a 0 or a 1, and the stop bit is always the opposite of the start bit
• The sender and receiver must use the same baud rate and need only synchronise their clocks for the duration of the data transmission.
