Communication and Networking Flashcards
What is a symbol?
A symbol is a particular pattern of bits that are represented by a signal.
What is communication?
The transfer or exchange of information between two parties via a medium.
What is meant by the bit rate?
The number of bits that are transmitted over a medium per second.
What is the baud rate?
The number of signal changes that take place across a medium per second.
What is the bandwidth of a communication medium?
The frequency range available within a communication medium. The difference between the highest and lowest frequency. Measured in Hertz (Hz).
What is the bit rate dependent on?
1) Bandwidth (and therefore baud rate)
2) Bits per symbol
Bit rate = Baud rate x Bits per symbol
What is the relationship between bit rate and bandwidth? What is the relationship between bit rate and bits per symbol?
1) Directly proportional
2) Directly proportional
What is latency?
The time delay between a message being transmitted and received.
What is a protocol?
A protocol is a set of rules that falicitate interaction or exchange of information between communicating parties or devices. This occurs regardless of there being different manufacturers or different countries.
What is serial data transmission?
Data is sent over a single wire, one bit at a time.
What is parallel data transmission?
Data is sent across multiple wires, sending multiple bits simultaneously.
In what conditions should parallel data transmissions be used?
- Over very short distances
- e.g. buses within computers (data, address, control bus)
What are the main problems with parallel data transmission?
1) Data Skew
2) Crosstalk
3) Expensive price of cabling
What is data skew?
In parallel communication, each communication medium will have slightly different electrical properties. This causes slightly different times taken to transfer data. This causes a problem called skew which is worse over long distances. It leads to pulses overlapping and causes corruption.
What is crosstalk?
Parallel communication lines cause interference with each other when tightly packed. This causes data corruption.
How does synchronous data transmission work?
The sender and receiver use a shared clock signal to keep continually synchronised.
Signals are sent at regular intervals will be received in the same order in which they are sent.
Where is synchronous data transmission used?
Within the buses of a computer’s processor in the fetch-execute cycle.
Suitable for real-time systems.
How does asynchronous transmission differ from synchronous communication?
Sender and receiver are synchronised only for the duration of the transmission.
How does asynchronous transmission occur?
1) The channel is idle. The sender sends the start bit, which is the opposite of the idle bit, to alert the receiver that they are about to transmit data and so they must synchronise their clock.
2) They will then serially transmit data and possibly include a parity bit.
3) They finally transmit the stop bit which is the opposite of the start and idle bits to indicate that they no longer have to synchronise clocks.
What is required to be agreed before transmission for asynchronous?
Baud rate (frequency at which to read data from the channel)
What is overhead?
The number of additional bits transmitted beyond the data itself.
What is a computer network?
Computer networks are two or more computing devices connected together in order to exchange information and share resources.
What is a local area network?
Computer networks where multiple computers are connected together within a small geographic area.
What is a wide area network?
A network where multiple computers are connected together over a large geographic area.