Communication

Question 1

What does communication rely on?

Answer 1

Transmitting and receiving data in the form of electromagnetic signals

Question 2

What is synchronous transmission?

Answer 2

Streams of bits are transferred over a communication channel at a constant rate, the transmitter and the receiver are synchronised using a common clock signal

Question 3

What is asynchronous transmission?

Answer 3

There is no clock signal so additional data (start & stop bits) is used to control the communication. Data is transmitted when it’s available rather than at specific intervals. This means there’s periods of time when the transmission channel is idle

Question 4

What pair has to be opposite in asynchronous transmission?

Answer 4

The start and stop bit

Question 5

Why would the stop bit be longer than 1 bit?

Answer 5

To give the receiver time to reset

Question 6

What other type of transmission is synchronous transmission used with?

Answer 6

Parallel

Question 7

Explain serial transmission

Answer 7

Data bits are sent in a sequence, one after the other, over a single wire

Question 8

Explain parallel transmission

Answer 8

Several bits are sent at the same time over their own wire

Question 9

When is parallel transmission used?

Answer 9

Inside computers as it’s unreliable over long distances

Question 10

What is crosstalk?

Answer 10

Electromagnetic interference between wires that are in proximity (such as parallel links) results in transmitting corrupted data that will need to be resent

Question 11

What is Skew?

Answer 11

When the bits that are transmitted across parallel links travel at different speeds, this can result in data falling out of sync with the clock signal

Question 12

What type of transmission operates better at higher bit rates?

Answer 12

Serial

Question 13

Advantages of serial transmission

Answer 13

It’s not affected by skew and uses fewer wires in close proximity reducing the risk of crosstalk
As it uses fewer wires it’s also cheaper and takes up little space

Question 14

Define bit rate

Answer 14

The number of bits transmitted over a channel each second

Question 15

What are the units for bit rate?

Answer 15

Bits per second

Question 16

What does a high bit rate mean?

Answer 16

Data arrives faster

Question 17

Define baud rate

Answer 17

The number of times the signal changes per second/ The symbol rate of a channel

Question 18

What’s a symbol?

Answer 18

A set of bits that are transmitted with every signal change

Question 19

How many signal levels does baseband support?

Answer 19

2

Question 20

How does baseband transmission work?

Answer 20

Every signal change represents one bit ( 0 or 1) so one symbol encodes one bit and the bit rate is equal to the baud rate

Question 21

How does broadband transmission work?

Answer 21

It supports more than 2 signal levels ( multiple frequency bands/voltage levels) so every signal change can represent more than one bit (2,4 or 8 bits)
So every second the number of bits that’s transmitted equals signal changes/s multiplied by the no.bits encoded per signal change

Question 22

Bit rate formula

Answer 22

Baud rate * number of bits per signal change

Question 23

Baud rate formula

Answer 23

Bit rate / Number of bits per signal change

Question 24

Define bandwidth

Answer 24

The maximum rate of data transfer of a communication channel

Question 25

What’s the relationship between bandwidth & bit rate?

Answer 25

Directly proportional, the greater the amount of data that can be transmitted over a channel, the more bits transferred per second

Question 26

Define latency

Answer 26

The delay from the time the signal’s sent to the time it’s received

Question 27

Define protocol

Answer 27

A set of rules that determine communication between devices

Question 28

What details of communication do protocols dictate?

Answer 28

The type of transmission
The types of interfaces
The transmission channel
The speed of transmission
The error checking techniques
The format of the transmitted data