Section 6 Chapter 31 - Communication Methods

Question 1

Where data communication is used

Answer 1

Between computers

Between computer components

Question 2

Serial Transmission

Answer 2

Bits are sent one at time over a single wire (or other communication media)

Question 3

Parallel Transmission

Answer 3

Several bits are sent simultaneously over a number of wires

Question 4

Skew

Answer 4

When bits travel at different speeds along parallel wires

Question 5

Crosstalk

Answer 5

Interference between parallel wires

Question 6

Where serial is used vs parallel

Answer 6

Serial used for long distance, parallel for short (e.g. in computer components)

Question 7

Advantages of serial over parallel (4)

Answer 7

• Cheaper due to lower size and complexity
• Crosstalk
• Reliable over longer distances
• Can use higher frequencies due to no inteference

Question 8

Bit rate

Answer 8

The rate at which data is serially transmitted

Question 9

Baud rate

Answer 9

The rate at which the signal changes

Question 10

Baseband

Answer 10

When only one bit is encoded per signal

baud rate = bit rate

Question 11

Bandwidth

Answer 11

The amount of data that can be transmitted in a fixed amount of time (essentially the maximum bit rate)

Question 12

Latency

Answer 12

The time delay between when a packet of communication is sent and when it is recieved

Question 13

Parity bit

Answer 13

A bit that is set to 1 or 0 to make the total number of 1s and 0s either even or odd. Used to check if data has been correctly transmitted

Question 14

Synchronous transmission

Answer 14

Data is transferred at regular intervals

Question 15

Where synchronous transmission is commonly used

Answer 15

With parallel communication, a cpu clock is an example of synchronising transmission

Question 16

Asynchronous transmission

Answer 16

One byte is sent at a time, with each byte encased with a stop and start bit

Question 17

Property of the stop and start bits of asynchronous transmission

Answer 17

They are always opposite, either start=1 and stop=0 or start=0 and stop=1

Question 18

Protocol

Answer 18

A set of rules relating to communication between devices which specifies how they should communicate and allows them to exchange details such as data format, speed, mode of transmission

Question 19

When does crosstalk get more pronounced

Answer 19

Higher frequencies

Question 20

Maximum length of parallel transmission

Answer 20

Around 2m

Question 21

Makeup of an asynchronously sent packet

Answer 21

stop-parity-data(7)-start

Question 22

Where asynchronous transmission is commonly used

Answer 22

Low speed connections such as a keyboard and mouse

Question 23

Things that a protocol needs to define (5)

Answer 23

• Standards for physical connections
• Rate of transmission
• Data format
• Synchronous or asynchronous
• Error checking procedures

Question 24

Broadband

Answer 24

More than one bit encoded onto each signal

Question 25

Purpose of the start and the stop bit

Answer 25

Start bit alerts the receiver and synchronises the clock inside the receiver so it is ready to receive the packet.
Stop bit tells the receiver that it has received the whole packet

Question 26

How bit rate is related to baud rate

Answer 26

Bit rate = Baud rate * bits per signal