Section 6: Communication

Question 1

serial data transmission:

B___ are _____via an in_______ __ bit at a ____ over a s_____ wire.

Answer 1

serial data transmission:

Bits are sent via an interface one bit at a time over a single wire.

Question 2

why use serial transmission:

Hi___ data _______ rate can be ac______ , e.g. fiber-optic cable.

Answer 2

why use serial transmission:

High data transmission rate can be achieved, e.g. fiber-optic cable.

Question 3

parallel data transmission:

S______ bits are sent sim#________, over a number of pa______ wires.

Answer 3

parallel data transmission:

several bits are sent simultaneously, over a number of parallel wires.

Question 4

use of parallel data transmission:

This form of tra_______ is used in int________ ci_____, and within the ___.

Answer 4

use of parallel data transmission:

this form of transmission is used in integrated circuits, and within the RAM.

Question 5

What is Skew:
this is a problem were b___ are tra_______ through pa_____ wires, were e___ bit trav___ at di_____ speeds, due to the di______ pro______ of the material of the wire. therefore it is not sui____ for l____ distance trans______.

Answer 5

What is Skew:
this is a problem were bits are transmitted through parallel wires, were each bit travels at different speeds, due to the different properties of the material of the wire. therefore it is not suitable for long distance transmission.

Question 6

what is Crosstalk:

This is the in______ of the wi____ have on each o___, this may cause the da__ transmitted to be_____ corr_____.

Answer 6

what is Crosstalk:

This is the interference of the wires have on each other, this may cause the data transmitted to become corrupted.

Question 7

bit rate and baud rate:
bit rate - this is the sp____ at which data is tra____ measured in (bps).
baud rate - the number of signal changes in a communication medium per second measured in (Bd - baud).

Answer 7

bit rate and baud rate:
bit rate - this is the speed at which data is transmitted measured in (bps).
baud rate - the number of signal changes in a communication medium per second measured in (Bd - baud).

Question 8

What is bandwidth.

Answer 8

this is the range of frequencies that a transmission medium can carry, it is measured in (Mbps).
- the larger the bandwidth the greater the amount of data transmitted.

Question 9

what is Latency.

Answer 9

this is the time delay between the moment the first byte is of a packet is sent to when it is received at its destination. this can be seen on satellites links such a TV.

Question 10

what is Parity.

Answer 10

this is a method used y a computer to check the data received for any errors, computer use other an odd or even parity. this means that the total number of ‘1’ must always add up to an odd or even number. this parity bit is signed to the most significant bit.

Question 11

Synchronous transmission.

Answer 11

Data is transferred at regular intervals that are timed by a clocking signal.

• This allows for a constant and reliable transmission, for time sensitive data, such as real-time video or voice.
• Parallel communication typically uses synchronous transmission.

Question 12

Asynchronous transmission.

Answer 12

one byte at a time is sent, with each character preceded by a start and by a stop bit, the start bit alerts the receiving device and synchronises the clock inside the receiver ready to recite the character.
- he baud rate at the receiving end must be the same as the senders baud rate, so the signal ca be received correctly.

Question 13

Advantages of serial over parallel transmission:
1. lo____ ____ due to the sig____ red______ in the si__ and ~_________ of connectors.
2. Se____ links are more rel______ over much gre_____ distance than pa_____ links.
3. Because of the la___ of int_______ at high fre_______, signal fre_____ can be much hi_____
with se____ transmission.

Answer 13

Advantages of serial over parallel transmission:
1. lower cost due to the significant reduction in the size and complexity of connectors.
2. Serial links are more reliable over much greater distance than parallel links.
3. Because of the lack of interference at high frequencies, signal frequency can be much higher
with serial transmission.

Question 14

calculating bit rate.

Answer 14

Bit rate of channel = baud rate * number of bits per signal.
- each signal change represent a different bit patter.
- the larger the baud rate the larger the bit patter per signal.
Example:
baud rate = 4 (voltage change) – number of bits per single = 2.
bit rate = 4 * 2
= 8bps.

Question 15

What is a protocol.

Answer 15

A set of rules relating to communication between devices.

• used for equipment from different providers to be networked.
• this protocol covers; physical connection, cabling, mode of transmission, speed, data format and error checking and correction.

Question 16

Define Protocol?

Answer 16

A set of rules relating to communication between devices.

Question 17

Define a star topology.

Answer 17

a network where nodes(computers, devices) are all connected to a main switch or hub.

Question 18

physical topology.

Answer 18

this is the actual physical set up of a network, where the cables and nodes are connected in a star or bus topology.

Question 19

logical topology.

Answer 19

this is the shape of the path the data travels in.

- and describes how components communicate across the physical topology.

Question 20

Local Area Network.

Answer 20

• A LAN consists of a number of computing devices on a single site or building, connected together by cables.
• the network may consists of a number of Pc’s, other devices that can be shared between nodes like printers and scanners and a central server.
• LAN’s can transmit data very fast but only over short distances.

Question 21

define a bus Topology.

Answer 21

in this topology all the devises are connected to a single cable (backbone), the ends of the backbone are plugged to a terminator.
- Terminator uses so the signal send through the main cable don’t bounce back and cause any data collision.

Question 22

Advantages and Disadvantages of a bus topology.

Answer 22

Adv:
- Inexpensive to install, as it requires little cabling and no additional hardware.

Disadv:

• If the main cable fails the whole network goes down as no data can be transmitted between nodes.
• network performance decreases as more nodes are added to the network, this creates more data collision.
• low security - all computers on the network can see all data transmissions.

Question 23

Advantages and Disadvantages of a star topology.

Answer 23

Adv:

• if one cable fails then one one device is affected and can be fund quickly.
• consistent performance even with heavy traffic.
• higher transmission speed.
• no data collision.
• more secure as data is directly send to the recipient.

Disadv:

• may be costly to install due to length of the cable and extra hardware is used.
• if the main device goes down, then the whole network fails.

Question 24

define MAC address

Answer 24

• MAC address; Media Access Control address.
• a unique code hard-coded on the Network Interface Card (NIC).
• NIC; used for any device to connect to a network.