6.1. Communication Methods

Revision using Qwizdom

Data Communication - Revision

What is SERIAL data transmission:A. A method to exchange signals between

devices that communication with each other

B. One character is sent as soon as it becomes available

C. Bits are sent one at a time over a single wire from source to destination

D. Several bits are sent simultaneously down many wires at the same time

Give one advantage of serial over parallel transmission

A. Can be transmitted over a longer distance

B. Is suitable for short distances e.g. from PC to a local printer

C. Data can be skewed

Which form of data transmission method is this

A. ParallelB. SynchronousC. AsynchronousD. None of the above

D

Identify the start bitABCD

D

One character is sent and received using Asynchronous transmission without errors. Is this odd or even parity?

A. oddB. even

D

What is meant by baudrate?

A. The number of bits per signalB. The number of bits transmitted per

secondC. The range of frequencies on which a

medium can transmitD. The number of signal changes per

second

Parity is used to check

A. For a correct baud rateB. The accuracy of transmissionC. The length of transmitted dataD. That the stop bit is correct

True or False

Bit rate is often lower than the baud rate

True or False

Bandwidth refers to the range of frequencies that a medium can transmit

True or False

Using even parity, has this byte been corrupted during transmission?

01000010

A computer word contains the bit pattern

00010111 What is the decimal if it

represents a pure binary number

A. 43B. 17C. 23D. 18

A computer word contains the bit pattern

0001 0111What is the hexadecimal value of this binary pattern?

A. A3B. 17C. 23D. 1A

 

 

6.2. Network Environments

What is a local area network?

A. Computers connected within one building

B. Computers and peripherals connected over a specified small distance, in one building or one site

C. Computers connected within one cityD. Computers connected over a large

geographically remote area

Communications NetworksLocal Area Network (LAN) Collection of computers and peripherals

confined in one building or a cluster of buildings

They are connected together by a direct, common electrical connection

Wide Area Network (WAN) A network in which computers are

geographically remote. A LAN can be connected to other LANs or to a

WAN

WAN connections

Public switched telephone network High speed, high-bandwidth

dedicated leased lines High-speed fibre-optic cable Microwave transmission links Satellite links Radio waves The internet

Examples of WANs

Mobile phone network. Circuit switching for voice calls Packet switching for text messages

These are piggybacked onto packets that mobile phone continually send so that bas stations can locate them.

Each packet has 160 bytes of spare capacity

Wireless

Find out: What kind of signals used for wireless? What is WI-FI? What is WEP? What is WPA? What is Bluetooth?

Wireless Networking WAP (wireless access point) using Radio frequencies Allows data to be relayed between the wireless

devices and wired devices. WAN

WI-FI = standard / trademark WEP (Wired Equivalent Privacy) WPA (WI-FI Protected Access)

LAN Bluetooth – short distances (PAN – personal area

networks) 1 Mbps Data is chopped up and sent using up to 79

frequencies

Internetworking

LANs connected by a WAN so they can communicate

E.g. ARPANET internet

Advantages of Networks Allows sharing of resources

Disk storage, printers, image scanners, modems, central servers

Allows sharing of information held on disk drives accessible by all users

Easier to store application programs on one computer and make them available to all users.

Allows electronic mail to be sent between users

Easier to set up new users and equipment Allows connection to different types of

computer which can communicate with each other

Disadvantages Users become dependent on them If network stops access to various

hardware and software may not be possible Efficiency of network is very dependent on

the skill of system manager Difficult to make network secure against

hackers, novices, or industrial espionage As traffic increases on network,

performance degrades unless it is properly designed

What is a disadvantage of a network

A. Difficult to share resources softwareB. Difficult to make network secure

against hackersC. Difficult to set up new usersD. Difficult to connect to different types

of computers