COMMS 3_INTRO TO DATA COMMS

LESSON 1

telecommunication

means communication at a distance

telecommunication

includes

1. telephony

2. telegraphy

3. television

tele

Greek for “far”

DATA

information presented in whatever form is agreed upon by the parties creating and using the data

DATA COMMUNICATIONS

EXCHANGE OF DATA between two devices via some form of

TRANSMISSION MEDIUM such as a wire cable.

For data communications to occur,

communicating devices must be part of a communication system made up of a combination of

1. hardware (physical equipment) and

2. software (programs)

4 FUNDAMENTAL CHARACTERISTSICS OF EFFECTIVE COMMUNICATIONS SYSTEM

(D.A.T. J)

1. Delivery

2. Accuracy

3. Timeliness

4. Jitter

DELIVERY

• system must deliver data to the correct DESTINATION

• Data must be RECEIVED by the intended device or user

ACCURACY

• system must deliver the data ACCURATELY.

• Data should not be altered in transmission and left uncorrected.

TIMELINESS

• system must deliver data in a timely manner.

• Data should not be DELIVERED LATE

JITTER

• refers to the VARIATION in the PACKET ARRIVAL TIME.

• It is the UNEVEN DELAY in the DELIVERY of audio or video packets.

5 COMPONENTS OF DATA COMMUNICATIONS

(SRMMP)

1. Sender

2. Receiver

3. Message

4. Medium

5. Protocol

MESSAGE

• is the INFORMATION to be COMMUNICATED

• include

  • text

  • numbers

  • pictures

  • audio

  • video.

SENDER

device that sends the data message. It can be a computer, workstation, telephone handset, video camera, and so on.

RECEIVER

device that receives the message. It can be a computer,

workstation, telephone handset, television, and so on.

Transmission medium

• physical path by which a message travels from sender to receiver.

• examples: twisted-pair wire, coaxial cable, fiber-optic cable, and radio waves.

PROTOCOL

• set of rules that govern data communications.

• represents an AGREEMENT between the communicating devices.

• Without a protocol, two devices may be connected but not communicating,

DATA REPRESENTATION

1. Text

2. Numbers

3. Images

4. Audio

5. Video

Text

• sets of bit patterns have been designed to represent text symbols.

  • CODE- each set of bit pattern

  • CODING- process of representing symbols

UNICODE

• prevalent coding system

• uses 32 bits to represent a symbol or character used in any language in the world.

American Standard Code for Information Interchange (ASCII)

• first 127 characters in Unicode

• is also referred to as Basic Latin.

NUMBERS

• are also represented by bit patterns.

• the number is directly converted to a binary number to simplify mathematical operations.

IMAGES

• is composed of a matrix of pixels (picture elements), where each pixel is a small dot.

size of the pixel

• depends on the resolution.

• better resolution= more memory needed

several methods to represent color images.

1. RGB: red, green, and blue.

2. YCM: yellow, cyan, and magenta.

AUDIO

• recording or broadcasting of sound or music.

• It is continuous, not discrete.

VIDEO

• recording or broadcasting of a picture or movie.

• can either be produced as a continuous entity or a discrete entity, arranged to convey the idea of motion.

DATA FLOW

1. simplex

2. half-duplex

3. full-duplex.

Simplex

• communication is unidirectional, as on a one-way street

• Only one of the two devices on a link can transmit; the

other can only receive.

Half-Duplex

• each station can both transmit and receive, but not at the same time.

Full-Duplex

• both stations can transmit and receive simultaneously.