WEEK 2 : DATA COMMUNICATION

what is data communication ?😕😕😕

1. data communication is a process of changing information in a form of a digital data (binary) in between two or more devices using electronic delivery system.
2. it is transmitted via mediums such as wires, cables, and radiated electromagnetic waves such as broadcast radio, infrared light, microwaves and satellites.
3. for further explanation, open this link 👇

http://encyclopedia2.thefreedictionary.com/data+communications

TYPES OF SIGNAL 

• data comes in variety styles such as text, voice, pictures and video.
• all this type of information need to be converted into signal that can be understood by the communication media in order to transmit the data from one place to another location. 
• data comes in 2 types of formation : 

               - analogue signal

               - digital signal

ANALOGUE SIGNAL 

• it is like human's voice
• it is formed by continuously varying voltage level that create wave than be grasped by an analogue transmitter like microphone.
• transmit through PSTN line such as phone line.
• involves 2 parameters which are : FREQUENCY & AMPLITUDE 

FREQUENCY : number of completed wave's cycles. measured in Hertz(Hz) which is cycle per second.

AMPLITUDE : wave's height that measured in voltan (v) or decibel(dB). A strong signal will create higher amplitudes. 

DIGITAL SIGNAL

the process of changing :

1. analogue to digital - modulation
2. digital to analogue - demodulation

modem is the hardware that used to do this changing process 💞








DATA TRANSMISSION

• data need to be digitized before it can be transmitted through the electrical transmission medium.
• when we enter data into a computer via keyboard (alphabet or numeric), the data is encoded into an equivalent binary coded using standard coding scheme such as : Extended Binary Coded Decimal Interchange Code (EBCDIC) & American Standards Code for Information Interchange

figure : data transmission mode

1. PARALLEL TRANSMISSION 😅

    - data is sent at least one byte at a each time, each bit in the byte taking separate path.

    - means that a group of bit is transmitted simultaneously by using separated line for each bit.

2. SERIAL TRANSMISSION 😅

    - data sent one bit at a time, one after another a long a single path.

    - a bit slower compared to parallel transmission

    -used for short communication such as : computer & printer

3 serial transmission mode

synchronous transmission

asynchronous transmission 

isochronous transmission

for further explanation, click this link 👇👇

http://ecomputernotes.com/computernetworkingnotes/communication-networks/data-transmission

this video explains about parallel and serial data transmission 💙

meanwhile this video describes what exactly is Asynchronous 💚

DIRECTIONS/FLOW of DATA TRANSMISSION

1. Simplex 

    -one way communication 

     -role of transmitter and receiver are fixed

     -radio : transmits the signal to its listener and listener               never allows listener transmitting back.

    

2. half duplex 

    -flow in 2 directions but never at the same time

     -one station transmit information to another station                   without any interruption.

     -the other station will response after that transmission has       been completed.

     -example : walkie-talkie

3. full duplex

     -data can move in both direction at the same time

     -both station can transmit and receive simultaneously

     -consists of 2 simple channels ; 1 channel used to forward         while another as the reverse channel, linking at the same         point.

     -many networks and most internet connections are full             duplex 

     -example : telephone

what is data compression ??

~data compression encoding information using fewer bits than the original representations.

~example of file compression formats ,such as ARC & ZIP

~it is useful in communications because it enables devices to transmit or store the same amount of data in fewer bits. 

this figure illustrates the data compression process 💜

           

REFLECTION

overall, this topic clearly brief how the data are transmitted over the network. I also learned about the types of signals which have their own functions besides i can compare the differences between asynchronous and synchronous and serial and parallel transmission. next, i can also differentiate the flow of data transmission which are simplex, half duplex and full duplex.