DATA COMMUNICATION

Data is "raw data" that had been processed, arranged, stored and used to get information.

Data Communication is a process of transferring information in a form of binary between to or more devices using electronic delivery system.
⇘
transmitted via mediums - fibre optics, wires, coaxial cables or radiated electromagnetic waves (radio, infrared light, microwaves)

2 types of signal - analog signal
                           = involves 2 parameters : frequency and amplitude
       
                           - digital signal
                           = 2 possible states : 0 and 1 (language of computer)
      
Process of changing
1. analogue-digital = modulation
2. digital-analogue = demodulation

Data transmission




                         

       

3 serial transmission modes

Synchronous and Asynchronous
       
Isochronous
- Data is sent at the same time as other related data to support certain types of real time applications
- e.g: streaming voice, video, music

Directions of Data Transmission

1. Simplex - 1 way communication
                  - role of transmitter and receiver fixed
                  - e.g: radio station

2. Half-duplex - 2 directions but not at the same time
                        - one station transmits information to other without interruption
                        - e.g: walkie-talkie

3. Full-duplex - moves in both directions at the same time
                       - both stations transmit and receive simultaneously
                       - e.g: telephone

Data Compression

• using fewer bits than original representation
• all images on web are compressed, typically in the JPEG or GIF format
• examples of file compression format - ARC and ZIP