Introduction_to_Digital_Communication___

Pengenalan sistem komunikasi digital

1. Introduction to Digital Communication System Pradini Puspitaningayu

2. Elements of a Digital Communication System Input transducer (source) Source encoder Channel encoder Digital modulator Channel Digital demodulator Channel encoder Source encoder Output transducer (destination)

3. The Proccess Source Provide information to be transfered Could be analog / digital Source Encoder Convert data into desirable format (ex. c onvert analog data to digital) Channel Encoder Adding redundancy to the original bits of data to overcome noise and interference Digital Modulator Modulate digital signals into analog carriers to be able to transfer in form of electrical signals (waveforms).

4. The Proccess -cont Channel Physical medium that is used to send the signal (could be guided or unguided) Signal transimitted through channel could be interfered by noises Digital Demodulator Separates digital signals from the waveforms Channel Decoder Remove redundancy from the original bits of data Source Decoder & Destination Decode signal into desirable form that can be proceed by the destination (can be analog or digital).

5. Communication Channels Twisted pair wire Carry electrical signal Optical fiber C arry information on a modulated light beam Underwater ocean channel T ransmit information accoustically through ocean waves Free-space channel I nformation-bearing signal is radiated by use of antenna Other storage media M agnetic tape, magnetic disks, and optical disks THEY ALL HAVE COMMON PROBLEM NOISE

6. The Additive Noise Channel The simplest mathematical model for a communication channel If the noise is produced by electronics components it is characterized as thermal noise and then called gaussian noise process. Hence the term is usually called “additive Gaussian noise channel”

7. The Linear Filter Channel

8. Homework Describe the convolution process of two signals : the information signal s(t) and the impulse response of the filter h(t) , with graphics using MATLAB simmulation