1. Sistem Jaringan dan Komunikasi Data #2

2. Data vs Information  What is data?  What is information?  What are differences between data and information?

3. Data vs Information  Data  Raw facts  No context  Just number and Text  Information  Data with context  Processed Data  Value-added to data  Summarized  Analized  Organized

4. Data vs Information  Data: 13330  Information:  13/3/30 The date of your final seminars.  Rp. 13.330 Price of a discounted choco bar

5. Data Information Summarizing the data Averaging the data Selecting part of the data Graphing the data Adding context Adding value Data vs Information

6. Signal and signalling  electric or electromagnetic representations of data, physically propagates along medium  signal is generated by the transmitter and transmitted over a medium

7. Analog vs Digital

8. Audio signal  freq range 20Hz-20kHz (speech 100Hz-7kHz)  easily converted into electromagnetic signals  varying volume converted to varying voltage  can limit frequency range for voice channel to 300-3400Hz

9. Digital Data  as generated by computers etc.  has two dc components  bandwidth depends on data rate

10. Analog Signal

11. Digital Signal

12. Adv&Disadv Digital Signal  cheaper  less susceptible to noise  but greater attenuation  digital now preferred choice

13. Transmission Impairment  signal received may differ from signal transmitted causing:  analog - degradation of signal quality  digital - bit errors  most significant impairments are  attenuation and attenuation distortion  delay distortion  noise

14. Attenuation  where signal strength falls off with distance  depends on medium  received signal strength must be:  strong enough to be detected  sufficiently higher than noise to receive without error  so increase strength using amplifiers/repeaters  is also an increasing function of frequency  so equalize attenuation across band of frequencies used  eg. using loading coils or amplifiers

15. Attenuation  Analog signals suffer far less from attenuation over long distances  Digital Data: 0 and 1. It is difficult to distinguish each state if the signal weak  Analog Data: continous. The value are infinites. Analog devices are equipped to handle the infinite value between 0 and 1

16. Data Transmission  data transmission occurs between a transmitter & receiver via some medium  guided medium  eg. twisted pair, coaxial cable, optical fiber  unguided / wireless medium  eg. air, water, vacuum

17. Data Transmission  direct link  no intermediate devices  point-to-point  direct link  only 2 devices share link  multi-point  more than two devices share the link

18. Transmission Mode  simplex  one direction  eg. television  half duplex  either direction, but only one way at a time  eg. police radio  full duplex  both directions at the same time  eg. telephone

19. Data Rate and Bandwith  any transmission system has a limited band of frequencies  this limits the data rate that can be carried  square have infinite components and hence bandwidth  but most energy in first few components  limited bandwidth increases distortion  have a direct relationship between data rate & bandwidth