DATA AND SIGNALS

DATA AND SIGNALS

1. analog signals

   • periodic
     • continous repetitive pattern whitin time frame
   • non- periodic
     • composite perioddic analog signal is composed of multiple sine waves

2. sine wave

   • amplitude
   • period
   • frequency
   • phase

3. composite signals

   • a single frequency sine wave is not useful in data communication, we need to send a composite signal

4. digital signals

   • described by bit interval(instead of period) and bit rate (instead of frequency)

5. Nyquist bit rate

   • BitRate = 2 x bandwidth x log2 L (L=the number of signal level used)

6. shannon capacity

   • Capacity = B x log2 (1 + SNR) SNR=the signal-to-noise ratio

7. transmission impairment

   • noise
     • thermal noise
     • induced noise
     • crosstalk
     • impulse noise or spike
   • distortion
   • attenuation

8. performance of network

   • troughput
   • propagation and transmission time
   • queuing time
   • bandwith
   • latency

9. digital to digital convertion

   • line coding
   • block coding
   • scrambling