?????????????(digital)?????(analog)???

1
???????

• ?3? ?????

2
????

• ????????
• ???????????
• ???????????
• ???????????????????? ?
• ???????????????? ?

3
????

• ????????????????????
• ?????????????(digital)?????(analog)???
• ???????????????????????,??????????????????(bandwid
  th) ,??????????????
• ???????????????????????????
• ?????????????????(impairment)????????

4
??????
5
????(Communications System)??????
6
???? ?????

• ???????
• ?????????????
• ??(Analog)
• ??(Digital)
• ?????
• ??(Bandwidth)???????(Data Rate)

7
????(Analog Signal)?????(Digital Signal)
8
????????
9
??(phase)???
10
?????????????
11
?????(Fourier series)
12
???????

• ????????(width of a frequency band) ,?Hz
  (Hertz)???
• ???????????????????(data rate),??bits per
  second???
• ???????????????????(throughput) ,???????

13
??????????
14
????????????
15
?????(radio spectrum)
16
????????(transmission impairment)

• ??(attenuation)?????(attenuation distortion) ?
• ????(delay distortion) ?
• ??(noise) ?

17
??????????????
18
?????(channel capacity)

• Nyquist Bandwidth
• ????(Shannon Capacity)??

19
????????????

• ??????????(radio channel impairments)
• ??????????
• ????????(large-scale propagation model)
• ????????(small-scale propagation model?fading
  model)

20
???????? ???????

• ????(path loss)
• ??????????(free space propagation model)
• ??????????(propagation mechanism)

21
??????????
22
?????????? ???(multipath)???
23
Fresnel zones???
24
???????

• ????(extra large zone)
• ???(extra large zone)
• ???????(middle zone)
• ???(small zone?microzone)

25
???????(Outdoor propagation models)

• Longley-Rice model
• Durkins model
• Okumura model
• Hata model
• Walfisch and Bertoni model
• Wideband PCS microcell model

26
???????? ???????

• ????????,????(multipath)????(Doppler)??
• ?????????(statistical distribution of received
  envelope)
• ???????(duration of fading)
• ?????

27
?????????????

• ??????????????????????
• ????????????????????(Doppler shifts),???????????(r
  andom frequency modulation)
• ?????????(multipath propagation
  dalay)???????(time dispersion) ?

28
?????????

• ??????(multipath propagation)
• ????????
• ?????????
• ???????

29
?????(Doppler effect)
30
???????(mobile radio channel)?????

• ??(bandwidth)?????????(received power)?????
• ???????????

31
??????????(mobile multipath radio channel)???

• ????(impulse response)
• ????(coherence bandwidth)????????????
• ????(coherence time)

32
????????
33
VSWR (voltage standing wave ratio)???
34
EIRP???

• ?????????(power output)??????????(cable)?????(conn
  ector)?????
• ?????(transmitter)????30 milliwatts,??????15
  milliwatts,???????5 milliwatts,???????????10
  milliwatts
• EIRP (equivalent isotropically radiated
  power)??????????????,FCC???????????????????????

35
AP??????
36
??(decibel)