OFDM????

1
????

• OFDM????
• OFDM????
• OFDM????
• ???OFDM??????

2
OFDM???

• ?????????????????????????????,?????????????????,??
  ??????,????????????,????????????
• ???????????????,??????????????????????????????????
  ??,?????????,??????????????????,????????????
• OFDM?????????????????????,????????????,???????????
  ??

3
OFDM??
????Orthogonal Frequency Division
Multiplexing ?????????? ??????????????????????
??,?????????????????????????,????????,????????????
???????OFDM?????????????,???????????? ????
1??????? 2????? 3????? 4?????
5???????? 6??????????
4
??OFDM??????????
OFDM??
???????
??,Sk ??di ??N ?IDFT?????,??,di ?????Sk ??N
?DFT????
???????????OFDM????
5
OFDM??
?1 FFT??OFDM????
6
OFDM??

• ????CP???
• ??????,??????????????????,???????????????????ISI??
  ??????????????????????ISI
• OFDM???????????????(GI Guard Interval),??????????
  ?????????????????????????????????????,????????????
  ?????
• ??????CP (Cyclic Prefix)??????,??????????????????,
  ??????????????ISI???????,????OFDM?????????L?????

7
OFDM??
?2 OFDM?????????
??TsTb Tg Ts OFDM???? Tb ?????? Tg ??????
8
OFDM??
??????????????????????,????????(ICI)
?3 ???????????
9
OFDM??
?4 ???????????????
??????????OFDM???FFT??????????????????????????????
?,???????????
10
OFDM??

• (1) ????????????????
• ????????????????
• ????????????
• (2) ???????
• ???????????,???????????????,??????????
• OFDM??????????????(??????)
• (3) ??????
• ????????????
• (4) ?????
• ?????????????????(IDFT)????????(DFT)???,?IDFT?DFT?
  ????????IFFT?FFT

11
?5 ??????FDM?OFDM???????
OFDM??
12
OFDM??????

• ????OFDM??????????????,??????????????????????????
  ??????????????????,??????????????,??ICI,??????????
  ?????,????????????
• ???????????D/A????????A/D????????????????,???????
  ????,????????????????
• ????IFFT?FFT?????????????????????FFT?,????????,?I
  SI(?????)???????????????????????,OFDM
  ???????????????????????????OFDM???????????????????
  
• ???????OFDM??????????????????????,???????????????
  ??

13
?????????

• ?????????FFT??????????OFDM??,?????OFDM?????(ISI)

? 6 FFT??????OFDM???????

• ??OFDM????????????????,??????,?????????FFT???????,
  ?FFT???????????????????????????FFT???????,?FFT????
  ??????????????????????????????,??????????????

14
????????

• ????????? ?Van de Beek?????? ,??CP?OFDM???????????
  ,??????????????
• ??????? ?T.M .Schmidl????,?????????????????????
• ???????????? Landstrom????????CP??????????????

15
T.M .Schmidl??
? 7 T.M .Schmidl?????????
??????????????????????,??????,??????????????
???????????
16
T.M .Schmidl??
??????????2L,??

?1 ??????????,??

?2 ????

?3 ???????????????????????

?4
17
T.M .Schmidl??

• ???????????????????????????????????,?????????2L???
  ??,?????????,??????????L?????????OFDM????????,????
  ??CP,???????????,????????????????????CP???????????
  ??
• ?????????????????????,????????????????????????????
  ?,????schmidl?????????

18
?????????
????????????????,???ICI,???????????
????????????????????,????OFDM?????????,?????????
???????????????
?8 ??????OFDM?????????
19
?????????

• ????(data-aided)??,?????,???????????????,????????,
  ????????????????????????????????????????,?????????
  ????
• ??????(non-data-aided),????,???OFDM?????,??,?????O
  FDM???????????????????????????????????????????????
  ?????????????????????????????????,????????????????
  ????OFDM??,????? ?

20
??????
????????
??
D??????????,??angle(z)????-p,p??,??????????? ?
????????,?D64,?????????2,???????,?D128,?????????
1????????1????????,??2?????????
21
??????

• ?????????????????????,???????????????????????,????
  ????????????????,????????r(n)?????????t(n)????????
  ??OFDM???????????????,???????n?????????????????

• ??????????????????????????????,?????0.5???,???????
  ????

22
??????
802 .16 a????????2.4G-11GH z,????????????20ppm,???
??????????????????,???????,??????????????40ppm,???
????????? ????????2m10 6Hz (m1,2,...),???????
? ?????? ????57??,???????????????
???????????????-2,2??????,?????????????s,???S?-
64,-2)?(2,64???,???????????,?????????????????????
??S?
23
OFDM??????
?9 OFDM???????
24
OFDM??????
1?????????????,????? 2?????????????? 3?????????,
?????????????? 4?????????????? 5???????,????????
??????? 6??????????????
25
?10 ??OFDM???????