ODFM CDMA WIMAX WIFI...begginer to digital communication

[eehero]

odfm spectrum

Hello all friends, i am just a begginer into digital communication field and want to make a decision in wich part to go in in details (ofdm, cdma, wimax or wifi).
may be i donot understand what each of them include and talking for, so i am waiting for ur help.

Added after 1 hours 15 minutes:

i am waiting for help

 

[FrankCh]

libya wifi standard

OFDM, WiMAX and WIFI are similar in that they use FFT/IFFT.
CDMA is different.

 

[eehero]

ok dear frankch, can u explain in more details

 

[eehero]

ok, now i understand that OFDM and CDMA are just like protocols, wimax an application uses OFDM protocol.

OFDM, uses multiple carriers to send digital data, and CDMA allows multiple users to use the same channel without any interference.
is that right friends.
i am waiting for more explination

 

[FrankCh]

ok dear frankch, can u explain in more details

well, that's all I know.
CDMA doesn't use frequency multiplexing.
The other jorgans use frequency multiplexing.

OFDM means IFFT/FFT pair and means frequency multiplexing.
Wimax and WIFI (802.11a) uses OFDM technology.

WIFI(802.11b) uses something similar to CDMA I think.

I think others in comm systems design understand them better than me.
:|

 

[eehero]

FrankCh, u do ur mission thanks for that.

 

[yesh_r1]

**broken link removed**

Refer this site for a good explanation of OFDM... (pages 9 and 10 may be unclear )

 

[vuday455]

hi ..

OFDM --> digital modulation technique where multiple carriers are meploymed such that carriers are orthogonal to each other.
it is used for eliminating the ISI and for effective use of the spectrum
and main advantage is here equaliser is very simple .. 1 tap equalizer.

CDMA --> assigns each code to the individual user so that all can access the channel at a time..
here equalizer is very complex... eg. rake receiver.

uday

 

[Ghitani]

WiFi : IEEE standard designated by 802.11 . It deals with wireless local area network (WLAN)

WiMax : IEEE standard designated by 802.16 . Using WiMax one can connect to internet wirelessly .
It also connects LAN's together wirelessly so it can be considered as wireless MAN .