Why do we use OFDM in Wimax ?

Hi,
Where do we use OFDM in WiMAX..?
In spec ,mentioned is qam OR QPSK...



If you search for OFDM in google..they say it is used in Wimax ..but where exactly?
Help..!!!

qpks modulation

It is just a access method... like CDMA FDMA MC-CDMA TDMA and so it should not be mis understood by modulation techniques such QPSK or QAM

Re: OFDM in Wimax

OFDM is a multicarrier modulation scheme. It can modulate 'n' signals at a time.
So, in Wimax each signal/bit is modulated using QPSK ,QAM ... and all those bits and bunched into symbol using OFDM modulation technique.

Re: OFDM in Wimax

OFDM is an efficient baseband multiplexing technique.
It is unlike QPKS , QAM which is RF modulation.

Re: OFDM in Wimax

OFDM (orthogonal frequency division multiplexing) is a technique for increasing the amount of information that can be carried over a wireless network.

In frequency-division multiplexing, multiple signals, or carriers, are sent simultaneously over different frequencies between two points. However, FDM has an inherent problem: Wireless signals can travel multiple paths from transmitter to receiver (by bouncing off buildings, mountains and even passing airplanes); receivers can have trouble sorting all the resulting data out.

Orthogonal FDM deals with this multipath problem by splitting carriers into smaller subcarriers, and then broadcasting those simultaneously. This reduces multipath distortion and reduces RF interference (a mathematical formula is used to ensure the subcarriers' specific frequencies are "orthogonal," or non-interfering, to each other), allowing for greater throughput.

Re: OFDM in Wimax

Thanks