OFDM - Muliple path mitigation capability

MULTIPATH MITIGATION CAPABILITY OF OFDM

OFDM Stands for Orthogonal Frequency Division Multiplexing . High spectrum efficiency of OFDM is already explained in earlier blogs ( Please refer to blog Wi-Max Technology).

Here I will explain about the multipath mitigation capability of OFDM.

In OFDM the frequency band available is multiplexed to multiple sub-bands.

And the data is transmitted in parallel over the multiple sub-bands for the longer period of time.

Now when the data is being transmitted serially  ( Non – OFDM ) and it is taking  multiple paths ( 2 paths in this example ) one is direct path and through reflection from any reflecting surface.

Lets say we have to transmit  1 0 1 0  and each bit will be transmitted for ta period of time now initially the transmitter will transmit bit 0 for ta period of time the bit 0 will be received in minimum time from direct path by the time 0 is received from shortest path the it will still be on the way on longer path after time ta collapses transmitter will start transmit bit 1 now 1 will be received by the receiver in shortest time from shortest path and it will also receive earlier bit 0 which was travelling through longer path so here the interference has occurred.

Now when the data is transmitted parallel ( OFDM ) The data which we were earlier transmitting serially will transmitted parallel and each bit will be transmitted for the longer period of time here the time period of each bit will become 4ta .

In this since each data stream is transmitted for a longer period of time so even if the time ta collapses same data will be travelling through the direct path and reflective path so interference will not occur.