===Single carrier approach & Multi carrier approach===
[[Image:single carrier approch.jpg|center|800px600px|thumb| [http://www.ert.rwth-aachen.de/Projekte/Theo/OFDM/node4.html <font size = "3">'''Single carrier approch'''</font>]]]
* As per above figure the general structure of a single carrier transmission system is depicted. The transmitted symbols are pulse formed by a transmitter filter. After passing the multipath channel in the receiver a filter matched to the channel is used to maximize signal to noise ratio a the device used to extract the data.
* Figure below shows the general structure of a multicarrier system.
[[Image:multi carrier approch.jpg|center|800px600px|thumb| [http://www.ert.rwth-aachen.de/Projekte/Theo/OFDM/node5.html <font size = "3">'''Multi carrier approch'''</font>]]]
*One key principle of OFDM is that since low symbol rate modulation schemes (i.e. where the symbols are relatively long compared to the channel time characteristics) suffer less from intersymbol interference caused by multipath, it is advantageous to transmit a number of low-rate streams in parallel instead of a single high-rate stream. Since the duration of each symbol is long, it is feasible to insert a guard interval between the OFDM symbols, thus eliminating the intersymbol interference. The guard interval also eliminates the need for a pulse-shaping filter, and it reduces the sensitivity to time synchronization problems.