Just look at the dimensions of the Reed-Solomon encoding scheme that is directed by the standard. U will see that when sub-channelization is applied the data becomes too small to use RS on a sub-channel basis...
thankx 4 ur reply... but my doubt is :why data becomes small in only subchannelization case... and moreover will it happen every time as soon as subchannelization comes into picture???
ya the MAC frame that comes from MAC layer is mapped onto the subchannels allocated according to the modulation scheme applied. So for a particular modulation scheme if the no. of subchannels is reduced it means that the no. of bits mapped on to those sub-channels is reduced. Yes it happens every time subchannelization comes into picture.