How OFDMA Transmitter in LTE ?
In the downlink, OFDM is selected to efficiently meet E-UTRA performance requirements. With OFDM, 
it is straightforward to exploit frequency selectivity of the multi-path channel with lowcomplexity
receivers. 
This allows frequency selective in addition to frequency diverse scheduling and one cell reuse of  available bandwidth.

Furthermore, due to its frequency domain nature, OFDM enables flexible bandwidth operation with low complexity. Smart antenna technologies are also easier to support with OFDM, since
each sub-carrier becomes flat faded and the antenna weights can be optimized on a per  sub-carrier (or block of sub-carriers) basis.

In addition, OFDM enables broadcast services on a synchronized single frequency network (SFN) with appropriate cyclic prefix design.

This allows broadcast signals from different cells to combine over the air, thus significantly increasing the received signal power and supportable data rates for broadcast services.