In transmission mode, payload data enters the symbol mapper where bits are mapped onto either BPSK, QPSK, 16-QAM or 64-QAM. The mapper provides a sequential series of 64 carriers to the IFFT, denoted as a OFDM symbol. The IFFT transforms the frequency domain constellation into a time domain sequence. Then the CP is added and the transmitted data sequence is sent to the low-IF upconversion stage [1].
In reception mode, data is provided from low-IF down-conversion stage to the gain control and timing synchronization stage. The preamble serves to estimate gain, frame start and carrier frequency offset. The CP is stripped off before entering the FFT. The FFT translates them into the frequency domain. The equalizer performs an initial channel estimate, based on BPSK reference symbol during the initialization and divides the received constellation by its channel response per subcarrier and provides decision through the demapper [1].