Advantages of OFDM method over single carrier QAM in digital modulation for Hitachi digital microwave link?

Question

What are the advantages of OFDM method over single carrier QAM in digital modulation for Hitachi digital microwave link?

Answer 1

The main difference is performance. The OFDM can transmit more bits/sec than the single carrier. It does this by transmitting 16 bits of data on 16 carriers simultaneously. As you move away from the transmitter, the signal will get weaker and more prone to noise errors. In this case, the OFDM will use less carriers and slow down the transfer. Under really bad conditions, the OFDM system will revert to BPSK which is Binary Phase Shift Keying and only 1 bit at a time will be transmitted. So, OFDM is adaptable, but QAM is not. It always has the same transfer rate.