A Study on Post-Detection Diversity Combining for OFDM Systems

Adaptive modulation, in which a transmitter could be adapting constellation size depending on the channel, and diversity combining, in which a transmitter and/or a receiver could be adapting branch size, are both transmission schemes to combat the fading. These two schemes can be applicable to each digital-modulated symbol in OFDM transmission. In this paper, we propose a frequency diversity scheme within one OFDM symbol. When we assume two branches diversity, the information bit rate results in half, but by combining the two symbols at a receiver, the BEP is improved owing to both binal bit energy and diversity gain. We verify the advantage of the proposed scheme with both theoretical analysis and Monte Carlo simulation.