Frequency-domain subcarrier diversity receiver for discrete Hartley transform OFDM systems

In recent years, there has been an increasing interest in the use of the discrete Hartley transform (DHT) for orthogonal frequency-division multiplexing (OFDM). Previous studies have not reported an improvement in bit error rate (BER) when using a DHT-based OFDM without substantial complexity increase due to the fact that the DHT cannot diagonalize a circulant channel matrix but rather produces a unique structured matrix that has only a main diagonal and anti-diagonal. In this paper, the coupling between symmetric carriers is exploited by introducing a frequency-domain subcarrier diversity receiver for DHT-based OFDM systems. The proposed simple receiver structure takes advantage of the coupling to enhance the BER performance of the DHT-OFDM system by increasing the diversity gain between subcarriers. A detailed statistical and performance analysis of the system is presented, in which closed-form expressions of the average BER were derived. The proposed system performance was compared to the conventional discrete Fourier transform OFDM (DFT-OFDM), the generalized DHT-OFDM, and the DHT-precoded OFDM systems in terms of average BER and peak-to-average power ratio (PAPR). The proposed DHT-OFDM system outperforms the generalized DHT-OFDM system by 12 dB and outperforms the conventional DFT-OFDM and the DHT-precoded OFDM systems by 17 dB at an average BER of 10(-5). In terms of PAPR, the proposed DHT-OFDM system suffers from an approximately 5.5, 2, and 1 dB increase in PAPR when compared to the DHT-precoded OFDM, the conventional DFT-OFDM, and the generalized DHT-OFDM systems, respectively.