Constellation Rotated Vector OFDM and Its Performance over Rayleigh Fading Channels

Although the single antenna vector OFDM (V-OFDM) proposed by Xia is robust to channel spectral nulls, it does not necessarily attain full diversity for multi-path fading channels. In this paper, we propose a novel constellation-rotated V-OFDM (CRV-OFDM) system based on modified V-OFDM, and analyze its performance over Rayleigh fading channels. In CRV-OFDM, we design rotation angles for each symbol to minimize upper bounds on bit error rate (BER) with full diversity order. Our simulation results show that, compared with V-OFDM, proposed CRV-OFDM always attains the maximum diversity order determined by the vector length M. As a result, for BER 10^-4, CRV-OFDM improves the performance of V-OFDM by 2 dB for both BPSK and QPSK modulation for M = 2, and, for M = 4, the improvement is about 1.3 dB. To verify optimality of the derived angles, we also test, in therms of BER, some other angles including the angles derived from minimum product distance (MPD) criterion and compare with the theoretical union bounds and show that the BERs take the smallest values at our derived optimal angles.