Constellation-rotated vector OFDM and its performance analysis over rayleigh fading channels

Although the single antenna vector OFDM (VOFDM) proposed by Xia shows performance robust to channel spectral nulls, it does not necessarily attain full diversity for multi-path fading channels. It is known that the degradation in diversity order is sometimes rescued by the rotation of constellation. A simple application of constellation rotation to the V-OFDM system does not, however, improve its performance. In this paper, we discuss the sub-channel spectral structure of the V-OFDM signal and give upper bounds on its pair-wise error probability over multi-path Rayleigh fading channels and propose a novel constellation-rotated V-OFDM (CRV-OFDM) with improved diversity. To this end, we design rotation angles for sub-channel symbols to minimize upper bounds on BER. Simulation results show that the proposed CRV-OFDM attains diversity order min{M,P} for the vector length M and the number of paths P. As the results, for BER 10^¿4, CRV-OFDM improves the performance of V-OFDM by 2 dB for both BPSK and QPSK modulation when M is 2, and, for M = 4, the improvement factor is about 1.3 dB. We also discuss the effects of M on the transmitter and receiver complexities and on the peak-to-averate power ratio. Finally, we compare several methods for rotational angle determination.