Space-time block code design for Asymmetric-OFDM systems

A considerable drawback of OFDM systems is their high peak-to-average power ratio (PAPR). The Asymmetric-OFDM (A-OFDM) system addresses this problem by reducing the size of fast Fourier transform (FFT) / inverse FFT (IFFT). Based on the layered concept in FFT algorithms and Alamouti-like space time block code (STBC), we extend the A-OFDM to an full diversity MIMO multicarrier system and apply it to vehicle-to-vehicle communications. Comparing with the conventional OFDM with STBC, the proposed system can be arbitrarily adjusted in the number of subchannels (or the length of each subchannel), typically in order to suit requirements for high reliability or low complexity, in different applications and scenarios. Theoretical analysis in a frequency selective channel and simulations in a vehicle-to-vehicle environment show that the proposed system, with any adjustable size of subchannels from 1 to N, N being the transmission block length, has higher reliability than an equivalent MIMO-OFDM system.