Inter-carrier interference-free Alamouti-coded OFDM for cooperative systems with frequency offsets in non-selective fading environments

A modified Alamouti-coded orthogonal frequency division multiplexing (OFDM) scheme is proposed for cooperative systems in non-selective fading environments. Even with the frequency offset between two distributed transmit antennas, the proposed scheme achieves ideal performance and full rate of Alamouti code. By switching subcarriers in the second OFDM symbol of each Alamouti-coded OFDM symbol pair after a simple-phase rotation in the first OFDM symbol, inter-carrier interference terms can be perfectly cancelled after a simple linear combining with the processing overhead of two times down-conversions and discrete Fourier transform (DFT) operations at each OFDM symbol.