A MIMO-OFDM transmission scheme employing subcarrier phase hopping

This paper proposes a subcarrier phase hopping scheme for space division multiplexing (SPH-SDM) and applies it to MIMO-OFDM mobile communications. The SPH-SDM scheme is an extended version of the conventional SPH scheme for transmit diversity that enables SDM transmission. The scheme introduces a phase shift into the reference phase of each subcarrier for the transmitted data stream. A unitary random phase matrix carries out the phase shift for a one-packet duration, and the phase shift depends on the indices of streams, subcarriers, and transmit antennas. Such a phase shift can randomize channel frequency responses and reduce the channel correlation between subcarriers. A computer simulation demonstrates that SPH-SDM can improve transmission performance by exploiting the inherent frequency diversity effect, and that it can easily adjust the tradeoff between the diversity gain and the transmission rate.