On Space-Time Trellis-Coded Offset QPSK

This paper describes the use of orthogonal space- time block codes to overcome the performance and complexity difficulties associated with the use of an offset modulation with space-time trellis codes in multiple-input multiple-output communication systems. The orthogonal space-time block code is applied to offset QPSK modulated waveforms in the same way it would be applied to symbols. The procedure allows the receiver to orthogonalize the link. The main benefits of this orthogonalization are 1) the removal of the noise correlation at the input to the space-time trellis decoder and 2) the elimination of I/Q interference resulting from multi-antenna transmission. These benefits are achieved at the expense of data rate. The data rate reduction is a function of the rate of the orthogonal space-time block code.