Detection of GMSK signals in MIMO systems with arrival time differences

Space-time coding (STC) for linear, non-offset modulation is well known. The paper examines the application of STC to Gaussian minimum shift keying (GMSK). GMSK is a desirable modulation in systems employing non-linear power amplifiers due to its constant envelope and spectral efficiency. GMSK can be interpreted as an offset quadrature shift keying (OQPSK) modulation that experiences intersymbol interference (ISI). When the transmit antennas in a multiple-input, multiple-output (MIMO) system are widely spaced, the path lengths from the transmit antennas to the receive antennas can vary sufficiently to cause the received signals to be offset in time. These arrival time differences can cause degradation in MIMO system performance. A method for detecting space-time coded GMSK in the presence of differential delays is presented and its performance is reported.