  We propose novel deep joint source-channel coding (DeepJSCC) algorithms for
wireless image transmission over multi-input multi-output (MIMO) Rayleigh
fading channels, when channel state information (CSI) is available only at the
receiver. We consider two different schemes; one exploiting the spatial
diversity and the other exploiting the spatial multiplexing gain of the MIMO
channel, respectively. For the former, we utilize an orthogonal space-time
block code (OSTBC) to achieve full diversity and increase the robustness
against channel variations. In the latter, we directly map the input to the
antennas, where the additional degree of freedom can be used to send more
information about the source signal. Simulation results show that the diversity
scheme outperforms the multiplexing scheme for lower signal-to-noise ratio
(SNR) values and a smaller number of receive antennas at the AP. When the
number of transmit antennas is greater than two, however, the full-diversity
scheme becomes less beneficial. We also show that both the diversity and
multiplexing schemes can achieve comparable performance with the
state-of-the-art BPG algorithm delivered at the instantaneous capacity of the
MIMO channel, which serves as an upper bound on the performance of
separation-based practical systems.
