  We consider distributed image transmission over a noisy multiple access
channel (MAC) using deep joint source-channel coding (DeepJSCC). It is known
that Shannon's separation theorem holds when transmitting independent sources
over a MAC in the asymptotic infinite block length regime. However, we are
interested in the practical finite block length regime, in which case separate
source and channel coding is known to be suboptimal. We introduce a novel joint
image compression and transmission scheme, where the devices send their
compressed image representations in a non-orthogonal manner. While
non-orthogonal multiple access (NOMA) is known to achieve the capacity region,
to the best of our knowledge, non-orthogonal joint source channel coding (JSCC)
scheme for practical systems has not been studied before. Through extensive
experiments, we show significant improvements in terms of the quality of the
reconstructed images compared to orthogonal transmission employing current
DeepJSCC approaches particularly for low bandwidth ratios. We publicly share
source code to facilitate further research and reproducibility.
