  This paper studies the transmission of Gaussian sources through additive
white Gaussian noise (AWGN) channels in bandwidth expansion regime, i.e., the
channel bandwidth is greater than the source bandwidth. To mitigate the error
propagation phenomenon of conventional digital transmission schemes, we propose
in this paper a new capacity-approaching joint source channel coding (JSCC)
scheme based on partially block Markov superposition transmission (BMST) of
nested lattice codes. In the proposed scheme, first, the Gaussian source
sequence is discretized by a lattice-based quantizer, resulting in a sequence
of lattice points. Second, these lattice points are encoded by a short
systematic group code. Third, the coded sequence is partitioned into blocks of
equal length and then transmitted in the BMST manner. Main characteristics of
the proposed JSCC scheme include: 1) Entropy coding is not used explicitly. 2)
Only parity-check sequence is superimposed, hence, termed partially BMST
(PBMST). This is different from the original BMST. To show the superior
performance of the proposed scheme, we present extensive simulation results
which show that the proposed scheme performs within 1.0 dB of the Shannon
limits. Hence, the proposed scheme provides an attractive candidate for
transmission of Gaussian sources.
