  We study the joint source channel coding problem of transmitting an analog
source over a Gaussian channel in two cases - (i) the presence of interference
known only to the transmitter and (ii) in the presence of side information
known only to the receiver. We introduce hybrid digital analog forms of the
Costa and Wyner-Ziv coding schemes. Our schemes are based on random coding
arguments and are different from the nested lattice schemes by Kochman and
Zamir that use dithered quantization. We also discuss superimposed digital and
analog schemes for the above problems which show that there are infinitely many
schemes for achieving the optimal distortion for these problems. This provides
an extension of the schemes by Bross et al to the interference/side information
case. We then discuss applications of the hybrid digital analog schemes for
transmitting under a channel signal-to-noise ratio mismatch and for
broadcasting a Gaussian source with bandwidth compression.
