  This paper considers a degraded Gaussian broadcast channel over which
Gaussian sources are to be communicated. When the sources are independent, this
paper shows that hybrid coding achieves the optimal distortion region, the same
as that of separate source and channel coding. It also shows that uncoded
transmission is not optimal for this setting. For correlated sources, the paper
shows that a hybrid coding strategy has a better distortion region than
separate source-channel coding below a certain signal to noise ratio threshold.
Thus, hybrid coding is a good choice for Gaussian broadcast channels with
correlated Gaussian sources.
