  In this paper, the analysis of excess distortion exponent for joint
source-channel coding (JSCC) in semantic-aware communication systems is
presented. By introducing an unobservable semantic source, we extend the
classical results by Csiszar to semantic-aware communication systems. Both
upper and lower bounds of the exponent for the discrete memoryless
source-channel pair are established. Moreover, an extended achievable bound of
the excess distortion exponent for MIMO systems is derived. Further analysis
explores how the block fading and numbers of antennas influence the exponent of
semanticaware MIMO systems. Our results offer some theoretical bounds of error
decay performance and can be used to guide future semantic communications with
joint source-channel coding scheme.
