  Semantic communication, as a novel communication paradigm, has attracted the
interest of many scholars, with multi-user, multi-input multi-output (MIMO)
scenarios being one of the critical contexts. This paper presents a semantic
importance-aware based communication system (SIA-SC) over MIMO Rayleigh fading
channels. Combining the semantic symbols' inequality and the equivalent
subchannels of MIMO channels based on Singular Value Decomposition (SVD)
maximizes the end-to-end semantic performance through the new layer mapping
method. For multi-user scenarios, a method of semantic interference
cancellation is proposed. Furthermore, a new metric, namely semantic
information distortion (SID), is established to unify the expressions of
semantic performance, which is affected by channel bandwidth ratio (CBR) and
signal-to-noise ratio (SNR). With the help of the proposed metric, we derived
performance expressions and Semantic Outage Probability (SOP) of SIA-SC for
Single-User Single-Input Single-Output (SU-SISO), Single-User MIMO (SU-MIMO),
Multi-Users SISO (MU-MIMO) and Multi-Users MIMO (MU-MIMO) scenarios. Numerical
experiments show that SIA-SC can significantly improve semantic performance
across various scenarios.
