  Semantic communications have shown its great potential to improve the
transmission reliability, especially in the low signal-to-noise regime.
However, resource allocation for semantic communications still remains
unexplored, which is a critical issue in guaranteeing the semantic transmission
reliability and the communication efficiency. To fill this gap, we investigate
the spectral efficiency in the semantic domain and rethink the semantic-aware
resource allocation issue. Specifically, taking text semantic communication as
an example, the semantic spectral efficiency (S-SE) is defined for the first
time, and is used to optimize resource allocation in terms of channel
assignment and the number of transmitted semantic symbols. Additionally, for
fair comparison of semantic and conventional communication systems, a transform
method is developed to convert the conventional bit-based spectral efficiency
to the S-SE. Simulation results demonstrate the validity and feasibility of the
proposed resource allocation method, as well as the superiority of semantic
communications in terms of the S-SE.
