  In this paper, we propose a novel transmissive reconfigurable intelligent
surface (TRIS) transmitter-enabled spatial modulation (SM) multiple-input
multiple-output (MIMO) system. In the transmission phase, a column-wise
activation strategy is implemented for the TRIS panel, where the specific
column elements are activated per time slot. Concurrently, the receiver employs
the maximum likelihood detection technique. Based on this, for the transmit
signals, we derive the closed-form expressions for the upper bounds of the
average bit error probability (ABEP) of the proposed scheme from different
perspectives, employing both vector-based and element-based approaches.
Furthermore, we provide the asymptotic closed-form expressions for the ABEP of
the TRIS-SM scheme, as well as the diversity gain. To improve the performance
of the proposed TRIS-SM system, we optimize ABEP with a fixed data rate.
Additionally, we provide lower bounds to simplify the computational complexity
of improved TRIS-SM scheme. The Monte Carlo simulation method is used to
validate the theoretical derivations exhaustively. The results demonstrate that
the proposed TRIS-SM scheme can achieve better ABEP performance compared to the
conventional SM scheme. Furthermore, the improved TRIS-SM scheme outperforms
the TRIS-SM scheme in terms of reliability.
