  In this paper, we consider a smart factory scenario where a set of actuators
receive critical control signals from an access point (AP) with reliability and
low latency requirements. We investigate jointly active beamforming at the AP
and passive phase shifting at the reconfigurable intelligent surface (RIS) for
successfully delivering the control signals from the AP to the actuators within
a required time duration. The transmission follows a two-stage design. In the
first stage, each actuator can both receive the direct signal from AP and the
reflected signal from the RIS. In the second stage, the actuators with
successful reception in the first stage, relay the message through the D2D
network to the actuators with failed receptions. We formulate a non-convex
optimization problem where we first obtain an equivalent but more tractable
form by addressing the problem with discrete indicator functions. Then,
Frobenius inner product based equality is applied for decoupling the
optimization variables. Further, we adopt a penalty-based approach to resolve
the rank-one constraints. Finally, we deal with the $\ell_0$-norm by
$\ell_1$-norm approximation and add an extra term $\ell_1-\ell_2$ for sparsity.
Numerical results reveal that the proposed two-stage RIS-aided D2D
communication protocol is effective for enabling reliable communication with
latency requirements.
