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.
翻译:在本文中,我们考虑的是智能工厂的情景,即一组活化器从可靠和低潜伏要求的入口点接收关键控制信号。我们共同调查AP的动态波束,在可重新配置的智能表面(RIS)进行被动移动,以便成功地在规定的时间内从AP向导动器传送控制信号。传输过程经过了两阶段设计。在第一阶段,每个活化器都能从一个入口点接收到关键控制信号,而RIS的反射信号。在第二阶段,在第一阶段,成功接收的驱动器通过D2D网络将信息传递给接收失败的动作器。我们形成了一个非 Convex优化问题,我们首先通过使用离散指示功能将控制信号从AP向导动器成功发送,而后又获得了同等但更可拉动的形式。随后,基于Frobenius内部产品的平等适用于消除优化变量。此外,我们采取了基于惩罚的方法来解决等级限制。在第一阶段,通过D2DDDDD网络向接收成功接收信号的操作器传递$_0美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元/美元