Active RIS Deployment Design and Its Detailed Optimal Solution under Overall Power Constraint

In this correspondence, we comprehensively study the optimal active reconfigurable intelligent surface (ARIS) deployment, aiming to address the open issue of its deployment details. For practical consideration, the overall power constraint is introduced into ARIS-assisted communications, including the transmit power at base station (BS) and amplifying power for signal reflection at ARIS. To better clarify the influence of ARIS deployment and power allocation on the achievable capacity, we first optimize the power allocation between BS and ARIS, then analyze the ARIS position. Subsequently, regarding to two dependent variables, an effective alternating optimization algorithm is further investigated to obtain the optimal amplifying factor of ARIS. Finally, simulation and numerical results confirming the correctness of our analysis, conclude that, when the amplifying power of ARIS is large, ARIS should be deployed close to BS to achieve a better capacity, and vice versa.