Optimizing Information Freshness in RIS-assisted NOMA-based IoT Networks

Abstract

This paper investigates the benefits of integrating reconfigurable intelligent surface (RIS) on minimizing the average sum age of information (AoI) in uplink non-orthogonal multiple access-based Internet-of-Things (IoT) networks. In this setup, an optimization problem is formulated to optimize the RIS configuration, the transmit power per IoT device and the clustering policy of IoT devices. The formulated problem is a mixedinteger non-convex one, and in order to solve it we obtain first the RIS configuration by adopting a semi-definite relaxation (SDR) approach. Afterwards, the joint power allocation and user-clustering problem is solved using the concept of bi-level optimization and is decomposed into an outer user clustering problem and an inner power allocation problem. Optimal closedform expressions are derived for the inner problem and the Hungarian method is employed to solve the outer one. Numerical results demonstrate the performance superiority of our approach.

Age Minimization in Outdoor and Indoor Communications with Relay-aided Dual RIS

“…In [9], a joint power allocation, hybrid beamforming and phase shifts design problem was investigated in a millimeter wave (mmWave) non-orthogonal multiple access (NOMA) network to optimize the system sum rate. Interestingly, RIS has been integrated into real-time networks to optimize the freshness of information [10]- [12].…”