Reconfigurable intelligent surfaces (RISs) represent a new technology that can shape the radio wave propagation and thus offers great variety of possible performance implementation gains. Motivated by this, we investigate achievable sum-rate optimization in broadcast channel (BC) presence RISs. We solve this problem exploiting well-known duality between Gaussian multiple-input multiple-output (...

The uplink of a cell-free massive multiple-input multiple-output with maximum-ratio combining (MRC) and zero-forcing (ZF) schemes are investigated. A power allocation optimization problem is considered, where two conflicting metrics, namely the sum rate fairness, jointly optimized. As there no closed-form expression for achievable in terms large scale-fading (LSF) components, fairness trade-off...

This paper proposes to deploy multiple reconfigurable intelligent surfaces (RISs) in device-to-device (D2D)-underlaid cellular systems. The uplink sum-rate of the system is maximized by jointly optimizing transmit powers users, pairing users (CUs) and D2D links, receive beamforming base station (BS), configuration RISs, subject power limits quality-of-service (QoS) users. To address non-convexi...

Nonorthogonal multiple access (NOMA) is seen as an important technology for tomorrow's Internet-of-Things (IoT) systems. In uplink power-domain NOMA (PD-NOMA), allocating the transmit power of IoT devices to maximize both sum rate and reliability devices. However, it challenging optimize when received signal affected by a random fading channel. Hence, in this article, problem assignment studied...

Cell-free massive multiple-input multiple-output (MIMO) employs a large number of distributed access points (APs) to serve small user equipments (UEs) via the same time/frequency resource. Due strong macro diversity gain, cell-free MIMO can considerably improve achievable sum-rate compared conventional cellular MIMO. However, performance is upper limited by inter-user interference (IUI) when em...

This paper studies the sum rate performance of a low complexity quantized CSI-based Tomlinson-Harashima (TH) precoding scheme for downlink multiuser MIMO tansmission, employing greedy user selection. The asymptotic distribution of the output signal to interference plus noise ratio of each selected user and the asymptotic sum rate as the number of users K grows large are derived by using extreme...