Sub-band full duplex (SBFD) operation, which enables simultaneous uplink (UL) and downlink (DL) transmissions over adjacent subbands, has been introduced as a promising duplexing technique for 6G and beyond. However, SBFD introduces cross-link interference (CLI), particularly between neighboring base stations (gNB-to-gNB), which can severely degrade uplink performance. Uniform UL resource muting algorithms have been proposed in the literature to make accurate CLI measurements for the effectiveness of gNB-to-gNB interference mitigation mechanisms. In this paper, we propose an adaptive and non-uniform UL resource muting scheme that dynamically adjusts the number and position of muted resource elements (REs) based on the estimated large-scale interference power distribution. Furthermore, we introduce a frequency-shaped adjacent channel leakage ratio (ACLR) model to reflect realistic leakage behavior in SBFD networks. Simulation results show that non-uniform muting pattern (NuMP) outperforms uniform muting pattern (UMP) in terms of estimation performance, while also requiring fewer muted resource elements, as demonstrated by lower normalized mean square error (NMSE) values and reduced muting overhead.

This paper presents a novel index modulation (IM) technique named hybrid reconfigurable intelligent surface (RIS) enabled enhanced reflection modulation (Hyb-ERM), which capitalizes on the hybrid RIS architecture comprising both active and passive elements. In Hyb-ERM, a hybrid RIS is partitioned into groups, with information bits transmitted through both conventional M-ary phase shift keying (PSK) modulated symbols and the number of active RIS groups. This approach, particularly the manipulation of transmitted symbols by the hybrid RIS based on the number of active groups, is designed to improve the minimum Euclidean distance, thereby significantly enhancing error performance. We have derived a theoretical upper bound for the bit error probability (BEP) and proposed two low-complexity detectors as alternatives to the maximum likelihood (ML) detector. Extensive simulation results validate the effectiveness of Hyb-ERM, showing its superior error performance compared to benchmark schemes under both ideal and non-ideal channel conditions. This study underscores the potential of Hyb-ERM in advancing RIS-assisted communications, paving the way for more efficient and robust 6G wireless networks.

This paper introduces a reconfigurable intelligent surface (RIS)-assisted grant-free non-orthogonal multiple access (GF-NOMA) scheme. To ensure the power reception disparity required by the power domain NOMA (PD-NOMA), we propose a joint user clustering and RIS assignment/alignment approach that maximizes the network sum rate by judiciously pairing user equipments (UEs) with distinct channel gains, assigning RISs to proper clusters, and aligning RIS phase shifts to the cluster members yielding the highest cluster sum rate. Once UEs are acknowledged with the cluster index, they are allowed to access their resource blocks (RBs) at any time requiring neither further grant acquisitions from the base station (BS) nor power control as all UEs are requested to transmit at the same power. In this way, the proposed approach performs an implicit over-the-air power control with minimal control signaling between the BS and UEs, which has shown to deliver up to 20% higher network sum rate than benchmark GF-NOMA and grant-based optimal (OPT) PD-NOMA schemes depending on the network parameters. The given numerical results also investigate the impact of UE density, RIS deployment, and RIS hardware specifications on the overall performance of the proposed RIS-aided GF-NOMA scheme.

Abstract Reconfigurable intelligent surface (RIS)‐empowered communications is on the rise and is a promising technology envisioned to aid in 6G and beyond wireless communication networks. RISs can manipulate impinging waves through their electromagnetic elements enabling some sort of control over the wireless channel. The potential of RIS technology is explored to perform a sort of virtual equalization over‐the‐air for frequency‐selective channels, whereas equalization is generally conducted at either the transmitter or receiver in conventional communication systems. Specifically, using an RIS, the frequency‐selective channel from the transmitter to the RIS is transformed to a frequency‐flat channel through elimination of inter‐symbol interference (ISI) components at the receiver. ISI is eliminated by adjusting the phases of impinging signals particularly to maximize the incoming signal of the strongest tap. First, a general end‐to‐end system model is provided and a continuous to discrete‐time signal model is presented. Subsequently, a probabilistic analysis for elimination of ISI terms is conducted and reinforced with computer simulations. Furthermore, a theoretical error probability analysis is performed along with computer simulations. It is analysed and demonstrated that conventional RIS phase alignment methods can successfully eliminate ISI, and the RIS‐aided communication channel can be converted from frequency‐selective to frequency‐flat.

Reconfigurable intelligent surface (RIS)-assisted communication appears as one of the potential enablers for sixth generation (6G) wireless networks by providing a new degree of freedom in the system design to telecom operators. Particularly, RIS-empowered millimeter wave (mmWave) communication systems can be a remedy to provide broadband and ubiquitous connectivity. This paper aims to fill an important gap in the open literature by providing a physical, accurate, open-source, and widely applicable RIS channel model for mmWave frequencies. Our model is not only applicable in various indoor and outdoor environments but also includes the physical characteristics of wireless propagation in the presence of RISs by considering 5G radio channel conditions. Various deployment scenarios are presented for RISs and useful insights are provided for system designers from the perspective of potential RIS use-cases and their efficient positioning. The scenarios in which the use of an RIS makes a big difference or might not have a big impact on the communication system performance, are revealed. The open-source and comprehensiveSimRIS Channel Simulatoris also introduced in this paper.