The adoption of a Reconfigurable Intelligent Surface (RIS) for downlink multi-user communication from multi-antenna base station is investigated in this paper. We develop energy-efficient designs both the transmit power allocation and phase shifts surface reflecting elements, subject to individual link budget guarantees mobile users. This leads non-convex design optimization problems which tackle we propose two computationally affordable approaches, capitalizing on alternating maximization,...

Future wireless networks are expected to evolve towards an intelligent and software reconfigurable paradigm enabling ubiquitous communications between humans mobile devices. They will be also capable of sensing, controlling, optimizing the environment fulfill visions low-power, high-throughput, massively-connected, low-latency communications. A key conceptual enabler that is recently gaining increasing popularity Holographic Multiple Input Output Surface (HMIMOS) refers a low-cost...

Recently, the reconfigurable intelligent surface (RIS), benefited from breakthrough on fabrication of programmable meta-material, has been speculated as one key enabling technologies for future six generation (6G) wireless communication systems scaled up beyond massive multiple input output (Massive-MIMO) technology to achieve smart radio environments. Employed reflecting arrays, RIS is able assist MIMO transmissions without need frequency chains resulting in considerable reduction power...

Reconfigurable Intelligent Surfaces (RISs) have been recently considered as an energy-efficient solution for future wireless networks due to their fast and low-power configuration, which has increased potential in enabling massive connectivity low-latency communications. Accurate low-overhead channel estimation RIS-based systems is one of the most critical challenges usually large number RIS unit elements distinctive hardware constraints. In this paper, we focus on uplink a RIS-empowered...

We consider a multi-user Multiple-Input Single-Output (MISO) communication system comprising of multiantenna base station communicating in the downlink simultaneously with multiple single-antenna mobile users. This is assumed to be assisted by Large Intelligent Surface (LIS) that consists many nearly passive antenna elements, whose parameters can tuned according desired objectives. The latest design advances on these surfaces suggest cheap elements effectively acting as low resolution (even...

This paper investigates the use of a Passive Intelligent Mirrors (PIM) to operate multi-user MISO downlink communication. The transmit powers and mirror reflection coefficients are designed for sum-rate maximization subject individual QoS guarantees mobile users. resulting problem is non-convex, tackled by combining alternating with majorization-minimization method. Numerical results show merits proposed approach, in particular that PIM increases system throughput at least 40%, without...

Wireless communication in the TeraHertz band (0.1--10 THz) is envisioned as one of key enabling technologies for future sixth generation (6G) wireless systems scaled up beyond massive multiple input output (Massive-MIMO) technology. However, very high propagation attenuations and molecular absorptions THz frequencies often limit signal transmission distance coverage range. Benefited from recent breakthrough on reconfigurable intelligent surfaces (RIS) realizing smart radio environment, we...

Reconfigurable Intelligent Surfaces (RISs) comprised of tunable unit elements have been recently considered in indoor communication environments for focusing signal reflections to intended user locations. However, the current proofs concept require complex operations RIS configuration, which are mainly realized via wired control connections. In this paper, we present a deep learning method efficient online wireless configuration RISs when deployed environments. According proposed method,...

The demanding objectives for the future sixth generation (6G) of wireless communication networks have spurred recent research efforts on novel materials and radio-frequency front-end architectures connectivity, as well revolutionary computing paradigms. Among pioneering candidate technologies 6G belong reconfigurable intelligent surfaces (RISs), which are artificial planar structures with integrated electronic circuits that can be programmed to manipulate incoming electromagnetic field in a...

For 6G in 2030 and beyond, key performance metrics long for terabit-per-second, one-tenth of millisecond latency with zero jitter, millimeter-preci-sion sensing positioning, seamless connectivity, among others. To meet these demands, the terahertz (0.1–10 THz) band comes into horizon, ultra-broad bandwidth sub-millimeter wavelength, which, however, suffers from distance limitation power consumption concerns. In this article, four interdisciplinary directions to address above challenges...

The energy efficiency (EE) of femtocells is always limited by the surrounding radio environments in heterogeneous networks (HetNets), such as walls and obstacles. In this paper, we propose to deploy reconfigurable intelligent surfaces (RISs) improve EE femtocells. However, perfect channel state information more difficult obtain due passive characteristics RISs non-cooperative relationship between different tiers. Besides, low-cost transceivers reflecting units suffer nontrivial hardware...

The multi-user Holographic Multiple-Input and Multiple-Output Surface (MU-HMIMOS) paradigm, which is capable of realizing large continuous apertures with minimal power consumption, has been recently considered as an energyefficient solution for future wireless networks, offering increased flexibility in impacting electromagnetic (EM) wave propagation according to the desired communication, localization, sensing objectives. tractable channel modeling MU-HMIMOS systems one most critical...

Reconfigurable intelligent surfaces (RISs) have been recently considered as a promising candidate for energy-efficient solutions in future wireless networks. Their dynamic and low-power configuration enables coverage extension, massive connectivity, low-latency communications. Due to large number of unknown variables referring the RIS unit elements transmitted signals, channel estimation signal recovery RIS-based systems are ones most critical technical challenges. To address this problem,...

A revolutionary technology relying on Stacked Intelligent Metasurfaces (SIM) is capable of carrying out advanced signal processing directly in the native electromagnetic (EM) wave regime. An SIM fabricated by a sophisticated amalgam multiple stacked metasurface layers, which may outperform its single-layer counterparts, such as reconfigurable intelligent surfaces (RIS) and lenses. We harness this new for implementing holographic multiple-input multiple-output (HMIMO) communications without...

Future wireless systems are envisioned to create an endogenously holography-capable, intelligent, and programmable radio propagation environment, that will offer unprecedented capabilities for high spectral energy efficiency, low latency, massive connectivity. A potential promising technology supporting the expected extreme requirements of sixth-generation (6G) communication is concept holographic multiple-input multiple-output (HMIMO), which actualize radios with reasonable power...

In this paper, the problem of wireless resource allocation and semantic information extraction for energy efficient communications over networks with rate splitting is investigated. considered model, a base station (BS) first extracts from its large-scale data, then transmits small-sized to each user which recovers original data based on local common knowledge. At BS side, probability graph used extract multi-level information. downlink transmission, scheme adopted, while private transmitted...

Unprecedented growth in wireless data traffic, and ever-increasing demand for highly secured, low-latency communication has motivated the research community to move towards sixth-generation (6 G) technology, where networks can cater rising need ubiquitous secure connectivity. One of promising technologies 6 G is reconfigurable intelligent surface (RIS) concept that proposed successfully deal with increasing security threats by smartly controlling channel conditions. This survey paper...

Envisioned as one of the most promising technologies, holographic multiple-input multiple-output (H-MIMO) recently attracts notable research interests for its great potential in expanding wireless possibilities and achieving fundamental limits. Empowered by nearly continuous, large energy-efficient surfaces with powerful electromagnetic (EM) wave control capabilities, H-MIMO opens up opportunity signal processing a more EM-domain, paving way realizing imaging level communications supporting...

We propose an iterative channel estimation algorithm based on the Least Square Estimation (LSE) and Sparse Message Passing (SMP) for Millimeter Wave (mmWave) MIMO systems. The coefficients of mmWave are approximately modeled as a Bernoulli-Gaussian distribution matrix is sparse with only few non-zero entries. By leveraging advantage sparseness, we that iteratively detects exact locations values entries matrix. At each iteration, detected by SMP, estimated LSE. also analyze Cram\'er-Rao Lower...

With recent advances on the dense low-Earth orbit (LEO) constellation, LEO satellite network has become one promising solution for providing global coverage Internet-of-Things (IoT) services. Confronted with sporadic transmission from randomly activated IoT devices, we consider random access (RA) mechanism and propose a grant-free RA (GF-RA) scheme to reduce delay mobile satellites. A Bernoulli–Rician message passing expectation–maximization (BR-MP-EM) algorithm is proposed this...

Reconfigurable Intelligent Surfaces (RISs) have been recently considered as an energy-efficient solution for future wireless networks due to their fast and low power configuration enabling massive connectivity latency communications. Channel estimation in RIS-based systems is one of the most critical challenges large number reflecting unit elements distinctive hardware constraints. In this paper, we focus on downlink a RIS-assisted multi-user Multiple Input Single Output (MISO) communication...

With the rapid development of autonomous driving technologies, it becomes difficult to reconcile conflict between ever-increasing demands for high process rate in intelligent automotive tasks and resource-constrained on-board processors. Fortunately, vehicular edge computing (VEC) has been proposed meet pressing resource demands. Due delay-sensitive traits tasks, only a heterogeneous network with multiple access technologies may be able handle these demanding challenges. In this article, we...

Reconfigurable intelligent surface (RIS) is a promising solution to build programmable wireless environment with reconfigurable passive elements, which can achieve high spectral and energy efficiency. In this paper, we investigate the ergodic capacity of RIS-assisted multi-user multiple-input single-output (MISO) systems in both uplink downlink scenarios. Unlike most prior works, where instantaneous channel state information (CSI) assumed, consider realistic scenario only statistical CSI....