Shannon Wireless’ Post

This paper aims to optimize multiple #reconfigurable #intelligent #surfaces (#RISs) to control the signal propagation environment for maximizing the signal-to-interference-plus-noise ratio (SINR) in a #multiuser #MIMO system. The authors examine two approaches for managing interference and determining the optimal phase shifts for the RIS elements. They also evaluate the asymptotic expressions for the optimal phase shifts and maximum SINRs as the number of base station antennas becomes very large. ---- Somayeh Aghashahi More details can be found at this link: https://lnkd.in/edgnRK4Z

#Reconfigurable #intelligent #surfaces (#RIS) have the potential to enable high-frequency wireless systems that could become essential for applications requiring high reliability and data rates. However, these systems are sensitive to #misalignment of components and #atmospheric #phenomena such as #turbulence. Motivated by this, this paper presents a theoretical framework for statistically characterizing the combined effects of cascaded turbulence and misalignment in channels. Specifically, it provides the probability density and cumulative distribution functions for channels experiencing both turbulence and misalignment together. ---- Alexandros-Apostolos A. Boulogeorgos More details can be found at this link: https://lnkd.in/gZjEZ28Z

This paper tackles one of the open problems in the #reconfigurable #intelligent #surfaces (#RISs) literature: the #optimal #placement. The authors propose a #model-#based and a #model-#free approach, respectively #RISA and #AI-#RISA, showcasing their large-scale solutions on synthetic topologies to improve communication performance while solving the "#dead-#zone" coverage problem. Additionally, their frameworks are empirically #validated within a #realistic #indoor #scenario, the #Rennes #railway #station, showing how a complex indoor propagation environment can be fully disciplined by an advanced RISs installation.----Guillermo E., Antonio Albanese, Vincenzo Sciancalepore, Xavier Costa Pérez, Albert Banchs, Dinh Thuy PHAN HUY More details can be found at this link: https://lnkd.in/gi_5bNBs

In this manuscript, the authors present a novel approach to jointly optimize active and passive beamforming in a #multiple-#input-#multiple-#output (#MIMO) #full-#duplex (#FD) system assisted by an #intelligent #reflecting #surfaces (#IRS) for #weighted #sum #rate (#WSR) maximization. Given the inherent difficulty in obtaining perfect #channel #state #information (#CSI) in practical scenarios, They consider imperfect CSI and propose a statistically robust beamforming strategy to maximize the ergodic WSR. ---- Chandan Kumar Sheemar, Sourabh Solanki, Jorge Querol, Sumit Kumar, Symeon Chatzinotas More details can be found at this link: https://lnkd.in/euMd5AfJ

This work investigates a #Holographic #Multiple-#Input #Multiple-#Output (#HMIMO) communication system consisting of a source and a receiver being #two #surfaces in the #LoS #configuration. The closed-form expressions of the electric field and the channel coupling coefficients are obtained leveraging an asymptotic expansion of the Green’s function. The derived approximations show satisfactory accuracy in both #near-#and #far-#field conditions, across low and high frequencies. These are then employed to obtain insights regarding (i) the #spatial #distribution of the #beams, and (ii) the #mapping #relation between #source and #receiver modes while ensuring sufficient orthogonality under prescribed conditions. ----Giovanni Iacovelli, @Claudio Iacovelli, Symeon Chatzinotas More details can be found at this link: https://lnkd.in/gKarga8n

This paper proposes an arrangement that partitions the channel training stage into several phases, where the #reconfigurable #intelligent #surfaces (#RISs) reflection coefficients are pre-designed and the effective superposed channel is estimated instead of separately training the source-destination and source-RIS-destination links. Based on this, the active beamformer can be designed at low complexity and the RIS reflection optimization is performed by selecting that one from the pre-designed training set which maximizes the achievable rate. Secondly, the authors propose novel techniques for generating the training set of RIS reflection coefficients. The theoretical performance of the proposed scheme is analyzed and compared to the optimal RIS configuration. ----Jiancheng An, Lajos Hanzo More details can be found at this link: https://lnkd.in/gUZGUFdy

This paper proposes a new #reconfigurable #intelligent #surfaces (#RIS) channel estimation technique, which is the first one that performs #minimum #mean #square #error (#MMSE) based interpolation for the sake of taking into account the time-varying nature of fading even within the coherence time. The RIS modeling invokes only passive elements without relying on RF chains, where both the direct link and RIS-reflected links, as well as both the #line-#of-#sight (#LoS) and #non-#LoS (#NLoS) paths, are taken into account. ----Jiancheng An, Shinya Sugiura, Lajos Hanzo More details can be found at this link: https://lnkd.in/gUarVc9B

This paper presents a multiuser system, employing #reconfigurable #intelligent #surfaces (#RIS) enabled #physical #network #coding (#PNC) alongside multiple antennas to minimize both #delay and #error #probability. Their aim is to establish reliable communication between the user pairs, which communicate through a #base #station (#BS) via RIS. Therefore, the reflecting coefficients including #both #phases and #amplitudes of the RIS are optimized by using the #alternating #direction #method #of #multipliers (#ADMM) algorithm for both single and multiple RIS cases.----Mert İlgüy, Berna Ozbek, Leila Musavian, Shahid Mumtaz More details can be found at this link: https://lnkd.in/ghy2y4kh

In this study, the authors explore a novel use case for #reconfigurable #intelligent #surfaces (#RIS): passive localization and tracking of a RIS-equipped object using monostatic sensing, where the fixed transmitter and receiver share the same single antenna, using OFDM signals. The authors develop a low-complexity algorithm that achieves centimeter-level accuracy using only 6 MHz bandwidth, and by applying temporal coding to random RIS phase profiles, separating signals from undesired multipath sources. In addition, they evaluate the impact of model uncertainty on the performance of the algorithm. ---- Zi Ye, Faryal Junaid, Emad Ibrahim, Rickard Nilsson, Jaap van de Beek More details can be found at this link: https://lnkd.in/dHcbyjSw

#Intelligent #reflecting #surfaces (#IRSs) are being widely investigated as a potential low-cost and energy-efficient alternative to active relays for improving coverage in next-generation cellular networks. However, technical constraints in the configuration of IRSs should be taken into account in the design of scheduling solutions and the assessment of their performance. To this end, they examine an IRS-assisted #time #division #multiple #access (#TDMA) cellular network where the reconfiguration of the #IRS incurs a communication cost; thus, they aim at limiting the number of reconfigurations over time. Along these lines, they propose a clustering-based heuristic scheduling scheme that maximizes the cell sum capacity, subject to a fixed number of reconfigurations within a #TDMA frame. ----Alberto Rech; @Matteo Pagin; @Leonardo Badia; @Stefano Tomasin; Marco Giordani; @Jonathan Gambini More details can be found at this link: https://lnkd.in/gr2SjUeB