Shannon Wireless

In this paper, the authors investigate the #channel #estimation problem in #stacked #intelligent #metasurfaces (#SIM)-#assisted #mmWave #communication #systems. Given that the number of #meta-#atoms far exceeds the number of #base #station (#BS) antennas, obtaining channel state information presents a challenge. They introduce a mutually orthogonal pilot strategy to mitigate #multi-#user #interference and apply a #hard #threshold #orthogonal #matching #pursuit (#HT-#OMP) algorithm for #sparse #channel #estimation. ---- Xianghao Yao; Jiancheng An; Guojun Huang; Hao Liu; Lu Gan; Chau Yuen More details can be found at this link: https://lnkd.in/gsZV-3GV

This article presents a novel #electromagnetic (#EM)-based framework to accurately model the #near-#field (#NF) #scattering #response of extended targets, which is then applied to three canonical shapes: a #flat #rectangular #plate, a #sphere, and a #cylinder. Mathematical expressions for the received signal are provided in each case. Based on this model, the influence of #bandwidth, #carrier #frequency, and #target #distance on localization accuracy is analyzed, showing how higher bandwidths and carrier frequencies improve resolution. Additionally, the impact of target curvature on localization performance is studied. ---- Baptiste Sambon; François De Saint Moulin; Guillaume Thiran; Claude Oestges; Luc Vandendorpe More details can be found at this link: https://lnkd.in/gTcbHb7S

In this article, the #ergodic #capacity (#EC) of #intelligent #reflecting #surface (#IRS)-#aided #multiple-#input-#multiple-#output (#MIMO) #wireless #systems is investigated. Analytical approximations for the ECs of active and passive IRS-aided MIMO systems are derived. As an application of the established theoretical approximations, an #optimization #problem is formulated to maximize the system’s #energy #efficiency (#EE) by determining the optimal number of IRS elements and the optimal transmission power. ---- Hadi Gharibi; Amir Masoud Rabiei; Ali Olfat More details can be found at this link: https://lnkd.in/gzxvYq_N

The authors propose a new, conceptually consistent #free-#space #path #loss (#PL) #model, based on firm #electromagnetic (#EM) theory principles as dictated by a more accurate #physical #optics (#PO) approximation. In particular, they calculate the scattering properties of the unit cell, as an equivalent impedance sheet, using equivalent surface electric and magnetic current density via the PO model. Based on the EM analysis findings, they use the complex #radar #cross #section (#RCS) #matrix to model each unit cell’s contribution to the overall scattering process. ---- Konstantinos Ntokos; Athanasios Iossifides (Iosifidis); Traianos Yioultsis More details can be found at this link: https://lnkd.in/g6qH9dFw

In this paper, a #distributed #chunk-#based #optimization #algorithm is proposed for the #resource #allocation in #broadband #ultra-#dense #small #cell #networks. Based on the proposed algorithm, the power and subcarrier allocation problems are jointly optimized. In order to make the resource allocation suitable for #large #scale #networks, the optimization problem is decomposed first based on an effective decomposition algorithm named #optimal #condition #decomposition (#OCD) algorithm. Furthermore, aiming at reducing implementation complexity, the subcarriers are divided into chunks and are allocated chunk by chunk. ---- Shaozheng Guo; Chengwen Xing; Zesong Fei; Gui Zhou; Yan Xinge More details can be found at this link: https://lnkd.in/gkjcug6b

The authors harness the new #Stacked #Intelligent #Metasurfaces (#SIM) for implementing #holographic #multiple-#input #multiple-#output (#HMIMO) #communications without requiring excessive #radio-#frequency (#RF) #chains, which is a substantial benefit compared to existing implementations. First of all, they propose an HMIMO communication system based on a pair of SIM at the #transmitter (#TX) and #receiver (#RX), respectively. In sharp contrast to the conventional MIMO designs, SIM is capable of automatically accomplishing transmit precoding and receiver combining, as the #EM #waves propagate through them. As such, each spatial stream can be directly radiated and recovered from the corresponding transmit and receive port. Secondly, they formulate the problem of minimizing the error between the #actual #end-#to-#end #channel #matrix and the target diagonal one, representing a flawless interference-free system of parallel subchannels. This is achieved by jointly optimizing the #phase #shifts associated with all the metasurface layers of both the TX-SIM and RX-SIM. They then design a #gradient #descent #algorithm to solve the resultant #non-#convex #problem. Furthermore, they theoretically analyze the HMIMO channel capacity bound and provide some fundamental insights. ---- Jiancheng An; Chao Xu; Derrick Wing Kwan Ng; George Alexandropoulos; Chongwen Huang; Chau Yuen More details can be found at this link: https://lnkd.in/gyzqNNWn

🎓 Join us for a doctoral defence! M.Sc (Tech) Nipuni Ginige will defend her dissertation: “𝐂𝐡𝐚𝐧𝐧𝐞𝐥 𝐄𝐬𝐭𝐢𝐦𝐚𝐭𝐢𝐨𝐧 𝐚𝐧𝐝 𝐎𝐩𝐭𝐢𝐦𝐚𝐥 𝐑𝐞𝐬𝐨𝐮𝐫𝐜𝐞 𝐀𝐥𝐥𝐨𝐜𝐚𝐭𝐢𝐨𝐧 𝐟𝐨𝐫 𝐑𝐞𝐜𝐨𝐧𝐟𝐢𝐠𝐮𝐫𝐚𝐛𝐥𝐞 𝐈𝐧𝐭𝐞𝐥𝐥𝐢𝐠𝐞𝐧𝐭 𝐒𝐮𝐫𝐟𝐚𝐜𝐞𝐬 𝐚𝐧𝐝 𝐒𝐭𝐚𝐜𝐤𝐞𝐝 𝐈𝐧𝐭𝐞𝐥𝐥𝐢𝐠𝐞𝐧𝐭 𝐌𝐞𝐭𝐚𝐬𝐮𝐫𝐟𝐚𝐜𝐞𝐬.” Her research explores efficient wireless communication methods using reconfigurable intelligent surfaces and stacked metasurfaces, focusing on how to optimize resource allocation and improve signal estimation. 📅 Date & Time: Thursday, 23 October 2025, at 14:00 📍 Location: L10, Linnanmaa Campus, University of Oulu 🎙️ Opponent: Professor Ertugrul Basar, Tampere University 🧑⚖️ Custos: Nandana Rajatheva 💻 Zoom: https://lnkd.in/dRpai7-F 🔗 More information: https://lnkd.in/db6FnNFp 📘 Thesis publication: https://lnkd.in/dfJCUeCN #UniOulu #6GFlagship #DoctoralDefence #WirelessCommunications #IntelligentSurfaces

This paper introduces a novel #stacked #intelligent #metasurfaces (#SIM) comprised of an array of programmable metasurface layers. The SIM aims to substitute conventional digital baseband architecture to execute computing tasks with ultra-low processing delay, albeit with a reduced number of #radio-#frequency (#RF) chains and low-resolution digital-to-analog converters. In this paper, the authors present a SIM-aided #multiuser #multiple-#input #single-#output (#MU-#MISO) #near-#field system, where the SIM is integrated into the #base #station (#BS) to perform beamfocusing in the wave domain and customize an end-to-end channel with minimized inter-user interference. ---- Xing Jia, Jiancheng An, Hao Liu, Lu Gan, Marco Di Renzo, Merouane Debbah More details can be found at this link: https://lnkd.in/eU7uZbeS

In this work, the authors exploit #stacked #intelligent #metasurfaces (#SIM) to enable transmit precoding and receiver combining in #holographic #multiple-#input #multiple-#output (#HMIMO) communications, and they study the achievable rate by formulating a joint optimization problem of the SIM phase shifts at both sides of the transceiver and the covariance matrix of the transmitted signal. Notably, they propose its solution by means of an iterative optimization algorithm that relies on the #projected #gradient #method, and accounts for all optimization parameters simultaneously. They also obtain the step size guaranteeing the convergence of the proposed algorithm. ---- Anastasios Papazafeiropoulos, Ph.D., SMIEEE, Jiancheng An, Pandelis Kourtessis, Tharmalingam Ratnarajah, Symeon Chatzinotas More details can be found at this link: https://lnkd.in/efWvWkmY