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Cell-free (CF) multiuser multiple-input multiple-output (MU-MIMO) systems are an emerging technology that provides service simultaneously to multiple users but suffers from multiuser interference (MUI). In this work, we propose a robust…

Information Theory · Computer Science 2025-02-27 A. Flores , R. de Lamare

Cell-free Massive MIMO systems consist of a large number of geographically distributed access points (APs) that serve users by coherent joint transmission. Downlink power allocation is important in these systems, to determine which APs…

Information Theory · Computer Science 2022-01-03 Sucharita Chakraborty , Emil Björnson , Luca Sanguinetti

This paper considers Cell-Free Massive Multiple Input Multiple Output (MIMO) systems with the assistance of an RIS for enhancing the system performance. Distributed maximum-ratio combining (MRC) is considered at the access points (APs). We…

Information Theory · Computer Science 2021-09-17 Trinh Van Chien , Hien Quoc Ngo , Symeon Chatzinotas , Marco Di Renzo , Björn Ottersten

This paper investigates the joint data and pilot power optimization for maximum sum spectral efficiency (SE) in multi-cell Massive MIMO systems, which is a non-convex problem. We first propose a new optimization algorithm, inspired by the…

Information Theory · Computer Science 2019-03-21 Trinh Van Chien , Emil Björnson , Erik G. Larsson

In this paper, we investigate the impact of channel aging on the performance of cell-free (CF) massive multiple-input multiple-output (MIMO) systems with both spatial correlation and pilot contamination. We derive novel closed-form uplink…

Information Theory · Computer Science 2021-04-26 Jiakang Zheng , Jiayi Zhang , Emil Björnson , Bo Ai

This paper develops a multi-user downlink communication framework for distributed low Earth orbit satellite networks serving ground users equipped with multiple antennas. Building upon the concept of cell-free multiple-input multiple-output…

Signal Processing · Electrical Eng. & Systems 2026-01-28 Parisa Ramezani , Emil Björnson

High-speed train (HST) communications with orthogonal frequency division multiplexing (OFDM) techniques have received significant attention in recent years. Besides, cell-free (CF) massive multiple-input multiple-output (MIMO) is considered…

Information Theory · Computer Science 2022-01-25 Jiakang Zheng , Jiayi Zhang , Enyu Shi , Jing Jiang , Bo Ai

This paper proposes a dynamic access point (AP) selection and pilot power allocation (DAPPA) framework for uplink cell-free massive multiple-input multiple-output (CFmMIMO) systems, aiming to mitigate inter-user interference and improve…

Signal Processing · Electrical Eng. & Systems 2026-02-24 Saeed Mohammadzadeh , Rodrigo C. De Lamare , Kanapathippillai Cumanan , Hien Quoc Ngo

The growing demand for efficient delivery of common content to multiple user equipments (UEs) has motivated significant research in physical-layer multicasting. By exploiting the beamforming capabilities of massive MIMO, multicasting…

Signal Processing · Electrical Eng. & Systems 2025-11-11 Mahmoud Zaher , Emil Björnson

We consider a cell-free massive multiple-input multiple-output (MIMO) system with multiple antennas on the users and access points (APs). In previous works, the downlink spectral efficiency (SE) has been evaluated using the hardening bound…

Information Theory · Computer Science 2026-01-01 Eren Berk Kama , Junbeom Kim , Emil Björnson

Cell-free massive MIMO (CF mMIMO) is a promising next generation wireless architecture to realize federated learning (FL). However, sensitive information of user equipments (UEs) may be exposed to the involved access points or the central…

Information Theory · Computer Science 2022-12-01 Jiayi Zhang , Jing Zhang , Derrick Wing Kwan Ng , Bo Ai

Cell-free (CF) massive multiple-input multiple-output (mMIMO) is a promising technique for achieving high spectral efficiency (SE) using multiple distributed access points (APs). However, harsh propagation environments often lead to…

Information Theory · Computer Science 2024-05-16 Yiyang Zhu , Enyu Shi , Ziheng Liu , Jiayi Zhang , Bo Ai

In this paper, we optimize user scheduling, power allocation and beamforming in distributed multiple-input multiple-output (MIMO) networks implementing user-centric clustering. We study both the coherent and non-coherent transmission modes,…

Information Theory · Computer Science 2021-08-16 Hussein A. Ammar , Raviraj Adve , Shahram Shahbazpanahi , Gary Boudreau , Kothapalli Venkata Srinivas

Cell-free massive MIMO (CF-mMIMO) provides wireless connectivity for a large number of user equipments (UEs) using access points (APs) distributed across a wide area with high spectral efficiency (SE). The energy efficiency (EE) of the…

Information Theory · Computer Science 2022-05-10 Thomas Choi , Masaaki Ito , Issei Kanno , Jorge Gomez-Ponce , Colton Bullard , Takeo Ohseki , Kosuke Yamazaki , Andreas F. Molisch

Cell-free massive MIMO (multiple-input multiple-output) enhances spectral and energy efficiency compared to conventional cellular networks by enabling joint transmission and reception across a large number of distributed access points…

Signal Processing · Electrical Eng. & Systems 2026-02-10 Özlem Tuğfe Demir , Emil Björnson

We study support for unmanned aerial vehicle (UAV) communications through a cell-free massive MIMO architecture. Under the general assumption that the propagation channel between the mobile stations, either UAVs or ground users, and the…

Signal Processing · Electrical Eng. & Systems 2019-02-12 Carmen D'Andrea , Adrian Garcia-Rodriguez , Giovanni Geraci , Lorenzo Galati Giordano , Stefano Buzzi

In this paper, a new optimization framework is presented for the joint design of user selection, power allocation, and precoding in multi-cell multi-user multiple-input multiple-output (MU-MIMO) systems when imperfect channel state…

Information Theory · Computer Science 2019-02-05 Jiwook Choi , Namyoon Lee , Song-Nam Hong , Giuseppe Caire

Ultra-reliable and low-latency communication (URLLC) is a pivotal technique for enabling the wireless control over industrial Internet-of-Things (IIoT) devices. By deploying distributed access points (APs), cell-free massive multiple-input…

Information Theory · Computer Science 2023-02-21 Qihao Peng , Hong Ren , Cunhua Pan , Nan Liu , Maged Elkashlan

We study internet of things (IoT) systems supported by cell-free (CF) massive MIMO (mMIMO) with optimal linear channel estimation. For the uplink, we consider optimal linear MIMO receiver and obtain an uplink SINR approximation involving…

Information Theory · Computer Science 2020-12-01 Hangsong Yan , Alexei Ashikhmin , Hong Yang

We consider a practical spatially correlated reconfigurable intelligent surface (RIS)-aided cell-free (CF) massive multiple-input-multiple-output (mMIMO) system with multi-antenna access points (APs) over spatially correlated Rician fading…

Information Theory · Computer Science 2022-09-29 Enyu Shi , Jiayi Zhang , Zhe Wang , Derrick Wing Kwan Ng , Bo Ai