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We consider the downlink of Cell-Free Massive MIMO systems, where a very large number of distributed access points (APs) simultaneously serve a much smaller number of users. Each AP uses local channel estimates obtained from received uplink…

Information Theory · Computer Science 2015-05-12 Hien Quoc Ngo , Alexei Ashikhmin , Hong Yang , Erik G. Larsson , Thomas L. Marzetta

A continuous goal in all communication systems is to enhance the users experience and provide them with the highest possible data rates. Recently, the concept of cell-free massive MIMO (CF-mMIMO) systems has been considered to enhance the…

Information Theory · Computer Science 2023-10-30 Ahmed Almehdhar , Mohanad Obeed , Anas Chaaban , Salam A. Zummo

Reconfigurable intelligent surfaces (RIS)-assisted cell-free massive multiple-input multiple-output (CF mMIMO) systems have emerged as a promising technology for sixth-generation communication systems. These systems capitalize on RIS to…

Signal Processing · Electrical Eng. & Systems 2024-12-24 Yu Lu , Jiayi Zhang , Enyu Shi , Peng Zhang , Derrick Wing Kwan Ng , Dusit Niyato , Bo Ai

Limited-backhaul cell-free Massive multiple-input multiple-output (MIMO), in which the fog radio access network (F-RAN) is implemented to exchange the information between access points (APs) and the central processing unit (CPU), is…

Information Theory · Computer Science 2018-11-27 Manijeh Bashar , Hien Quoc Ngo , Alister G. Burr , Dick Maryopi , Kanapathippillai Cumanan , Erik G. Larsson

Reconfigurable intelligent surface (RIS)-assisted cell-free (CF) multiple-input multiple-output (MIMO) networks can significantly enhance system performance. However, the extensive deployment of RIS elements imposes considerable channel…

Signal Processing · Electrical Eng. & Systems 2025-06-30 Hongqin Ke , Jindan Xu , Wei Xu , Chau Yuen , Zhaohua Lu

In this letter, we develop a continuous fluid antenna (FA) framework for uplink channel estimation in cell-free massive multiple-input and multiple-output (CF-mMIMO) systems. By modeling the wireless channel as a spatially correlated…

Information Theory · Computer Science 2026-02-19 Masoud Kaveh , Farshad Rostami Ghadi , Francisco Hernando-Gallego , Diego Martin , Riku Jantti , Kai-Kit Wong

In this paper, we consider the uplink channel estimation phase and downlink data transmission phase of cell-free millimeter wave (mmWave) massive multiple-input multiple-output (MIMO) systems with low-capacity fronthaul links and…

Information Theory · Computer Science 2022-11-01 In-soo Kim , Mehdi Bennis , Junil Choi

Massive multi-user (MU) multiple-input multiple-output (MIMO) promises significant gains in spectral efficiency compared to traditional, small-scale MIMO technology. Linear equalization algorithms, such as zero forcing (ZF) or minimum…

Information Theory · Computer Science 2018-11-12 Charles Jeon , Kaipeng Li , Joseph R. Cavallaro , Christoph Studer

This paper investigates a cell-free massive multiple-input-multiple-output (CF-mMIMO) integrated sensing and communication (ISAC) system that addresses the critical challenge of information leakage to potential eavesdroppers located within…

Signal Processing · Electrical Eng. & Systems 2026-03-20 Ruiguang Wang , Takumi Takahashi , Hideki Ochiai

Large-scale multiple-input and multiple-output (MIMO) systems are capable of achieving high date rate. However, given the high hardware cost and excessive power consumption of massive MIMO systems, as a remedy, intelligent metasurfaces have…

Information Theory · Computer Science 2024-05-17 Qingchao Li , Mohammed El-Hajjar , Chao Xu , Jiancheng An , Chau Yuen , Lajos Hanzo

In this paper, we study a cell-free multiple-input multiple-output network equipped with integrated sensing and communication (ISAC) access points (APs). The distributed APs are used to jointly serve the communication needs of user…

Information Theory · Computer Science 2026-05-26 Steven Rivetti , Emil Bjornson , Mikael Skoglund

In this work, we consider the uplink of a scalable cell-free massive MIMO system where the users are served only by a subset of access points (APs) in the network. The APs are physically grouped into predetermined "cell-centric clusters",…

Information Theory · Computer Science 2021-03-10 Carmen D'Andrea , Erik G. Larsson

Pilot contamination remains a major bottleneck in realizing the full potential of distributed massive MIMO systems. We propose two dynamic and scalable pilot assignment schemes designed for practical deployment in such networks. First, we…

Networking and Internet Architecture · Computer Science 2025-10-27 Mohd Saif Ali Khan , Karthik RM , Samar Agnihotri

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

This letter proposes a multi-stream selection framework for \ac{CF-MIMO} networks. Partially coherent transmission has been considered by clustering \acp{AP} into phase-aligned clusters to address the challenges of phase misalignment and…

Signal Processing · Electrical Eng. & Systems 2025-06-09 Esra Aycan Beyazıt , Jeroen Famaey , Nina Slamnik-Kriještorac , Johann M. Marquez-Barja , Miguel Camelo Botero

This paper addresses the problem of channel estimation in multi-cell interference-limited cellular networks. We consider systems employing multiple antennas and are interested in both the finite and large-scale antenna number regimes…

Information Theory · Computer Science 2016-11-15 Haifan Yin , David Gesbert , Miltiades Filippou , Yingzhuang Liu

Cell-free massive multiple-input multiple-output (mMIMO) offers significant advantages in mobility scenarios, mainly due to the elimination of cell boundaries and strong macro diversity. In this paper, we examine the downlink performance of…

Information Theory · Computer Science 2024-12-04 Ziheng Liu , Jiayi Zhang , Yiyang Zhu , Enyu Shi , Bo Ai

In this paper, we investigate joint power control and access point (AP) selection scheme in a cell-free massive multiple-input multiple-output (CF-mMIMO) system under an active eavesdropping attack, where an eavesdropper tries to overhear…

Signal Processing · Electrical Eng. & Systems 2024-01-17 Yasseen Sadoon Atiya , Zahra Mobini , Hien Quoc Ngo , Michail Matthaiou

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

Traditional cellular networks struggle with poor quality of service (QoS) for cell-edge users, while cell-free (CF) systems offer uniform QoS but incur high roll-out costs due to acquiring numerous access point (AP) sites and deploying a…

Information Theory · Computer Science 2026-01-27 Wei Jiang , Hans D. Schotten