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Cell-free massive multiple-input multiple-output (CF mMIMO) systems are characterized by having many more access points (APs) than user equipments (UEs). A key challenge is to determine which APs should serve which UEs. Previous work has…

Information Theory · Computer Science 2022-05-09 Shuaifei Chen , Jiayi Zhang , Emil Björnson , Özlem Tuğfe Demir , Bo Ai

This paper considers cell-free massive multiple-input multiple-output systems where the multiple-antenna access points (APs) assist the single-antenna user equipments (UEs) by wireless power transfer. The UEs utilize the energy harvested in…

Information Theory · Computer Science 2020-01-28 Özlem Tuğfe Demir , Emil Björnson

Cell-free massive multiple-input multiple-output (CF mMIMO) systems are expected to provide faster and more robust connections to user equipments (UEs) by cooperation of a massive number of distributed access points, and to be one of the…

Signal Processing · Electrical Eng. & Systems 2021-10-05 Masaaki Ito , Issei Kanno , Takeo Ohseki , Kosuke Yamazaki , Yoji Kishi , Thomas Choi , Andreas F. Molisch

Integrating cell-free massive MIMO (CF-mMIMO) into satellite-unmanned aerial vehicle (UAV) networks offers an effective solution for enhancing connectivity. In this setup, UAVs serve as access points (APs) of a terrestrial CF-mMIMO network…

Information Theory · Computer Science 2024-07-25 Thong-Nhat Tran , Giovanni Interdonato

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

In this paper we consider a time-division duplex cell-free massive multiple-input multiple-output (MIMO) system where many distributed access points (APs) simultaneously serve many users. A normalized conjugate beamforming scheme, which…

Information Theory · Computer Science 2019-09-10 Giovanni Interdonato , Hien Quoc Ngo , Erik G. Larsson , Pål Frenger

Large-scale MIMO systems can yield a substantial improvement in spectral efficiency for future communication systems. Due to the finer spatial resolution achieved by a huge number of antennas at the base stations, these systems have shown…

Information Theory · Computer Science 2014-10-15 Abla Kammoun , Axel Müller , Emil Björnson , Mérouane Debbah

Cell-free massive multiple-input multiple-output (MIMO) is a promising technology for next-generation communication systems. This work proposes a novel partially coherent (PC) transmission framework to cope with the challenge of phase…

Information Theory · Computer Science 2024-04-04 Unnikrishnan Kunnath Ganesan , Tung Thanh Vu , Erik G. Larsson

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

We consider the downlink of a cell-free massive multiple-input multiple-output (MIMO) network where numerous distributed access points (APs) serve a smaller number of users under time division duplex operation. An important issue in…

Information Theory · Computer Science 2017-04-12 L. D. Nguyen , T. Q. Duong , H. Q. Ngo , K. Tourki

Cell-free massive multiple-input-multiple-output (mMIMO) is an emerging technology for beyond 5G with its promising features such as higher spectral efficiency and superior spatial diversity as compared to conventional…

Information Theory · Computer Science 2020-12-29 Zakir Hussain Shaik , Emil Björnson , Erik G. Larsson

We propose a cell-edge-aware (CEA) zero forcing (ZF) precoder that exploits the excess spatial degrees of freedom provided by a large number of base station (BS) antennas to suppress inter-cell interference at the most vulnerable user…

Information Theory · Computer Science 2017-05-24 Howard H. Yang , Giovanni Geraci , Tony Q. S. Quek , Jeffrey G. Andrews

A wireless massive MIMO system entails a large number (tens or hundreds) of base station antennas serving a much smaller number of users, with large gains in spectral-efficiency and energy-efficiency compared with conventional MIMO…

Information Theory · Computer Science 2014-11-18 Alexei Ashikhmin , Thomas L. Marzetta , Liangbin Li

In this paper, we analyze the achievable downlink spectral efficiency of cell-free massive multiple input multiple output (CF-mMIMO) systems, accounting for the effects of channel aging (caused by user mobility) and pilot contamination. We…

Information Theory · Computer Science 2022-09-08 Abhinav Anand , Chandra R. Murthy , Ribhu Chopra

Pilot contamination is known to be one of the main impairments for massive MIMO multi-cell communications. Inspired by the concept of fractional frequency reuse and by recent contributions on pilot reutilization among non-adjacent cells, we…

Information Theory · Computer Science 2016-11-15 Italo Atzeni , Jesús Arnau , Mérouane Debbah

In this paper, we study the sum rate performance of zero-forcing (ZF) and regularized ZF (RZF) precoding in large MISO broadcast systems under the assumptions of imperfect channel state information at the transmitter and per-user channel…

Information Theory · Computer Science 2012-09-11 Sebastian Wagner , Romain Couillet , Merouane Debbah , Dirk. T. M. Slock

We consider fronthaul-limited generalized zeroforcing-based cell-free massive multiple-input multiple-output (CF-mMIMO) systems with multiple-antenna users and multipleantenna access points (APs) relying on both cooperative beamforming (CB)…

Information Theory · Computer Science 2025-06-18 Zahra Mobini , Ahmet Hasim Gokceoglu , Li Wang , Gunnar Peters , Hien Quoc Ngo

Imagine a coverage area with many wireless access points that cooperate to jointly serve the users, instead of creating autonomous cells. Such a cell-free network operation can potentially resolve many of the interference issues that appear…

Information Theory · Computer Science 2020-05-11 Emil Björnson , Luca Sanguinetti

Cell-Free Massive MIMO systems aim to expand the coverage area of wireless networks by replacing a single high-performance Access Point (AP) with multiple small, distributed APs connected to a Central Processing Unit (CPU) through a…

Information Theory · Computer Science 2023-11-13 Michail Gkagkos , Jean-Francois Chamberland , Costas N. Georghiades , Krishna R. Narayanan

This paper studies the transmit power optimization in multi-cell massive multiple-input multiple-output (MIMO) systems. Network-wide max-min fairness (NW-MMF) and network-wide proportional fairness (NW-PF) are two well-known power control…

Information Theory · Computer Science 2021-05-25 Amin Ghazanfari , Hei Victor Cheng , Emil Björnson , Erik G. Larsson