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Cell-Free Massive Multiple-input Multiple-output (mMIMO) consists of many access points (APs) in a coverage area that jointly serve the users. These systems can significantly reduce the interference among the users compared to conventional…

Information Theory · Computer Science 2021-11-16 Abbas Khalili , Alexei Ashikhmin , Hong Yang

This paper studies the security aspect of a recently introduced network ("cell-free massive MIMO") under a pilot spoofing attack. Firstly, a simple method to recognize the presence of this type of an active eavesdropping attack to a…

Information Theory · Computer Science 2018-05-14 Tiep M. Hoang , Hien Quoc Ngo , Trung Q. Duong , Hoang D. Tuan , Alan Marshall

Massive access is one of the main use cases of beyond 5G (B5G) wireless networks and massive MIMO is a key technology for supporting it. Prior works studied massive access in the co-located massive MIMO framework. In this paper, we…

Information Theory · Computer Science 2021-05-24 Unnikrishnan Kunnath Ganesan , Emil Björnson , Erik G. Larsson

Cell-free widely distributed massive multiple-input multiple-output (MIMO) systems utilize radio units spread out over a large geographical area. The radio signal of a user equipment (UE) is coherently detected by a subset of radio units…

Signal Processing · Electrical Eng. & Systems 2022-08-31 David Löschenbrand , Markus Hofer , Laura Bernadó , Stefan Zelenbaba , Thomas Zemen

Cell-free massive MIMO and symbiotic radio are promising beyond 5G (B5G) networking architecture and transmission technology, respectively. This paper studies cell-free symbiotic radio systems, where a number of distributed access points…

Information Theory · Computer Science 2021-06-14 Zhuoyin Dai , Ruoguang Li , Jingran Xu , Yong Zeng , Shi Jin

We consider a multi-cell Massive MIMO system in a line-of-sight (LoS) propagation environment, for which each user is served by one base station, with no cooperation among the base stations. Each base station knows the channel between its…

Signal Processing · Electrical Eng. & Systems 2018-08-14 Hong Yang , Hien Quoc Ngo , Erik G. Larsson

Intelligent terminals often produce a large number of data packets of small lengths. For these packets, it is inefficient to follow the conventional medium access control (MAC) protocols because they lead to poor utilization of service…

Information Theory · Computer Science 2016-11-18 Ronggui Xie , Huarui Yin , Zhengdao Wang , Xiaohui Chen

Large-scale distributed antenna systems with many access points (APs) that serve the users by coherent joint transmission is being considered for 5G-and-beyond networks. The technology is called Cell-free Massive MIMO and can provide a more…

Information Theory · Computer Science 2020-06-30 Trinh Van Chien , Emil Björnson , Erik G. Larsson

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

Imagine a coverage area where each mobile device is communicating with a preferred set of wireless access points (among many) that are selected based on its needs and cooperate to jointly serve it, instead of creating autonomous cells. This…

Information Theory · Computer Science 2023-11-29 Özlem Tuğfe Demir , Emil Björnson , Luca Sanguinetti

Cell-free massive multi-input multi-output (MIMO) has recently attracted much attention, attributed to its potential to deliver uniform service quality. However, the adoption of a cell-free architecture raises concerns about the high…

Information Theory · Computer Science 2024-06-04 Wei Jiang , Hans D. Schotten

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

In this paper, we analyze the performance of the uplink communication of massive multi-cell multiple-input multiple-output (MIMO) systems under the effects of pilot contamination and delayed channels because of terminal mobility. The base…

Information Theory · Computer Science 2016-11-17 Anastasios K. Papazafeiropoulos , Hien Quoc Ngo , Tharm Ratnarajah

We consider a cell-free massive MIMO system with multiple antennas on the users and access points. In previous works, the downlink spectral efficiency (SE) has been evaluated using the hardening bound that requires no downlink pilots. This…

Signal Processing · Electrical Eng. & Systems 2024-04-30 Eren Berk Kama , Junbeom Kim , Emil Björnson

We consider a multi-cell massive MIMO system where a time-division duplex protocol is used to estimate the channel state information via uplink pilots. When maximum ratio combining (MRC) is used at the BSs, the re-use of pilots across cells…

Information Theory · Computer Science 2019-11-26 Meysam Shahrbaf Motlagh , Subhajit Majhi , Patrick Mitran

This paper considers a deterministic physical model of massive multiple-input multiple-output (MIMO) systems with uniform linear antenna arrays. It is known that the maximum spatial degrees of freedom is achieved by spacing antenna elements…

Information Theory · Computer Science 2016-01-22 Keigo Takeuchi

Cell-free (CF) massive multiple-input multiple-output (MIMO) is a promising solution to provide uniform good performance for unmanned aerial vehicle (UAV) communications. In this paper, we propose the UAV communication with wireless power…

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

The recently commercialized fifth-generation (5G) wireless communication networks achieved many improvements, including air interface enhancement, spectrum expansion, and network intensification by several key technologies, such as massive…

Information Theory · Computer Science 2021-12-01 Hengtao He , Xianghao Yu , Jun Zhang , S. H. Song , Khaled B. Letaief

We consider the cell-free massive multiple-input multiple-output (MIMO) downlink, where a very large number of distributed multiple-antenna access points (APs) serve many single-antenna users in the same time-frequency resource. A simple…

Information Theory · Computer Science 2017-11-27 Hien Quoc Ngo , Le-Nam Tran , Trung Q. Duong , Michail Matthaiou , Erik G. Larsson

Massive machine-type communications protocols have typically been designed under the assumption that coordination between users requires significant communication overhead and is thus impractical. Recent progress in efficient activity…

Information Theory · Computer Science 2022-07-12 Justin Kang , Wei Yu