109 citations · 144 across the 34 of their papers we have counts for
19 papers · 1 filter
Spectral Efficiency Analysis of Massive MIMO-OFDM Systems with Double Quantization
Bengu Bilgic Keskin, A. Oguz Kislal, Ali Gorcin +1
Massive multiple-input multiple-output (MIMO) achieves a high spectral efficiency (SE) by employing a large number of receive antennas in the uplink. Employing many receive antenna…
Fundamentals of Energy-Efficient Hardware Configurations for Wireless Links with Sleep Modes
Anders Enqvist, Özlem Tuğfe Demir, Cicek Cavdar +1
In this paper, we examine the energy efficiency (EE) of a base station (BS) with multiple antennas. We use a state-of-the-art power consumption (PC) model that captures the passive…
Fronthaul-Efficient Cell-Free Massive MIMO via Stream-Adaptive Resolution Control
Özlem Tuğfe Demir, Sinan Gezici
We consider the uplink of a fronthaul-constrained cell-free massive MIMO system with a single multi-antenna user equipment (UE) transmitting multiple spatial streams to distributed…
Joint Quantized Precoding and Bit Allocation for Fronthaul-Constrained Cell-Free Massive MIMO
Özlem Tuğfe Demir
We study quantization-aware precoding for the downlink of cell-free massive MIMO systems with limited-resolution fronthaul. In such systems, the centrally designed precoder must be…
RIS-Assisted Survivable Backhaul Recovery in Small-Cell Systems
Zhenyu Li, Özlem Tuğfe Demir, Emil Björnson +1
The increasing densification of small-cell networks substantially expands cable-based backhaul infrastructure, creating heightened vulnerability to cable link failures. This paper…
Destructive and constructive RIS beamforming in an ISAC-multi-user MIMO network
Steven Rivetti, Ozlem Tugfe Demir, Emil Bjornson +1
Integrated sensing and communication (ISAC) has already established itself as a promising solution to the spectrum scarcity problem, even more so when paired with a reconfigurable…
Multi-agent Reinforcement Learning for Energy Saving in Multi-Cell Massive MIMO Systems
Tianzhang Cai, Qichen Wang, Shuai Zhang +2
We develop a multi-agent reinforcement learning (MARL) algorithm to minimize the total energy consumption of multiple massive MIMO (multiple-input multiple-output) base stations (B…
Pilot Length Optimization with RS-LS Channel Estimation for Extremely Large Aperture Arrays
Mert Alıcıoğlu, Özlem Tuğfe Demir, Emil Björnson
Extremely large aperture arrays can enable unprecedented spatial multiplexing in beyond 5G systems due to their extremely narrow beamfocusing capabilities. However, acquiring the s…
Mixed Static and Reconfigurable Metasurface Deployment in Indoor Dense Spaces: How Much Reconfigurability is Needed?
Zhenyu Li, Ozan Alp Topal, Özlem Tuğfe Demir +2
In this paper, we investigate how metasurfaces can be deployed to deliver high data rates in a millimeter-wave (mmWave) indoor dense space with many blocking objects. These surface…
Interplay between Sensing and Communication in Cell-Free Massive MIMO with URLLC Users
Zinat Behdad, Özlem Tuğfe Demir, Ki Won Sung +1
This paper studies integrated sensing and communication (ISAC) in the downlink of a cell-free massive multiple-input multiple-output (MIMO) system with multi-static sensing and ult…
Energy Saving in Cell-Free Massive MIMO ISAC for Ultra-Reliable Target-Aware Actuation
Zinat Behdad, Özlem Tuğfe Demir, Ki Won Sung +1
Emerging 6G sensing-based applications rely on ultra-reliable target-aware actuation, where timely and accurate sensing information triggers critical actions. Achieving this requir…
Multi-Static Target Detection and Power Allocation for Integrated Sensing and Communication in Cell-Free Massive MIMO
Zinat Behdad, Özlem Tuğfe Demir, Ki Won Sung +2
This paper studies an integrated sensing and communication (ISAC) system within a centralized cell-free massive MIMO (multiple-input multiple-output) network for target detection.…
Optimizing Reconfigurable Intelligent Surfaces for Short Transmissions: How Detailed Configurations can be Afforded?
Anders Enqvist, Özlem Tuğfe Demir, Cicek Cavdar +1
This paper examines how to minimize the energy consumption of a user equipment (UE) when transmitting short data payloads. The receiving base station (BS) controls a reconfigurable…
mmWave Coverage Extension Using Reconfigurable Intelligent Surfaces in Indoor Dense Spaces
Zhenyu Li, Ozan Alp Topal, Özlem Tuğfe Demir +2
In this work, we consider the deployment of reconfigurable intelligent surfaces (RISs) to extend the coverage of a millimeter-wave (mmWave) network in indoor dense spaces. We first…
A Primer on Near-Field Beamforming for Arrays and Reconfigurable Intelligent Surfaces
Emil Björnson, Özlem Tugfe Demir, Luca Sanguinetti
Wireless communication systems have almost exclusively operated in the far-field of antennas and antenna arrays, which is conventionally characterized by having propagation distanc…
Channel Modeling and Channel Estimation for Holographic Massive MIMO with Planar Arrays
Özlem Tuğfe Demir, Emil Björnson, Luca Sanguinetti
In a realistic wireless environment, the multi-antenna channel usually exhibits spatially correlation fading. This is more emphasized when a large number of antennas is densely dep…
Is Channel Estimation Necessary to Select Phase-Shifts for RIS-Assisted Massive MIMO?
Özlem Tuğfe Demir, Emil Björnson
Reconfigurable intelligent surfaces (RISs) consist of many passive elements of metamaterials whose impedance can be controllable to change the characteristics of wireless signals i…
Joint Power Control and LSFD for Wireless-Powered Cell-Free Massive MIMO
Özlem Tuğfe Demir, Emil Björnson
This paper considers wireless uplink information and downlink power transfer in cell-free massive multiple-input multiple-output systems. The single-antenna user equipments (UEs) u…
Channel Estimation in Massive MIMO under Hardware Non-Linearities: Bayesian Methods versus Deep Learning
Özlem Tugfe Demir, Emil Björnson
This paper considers the joint impact of non-linear hardware impairments at the base station (BS) and user equipments (UEs) on the uplink performance of single-cell massive MIMO (m…