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Browsing University of Hertfordshire by Author "Chatzinotas, Symeon"
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Deep Channel Learning For Large Intelligent Surfaces Aided mm-Wave Massive MIMO Systems
Elbir, Ahmet M.; Papazafeiropoulos, Anastasios; Kourtessis, Pandelis; Chatzinotas, Symeon; Senior, John (2020-09)This letter presents the first work introducing a deep learning (DL) framework for channel estimation in large intelligent surface (LIS) assisted massive MIMO (multiple-input multiple-output) systems. A twin convolutional ... -
Ergodic Capacity Analysis of AF DH MIMO Relay Systems with Residual Transceiver Hardware Impairments : Conventional and Large System Limits
Papazafeiropoulos, Anastasios K.; Sharma, Shree Krishna; Chatzinotas, Symeon; Ottersten, Bjorn (2017-08-31)Despite the inevitable presence of transceiver impairments, most prior work on multiple-input multiple-output (MIMO) wireless systems assumes perfect transceiver hardware, which is unrealistic in practice. In this direction, ... -
A Hybrid Architecture for Federated and Centralized Learning
Elbir, Ahmet M.; Coleri, Sinem; Papazafeiropoulos, Anastasios K.; Kourtessis, Pandelis; Chatzinotas, Symeon (2022-09-01)Many of the machine learning tasks rely on centralized learning (CL), which requires the transmission of local datasets from the clients to a parameter server (PS) entailing huge communication overhead. To overcome this, ... -
Impact of Phase-Noise and Spatial Correlation on Double-RIS-Assisted Multiuser MISO Networks
Abdullah, Zaid; Papazafeiropoulos, Anastasios; Kisseleff, Steven; Chatzinotas, Symeon; Ottersten, Bjorn (2022-05-17)We study the performance of a phase-noise impaired double reconfigurable intelligent surface (RIS)-aided multiuser (MU) multiple-input single-output (MISO) system under spatial correlation at both RISs and base-station ... -
Impact of Residual Additive Transceiver Hardware Impairments on Rayleigh-Product MIMO Channels with Linear Receivers : Exact and Asymptotic Analyses
Papazafeiropoulos, Anastasios; Sharma, Shree Krishna; Ratnarajah, Tharmalingam; Chatzinotas, Symeon (2018-01-31)Despite the importance of Rayleigh-product multiple-input multiple-output channels and their experimental validations, there is no work investigating their performance in the presence of residual additive transceiver ... -
Joint Spatial Division and Multiplexing for FDD in Intelligent Reflecting Surface-assisted Massive MIMO Systems
Papazafeiropoulos, Anastasios; Kourtessis, Pandelis; Ntontin, Konstantinos; Chatzinotas, Symeon (2022-06-30)Intelligent reflecting surface (IRS) is a promising technology to deliver the higher spectral and energy requirements in fifth-generation (5G) and beyond wireless networks while shaping the propagation environment. Such a ... -
Near-Field Terahertz Communications: Model-Based and Model-Free Channel Estimation
Elbir, Ahmet M.; Shi, Wei; Papazafeiropoulos, Anastasios K.; Kourtessis, Pandelis; Chatzinotas, Symeon (2023-04-11)Terahertz (THz) band is expected to be one of the key enabling technologies of the sixth generation (6G) wireless networks because of its abundant available bandwidth and very narrow beamwidth. Due to high frequency ... -
Nuts and Bolts of a Realistic Stochastic Geometric Analysis of mmWave HetNets: Hardware Impairments and Channel Aging
Papazafeiropoulos, Anastasios; Ratnarajah, Tharmalingam; Kourtessis, Pandelis; Chatzinotas, Symeon (2019-03-28)Motivated by heterogeneous network (HetNet) design in improving coverage and by millimeter-wave (mmWave) transmission offering an abundance of extra spectrum, we present a general analytical framework shedding light on the ... -
Optimal energy efficiency in cell-free massive MIMO systems: A stochastic geometry approach
Papazafeiropoulos, Anastasios; Ngo, Hien Quoc; Kourtessis, Pandelis; Chatzinotas, Symeon; Senior, John M. (Institute of Electrical and Electronics Engineers (IEEE), 2020-10-08)The increasing demand for green wireless communications and the benefits of the promising cell-free (CF) massive multiple-input-multiple-output (mMIMO) systems towards their optimal energy efficiency (EE) are the focal ... -
Performance Analysis of Cell-Free Massive MIMO Systems: A Stochastic Geometry Approach
Papazafeiropoulos, Anastasios; Kourtessis, Pandelis; Renzo, Marco Di; Chatzinotas, Symeon; Senior, John (2020-04)Cell-free (CF) massive multiple-input-multiple-output (MIMO) has emerged as an alternative deployment for conventional cellular massive MIMO networks. As revealed by its name, this topology considers no cells, while a large ... -
SDN-enabled MIMO Heterogeneous Cooperative Networks with Flexible Cell Association
Papazafeiropoulos, Anastasios; Kourtessis, Pandelis; Renzo, Marco Di; Senior, John M.; Chatzinotas, Symeon (2019-04-01)Small-cell densification is a strategy enabling the offloading of users from macro base stations (MBSs), in order to alleviate their load and increase the coverage, especially, for cell-edge users. In parallel, as the ... -
Wireless Energy Harvesting For Autonomous Reconfigurable Intelligent Surfaces
Ntontin, Konstantinos; Boulogeorgos, Alexandros Apostolos A.; Bjornson, Emil; Martins, Wallace Alves; Kisseleff, Steven; Abadal, Sergi; Alarcon, Eduard; Papazafeiropoulos, Anastasios; Lazarakis, Fotis; Chatzinotas, Symeon (2023-03-30)In the current contribution, we examine the feasibility of fully-energy-autonomous operation of reconfigurable intelligent surfaces (RIS) through wireless energy harvesting (EH) from incident information signals. Towards ...