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Browsing by Author "Papazafeiropoulos, Anastasios K."
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Deterministic equivalent performance analysis of time-varying massive MIMO systems
Papazafeiropoulos, Anastasios K.; Ratnarajah, Tharmalingam (2015-10-01)Delayed channel state information at the transmitter (CSIT) due to time variation of the channel, coming from the users' relative movement with regard to the BS antennas, is an inevitable degrading performance factor in ... -
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 General Channel Aging Conditions on the Downlink Performance of Massive MIMO
Papazafeiropoulos, Anastasios K. (2017-02-01)Recent works have identified massive multiple-input multiple-output (MIMO) as a key technology for achieving substantial gains in spectral and energy efficiency. Additionally, the turn to low-cost transceivers, being prone ... -
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 ... -
Performance of massive MIMO uplink with zero-forcing receivers under delayed channels
Papazafeiropoulos, Anastasios K.; Ngo, Hien Quoc; Ratnarajah, Tharmalingam (2017-04-01)In this paper, we analyze the performance of the uplink communication of massive multicell multiple-input multiple-output (MIMO) systems under the effects of pilot contamination and delayed channels because of terminal ... -
Sum-Rate and Power Scaling of Massive MIMO Systems with Channel Aging
Kong, Chuili; Zhong, Caijun; Papazafeiropoulos, Anastasios K.; Matthaiou, Michail; Zhang, Zhaoyang (2015-10-26)This paper investigates the achievable sum-rate of massive multiple-input multiple-output (MIMO) systems in the presence of channel aging. For the uplink, by assuming that the base station (BS) deploys maximum ratio combining ...