George Karagiannidis | Aristotle University of Thessaloniki (original) (raw)

Papers by George Karagiannidis

Electronics, 2021

Artificial Intelligence (AI) and especially Machine Learning (ML) can play a very important role ... more Artificial Intelligence (AI) and especially Machine Learning (ML) can play a very important role in realizing and optimizing 6G network applications. In this paper, we present a brief summary of ML methods, as well as an up-to-date review of ML approaches in 6G wireless communication systems. These methods include supervised, unsupervised and reinforcement techniques. Additionally, we discuss open issues in the field of ML for 6G networks and wireless communications in general, as well as some potential future trends to motivate further research into this area.

IEEE Transactions on Communications, 2016

IEEE Transactions on Wireless Communications

IEEE Wireless Communications Letters, 2015

ABSTRACT

We study the impact of residual radio frequency (RF) impairments and fading on the spectrum sensi... more We study the impact of residual radio frequency (RF) impairments and fading on the spectrum sensing performance of a classical energy detector (ED), which is employed in a full-duplex wireless system. Specifically, we present novel closed-form expressions for the false-alarm and detection probabilities, assuming Nakagami-m fading, and the impact of residual RF impairments. The results reveal the importance of taking into account the wireless environment and the ED's capabilities, when evaluating the ED performance and setting its threshold.

The next generation wireless networks are envisioned to deal with the expected thousand-fold incr... more The next generation wireless networks are envisioned to deal with the expected thousand-fold increase in total mobile broadband data and the hundred-fold increase in connected devices. In order to provide higher data rates, improved end-to-end performance, low latency, and low energy consumption at low cost per transmission, the fifth generation (5G) systems are required to overcome various handicaps of current cellular networks and wireless links. One of the key handicaps of 5G systems is the performance degradation of the communication link, due to the use of low-cost transceiver in high data rate. Motivated by this in this paper, we discuss the impact of transceiver front-end hardware imperfections on the spectrum sensing performance of cognitive radios.

—We evaluate and quantify the joint effect of fading and multiple interferers on the physical-lay... more —We evaluate and quantify the joint effect of fading and multiple interferers on the physical-layer (PHY) security of a system consisted of a base-station (BS), a legitimate user, and an eavesdropper. To this end, we present a novel closed-form expression for the secrecy outage probability, which takes into account the fading characteristics of the wireless environment, the location and the number of interferers, as well as the transmission power of the BS and the interference. The results reveal that the impact of interference should be seriously taken into account in the design and deployment of a wireless system with PHY security.

—We study the error performance of an heterodyne differential phase-shift keying (DPSK) optical w... more —We study the error performance of an heterodyne differential phase-shift keying (DPSK) optical wireless (OW) communication system operating under various intensity fluctuations conditions. Specifically, it is assumed that the propagating signal suffers from the combined effects of atmospheric turbulence-induced fading, misalignment fading (i.e., pointing errors) and path-loss. Novel closed-form expressions for the statistics of the random at-tenuation of the propagation channel are derived and the bit-error rate (BER) performance is investigated for all the above fading effects. Numerical results are provided to evaluate the error performance of OW systems with the presence of atmospheric turbulence and/or misalignment. Moreover, nonlinear optimization is also considered to find the optimum beamwidth that achieves the minimum BER for a given signal-to-noise ratio value.

European Transactions on Telecommunications, 2004

A novel closed-form expression for the achievable average channel capacity of a generalized-selec... more A novel closed-form expression for the achievable average channel capacity of a generalized-selection combining RAKE receiver in Rayleigh fading, is derived. Performance comparison for the capacity achieved with maximal-ratio combining and RAKE receivers is also presented. The expression derived, fully conforms to the upper bound of the Shannon–Hartley theorem. Copyright © 2004 AEI.

Motivated by the suitability of the Weibull distribution to model multipath fading channels, the ... more Motivated by the suitability of the Weibull distribution to model multipath fading channels, the second order statistics and the spectral efficiency (SE) of L-branch SC receivers are studied. Deriving a novel closed-form expression for the probability density function (pdf) of the SC output SNR, the average level crossing rate (LCR), the average fade duration (AFD) and the Shannon's average SE, at the output of the SC, are derived in closed-forms. Our results are sufficiently general to handle arbitrary fading parameter and dissimilar branch powers.

Electronics Letters, 2003

IEEE Transactions on Communications, 2004

Journal of The Franklin Institute-engineering and Applied Mathematics, 2008

... Numerical results reveal that, as expected, the diversity gain that such systems offer is, un... more ... Numerical results reveal that, as expected, the diversity gain that such systems offer is, under the weak source–destination channel assumption, on the order of the ... [5] GK Karagiannidis, NC Sagias and TA Tsiftsis, Closed-form statistics for the sum of squared Nakagami-m ...

—In this paper, we systematically study the average rate and outage probability tradeoffs of full... more —In this paper, we systematically study the average rate and outage probability tradeoffs of full-duplex two-way and one-way relaying under residual self-interference. Among various relaying protocols, two common of them are considered: amplify-and-forward (AF) and decode-and-forward (DF). Furthermore, we consider the application of physical-layer network coding (PNC) and analog network coding (ANC) to full-duplex two-way relaying. Novel closed-form expressions for the average rate and outage probability, are presented. The results show that full-duplex two-way relaying can achieve higher rate than one-way relaying in the medium to high signal-to-noise ratio (SNR) region, at the cost of a certain loss in the outage performance. Moreover, DF protocol can achieve better outage performance than the AF one, but it suffers from a certain loss in the rate in the high SNR region. It is also shown that PNC can further improve the rate and outage performance. In addition, the results clearly reveal the effects of time multiplexing, forward protocol, and network coding on relaying systems, which would shed light on designing practical full-duplex relaying schemes.

We investigate the physical layer (PHY) security of a system with a base-station (BS), a legitima... more We investigate the physical layer (PHY) security of a system with a base-station (BS), a legitimate user, and an eavesdropper, whose exact location is unknown but within a ring-shaped area around the BS. To this end, we present novel closed-form expressions for the secrecy outage probability, which take into consideration both the impact of fading, as well as the eavesdropper's location uncertainty. The derived expressions are validated through simulations, which reveal that the level of uncertainty should be seriously taken into account in the design and deployment of a wireless system with PHY security.

In this paper, a downlink multiple-input-multiple-output (MIMO) non-orthogonal multiple access (N... more In this paper, a downlink multiple-input-multiple-output (MIMO) non-orthogonal multiple access (NOMA) scenario is considered. We investigate a dynamic user clustering problem from a fairness perspective. In order to solve this optimization problem, three sub-optimal algorithms, namely top-down A, top-down B, and bottom up, are proposed to realize different tradeoffs of complexity and throughput of the worst user. In addition, for each given user clustering case, we optimize the power allocation coefficients for the users in each cluster by adopting a bisection search based algorithm. Numerical results show that the proposed algorithms can lower the complexity with an acceptable degradation on throughput compared with the exhaustive search method. It is worth noting that top-down B algorithm can achieve a good tradeoff between complexity and throughput among the three proposed algorithms.

2011 IEEE International Conference on Communications (ICC), 2011

Page 1. Diversity Combining in Hybrid RF/FSO Systems with PSK Modulation Nestor D. Chatzidiamanti... more Page 1. Diversity Combining in Hybrid RF/FSO Systems with PSK Modulation Nestor D. Chatzidiamantis ∗ , George K. Karagiannidis ∗ , Emmanouil E. Kriezis ∗ and Michail Matthaiou † ∗Department of Electrical & Computer ...

Electronics, 2021

Artificial Intelligence (AI) and especially Machine Learning (ML) can play a very important role ... more Artificial Intelligence (AI) and especially Machine Learning (ML) can play a very important role in realizing and optimizing 6G network applications. In this paper, we present a brief summary of ML methods, as well as an up-to-date review of ML approaches in 6G wireless communication systems. These methods include supervised, unsupervised and reinforcement techniques. Additionally, we discuss open issues in the field of ML for 6G networks and wireless communications in general, as well as some potential future trends to motivate further research into this area.

IEEE Transactions on Communications, 2016

IEEE Transactions on Wireless Communications

IEEE Wireless Communications Letters, 2015

ABSTRACT

We study the impact of residual radio frequency (RF) impairments and fading on the spectrum sensi... more We study the impact of residual radio frequency (RF) impairments and fading on the spectrum sensing performance of a classical energy detector (ED), which is employed in a full-duplex wireless system. Specifically, we present novel closed-form expressions for the false-alarm and detection probabilities, assuming Nakagami-m fading, and the impact of residual RF impairments. The results reveal the importance of taking into account the wireless environment and the ED's capabilities, when evaluating the ED performance and setting its threshold.

The next generation wireless networks are envisioned to deal with the expected thousand-fold incr... more The next generation wireless networks are envisioned to deal with the expected thousand-fold increase in total mobile broadband data and the hundred-fold increase in connected devices. In order to provide higher data rates, improved end-to-end performance, low latency, and low energy consumption at low cost per transmission, the fifth generation (5G) systems are required to overcome various handicaps of current cellular networks and wireless links. One of the key handicaps of 5G systems is the performance degradation of the communication link, due to the use of low-cost transceiver in high data rate. Motivated by this in this paper, we discuss the impact of transceiver front-end hardware imperfections on the spectrum sensing performance of cognitive radios.

—We evaluate and quantify the joint effect of fading and multiple interferers on the physical-lay... more —We evaluate and quantify the joint effect of fading and multiple interferers on the physical-layer (PHY) security of a system consisted of a base-station (BS), a legitimate user, and an eavesdropper. To this end, we present a novel closed-form expression for the secrecy outage probability, which takes into account the fading characteristics of the wireless environment, the location and the number of interferers, as well as the transmission power of the BS and the interference. The results reveal that the impact of interference should be seriously taken into account in the design and deployment of a wireless system with PHY security.

—We study the error performance of an heterodyne differential phase-shift keying (DPSK) optical w... more —We study the error performance of an heterodyne differential phase-shift keying (DPSK) optical wireless (OW) communication system operating under various intensity fluctuations conditions. Specifically, it is assumed that the propagating signal suffers from the combined effects of atmospheric turbulence-induced fading, misalignment fading (i.e., pointing errors) and path-loss. Novel closed-form expressions for the statistics of the random at-tenuation of the propagation channel are derived and the bit-error rate (BER) performance is investigated for all the above fading effects. Numerical results are provided to evaluate the error performance of OW systems with the presence of atmospheric turbulence and/or misalignment. Moreover, nonlinear optimization is also considered to find the optimum beamwidth that achieves the minimum BER for a given signal-to-noise ratio value.

European Transactions on Telecommunications, 2004

A novel closed-form expression for the achievable average channel capacity of a generalized-selec... more A novel closed-form expression for the achievable average channel capacity of a generalized-selection combining RAKE receiver in Rayleigh fading, is derived. Performance comparison for the capacity achieved with maximal-ratio combining and RAKE receivers is also presented. The expression derived, fully conforms to the upper bound of the Shannon–Hartley theorem. Copyright © 2004 AEI.

Motivated by the suitability of the Weibull distribution to model multipath fading channels, the ... more Motivated by the suitability of the Weibull distribution to model multipath fading channels, the second order statistics and the spectral efficiency (SE) of L-branch SC receivers are studied. Deriving a novel closed-form expression for the probability density function (pdf) of the SC output SNR, the average level crossing rate (LCR), the average fade duration (AFD) and the Shannon's average SE, at the output of the SC, are derived in closed-forms. Our results are sufficiently general to handle arbitrary fading parameter and dissimilar branch powers.

Electronics Letters, 2003

IEEE Transactions on Communications, 2004

Journal of The Franklin Institute-engineering and Applied Mathematics, 2008

... Numerical results reveal that, as expected, the diversity gain that such systems offer is, un... more ... Numerical results reveal that, as expected, the diversity gain that such systems offer is, under the weak source–destination channel assumption, on the order of the ... [5] GK Karagiannidis, NC Sagias and TA Tsiftsis, Closed-form statistics for the sum of squared Nakagami-m ...

—In this paper, we systematically study the average rate and outage probability tradeoffs of full... more —In this paper, we systematically study the average rate and outage probability tradeoffs of full-duplex two-way and one-way relaying under residual self-interference. Among various relaying protocols, two common of them are considered: amplify-and-forward (AF) and decode-and-forward (DF). Furthermore, we consider the application of physical-layer network coding (PNC) and analog network coding (ANC) to full-duplex two-way relaying. Novel closed-form expressions for the average rate and outage probability, are presented. The results show that full-duplex two-way relaying can achieve higher rate than one-way relaying in the medium to high signal-to-noise ratio (SNR) region, at the cost of a certain loss in the outage performance. Moreover, DF protocol can achieve better outage performance than the AF one, but it suffers from a certain loss in the rate in the high SNR region. It is also shown that PNC can further improve the rate and outage performance. In addition, the results clearly reveal the effects of time multiplexing, forward protocol, and network coding on relaying systems, which would shed light on designing practical full-duplex relaying schemes.

We investigate the physical layer (PHY) security of a system with a base-station (BS), a legitima... more We investigate the physical layer (PHY) security of a system with a base-station (BS), a legitimate user, and an eavesdropper, whose exact location is unknown but within a ring-shaped area around the BS. To this end, we present novel closed-form expressions for the secrecy outage probability, which take into consideration both the impact of fading, as well as the eavesdropper's location uncertainty. The derived expressions are validated through simulations, which reveal that the level of uncertainty should be seriously taken into account in the design and deployment of a wireless system with PHY security.

In this paper, a downlink multiple-input-multiple-output (MIMO) non-orthogonal multiple access (N... more In this paper, a downlink multiple-input-multiple-output (MIMO) non-orthogonal multiple access (NOMA) scenario is considered. We investigate a dynamic user clustering problem from a fairness perspective. In order to solve this optimization problem, three sub-optimal algorithms, namely top-down A, top-down B, and bottom up, are proposed to realize different tradeoffs of complexity and throughput of the worst user. In addition, for each given user clustering case, we optimize the power allocation coefficients for the users in each cluster by adopting a bisection search based algorithm. Numerical results show that the proposed algorithms can lower the complexity with an acceptable degradation on throughput compared with the exhaustive search method. It is worth noting that top-down B algorithm can achieve a good tradeoff between complexity and throughput among the three proposed algorithms.

2011 IEEE International Conference on Communications (ICC), 2011

Page 1. Diversity Combining in Hybrid RF/FSO Systems with PSK Modulation Nestor D. Chatzidiamanti... more Page 1. Diversity Combining in Hybrid RF/FSO Systems with PSK Modulation Nestor D. Chatzidiamantis ∗ , George K. Karagiannidis ∗ , Emmanouil E. Kriezis ∗ and Michail Matthaiou † ∗Department of Electrical & Computer ...

IEEE Transactions on Vehicular Technology, 2017

This paper studies the secrecy rate maximization problem of a secure wireless communication syste... more This paper studies the secrecy rate maximization problem of a secure wireless communication system, in the presence of multiple eavesdroppers. The security of the communication link is enhanced through cooperative jamming, with the help of multiple jammers. First, a feasibility condition is derived to achieve a positive secrecy rate at the destination. Then, we solve the original secrecy rate maximization problem, which is not convex in terms of power allocation at the jammers. To circumvent this non-convexity, the achievable secrecy rate is approximated for a given power allocation at the jammers and the approximated problem is formulated into a geometric programming one. Based on this approximation, an iterative algorithm has been developed to obtain the optimal power allocation at the jammers. Next, we provide a bisection approach, based on one-dimensional search, to validate the optimality of the proposed algorithm. In addition, by assuming Rayleigh fading, the secrecy outage probability (SOP) of the proposed cooperative jamming scheme is analyzed. More specifically, a single-integral form expression for SOP is derived for the most general case as well as a closed-form expression for the special case of two cooperative jammers and one eavesdropper. Simulation results have been provided to validate the convergence and the optimality of the proposed algorithm as well as the theoretical derivations of the presented SOP analysis.