References of "Chatzinotas, Symeon 50001234"
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See detailModeling and Implementation of 5G Edge Caching over Satellite
Vu, Thang Xuan UL; Poirier, Yannick; Chatzinotas, Symeon UL et al

in International Journal of Satellite Communications and Networking (2020)

The fifth generation (5G) wireless networks have to deal with the high data rate and stringent latency requirements due to the massive invasion of connected devices and data-hungry applications. Edge ... [more ▼]

The fifth generation (5G) wireless networks have to deal with the high data rate and stringent latency requirements due to the massive invasion of connected devices and data-hungry applications. Edge caching is a promising technique to overcome these challenges by prefetching the content closer to the end users at the edge node’s local storage. In this paper, we analyze the performance of edge caching 5G networks with the aid of satellite communication systems. Firstly, we investigate the satellite-aided edge caching systems in two promising use cases: a) in dense urban areas, and b) in sparsely populated regions, e.g., rural areas. Secondly, we study the effectiveness of satellite systems via the proposed satellite-aided caching algorithm, which can be used in three configurations: i) mono-beam satellite, ii) multi-beam satellite, and iii) hybrid mode. Thirdly, the proposed caching algorithm is evaluated by using both empirical Zipf-distribution data and the more realistic Movielens dataset. Last but not least, the proposed caching scheme is implemented and tested by our developed demonstrators which allow real-time analysis of the cache hit ratio and cost analysis. [less ▲]

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See detailFull-Duplex Enabled Mobile Edge Caching: From Distributed to Cooperative Caching
Vu, Thang Xuan UL; Chatzinotas, Symeon UL; Ottersten, Björn UL et al

in IEEE Transactions on Wireless Communications (2020)

Mobile edge caching (MEC) has received much attention as a promising technique to overcome the stringent latency and data hungry requirements in future generation wireless networks. Meanwhile, full-duplex ... [more ▼]

Mobile edge caching (MEC) has received much attention as a promising technique to overcome the stringent latency and data hungry requirements in future generation wireless networks. Meanwhile, full-duplex (FD) transmission can potentially double the spectral efficiency by allowing a node to receive and transmit in the same time/frequency block simultaneously. In this paper, we investigate the delivery time performance of full-duplex enabled MEC (FD-MEC) systems, in which the users are served by distributed edge nodes (ENs), which operate in FD mode and are equipped with a limited storage memory. Firstly, we analyse the FD-MEC with different levels of cooperation among the ENs and take into account a realistic model of self-interference cancellation. Secondly, we propose a framework to minimize the system delivery time of FD-MEC under both linear and optimal precoding designs. Thirdly, to deal with the non-convexity of the formulated problems, two iterative optimization algorithms are proposed based on the inner approximation method, whose convergence is analytically guaranteed. Finally, the effectiveness of the proposed designs are demonstrated via extensive numerical results. It is shown that the cooperative scheme mitigates inter-user and self interference significantly better than the distributed scheme at an expense of inter-EN cooperation. In addition, we show that minimum mean square error (MMSE)-based precoding design achieves the best performance-complexity trade-off, compared with the zero-forcing and optimal designs. [less ▲]

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See detailJoint Power Allocation and Access Point Selection for Cell-free Massive MIMO
Vu, Thang Xuan UL; Chatzinotas, Symeon UL; ShahbazPanahi, Shahram et al

in IEEE International Conference on Communications (2020)

Cell-free massive multiple-input multiple-output (CF-MIMO) is a promising technological enabler for fifth generation (5G) networks in which a large number of access points (APs) jointly serve the users ... [more ▼]

Cell-free massive multiple-input multiple-output (CF-MIMO) is a promising technological enabler for fifth generation (5G) networks in which a large number of access points (APs) jointly serve the users. Each AP applies conjugate beamforming to precode data, which is based only on the AP's local channel state information. However, by having the nature of a (very) large number of APs, the operation of CF-MIMO can be energy-inefficient. In this paper, we investigate the energy efficiency performance of CF-MIMO by considering a practical energy consumption model which includes both the signal transmit energy as well as the static energy consumed by hardware components. In particular, a joint power allocation and AP selection design is proposed to minimize the total energy consumption subject to given quality of service (QoS) constraints. In order to deal with the combinatorial complexity of the formulated problem, we employ norm $l_{2,1}$-based block-sparsity and successive convex optimization to leverage the AP selection process. Numerical results show significant energy savings obtained by the proposed design, compared to all-active APs scheme and the large-scale based AP selection. [less ▲]

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See detailInterference Exploitation via Symbol-Level Precoding: Overview, State-of-the-Art and Future Directions
Li, Ang; Spano, Danilo UL; Krivochiza, Jevgenij UL et al

in IEEE Communications Surveys and Tutorials (2020), 22(2), 796-839

Interference is traditionally viewed as a performance limiting factor in wireless communication systems, which is to be minimized or mitigated. Nevertheless, a recent line of work has shown that by ... [more ▼]

Interference is traditionally viewed as a performance limiting factor in wireless communication systems, which is to be minimized or mitigated. Nevertheless, a recent line of work has shown that by manipulating the interfering signals such that they add up constructively at the receiver side, known interference can be made beneficial and further improve the system performance in a variety of wireless scenarios, achieved by symbol-level precoding (SLP). This paper aims to provide a tutorial on interference exploitation techniques from the perspective of precoding design in a multi-antenna wireless communication system, by beginning with the classification of constructive interference (CI) and destructive interference (DI). The definition for CI is presented and the corresponding mathematical characterization is formulated for popular modulation types, based on which optimization-based precoding techniques are discussed. In addition, the extension of CI precoding to other application scenarios as well as for hardware efficiency is also described. Proof-of-concept testbeds are demonstrated for the potential practical implementation of CI precoding, and finally a list of open problems and practical challenges are presented to inspire and motivate further research directions in this area. [less ▲]

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See detailCarrier Aggregation in Multi-Beam High Throughput Satellite Systems
Kibria, Mirza UL; Lagunas, Eva UL; Maturo, Nicola UL et al

in Carrier Aggregation in Multi-Beam High Throughput Satellite Systems (2019, December 10)

Carrier Aggregation (CA) is an integral part of current terrestrial networks. Its ability to enhance the peak data rate, to efficiently utilize the limited available spectrum resources and to satisfy the ... [more ▼]

Carrier Aggregation (CA) is an integral part of current terrestrial networks. Its ability to enhance the peak data rate, to efficiently utilize the limited available spectrum resources and to satisfy the demand for data-hungry applications has drawn large attention from different wireless network communities. Given the benefits of CA in the terrestrial wireless environment, it is of great interest to analyze and evaluate the potential impact of CA in the satellite domain. In this paper, we study CA in multi-beam high throughput satellite systems. We consider both inter-transponder and intra-transponder CA at the satellite payload level of the communication stack, and we address the problem of carrier-user assignment assuming that multiple users can be multiplexed in each carrier. The transmission parameters of different carriers are generated considering the transmission characteristics of carriers in different transponders. In particular, we propose a flexible carrier allocation approach for a CA enabled multi-beam satellite system targeting a proportionally fair user demand satisfaction. Simulation results and analysis shed some light on this rather unexplored scenario and demonstrate the feasibility of the CA in satellite communication systems. [less ▲]

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See detailJoint Scheduling and Precoding for Frame-Based Multigroup Multicasting in Satellite Communications
Bandi, Ashok UL; Shankar, Bhavani UL; Chatzinotas, Symeon UL et al

in Bandi, Ashok; Shankar, Bhavani; Chatzinotas, Symeon (Eds.) et al Joint Scheduling and Precoding for Frame-Based Multigroup Multicasting in Satellite Communications (2019, December 09)

Recent satellite standards enforce the coding of multiple users’ data in a frame. This transmission strategy mimics the well-known physical layer multigroup multicasting (MGMC). However, typical beam ... [more ▼]

Recent satellite standards enforce the coding of multiple users’ data in a frame. This transmission strategy mimics the well-known physical layer multigroup multicasting (MGMC). However, typical beam coverage with a large number of users and limited frame length lead to the scheduling of only a few users. Moreover, in emerging aggressive frequency reuse systems, scheduling is coupled with precoding. This is addressed in this work, through the joint design of scheduling and precoding for frame-based MGMC satellite systems. This aim is formulated as the maximization of the sum-rate under per beam power constraint and minimum SINR requirement of scheduled users. Further, a framework is proposed to transform the non-smooth SR objective with integer scheduling and nonconvex SINR constraints as a difference-of-convex problem that facilitates the joint update of scheduling and precoding. Therein, an efficient convex-concave procedure based algorithm is proposed. Finally, the gains (up to 50%) obtained by the jointed design over state-of-the-art methods is shown through Monte-Carlo simulations. [less ▲]

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See detailMachine learning for physical-layer security: Attacks and SLP Countermeasures for Multiantenna Downlink Systems
Mayouche, Abderrahmane UL; Spano, Danilo; Tsinos, Christos UL et al

in 2019 IEEE Global Communications Conference (2019)

Most physical-layer security (PLS) work employ information theoretic metrics for performance analysis. In this paper, however, we investigate PLS from a signal processing point of view, where we rely on ... [more ▼]

Most physical-layer security (PLS) work employ information theoretic metrics for performance analysis. In this paper, however, we investigate PLS from a signal processing point of view, where we rely on bit-error rate (BER) at the eavesdropper (Eve) as a metric for information leakage. Meanwhile, recently, symbol-level precoding (SLP) has been shown to provide PLS gains as a new way for security. However, in this work, we introduce a machine learning (ML) based attack, where we show that even SLP schemes can be vulnerable to such attacks. Namely, this attack manifests when an eavesdropper (Eve) utilizes ML in order to learn the precoding pattern when precoded pilots are sent. With this ability, an Eve can decode data with favorable accuracy. As a countermeasure to this attack, we propose a novel precoding design. The proposed countermeasure yields high BER at the Eve, which makes symbol detection practically infeasible for the latter, thus providing physical-layer security between the base station (BS) and the users. In the numerical results, we validate both the attack and the countermeasure, and show that this gain in security can be achieved at the expense of only a small additional power consumption at the transmitter. [less ▲]

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See detailMultigroup Multicast Precoding for Energy Optimization in SWIPT Systems with Heterogeneous Users
Gautam, Sumit UL; Lagunas, Eva UL; Bandi, Ashok UL et al

in IEEE Communications Society Magazine (2019)

The key to developing future generations of wireless communication systems lies in the expansion of extant methodologies, which ensures the coexistence of a variety of devices within a system. In this ... [more ▼]

The key to developing future generations of wireless communication systems lies in the expansion of extant methodologies, which ensures the coexistence of a variety of devices within a system. In this paper, we assume several multicasting (MC) groups comprising three types of heterogeneous users including Information Decoding (ID), Energy Harvesting (EH) and both ID and EH. We present a novel framework to investigate the multi-group (MG) - MC precoder designs for three different scenarios, namely, Separate Multicast and Energy Precoding Design (SMEP), Joint Multicast and Energy Precoding Design (JMEP), and Per-User Information and/or Energy Precoding Design (PIEP). In the considered system, a multi-antenna source transmits the relevant information and/or energy to the groups of corresponding receivers using more than one MC streams. The data processing users employ the conventional ID receiver architectures, the EH users make use of a non-linear EH module for energy acquisition, while the users capable of performing both ID and EH utilize the separated architecture with disparate ID and non-linear EH units. Our contribution is threefold. Firstly, we propose an optimization framework to i) minimize the total transmit power and ii) to maximize the sum harvested energy, the two key performance metrics of MG-MC systems. The proposed framework allows the analysis of the system under arbitrary given quality of service and harvested energy requirements. Secondly, to deal with the non-convexity of the formulated problems, we transform the original problems respectively into equivalent forms, which can be effectively solved by semi-definite relaxation (SDR) and alternating optimization. The convergence of the proposed algorithms is analytically guaranteed. Thirdly, a comparative study between the proposed schemes is conducted via extensive numerical results, wherein the benefits of adopting SMEP over JMEP and PIEP models are discussed [less ▲]

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See detailPerformance Analysis of Integrated Satellite-Terrestrial Multiantenna Relay Networks with Multiuser Scheduling
Huang, Qingquan; Lin, Min; Zhu, Wei-Ping et al

in IEEE Transactions on Aerospace and Electronic Systems (2019)

In this paper, we investigate the performance of a multiuser integrated satellite-terrestrial relay network (ISTRN) with threshold-based decode-and-forward protocol, where the satellite-relay link ... [more ▼]

In this paper, we investigate the performance of a multiuser integrated satellite-terrestrial relay network (ISTRN) with threshold-based decode-and-forward protocol, where the satellite-relay link undergoes Shadowed-Rician (SR) fading while the relay-user links experience Nakagami-m fading. We first formulate a constrained optimization problem with an objective to maximize the system capacity in order to determine the beamforming weight vectors at the relay, and thereby develop two multiuser scheduling schemes, namely, best user scheduling and user fairness scheduling. Then, we present a closedform expression for the probability density function (PDF) of the square sum of independent and identically distributed SR random variables, which is more accurate and concise than the existing solutions. Based on the new PDF results, we derive closedform expressions for the outage probability (OP) and ergodic capacity of the considered network using the two scheduling schemes. Furthermore, the asymptotic OP expressions at high signal-to-noise ratio are also deduced to reveal the asymptotic behavior of the considered ISTRN. Finally, simulation results are provided to validate our theoretical analysis, and show the impact of various parameters on the system performance. [less ▲]

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See detailEnergy-efficient Trajectory Design for UAV-enabled Wireless Communications with Latency Constraints
Tran Dinh, Hieu UL; Vu, Thang Xuan UL; Chatzinotas, Symeon UL et al

Scientific Conference (2019, November 03)

This paper studies a new energy-efficient unmanned aerial vehicle (UAV)-enabled wireless communications, where the UAV acts as a flying base station (BS) to serve the ground users (GUs) within some ... [more ▼]

This paper studies a new energy-efficient unmanned aerial vehicle (UAV)-enabled wireless communications, where the UAV acts as a flying base station (BS) to serve the ground users (GUs) within some predetermined latency limitations, e.g., requested timeout (RT). Our goal is to design the UAV trajectory to minimize the total energy consumption while satisfying the RT requirement from every GU, which is accomplished via two consecutive subproblems: traveling time minimization and energy minimization problems. Firstly, we propose two exhaustive search and heuristic algorithms based on the traveling salesman problem with time window (TSPTW) in order to minimize the UAV’s traveling time without violating the GUs’ RT requirements. While the exhaustive algorithm achieves the best performance at a high computation cost, the heuristic algorithm achieves a trade-off between the performance and complexity. Secondly, we minimize the total energy consumption, for a given trajectory, via a joint optimization of the UAV’s velocity along subsequent hops. Finally, numerical results are presented to demonstrate the effectiveness of our proposed algorithms. In particular, it is shown that the proposed solutions outperform the reference in terms of both energy consumption and outage performance. [less ▲]

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See detailActive Content Popularity Learning via Query-by-Committee for Edge Caching
Bommaraveni, Srikanth UL; Vu, Thang; Vuppala, Satyanarayana et al

Scientific Conference (2019, November 03)

Edge caching has received much attention as an effective solution to face the stringent latency requirements in 5G networks due to the proliferation of handset devices as well as data-hungry applications ... [more ▼]

Edge caching has received much attention as an effective solution to face the stringent latency requirements in 5G networks due to the proliferation of handset devices as well as data-hungry applications. One of the challenges in edge caching systems is to optimally cache strategic contents to maximize the percentage of total requests served by the edge caches. To enable the optimal caching strategy, we propose an Active Learning approach (AL) to learn and design an accurate content request prediction algorithm. Specifically, we use an AL based Query-by-committee (QBC) matrix completion algorithm with a strategy of querying the most informative missing entries of the content popularity matrix. The proposed AL framework leverage's the trade-off between exploration and exploitation of the network, and learn the user's preferences by posing queries or recommendations. Later, it exploits the known information to maximize the system performance. The effectiveness of proposed AL based QBC content learning algorithm is demonstrated via numerical results. [less ▲]

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See detailHardware Precoding Demonstration in Multi-Beam UHTS Communications under Realistic Payload Characteristics
Merlano Duncan, Juan Carlos UL; Querol Borras, Jorge UL; Maturo, Nicola UL et al

in Proceedings of the 37th International Communications Satellite Systems Conference (2019, November 01)

In this paper, we present a new hardware test-bed to demonstrate closed-loop precoded communications for interference mitigation in multi-beam ultra high throughput satellite systems under realistic ... [more ▼]

In this paper, we present a new hardware test-bed to demonstrate closed-loop precoded communications for interference mitigation in multi-beam ultra high throughput satellite systems under realistic payload and channel impairments. We build the test-bed to demonstrate a real-time channel aided precoded transmission under realistic conditions such as the power constraints and satellite-payload non-linearities. We develop a scalable architecture of an SDR platform with the DVB-S2X piloting. The SDR platform consists of two parts: analog-to-digital (ADC) and digital-to-analog (DAC) converters preceded by radio frequency (RF) front-end and Field-Programmable Gate Array (FPGA) backend. The former introduces realistic impairments in the transmission chain such as carrier frequency and phase misalignments, quantization noise of multichannel ADC and DAC and non-linearities of RF components. It allows evaluating the performance of the precoded transmission in a more realistic environment rather than using only numerical simulations. We benchmark the performance of the communication standard in realistic channel scenarios, evaluate received signal SNR, and measure the actual channel throughput using LDPC codes. [less ▲]

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See detailUser Terminal Wideband Modem for Very High Throughput Satellites
Kisseleff, Steven UL; Maturo, Nicola UL; Chatzinotas, Symeon UL et al

in 37th International Communications Satellite Systems Conference (ICSSC), Japan, October 2019 (2019, November)

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See detailEFFECTS OF MULTIPLE OSCILLATOR PHASE NOISE IN PRECODING PERFORMANCE
Martinez Marrero, Liz UL; Merlano Duncan, Juan Carlos UL; Querol, Jorge UL et al

Scientific Conference (2019, October)

Satellite Precoding is a promising technique to meet the target data rates of the future high throughput satellite systems and the costs per bit as required by 5G applications and networks, but it ... [more ▼]

Satellite Precoding is a promising technique to meet the target data rates of the future high throughput satellite systems and the costs per bit as required by 5G applications and networks, but it requires strict synchronization among the transmitted waveforms, in addition to accurate channel state information. Most of the published work about this topic consider ideal oscillators, but in practice, the output of an oscillator is not a single spectral line at the nominal frequency. This paper proposes a model for the oscillator phase noise and analyzes the resulting received signal to interference plus noise ratio (SNIR) in a satellite communication system using Precoding. Simulations of a communication satellite system with a two-beam transponder and two receivers were performed to compute the effective SNIR. This work uses a simulator which also considers practical impairments such as time misalignment, errors in the channel state information, interference, thermal noise and phase noise masks for satellite oscillators. The Precoding methods used for the analysis are Zero Forcing (ZF) and Minimum Mean Square Error (MMSE). The obtained results prove that there is a degradation in the performance due to the use of independent oscillators but this effect is compensated by the precoding matrix. [less ▲]

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See detailA Joint Solution for Scheduling and Precoding in Multiuser MISO Downlink Channels
Bandi, Ashok UL; Shankar, Bhavani UL; Chatzinotas, Symeon UL et al

in IEEE Transactions on Wireless Communications (2019)

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See detailLearning-based Physical Layer Communications for Multiagent Collaboration
Mostaani, Arsham UL; Simeone, Osvaldo; Chatzinotas, Symeon UL et al

in Mostaani, Arsham; Simeone, Osvaldo; Chatzinotas, Symeon (Eds.) et al PIMRC 2019 Proceedings (2019, September 11)

Consider a collaborative task carried out by two autonomous agents that can communicate over a noisy channel. Each agent is only aware of its own state, while the accomplishment of the task depends on the ... [more ▼]

Consider a collaborative task carried out by two autonomous agents that can communicate over a noisy channel. Each agent is only aware of its own state, while the accomplishment of the task depends on the value of the joint state of both agents. As an example, both agents must simultaneously reach a certain location of the environment, while only being aware of their own positions. Assuming the presence of feedback in the form of a common reward to the agents, a conventional approach would apply separately: (\emph{i}) an off-the-shelf coding and decoding scheme in order to enhance the reliability of the communication of the state of one agent to the other; and (\emph{ii}) a standard multiagent reinforcement learning strategy to learn how to act in the resulting environment. In this work, it is argued that the performance of the collaborative task can be improved if the agents learn how to jointly communicate and act. In particular, numerical results for a baseline grid world example demonstrate that the jointly learned policy carries out compression and unequal error protection by leveraging information about the action policy. [less ▲]

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See detailWireless Multi-group Multicast Precoding with Selective RF Energy Harvesting
Gautam, Sumit UL; Lagunas, Eva UL; Chatzinotas, Symeon UL et al

Scientific Conference (2019, September 05)

We present a novel framework for multi-group multicast precoding in the presence of three types of wireless users which are distributed among various multicast groups. A multi-antenna transmitter conveys ... [more ▼]

We present a novel framework for multi-group multicast precoding in the presence of three types of wireless users which are distributed among various multicast groups. A multi-antenna transmitter conveys information and/or energy to the groups of corresponding receivers using more than one multicast streams. The information specific users have conventional receiver architectures to process data, energy harvesting users collect energy using the non-linear energy harvesting module and each of the joint information decoding and energy harvesting capable user is assumed to employ the separated architecture with disparate non-linear energy harvesting and conventional information decoding units. In this context, we formulate and analyze the problem of total transmit power minimization for optimal precoder design subjected to minimum signal-to-interference-and-noise ratio and harvested energy demands at the respective users under three different scenarios. This problem is solved via semi-definite relaxation and the advantages of employing separate information and energy precoders are shown over joint and per-user information and energy precoder designs. Simulation results illustrate the benefits of proposed framework under several operating conditions and parameter values. [less ▲]

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See detailOptimal Resource Allocation for NOMA-Enabled Cache Replacement and Content Delivery
Lei, Lei UL; Vu, Thang Xuan UL; Xiang, Lin UL et al

in IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (IEEE PIMRC 2019) (2019, September)

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See detailJoint User Grouping and Power Allocation for MISO Systems: Learning to Schedule
Yuan, Yaxiong; Vu, Thang Xuan UL; Lei, Lei UL et al

in IEEE European Signal Processing Conference 2019 (2019, September)

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See detailLearning-Assisted Optimization for Energy-Efficient Scheduling in Deadline-Aware NOMA Systems
Lei, Lei UL; You, Lei; He, Qing et al

in IEEE Transactions on Green Communications and Networking (2019)

Detailed reference viewed: 56 (8 UL)