References of "Chatzinotas, Symeon 50001234"
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See detailMultigroup Multicast Beamforming and Antenna Selection with Rate-Splitting in Multicell Systems
Tervo, Oskari; Trant, Le-Nam; Chatzinotas, Symeon UL et al

in 2018 IEEE 19th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC) (2018)

This paper studies energy-efficient joint coordinated beamforming and antenna selection in multi-cell multi-user multigroup multicast multiple-input single-output systems. We focus on interference-limited ... [more ▼]

This paper studies energy-efficient joint coordinated beamforming and antenna selection in multi-cell multi-user multigroup multicast multiple-input single-output systems. We focus on interference-limited scenarios, e.g., when the number of radio frequency (RF) chains is of the same order as the number of multicasting groups. To tackle the interference, we exploit rate-splitting to divide the group messages into common and group-specific sub-messages. We propose a per-cell rate-splitting approach, where the common message is locally designed to be decoded by the in-cell users, while treated as noise by the out-cell users. We consider the case where the number of RF chains is smaller than that of antennas, and consider a switching architecture, that is, the antenna selection is employed to choose the best antennas for transmission. Numerical results illustrate the potential of the proposed approach to significantly improve the energy efficiency in the interference-limited regime. [less ▲]

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See detailFaster-than-Nyquist Signaling through Spatio-temporal Symbol-level Precoding for the Multiuser MISO Downlink Channel
Spano, Danilo UL; Alodeh, Maha; Chatzinotas, Symeon UL et al

in IEEE Transactions on Wireless Communications (2018)

This paper deals with the problem of the interference between multiple co-channel transmissions in the downlink of a multi-antenna wireless system. In this framework, symbol-level precoding is a promising ... [more ▼]

This paper deals with the problem of the interference between multiple co-channel transmissions in the downlink of a multi-antenna wireless system. In this framework, symbol-level precoding is a promising technique which is able to constructively exploit the multi-user interference and to transform it into useful power at the receiver side. While previous works on symbol-level precoding were focused on exploiting the multi-user interference, in this paper we extend this concept by jointly handling the interference both in the spatial dimension (multi-user interference) and in the temporal dimension (inter-symbol interference). Accordingly, we propose a novel precoding method, referred to as spatio-temporal symbol-level precoding. In this new precoding paradigm, faster-than-Nyquist signaling can be applied over multi-user MISO systems, and the inter-symbol interference can be tackled at the transmitter side, without additional complexity for the user terminals. While applying faster-than-Nyquist signaling, the proposed optimization strategies perform a sum power minimization with Quality-of-Service constraints. Numerical results are presented in a comparative fashion to show the effectiveness of the proposed techniques, which outperform the state of the art symbol-level precoding schemes in terms of symbol error rate, effective rate, and energy efficiency. [less ▲]

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See detailIntegrated Terrestrial-Satellite Wireless Backhauling: Resource Management and Benefits for 5G
Shaat, Musbah; Lagunas, Eva UL; Pérez-Neira, Ana et al

in IEEE Vehicular Technology Magazine (2018)

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See detailEnergy-Efficient and Secure Resource Allocation for Multiple-Antenna NOMA with Wireless Power Transfer
Chang, Zheng; Lei, Lei UL; Zhang, Huaqing et al

in IEEE Transactions on Green Communications and Networking (2018)

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See detail2018 IEEE 23rd International Workshop on Computer Aided Modeling and Design of Communication Links and Networks (CAMAD)
Domouchtsidis, Stavros; Tsinos, Christos UL; Chatzinotas, Symeon UL et al

in 2018 IEEE 23rd International Workshop on Computer Aided Modeling and Design of Communication Links and Networks (CAMAD) (2018)

Large-Scale Antenna Array Systems may be used to serve multiple users in the same time-frequency resource block which results to harmful multi-user interference (MUI). In the literature precoding ... [more ▼]

Large-Scale Antenna Array Systems may be used to serve multiple users in the same time-frequency resource block which results to harmful multi-user interference (MUI). In the literature precoding techniques have been proposed as a way to mitigate the induced MUI, by designing the transmitted signals using the knowledge of the Channel State Information (CSI), in block-level precoding (BLP) or both the CSI and the information-bearing symbols, in symbol-level precoding (SLP). However, the proposed SLP techniques require fully digital baseband processing which is infeasible in large-scale antenna array systems because of the high cost and power consumption of radio frequency (RF) components. In order to reduce the number of y-RF chains, we address an Antenna Selection Symbol-Level Precoding (AS-SLP) scheme, which minimizes the MUI by activating only a subset of the available antennas. For this scheme we develop an efficient algorithm, based on Coordinate Descent. Simulations provide an insight on the efficiency of the proposed approach and its improvement with respect to the fully digitally approaches. [less ▲]

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See detailSymbol-level precoding with low resolution DACs for large-scale array MU-MIMO systems
Tsinos, Christos UL; Kalantari, Ashkan UL; Chatzinotas, Symeon UL et al

in 2018 IEEE 19th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC) (2018)

While (Multiple Input-Multiple Output) MIMO systems based on large-scale antenna arrays are seen as the solution to the continuously increasing demands in modern wireless systems, they require high ... [more ▼]

While (Multiple Input-Multiple Output) MIMO systems based on large-scale antenna arrays are seen as the solution to the continuously increasing demands in modern wireless systems, they require high hardware complexity and power consumption. To tackle this, solutions based on low resolution Analog-to-Digital Converters (ADCs) / Digital-to-Analog Converters (DACs) have been developed in the literature where they mainly propose quantized versions of typical channel dependent linear precoding solutions. Alternatively, nonlinear Symbol level Precoding techniques have been recently proposed for downlink Multi User (MU)-MIMO systems with low resolution DACs that achieve significantly improved performance in several cases. The existing SLP approaches support only DACs of 1-bit resolution which result in significant performance degradations, especially when constellations with order greater than 4 are employed. To that end, in this work a novel SLP approach is developed that supports systems with DACs of any resolution and it is applicable for any type of constellation. As it is verified by the presented numerical results, the proposed approach exhibits significantly improved performance when constellations with order greater than 4 are employed and require reduced computational complexity, compared to the existing solutions for the 1-bit DAC case. [less ▲]

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See detailCross-Layer Forward Packet Scheduling for Emerging Precoded Broadband Multibeam Satellite System
Lagunas, Eva UL; Andrenacci, Stefano UL; Chatzinotas, Symeon UL et al

in 9th Advanced Satellite Multimedia Systems Conference (ASMS) and 15th Signal Processing for Space Communications Workshop (SPSC), Berlin, Germany, 10-12 September 2018 (2018)

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See detail2018 25th International Conference on Telecommunications (ICT)
Lagunas, Eva UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in 2018 25th International Conference on Telecommunications (ICT) (2018)

The anticipated exponential growth in network traffic is posing significant challenges for the implementation of 5G networks. In this context, a major problem is the backhaul network which acts as a ... [more ▼]

The anticipated exponential growth in network traffic is posing significant challenges for the implementation of 5G networks. In this context, a major problem is the backhaul network which acts as a bottleneck preventing the efficient flow of ultra-dense and heavy traffic between the end users and the core network. Spectrum scarcity has emerged as the primary problem encountered when trying to accommodate the traffic upsurge. In this paper, we investigate the carrier allocation problem in the context of Integrated Satellite-Terrestrial Backhaul (ISTB) networks. In particular, we consider the satellite component to be integrated with the conventional terrestrial wireless backhaul network thus providing evident benefits in terms of data-offloading. To enhance the overall spectral efficiency of the proposed network, we consider that both terrestrial and satellite segments operate in the Ka band, where the sharing between terrestrial microwave links and satellite communications is already allowed. A novel carrier allocation algorithm based on fairness is proposed, which ensures that all backhaul links are continuously active to satisfy the operator's coverage needs. The problem is NP-hard by definition. As a consequence, we present a two-step sequential carrier allocation strategy specifically tailored to tackle the interference issues emerging from the spectral co-existence. Supporting results based on numerical simulations show that the proposed carrier allocation can provide a 2x improvement in terms of spectral efficiency when compared to benchmark terrestrial-only backhaul networks. [less ▲]

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See detailCache-aided Simultaneous Wireless Information and Power Transfer (SWIPT) with Relay Selection
Gautam, Sumit UL; Vu, Thang Xuan UL; Chatzinotas, Symeon UL et al

in IEEE Journal on Selected Areas In Communications (2018)

In this paper, we investigate the performance of cache-assisted simultaneous wireless information and power transfer (SWIPT) cooperative systems, in which one source communicates with one destination via ... [more ▼]

In this paper, we investigate the performance of cache-assisted simultaneous wireless information and power transfer (SWIPT) cooperative systems, in which one source communicates with one destination via the aid of multiple relays. In order to prolong the relays’ serving time, the relays are assumed to be equipped with a cache memory and energy harvesting (EH) capability. Based on the time-splitting mechanism, we analyze the effect of caching on the system performance in terms of the serving throughput and the stored energy at the relay. In particular, two optimization problems are formulated to maximize the relay-destination throughput and the energy stored at the relay subject to some quality-of-service (QoS) constraints, respectively. By using the KKT conditions and with the help of the Lambert function, closed-form solutions are obtained for the two formulated problems. In order to further improve the performance, a relay selection policy is introduced to select the best relay based on either the maximum throughput between the relays’ and destination link or maximum stored energy at the relay, for conveying information to the destination. Numerical results reveal significant benefits of incorporating caching capabilities to SWIPT systems, in terms of improved serving time, throughput and energy harvesting performance at the relays. [less ▲]

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See detailHybrid analog-digital transceiver designs for mmwave amplify-and-forward relaying systems
Tsinos, Christos UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in 2018 41st International Conference on Telecommunications and Signal Processing (TSP) (2018)

Hybrid Analog/Digital (A/D) pre-/post-coding solutions aim at the reduction of the hardware complexity and power consumption of a system employed with a large-scale antenna array functioning in the ... [more ▼]

Hybrid Analog/Digital (A/D) pre-/post-coding solutions aim at the reduction of the hardware complexity and power consumption of a system employed with a large-scale antenna array functioning in the millimeter (mmWave) band. This is achieved by enabling the transceiver design with fewer Radio Frequency (RF) chains than antennas. In this work, hybrid A/D transceiver designs are developed for a relay assisted mmWave system that aims at data transmission from a source to a destination node via the well-known amplify-and-forward cooperative protocol. To that end, hybrid solutions are proposed for the joint design of the source and relay nodes precoders and for the destination ones, as well. Contrariwise to existing literature approaches that develop codebook-based solutions and exhibit limitations on the performance, the proposed approaches are codebook-free and present significantly improved spectral efficiency, as it is verified via the presented simulations. [less ▲]

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See detailUser Selection for symbol-level multigroup multicasting precoding in the downlink of MISO channels
Alodeh, Maha UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in 2018 IEEE International Conference on Communications (ICC) (2018)

We consider the problem of user selection for symbol-level multigroup multicasting in the downlink of multiuser MISO systems. Symbol-level precoding is a new paradigm for multiuser multiple-antenna ... [more ▼]

We consider the problem of user selection for symbol-level multigroup multicasting in the downlink of multiuser MISO systems. Symbol-level precoding is a new paradigm for multiuser multiple-antenna downlink systems which aims at creating constructive interference among the simultaneous data streams. This can be enabled by designing the precoded signal of the multiantenna transmitter on a symbol level, taking into account both channel state information and data symbols. This work proposes a user selection algorithm to facilitate serving multiple groups of users, by transmitting a stream of common symbols to each group on symbol-by-symbol basis if we have large number of users. We provide numerical results to validate the proposed algorithm. [less ▲]

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See detailGraph Similarity based on Graph Fourier Distances
Lagunas, Eva UL; Marques, Antonio G.; Chatzinotas, Symeon UL et al

in European Signal Processing Conference (EUSIPCO), Rome, Italy, 3-7 September 2018 (2018)

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See detailPerformance Limits of Cognitive Uplink FSS and Terrestrial FS for Ka-Band
An, K.; Liang, T.; Zheng, Gan UL et al

in IEEE Transactions on Aerospace and Electronic Systems (2018)

This paper investigates the performance limits of cognitive uplink Fixed Satellite Service (FSS) and terrestrial Fixed Service (FS) operating in 27.5-29.5 GHz for Ka-band. In light of standard ... [more ▼]

This paper investigates the performance limits of cognitive uplink Fixed Satellite Service (FSS) and terrestrial Fixed Service (FS) operating in 27.5-29.5 GHz for Ka-band. In light of standard International Telecommunications Union (ITU) recommendations and a rain fading channel model, we analyze the interference level at the FS receiver by considering the channel statistical properties, propagation losses and antenna patterns. By employing the interference constraint criterion at the FS, an analytical expression for the capacity of the cognitive uplink FSS is derived, which is useful in understanding the performance limits and the potential application of the considered coexistence scenario. Simulation results are carried out to verify the theoretical derivations, and highlight the impact of key parameters on the performance limits. [less ▲]

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See detailBeamforming for Secure Wireless Information and Power Transfer in Terrestrial Networks Coexisting With Satellite Networks
Lin, Zhi; Lin, Min; Ouyang, Jian et al

in IEEE Signal Processing Letters (2018)

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See detailBeamforming for Secure Wireless Information and Power Transfer in Terrestrial Networks Coexisting With Satellite Networks
Z. Lin; M. Lin; J. Ouyang et al

in IEEE Signal Processing Letters (2018)

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See detailOptimal Deployment of Base Stations in Cognitive Satellite Terrestrial Networks
Vuppala, Satyanarayana UL; Sellathurai, Mathini; Chatzinotas, Symeon UL

in 2018 9th Advanced Satellite Multimedia Systems Conference and the 15th Signal Processing for Space Communications Workshop (ASMS/SPSC) (2018)

The application of linear precoding at the gateway side enables broadband multibeam satellite systems to use more aggressive frequency reuse patterns increasing the overall capacity of future High ... [more ▼]

The application of linear precoding at the gateway side enables broadband multibeam satellite systems to use more aggressive frequency reuse patterns increasing the overall capacity of future High Throughput Satellites (HTS). However, although some previous works about precoding consider imperfect CSIT (Chanel State Information at the Transmitter) adding some CSI estimation errors, that is not the main cause of CSI degradation. In practice, receivers can only detect and estimate a few coefficients of the CSI vector being the other nullified, replaced by zeros. This introduces errors in the SINR calculation by the gateway that lead to the assignment of Modulation and Coding Schemes (MCS) over the decoding possibilities of the users, increasing the rate of erroneous frames. In this work, the errors in the SINR calculation caused by the nullification of the CSI are analyzing statistically and geographically using a radiation diagram of 245 beams over Europe. Furthermore, a solution based on a link adaptation algorithm with a per user adaptive margin is proposed, helping to achieve the QEF (Quasi-error Free) target of DVB-S2X systems. [less ▲]

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See detailConstrained bayesian active learning of linear classifier
Tsakmalis, Anestis UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in 2018 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) (2018)

In this paper, an on-line interactive method is proposed for learning a linear classifier. This problem is studied within the Active Learning (AL) framework where the learning algorithm sequentially ... [more ▼]

In this paper, an on-line interactive method is proposed for learning a linear classifier. This problem is studied within the Active Learning (AL) framework where the learning algorithm sequentially chooses unlabelled training samples and requests their class labels from an oracle in order to learn the classifier with the least queries to the oracle possible. Additionally' a constraint is introduced into this interactive learning process which limits the percentage of the samples from one “unwanted” class under a certain threshold. An optimal AL solution is derived and implemented with a sophisticated, accurate and fast Bayesian Learning method, the Expectation Propagation (EP) and its performance is demonstrated through numerical simulations. [less ▲]

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See detailSequential spatio-temporal symbol-level precoding enabling faster-than-Nyquist signaling for multi-user MISO systems
Spano, Danilo UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in 2018 26th European Signal Processing Conference (EUSIPCO) (2018)

This paper addresses the problem of the interference between multiple co-channel transmissions in the downlink of a multi-antenna wireless system. In this context, symbol-level precoding achieves a ... [more ▼]

This paper addresses the problem of the interference between multiple co-channel transmissions in the downlink of a multi-antenna wireless system. In this context, symbol-level precoding achieves a constructive interference effect which results in SINR gains at the receivers side. Usually the constructive interference is exploited in the spatial dimension (multi-user interference), however in this work we consider a spatio-temporal precoding model which allows to exploit the interference also in the temporal dimension (inter-symbol interference). The proposed method, which optimizes the overs ampled transmit waveforms by minimizing the per-antenna transmit power, allows faster-than-Nyquist signaling over multi-user MISO systems without imposing additional complexity at the user terminals. The optimization is performed in a sequential fashion, by splitting the data streams in blocks and handling the inter-block interference. Numerical results are presented to assess the gains of the scheme in terms of effective rate and energy efficiency. [less ▲]

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See detailSatellite Multi-Beam Precoding Hardware Demonstrator, Satellite Communications in the 5G Era
Andrenacci, Stefano UL; Duncan, J.C.M.; Krivochiza, Jevgenij UL et al

Book published by IET (2018)

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See detailEnergy-Efficient Multicell Multigroup Multicasting With Joint Beamforming and Antenna Selection
Tervo, Oskari; Tran, Le-Nam; Pennanen, Harri et al

in IEEE Transactions on Signal Processing (2018)

Detailed reference viewed: 83 (6 UL)