References of "Ottersten, Björn 50002797"
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See detailEnergy-efficient coordinated multi-cell multi-group multicast beamforming with antenna selection
Tervo, O.; Tran, L. N.; Pennanen, H. et al

in 2017 IEEE International Conference on Communications Workshops (ICC) (2017)

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See detailEnergy-efficient joint unicast and multicast beamforming with multi-antenna user terminals
Tervo, O.; Tran, L. N.; Chatzinotas, Symeon UL et al

in 2017 IEEE 18th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC) (2017)

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See detailSTARR - Decision SupporT and self-mAnagement system for stRoke survivoRs Vision based Rehabilitation System
Shabayek, Abd El Rahman UL; Baptista, Renato UL; Papadopoulos, Konstantinos UL et al

in European Project Space on Networks, Systems and Technologies (2017)

This chapter explains a vision based platform developed within a European project on decision support and self-management for stroke survivors. The objective is to provide a low cost home rehabilitation ... [more ▼]

This chapter explains a vision based platform developed within a European project on decision support and self-management for stroke survivors. The objective is to provide a low cost home rehabilitation system. Our main concern is to maintain the patients' physical activity while carrying a continuous monitoring of his physical and emotional state. This is essential for recovering some autonomy in daily life activities and preventing a second damaging stroke. Post-stroke patients are initially subject to physical therapy under the supervision of a health professional to follow up on their daily physical activity and monitor their emotional state. However, due to social and economical constraints, home based rehabilitation is eventually suggested. Our vision platform paves the way towards having low cost home rehabilitation. [less ▲]

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See detailOn the Energy-Efficiency of Hybrid Analog-Digital Transceivers for Single- and Multi-carrier Large Antenna Array Systems
Tsinos, Christos UL; Maleki, Sina UL; Chatzinotas, Symeon UL et al

in IEEE Journal on Selected Areas In Communications (2017)

Hybrid Analog-Digital transceivers are employed with the view to reduce the hardware complexity and the energy consumption in millimeter wave/large antenna array systems by reducing the number of their ... [more ▼]

Hybrid Analog-Digital transceivers are employed with the view to reduce the hardware complexity and the energy consumption in millimeter wave/large antenna array systems by reducing the number of their Radio Frequency (RF) chains. However, the analog processing network requires power for its operation and it further introduces power losses, dependent on the number of the transceiver antennas and RF chains, that have to be compensated. Thus, the reduction in the power consumption is usually much less than it is expected and given that the hybrid solutions present in general inferior spectral efficiency than a fully digital one, it is possible for the former to be less energy efficient than the latter in several cases. Existing approaches propose hybrid solutions that maximize the spectral efficiency of the system without providing any insight on their energy requirements/efficiency. To that end, in this paper, a novel algorithmic framework is developed based on which energy efficient hybrid transceiver designs are derived and their performance is examined with respect to the number of RF chains and antennas. Solutions are proposed for fully and partially connected hybrid architectures and for both single- and multi-carrier systems under the Orthogonal Frequency Division Multiplexing (OFDM) modulation. Simulations and theoretical results provide insight on the cases where a hybrid transceiver is the most energy efficient solution or not. [less ▲]

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See detailWeak Interference Detection with Signal Cancellation in Satellite Communications
Politis, Christos UL; Maleki, Sina UL; Tsinos, Christos UL et al

in The 42nd IEEE International Conference on Acoustics, Speech and Signal Processing, ICASSP 2017 (2017)

Interference is identified as a critical issue for satellite communication (SATCOM) systems and services. There is a growing concern in the satellite industry to manage and mitigate interference ... [more ▼]

Interference is identified as a critical issue for satellite communication (SATCOM) systems and services. There is a growing concern in the satellite industry to manage and mitigate interference efficiently. While there are efficient techniques to monitor strong interference in SATCOM, weak interference is not so easily detected because of its low interference to signal and noise ratio (ISNR). To address this issue, this paper proposes and develops a technique which takes place on-board the satellite by decoding the desired signal, removing it from the total received signal and applying an Energy Detector (ED) in the remaining signal for the detection of interference. Different from the existing literature, this paper considers imperfect signal cancellation, examining how the decoding errors affect the sensing performance, derives the expressions for the probability of false alarm and provides a set of simulations results, verifying the efficiency of the technique. [less ▲]

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See detailFlexible Feedback System for Posture Monitoring and Correction
Baptista, Renato UL; Antunes, Michel; Shabayek, Abd El Rahman UL et al

in IEEE International Conference on Image Information Processing (ICIIP) (2017)

In this paper, we propose a framework for guiding patients and/or users in how to correct their posture in real-time without requiring a physical or a direct intervention of a therapist or a sports ... [more ▼]

In this paper, we propose a framework for guiding patients and/or users in how to correct their posture in real-time without requiring a physical or a direct intervention of a therapist or a sports specialist. In order to support posture monitoring and correction, this paper presents a flexible system that continuously evaluates postural defects of the user. In case deviations from a correct posture are identified, then feedback information is provided in order to guide the user to converge to an appropriate and stable body condition. The core of the proposed approach is the analysis of the motion required for aligning body-parts with respect to postural constraints and pre-specified template skeleton poses. Experimental results in two scenarios (sitting and weight lifting) show the potential of the proposed framework. [less ▲]

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See detailSimultaneous Sensing and Transmission for Cognitive Radios with Imperfect Signal Cancellation
Politis, Christos UL; Maleki, Sina UL; Tsinos, Christos UL et al

in IEEE Transactions on Wireless Communications (2017)

In conventional cognitive radio systems, the secondary user employs a “listen-before-talk” paradigm, where it senses if the primary user is active or idle, before it decides to access the licensed ... [more ▼]

In conventional cognitive radio systems, the secondary user employs a “listen-before-talk” paradigm, where it senses if the primary user is active or idle, before it decides to access the licensed spectrum. However, this method faces challenges with the most important being the reduction of the secondary user’s throughput, as no data transmission takes place during the sensing period. In this context, the idea of simultaneous spectrum sensing and data transmission is proposed. The present work studies a system model where this concept is obtained through the collaboration of the secondary transmitter with the secondary receiver. First, the secondary receiver decodes the signal from the secondary transmitter, subsequently, removes it from the total received signal and then, carries out spectrum sensing in the remaining signal in order to decide about the presence/absence of the primary user. Different from the existing literature, this paper takes into account the imperfect signal cancellation, evaluating how the decoding errors affect the sensing reliability and derives the analytical expressions for the probability of false alarm. Finally, numerical results are presented illustrating the accuracy of the proposed analysis. [less ▲]

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See detailSpectral coexistence for next generation wireless backhaul networks
Sharma, Shree Krishna; Lagunas, Eva UL; Tsinos, Christos UL et al

in Access, Fronthaul and Backhaul Networks for 5G and Beyond (2017)

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See detailMulti-cell interference coordination for multigroup multicast transmission
Tervo, O.; Pennanen, H.; Chatzinotas, Symeon UL et al

in 2017 European Conference on Networks and Communications (EuCNC) (2017)

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See detailEnergy Optimization for Full-Duplex Self-Backhauled HetNet with Non-Orthogonal Multiple Access
Lei, Lei UL; Lagunas, Eva UL; Maleki, Sina UL et al

in International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), Sapporo, Japan, July 2017 (2017)

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See detailModelling and Performance Analysis of Cognitive Radio Systems from a Deployment Perspective
Kaushik, Ankit; Sharma, Shree Krishna; Chatzinotas, Symeon UL et al

in Handbook of Cognitive Radio (2017)

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See detailOn the energy-efficiency of hybrid analog-digital transceivers for large antenna array systems
Tsinos, Christos UL; Maleki, Sina UL; Chatzinotas, Symeon UL et al

in On the energy-efficiency of hybrid analog-digital transceivers for large antenna array systems (2017)

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See detailPer-antenna Power Minimization in Symbol-Level Precoding
Spano, Danilo UL; Alodeh, Maha UL; Chatzinotas, Symeon UL et al

in IEEE GLOBECOM 2016 (2016, December)

This paper investigates the problem of the interference among multiple simultaneous transmissions in the downlink channel of a multi-antenna wireless system. A symbol-level precoding scheme is considered ... [more ▼]

This paper investigates the problem of the interference among multiple simultaneous transmissions in the downlink channel of a multi-antenna wireless system. A symbol-level precoding scheme is considered, where the data information is used, along with the channel state information, in order to exploit the multi-user interference and transform it into useful power at the receiver side. In this framework, it is important to consider the power limitations individually for each transmitting antenna, since a common practice in multi-antenna systems is the use of separate per-antenna amplifiers. Thus, herein the problem of per-antenna power minimization in symbol-level precoding is formulated and solved, under Quality-of-Service constraints. In the proposed approach, the precoding design is optimized in order to control the instantaneous power transmitted by the antennas, and more specifically to limit the power peaks, while guaranteeing some specific target signal-to-noise ratios at the receivers. Numerical results are presented to show the effectiveness of the proposed scheme, which outperforms the existing state of the art techniques in terms of reduction of the power peaks and of the peak-to-average power ratio across the transmitting antennas. [less ▲]

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See detailReliability problems and Pareto-optimality in cognitive radar (Invited paper)
Soltanalian, M.; Mysore, R.B.S.; Ottersten, Björn UL

in Signal Processing Conference (EUSIPCO), 2016 24th European (2016, December)

Cognitive radar refers to an adaptive sensing system exhibiting high degree of waveform adaptivity and diversity enabled by intelligent processing and exploitation of information from the environment. The ... [more ▼]

Cognitive radar refers to an adaptive sensing system exhibiting high degree of waveform adaptivity and diversity enabled by intelligent processing and exploitation of information from the environment. The next generation of radar systems are characterized by their application to scenarios exhibiting non-stationary scenes as well as interference caused by use of shared spectrum. Cognitive radar systems, by their inherent adaptivity, seem to be the natural choice for such applications. However, adaptivity opens up reliability issues due to uncertainties induced in the information gathering and processing. This paper lists some of the reliability aspects foreseen for cognitive radar systems and motivates the need for waveform designs satisfying different metrics simultaneously towards enhancing the reliability. An iterative framework based on multi-objective optimization is proposed to provide Pareto-optimal waveform designs. [less ▲]

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See detailMax-min transmit beamforming via iterative regularization
Gharanjik, Ahmad UL; Shankar, Bhavani UL; Soltanalian, Mojtaba et al

in 50th Asilomar Conference on Signals, Systems and Computers, November 2016 (2016, November)

This paper introduces an iterative optimization framework to tackle the multi-group multicast Max-Min transmit beamforming problem. In each iteration, the optimization problem is decomposed into four sub ... [more ▼]

This paper introduces an iterative optimization framework to tackle the multi-group multicast Max-Min transmit beamforming problem. In each iteration, the optimization problem is decomposed into four sub-problems, all of which can be solved using computationally efficient algorithms. The advantage of proposed method lies in its ability to handle different types of signal constraints like total power and unimodularity; a feature not exhibited by other techniques. The proposed technique outperforms the well-known semidefinite relaxation method in terms of quality of solutions [less ▲]

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See detailReal-Time Enhancement of Dynamic Depth Videos with Non-Rigid Deformations
Al Ismaeil, Kassem; Aouada, Djamila UL; Solignac, Thomas et al

in IEEE Transactions on Pattern Analysis & Machine Intelligence (2016), 39(10), 2045-2059

We propose a novel approach for enhancing depth videos containing non-rigidly deforming objects. Depth sensors are capable of capturing depth maps in real-time but suffer from high noise levels and low ... [more ▼]

We propose a novel approach for enhancing depth videos containing non-rigidly deforming objects. Depth sensors are capable of capturing depth maps in real-time but suffer from high noise levels and low spatial resolutions. While solutions for reconstructing 3D details in static scenes, or scenes with rigid global motions have been recently proposed, handling unconstrained non-rigid deformations in relative complex scenes remains a challenge. Our solution consists in a recursive dynamic multi-frame superresolution algorithm where the relative local 3D motions between consecutive frames are directly accounted for. We rely on the assumption that these 3D motions can be decoupled into lateral motions and radial displacements. This allows to perform a simple local per-pixel tracking where both depth measurements and deformations are dynamically optimized. The geometric smoothness is subsequently added using a multi-level L1 minimization with a bilateral total variation regularization. The performance of this method is thoroughly evaluated on both real and synthetic data. As compared to alternative approaches, the results show a clear improvement in reconstruction accuracy and in robustness to noise, to relative large non-rigid deformations, and to topological changes. Moreover, the proposed approach, implemented on a CPU, is shown to be computationally efficient and working in real-time. [less ▲]

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See detailMulticast multigroup precoding for frame-based multi-gateway satellite communications
Christopoulos, Dimitrios UL; Pennanen, Harri UL; Chatzinotas, Symeon UL et al

in Advanced Satellite Multimedia Systems Conference and the 14th Signal Processing for Space Communications Workshop (ASMS/SPSC), 2016 8th (2016, October 24)

The present work focuses on the forward link of fixed multibeam broadband satellite systems which employ aggressive frequency reuse patterns in the user-link. For such scenarios, the state-of-the art ... [more ▼]

The present work focuses on the forward link of fixed multibeam broadband satellite systems which employ aggressive frequency reuse patterns in the user-link. For such scenarios, the state-of-the art frame based precoding methods can improve the system performance, exploiting the super framing structure of the latest physical layer evolutions in satellite communications. Nevertheless, the limitations of feeder link need to be considered. Since the increase of the user link capacity leads to a proportional increase in the capacity requirements of the point-to-point feeder link, the deployment of multiple gateways to feed the satellite is examined. The main concept lies in each earth station being dedicated to serve a cluster of beams. In this context, the performance degradation due to inter-cluster interference is quantified. Since inter-cluster interference is expected to primarily affect cluster-edge users, the chosen performance metric is system fairness. Next, coordination between the multiple gateways is proposed as a means to mitigate interference between the different clusters and thus increase the minimum SINR over the coverage. Consequently, the gains in terms of system availability, a crucial metric in satellite communications, are exhibited via numerical system level simulations. The energy efficiency of the proposed system is also presented. [less ▲]

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See detailPeak Power Minimization in Symbol-level Precoding for Cognitive MISO Downlink Channels
Alodeh, Maha UL; Spano, Danilo UL; Chatzinotas, Symeon UL et al

in IEEE Digital Signal Processing Conference (2016, October 16)

This paper proposes a new symbol-level precoding scheme at the cognitive transmitter that jointly utilizes the data and channel information to reduce the effect of nonlinear amplifiers, by reducing the ... [more ▼]

This paper proposes a new symbol-level precoding scheme at the cognitive transmitter that jointly utilizes the data and channel information to reduce the effect of nonlinear amplifiers, by reducing the maximum antenna power under quality of service constraint at the cognitive receivers. In practice, each transmit antenna has a separate amplifier with individual characteristics. In the proposed approach, the precoding design is optimized in order to control the instantaneous power transmitted by the antennas, and more specifically to limit the power peaks, while guaranteeing some specific target signal-to-noise ratios at the receivers and respecting the interference temperature constraint imposed by the primary system. Numerical results show the effectiveness of the proposed scheme, which outperforms the existing state of the art techniques in terms of reduction of the power peaks. [less ▲]

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See detailTerminal-side interference mitigation for spectral coexistence of satellite and terrestrial systems in non-exclusive Ka-band
Sharma, Shree Krishna UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in 34th AIAA International Communications Satellite Systems Conference (2016, October)

Detailed reference viewed: 120 (7 UL)