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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 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 detailMIMO directional modulation M-QAM precoding for transceivers performance enhancement.
Kalantari, Ashkan UL; Tsinos, Christos UL; Soltanalian, Mojtaba UL et al

in MIMO directional modulation M-QAM precoding for transceivers performance enhancement. (2017)

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See detailSpatial peak power minimization for relaxed phase M-PSK MIMO directional modulation transmitter
Kalantari, Ashkan UL; Tsinos, Christos UL; Soltanalian, Mojtaba UL et al

in Spatial peak power minimization for relaxed phase M-PSK MIMO directional modulation transmitter (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 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 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 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 and 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: 159 (7 UL)
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See detailUniversal Intelligent Small Cell for Next Generation Cellular Networks
Patwary, M.; Sharma, Shree Krishna UL; Chatzinotas, Symeon UL et al

in Digital Communications and Networks (2016), 2(4), 167174

Exploring innovative cellular architectures to achieve enhanced system capacity and good coverage has become a critical issue towards realizing the next generation of wireless communications. In this ... [more ▼]

Exploring innovative cellular architectures to achieve enhanced system capacity and good coverage has become a critical issue towards realizing the next generation of wireless communications. In this context, this paper proposes a novel concept of Universal Intelligent Small Cell (UnISCell) for enabling the densification of the next generation of cellular networks. The proposed novel concept envisions an integrated platform of providing a strong linkage between different stakeholders such as street lighting networks, landline telephone networks and future wireless networks, and is universal in nature being independent of the operating frequency bands and traffic types. The main motivating factors for the proposed small cell concept are the need of public infrastructure re-engineering, and the recent advances in several enabling technologies. First, we highlight the main concepts of the proposed UnISCell platform. Subsequently, we present two deployment scenarios for the proposed UnISCell concept considering infrastructure sharing and service sharing as important aspects. We then describe the key future technologies for enabling the proposed UnISCell concept and present a use case example with the help of numerical results. Finally, we conclude this article by providing some interesting future recommendations. [less ▲]

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See detailCentralized Power Control in Cognitive Radio Networks Using Modulation and Coding Classification Feedback
Tsakmalis, Anestis UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in IEEE Transactions on Cognitive Communications and Networking (2016), 2(3),

In this paper, a centralized Power Control (PC) scheme and an interference channel learning method are jointly tackled to allow a Cognitive Radio Network (CRN) access to the frequency band of a Primary ... [more ▼]

In this paper, a centralized Power Control (PC) scheme and an interference channel learning method are jointly tackled to allow a Cognitive Radio Network (CRN) access to the frequency band of a Primary User (PU) operating based on an Adaptive Coding and Modulation (ACM) protocol. The learning process enabler is a cooperative Modulation and Coding Classification (MCC) technique which estimates the Modulation and Coding scheme (MCS) of the PU. Due to the lack of cooperation between the PU and the CRN, the CRN exploits this multilevel MCC sensing feedback as implicit channel state information (CSI) of the PU link in order to constantly monitor the impact of the aggregated interference it causes. In this paper, an algorithm is developed for maximizing the CRN throughput (the PC optimization objective) and simultaneously learning how to mitigate PU interference (the optimization problem constraint) by using only the MCC information. Ideal approaches for this problem setting with high convergence rate are the cutting plane methods (CPM). Here, we focus on the analytic center cutting plane method (ACCPM) and the center of gravity cutting plane method (CGCPM) whose effectiveness in the proposed simultaneous PC and interference channel learning algorithm is demonstrated through numerical simulations. [less ▲]

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See detailCognitive Interference Management Techniques for the Spectral Co-existence of GSO and NGSO Satellites
Pourmoghaddaslangroudi, Ameneh UL; Sharma, Shree Krishna UL; Chatzinotas, Symeon UL et al

in International Conference on Wireless and Satellite Systems (WiSATS, formerly PSATS), Cardiff, UK, Sep 2016 (2016, September 19)

One of the main challenges in the co-existence of geostationary satellite orbit (GSO) and non-geostationary satellite orbit (NGSO) satellite networks is to mitigate the in-line interference caused by an ... [more ▼]

One of the main challenges in the co-existence of geostationary satellite orbit (GSO) and non-geostationary satellite orbit (NGSO) satellite networks is to mitigate the in-line interference caused by an NGSO satellite to the GSO earth terminal, while the NGSO satellite is crossing the GSO satellite's illumination zone. The method recommended in ITU-R S.1325-3 involves utilizing a range-based power control on the NGSO satellite for downlink communication to the NGSO earth terminals. In this paper, we investigate a cognitive range-based power control algorithm while taking into account the imposed interference level to the GSO fixed satellite service (FSS) system. Results show that the proposed cognitive power control algorithm can mitigate the harmful in-line interference on the GSO terminal receiver, while also providing the desired link quality for the NGSO system. More importantly, we formulate and solve an optimization problem with the objective of minimizing the inter-site distance (ISD) of the GSO-NGSO earth user-terminals. Finally, we develop an analytical method to calculate the ISD between GSO and NGSO earth terminals and validate this with the help of simulation results. [less ▲]

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See detailOn the Performance Analysis of Underlay Cognitive Radio Systems: A Deployment Perspective
Kaushik, A.; Sharma, Shree Krishna UL; Chatzinotas, Symeon UL et al

in IEEE Transactions on Cognitive Communications and Networking (2016), 2(3), 273-287

We study the performance of a cognitive underlay system (US) that employs a power control mechanism at the secondary transmitter (ST) from a deployment perspective. Existing baseline models considered for ... [more ▼]

We study the performance of a cognitive underlay system (US) that employs a power control mechanism at the secondary transmitter (ST) from a deployment perspective. Existing baseline models considered for performance analysis either assume the knowledge of involved channels at the ST or retrieve this information by means of a band manager or a feedback channel; however, such situations rarely exist in practice. Motivated by this fact, we propose a novel approach that incorporates estimation of the involved channels at the ST in order to characterize the performance of the US in terms of interference power received at the primary receiver and throughput at the secondary receiver (or secondary throughput). Moreover, we apply an outage constraint that captures the impact of imperfect channel knowledge, particularly on the uncertain interference. Besides this, we employ a transmit power constraint at the ST to classify the operation of the US in terms of an interference-limited regime and a power-limited regime. In addition, we characterize the expressions of the uncertain interference and the secondary throughput for the case where the involved channels encounter Nakagami-m fading. Finally, we investigate a fundamental tradeoff between the estimation time and the secondary throughput depicting an optimized performance of the US. [less ▲]

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See detailLow Complexity Transmit Processing for Multibeam Satellite Systems with Non-Linear Channels
Mengali, Alberto UL; Kayhan, Farbod UL; Shankar, Bhavani UL et al

in Proceedings of ASMS Conference (2016, September)

Detailed reference viewed: 221 (8 UL)