References of "Ottersten, Björn 50002797"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailHybrid Analog-Digital Transceiver Designs for Cognitive Radio Millimiter Wave Systems
Tsinos, Christos UL; Maleki, Sina UL; Chatzinotas, Symeon UL et al

in Hybrid Analog-Digital Transceiver Designs for Cognitive Radio Millimiter Wave Systems (in press)

Recent advances in Milimeter wave (mmWave) band mobile communications may provide solutions to the increasing traffic demand in modern wireless systems. Even though mmWave bands are scarcely occupied, the ... [more ▼]

Recent advances in Milimeter wave (mmWave) band mobile communications may provide solutions to the increasing traffic demand in modern wireless systems. Even though mmWave bands are scarcely occupied, the design of a prospect transceiver should guarantee the efficient coexistence with the incumbent services in these bands. To that end, in this paper, two underlay cognitive transceiver designs are proposed based on a hybrid Analog/Digital transceiver architecture that enables the mmWave spectrum access while controlling the interference to the incumbent users with low hardware complexity and power consumption. The first cognitive solution designs a codebook free cognitive hybrid pre-coder by maximizing the mutual information between its two ends subject to interference, power and hardware constraints related to the analog counterpart. The second solution is codebook based and exhibits less complexity than the first one at the cost of inferior spectral efficiency. A novel codebook free solution for the post-coder at the cognitive receiver part is further proposed, based on a hardware constrained Minimum Mean Square Error criterion. Simulations study the performance of both the proposed hybrid approaches and compare it to the one of a fully digital solution for typical wireless environments. [less ▲]

Detailed reference viewed: 102 (9 UL)
Full Text
Peer Reviewed
See detailRandom Phase Center Motion Technique for Enhanced Angle-Doppler Discrimination Using MIMO Radars
Hammes, Christian UL; Shankar, Bhavani UL; Nijsure, Yogesh UL et al

Scientific Conference (2017, August)

A random Phase Center Motion (PCM) technique is presented in this paper, based on Frequency Modulated Continuous Wave (FMCW) radar, in order to suppress the angle- Doppler coupling in Time Division ... [more ▼]

A random Phase Center Motion (PCM) technique is presented in this paper, based on Frequency Modulated Continuous Wave (FMCW) radar, in order to suppress the angle- Doppler coupling in Time Division Multiplex (TDM) Multiple- Input-Multiple-Output (MIMO) radar when employing sparse array structures. The presented approach exploits an apparently moving transmit platform or PCM due to spatio-temporal transmit array modulation. In particular, the work considers a framework utilizing a random PCM trajectory. The statistical characterization of the random PCM trajectory is devised, such that the PCM and the target motion coupling is minimal, while the angular resolution is increased by enabling the virtual MIMO concept. In more details, this paper discusses sidelobe suppression approaches within the angle-Doppler Ambiguity Function (AF) by introducing a phase center probability density function within the array. This allows for enhanced discrimination of multiple targets. Simulation results demonstrate the suppression angle- Doppler coupling by more than 30 dB, even though spatiotemporal transmit array modulation is done across chirps which leads usually to strong angle-Doppler coupling. [less ▲]

Detailed reference viewed: 12 (0 UL)
Full Text
Peer Reviewed
See detailSpatial PAPR Reduction in Symbol-level Precoding for the Multi-beam Satellite Downlink
Spano, Danilo UL; Alodeh, Maha UL; Chatzinotas, Symeon UL et al

in IEEE SPAWC 2017 (2017, July)

In this work, a novel symbol-level precoding scheme is proposed, for managing the multi-user interference in the forward downlink channel of a multi-beam satellite system. Besides exploiting the ... [more ▼]

In this work, a novel symbol-level precoding scheme is proposed, for managing the multi-user interference in the forward downlink channel of a multi-beam satellite system. Besides exploiting the constructive interference effect, the proposed scheme aims at improving the robustness of the transmitted signals to the non-linear distortions of practical satellite systems. This is done by reducing the imbalances between the instantaneous power transmitted by the multiple antennas, which are detrimental in non-linear systems. More specifically, this work proposes a symbol-level precoding scheme performing the minimization of the spatial peak-to-average power ratio, under Quality-of-Service constraints. An iterative algorithm is proposed to solve the related optimization problem. Numerical results are presented to assess the performance of the proposed scheme, which outperforms the state of the art symbol-level precoding techniques in terms of spatial peak-to-average power ratio across the transmitting antennas. [less ▲]

Detailed reference viewed: 51 (9 UL)
Full Text
Peer Reviewed
See detailEnergy-Efficient Design for Edge-caching Wireless Networks: When is Coded-caching beneficial?
Vu, Thang Xuan UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in Abstract book of IEEE 18th International Workshop on Signal Processing Advances in Wireless Communications (SPAWC) (2017, July)

Detailed reference viewed: 25 (9 UL)
Full Text
Peer Reviewed
See detailPower Allocation for In-Band Full-Duplex Self-Backhauling
Lagunas, Eva UL; Lei, Lei UL; Maleki, Sina UL et al

in International Conference on Telecommunications and Signal Processing (TSP), Barcelona, Spain, July 2017 (2017, July)

Detailed reference viewed: 23 (4 UL)
Full Text
Peer Reviewed
See detailLow Complexity Symbol-Level Design for Linear Precoding Systems
Krivochiza, Jevgenij UL; Kalantari, Ashkan UL; Chatzinotas, Symeon UL et al

in Heusdens, Richard; Weber, Jos H. (Eds.) PROCEEDINGS of the 2017 Symposium on Information Theory and Signal Processing in the Benelux (2017, May 11)

The practical utilization of the symbol-level precoding in MIMO systems is challenging since the implementation of the sophisticated optimization algorithms must be done with reasonable computational ... [more ▼]

The practical utilization of the symbol-level precoding in MIMO systems is challenging since the implementation of the sophisticated optimization algorithms must be done with reasonable computational resources. In the real implementation of MIMO precoding systems, the processing time for each set of symbols is a crucial parameter, especially in the high-throughput mode. In this work, a symbol-level optimization algorithm with reduced complexity is devised. Performance of a symbol-level precoder is shown to improve in terms of the processing times per set of symbols. [less ▲]

Detailed reference viewed: 36 (18 UL)
Full Text
Peer Reviewed
See detailOn the Diversity of Partial Relaying Cooperation with Relay Selection in Finite-SNR Regime
Vu, Thang Xuan UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in IEEE International Conference on Communications (2017, May)

Detailed reference viewed: 9 (1 UL)
Full Text
Peer Reviewed
See detailSpectral-Efficient Model for Multiuser Massive MIMO: Exploiting User Velocity
Vu, Thang Xuan UL; Trinh, Anh Vu; Chatzinotas, Symeon UL et al

in IEEE international Conference on Communications (2017, May)

Detailed reference viewed: 9 (1 UL)
Full Text
Peer Reviewed
See detailFinite-SNR analysis for partial relaying cooperation with channel coding and opportunistic relay selection
Vu, Thang Xuan UL; Duhamel, Pierre; Chatzinotas, Symeon UL et al

in EURASIP Journal on Advances in Signal Processing (2017)

Detailed reference viewed: 21 (5 UL)
Full Text
See detailDiscrimination of Angle-Doppler Signatures using Arbitrary Phase Center Motion for MIMO Radars
Hammes, Christian UL; Nijsure, Yogesh UL; Shankar, Bhavani UL et al

Scientific Conference (2017, May)

A novel Phase Center Motion (PCM) based technique for discriminating angle-Doppler signatures within Multiple-Input-Multiple-Output (MIMO) radars using Frequency Modulated Continuous Wave (FMCW) has been ... [more ▼]

A novel Phase Center Motion (PCM) based technique for discriminating angle-Doppler signatures within Multiple-Input-Multiple-Output (MIMO) radars using Frequency Modulated Continuous Wave (FMCW) has been explored in this work. The PCM technique induces angle dependent Doppler shifts in the back-scattered signal, wherein a modified Doppler post processing for FMCW leads to joint angle-Doppler processing. Specifically, we intend to design unique spatialtemporal motion of the phase center on each individual MIMO radar channel in an effort to synthesize nearly orthogonal angle- Doppler signatures. Subsequently, we also develop a MIMO radar receiver design, which would be capable of discriminating between these induced angle-Doppler signatures. The asymptotic investigation provides a Bessel function characteristic. Simulation results demonstrate a significant side-lobe suppression of 8:5 dB for an individual PCM trajectory and 7 dB over distinct PCM trajectories, in an attempt towards realization of nearly orthogonal MIMO radar channels. [less ▲]

Detailed reference viewed: 36 (1 UL)
Full Text
Peer Reviewed
See detailCarrier Allocation for Hybrid Satellite-Terrestrial Backhaul Networks
Lagunas, Eva UL; Maleki, Sina UL; Lei, Lei UL et al

in ICC Workshop on Satellite Communications: Challenges and Integration in the 5G ecosystem, Paris, France, May 2017 (2017, May)

Detailed reference viewed: 32 (5 UL)
Full Text
Peer Reviewed
See detailFaster-than-Nyquist Spatiotemporal Symbol-level Precoding in the Downlink of Multiuser MISO Channels
Alodeh, Maha UL; Spano, Danilo UL; Chatzinotas, Symeon UL et al

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

Detailed reference viewed: 30 (7 UL)
Full Text
Peer Reviewed
See detailEnhanced Trajectory-based Action Recognition using Human Pose
Papadopoulos, Konstantinos UL; Goncalves Almeida Antunes, Michel UL; Aouada, Djamila UL et al

in IEEE International Conference on Image Processing, Beijing 17-20 Spetember 2017 (2017)

Action recognition using dense trajectories is a popular concept. However, many spatio-temporal characteristics of the trajectories are lost in the final video representation when using a single Bag-of ... [more ▼]

Action recognition using dense trajectories is a popular concept. However, many spatio-temporal characteristics of the trajectories are lost in the final video representation when using a single Bag-of-Words model. Also, there is a significant amount of extracted trajectory features that are actually irrelevant to the activity being analyzed, which can considerably degrade the recognition performance. In this paper, we propose a human-tailored trajectory extraction scheme, in which trajectories are clustered using information from the human pose. Two configurations are considered; first, when exact skeleton joint positions are provided, and second, when only an estimate thereof is available. In both cases, the proposed method is further strengthened by using the concept of local Bag-of-Words, where a specific codebook is generated for each skeleton joint group. This has the advantage of adding spatial human pose awareness in the video representation, effectively increasing its discriminative power. We experimentally compare the proposed method with the standard dense trajectories approach on two challenging datasets. [less ▲]

Detailed reference viewed: 31 (18 UL)
Full Text
Peer Reviewed
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)

Detailed reference viewed: 15 (1 UL)
Full Text
Peer Reviewed
See detailDeformation Based Curved Shape Representation
Demisse, Girum UL; Aouada, Djamila UL; Ottersten, Björn UL

in IEEE Transactions on Pattern Analysis & Machine Intelligence (2017)

In this paper, we introduce a deformation based representation space for curved shapes in Rn. Given an ordered set of points sampled from a curved shape, the proposed method represents the set as an ... [more ▼]

In this paper, we introduce a deformation based representation space for curved shapes in Rn. Given an ordered set of points sampled from a curved shape, the proposed method represents the set as an element of a finite dimensional matrix Lie group. Variation due to scale and location are filtered in a preprocessing stage, while shapes that vary only in rotation are identified by an equivalence relationship. The use of a finite dimensional matrix Lie group leads to a similarity metric with an explicit geodesic solution. Subsequently, we discuss some of the properties of the metric and its relationship with a deformation by least action. Furthermore, invariance to reparametrization or estimation of point correspondence between shapes is formulated as an estimation of sampling function. Thereafter, two possible approaches are presented to solve the point correspondence estimation problem. Finally, we propose an adaptation of k-means clustering for shape analysis in the proposed representation space. Experimental results show that the proposed representation is robust to uninformative cues, e.g. local shape perturbation and displacement. In comparison to state of the art methods, it achieves a high precision on the Swedish and the Flavia leaf datasets and a comparable result on MPEG-7, Kimia99 and Kimia216 datasets. [less ▲]

Detailed reference viewed: 50 (5 UL)
Full Text
Peer Reviewed
See detailDEFORMATION TRANSFER OF 3D HUMAN SHAPES AND POSES ON MANIFOLDS
Shabayek, Abd El Rahman UL; Aouada, Djamila UL; Saint, Alexandre Fabian A UL et al

in IEEE International Conference on Image Processing, Beijing 17-20 Spetember 2017 (2017)

Detailed reference viewed: 41 (4 UL)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 53 (11 UL)
Full Text
Peer Reviewed
See detailUnsupervised Vanishing Point Detection and Camera Calibration from a Single Manhattan Image with Radial Distortion
Goncalves Almeida Antunes, Michel UL; Barreto, Joao P.; Aouada, Djamila UL et al

in IEEE Conference on Computer Vision and Pattern Recognition (CVPR), 2017 (2017)

The article concerns the automatic calibration of a camera with radial distortion from a single image. It is known that, under the mild assumption of square pixels and zero skew, lines in the scene ... [more ▼]

The article concerns the automatic calibration of a camera with radial distortion from a single image. It is known that, under the mild assumption of square pixels and zero skew, lines in the scene project into circles in the image, and three lines suffice to calibrate the camera up to an ambiguity between focal length and radial distortion. The calibration results highly depend on accurate circle estimation, which is hard to accomplish, because lines tend to project into short circular arcs. To overcome this problem, we show that, given a short circular arc edge, it is possible to robustly determine a line that goes through the center of the corresponding circle. These lines, henceforth called Lines of Circle Centres (LCCs), are used in a new method that detects sets of parallel lines and estimates the calibration parameters, including the center and amount of distortion, focal length, and camera orientation with respect to the Manhattan frame. Extensive experiments in both semi-synthetic and real images show that our algorithm outperforms state- of-the-art approaches in unsupervised calibration from a single image, while providing more information. [less ▲]

Detailed reference viewed: 212 (17 UL)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 58 (8 UL)
Full Text
Peer Reviewed
See detailSymbol-Level Multiuser MISO Precoding for Multi-level Adaptive Modulation
Alodeh, Maha UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in IEEE Transactions on Wireless Communications (2017)

Symbol-level precoding is a new paradigm for multiuser multiple-antenna downlink systems which aims at creating constructive interference among the transmitted data streams. This can be enabled by ... [more ▼]

Symbol-level precoding is a new paradigm for multiuser multiple-antenna downlink systems which aims at creating constructive interference among the transmitted 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. Previous literature has studied this paradigm for Mary phase shift keying (MPSK) modulations by addressing various performance metrics, such as power minimization and maximization of the minimum rate. In this paper, we extend this to generic multi-level modulations i.e. Mary quadrature amplitude modulation (MQAM) by establishing connection to PHY layer multicasting with phase constraints. Furthermore, we address adaptive modulation schemes which are crucial in enabling the throughput scaling of symbol-level precoded systems. In this direction, we design signal processing algorithms for minimizing the required power under per-user signal to interference noise ratio (SINR) or goodput constraints. Extensive numerical results show that the proposed algorithm provides considerable power and energy efficiency gains, while adapting the employed modulation scheme to match the requested data rate. [less ▲]

Detailed reference viewed: 30 (1 UL)