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See detailNOMA Aided Interference Management for Full-Duplex Self-Backhauling HetNets
Lei, Lei UL; Lagunas, Eva UL; Chatzinotas, Symeon UL et al

in IEEE Communications Letters (2018), 22(8), 1696-1699

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See detailCarrier Allocation for 5G Integrated Satellite-Terrestrial Backhaul Networks
Lagunas, Eva UL; Chatzinotas, Symeon UL; Ottersten, Björn UL

in International Conference on Communications (ICT), Saint-Malo, France, June 2018. (2018, June)

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See detailComputationally and Energy Efficient Symbol-Level Precoding Communications Demonstrator
Krivochiza, Jevgenij UL; Merlano Duncan, Juan Carlos UL; Andrenacci, Stefano UL et al

in Physical Communication (2018), 28

We present a precoded multi-user communication test-bed to demonstrate forward link interference mitigation techniques in a multi-beam satellite system scenario, which will enable a full frequency reuse ... [more ▼]

We present a precoded multi-user communication test-bed to demonstrate forward link interference mitigation techniques in a multi-beam satellite system scenario, which will enable a full frequency reuse scheme. The developed test-bed provides an end-to-end precoding demonstration, which includes a transmitter, a multi-beam satellite channel emulator and user receivers. Each of these parts can be reconfigured accordingly to the desired test scenario. Precoded communications allow full frequency reuse in multiple-input multiple-output (MIMO) channel environments, where several coordinated antennas simultaneously transmit to a number of independent receivers. The developed real-time transmission test-bed assist in demonstrating, designing and benchmarking of the new Symbol-Level Precoding (SLP) techniques, where the data information is used, along with the channel state information, in order to exploit the multi-user interference and transform it into the useful power at the receiver side. The demonstrated SLP technique is designed in order to be computationally efficient, and can be generalized to others multi-channel interference scenarios. [less ▲]

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See detailEnergy Minimization for Cache-Assisted Content Delivery Networks With Wireless Backhaul
Vu, Thang Xuan UL; Chatzinotas, Symeon UL; Ottersten, Björn UL et al

in IEEE Wireless Communications Letters (2018), 7(3), 332-335

Content caching is an efficient technique to reduce delivery latency and system congestion during peak-traffic time by bringing data closer to end users. In this letter, we investigate energy-efficiency ... [more ▼]

Content caching is an efficient technique to reduce delivery latency and system congestion during peak-traffic time by bringing data closer to end users. In this letter, we investigate energy-efficiency performance of cache-assisted content delivery networks with wireless backhaul by taking into account cache capability when designing the signal transmission. We consider multi-layer caching and the performance in cases when both base station and users are capable of storing content data in their local cache. Specifically, we analyze energy consumption in both backhaul and access links under two uncoded and coded caching strategies. Then two optimization problems are formulated to minimize total energy cost for the two caching strategies while satisfying some given quality of service constraint. We demonstrate via numerical results that the uncoded caching achieves higher energy efficiency than the coded caching in the small user cache size regime. [less ▲]

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See detailKey-Skeleton Based Feedback Tool for Assisting Physical Activity
Baptista, Renato UL; Ghorbel, Enjie UL; Shabayek, Abd El Rahman UL et al

in 2018 Zooming Innovation in Consumer Electronics International Conference (ZINC), 30-31 May 2018 (2018, May 31)

This paper presents an intuitive feedback tool able to implicitly guide motion with respect to a reference movement. Such a tool is important in multiple applications requiring assisting physical ... [more ▼]

This paper presents an intuitive feedback tool able to implicitly guide motion with respect to a reference movement. Such a tool is important in multiple applications requiring assisting physical activities as in sports or rehabilitation. Our proposed approach is based on detecting key skeleton frames from a reference sequence of skeletons. The feedback is based on the 3D geometry analysis of the skeletons by taking into account the key-skeletons. Finally, the feedback is illustrated by a color-coded tool, which reflects the motion accuracy. [less ▲]

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See detailReduced complexity satellite broadcast receiver with interference mitigation in correlated noise
Abu Shaban, Zohair UL; Mehrpouyan, Hani UL; Shankar, Bhavani UL et al

in International Journal of Satellite Communications and Networking (2018), 36(5),

ry The recent commercial trends towards using smaller dish antennas for satellite receivers and the growing density of broadcasting satellites necessitate the application of robust adjacent satellite ... [more ▼]

ry The recent commercial trends towards using smaller dish antennas for satellite receivers and the growing density of broadcasting satellites necessitate the application of robust adjacent satellite interference cancellation schemes. This orbital density growth along with the wider beamwidth of a smaller dish have imposed an overloaded scenario at the satellite receiver, where the number of transmitting satellites exceeds the number of receiving elements at the dish antenna. To ensure successful operation in this practical scenario, we propose a satellite receiver that enhances signal detection from the desired satellite by mitigating the interference from neighboring satellites. Towards this objective, we propose an enhanced list‐based group‐wise search detection (E‐LGSD) receiver under the assumption of spatially correlated additive noise. To further enhance detection performance, the proposed satellite receiver utilizes a newly designed whitening filter to remove the spatial correlation among the noise parameters, while also applying a preprocessor that maximizes the signal‐to‐interference‐plus‐noise ratio. We exploit the structure of this filter and propose a reduced complexity LGSD (RC‐LGSD) receiver. Extensive simulations under practical scenarios show that the proposed receiver enhances the performance of satellite broadcast systems in the presence of adjacent satellite interference compared with existing methods. Also, under pointing error, RC‐LGSD exhibits similar behavior to that of the optimum receiver. [less ▲]

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See detailEfficient Resource Optimization in Wireless Networks: A Deep-Learning Assisted Approach
Lei, Lei UL; You, Lei; Yuan, Di et al

in 2018 INFORMS Telecommunications Conference (2018, May)

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See detailEnergy-efficient design for latency-tolerant content delivery networks
Vu, Thang Xuan UL; Lei, Lei UL; Vuppala, Satyanarayana et al

in 2018 IEEE Wireless Communications and Networking Conference (WCNC) (2018, May)

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See detailLatency Minimization for Content Delivery Networks with Wireless Edge Caching
Vu, Thang Xuan UL; Lei, Lei UL; Vuppala, Satyanarayana et al

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

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See detailPAPR Minimization through Spatio-temporal Symbol-level Precoding for the Non-linear Multi-user MISO Channel
Spano, Danilo UL; Alodeh, Maha; Chatzinotas, Symeon UL et al

in 2018 International Conference on Acoustics, Speech, and Signal Processing (ICASSP 2018) (2018, April 19)

Symbol-level precoding (SLP) is a promising technique which allows to constructively exploit the multi-user interference in the downlink of multiple antenna systems. Recently, this approach has also been ... [more ▼]

Symbol-level precoding (SLP) is a promising technique which allows to constructively exploit the multi-user interference in the downlink of multiple antenna systems. Recently, this approach has also been used in the context of non-linear systems for reducing the instantaneous power imbalances among the antennas. However, previous works have not exploited SLP to improve the dynamic properties of the waveforms in the temporal dimension, which are fundamental for non-linear systems. To fill this gap, this paper proposes a novel precoding method, referred to as spatio-temporal SLP, which minimizes the peak-to-average power ratio of the transmitted waveforms both in the spatial and in the temporal dimensions, while at the same time exploiting the constructive interference effect. Numerical results are presented to highlight the enhanced performance of the proposed scheme with respect to state of the art SLP techniques, in terms of power distribution and symbol error rate over non-linear channels. [less ▲]

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See detailDesigning Joint Precoding and Beamforming in a Multiple Gateway Multibeam Satellite System
Joroughi, Vahid; Shankar, Bhavani UL; Maleki, Sina UL et al

in IEEE WCNC 2018 (2018, April 18)

This paper aims to design joint on-ground precoding and on-board beamforming of a multiple gateway multibeam satellite system in a hybrid space-ground mode where full frequency reuse pattern is considered ... [more ▼]

This paper aims to design joint on-ground precoding and on-board beamforming of a multiple gateway multibeam satellite system in a hybrid space-ground mode where full frequency reuse pattern is considered among the beams. In such an architecture, each gateway serves a cluster of adjacent beams such that the adjacent clusters are served through a set of gateways that are located at different geographical areas. However, such a system brings in two challenges to overcome. First, the inter-beam interference is the bottleneck of the whole system and applying interference mitigation techniques becomes necessary. Second, as the data demand increases, the ground and space segments should employ extensive bandwidth resources in the feeder link accordingly. This entails embedding an extra number of gateways aiming to support a fair balance between the increasing demand and the corresponding required feeder link resources. To solve these problems, this study investigates the impact of employing a joint multiple gateway architecture and on-board beamforming scheme. It is shown that by properly designing the on-board beamforming scheme, the number of gateways can be kept affordable even if the data demand increases. Moreover, Zero Forcing (ZF) precoding technique is considered to cope with the inter-beam interference where each gateway constructs a part of block ZF precoding matrix. The conceived designs are evaluated with a close-to-real beam pattern and the latest broadband communication standard for satellite communications. [less ▲]

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See detailOptimal Relay Selection Strategy for Joint Data and Energy Transfer in Wireless Systems
Gautam, Sumit UL; Lagunas, Eva UL; Chatzinotas, Symeon UL et al

Presentation (2018, April 17)

We study a problem of relay selection in a two-hop amplify-and-forward (AF) enabled relaying network for facilitating simultaneous Wireless Transmission of Information and Energy (Wi-TIE) to a destination ... [more ▼]

We study a problem of relay selection in a two-hop amplify-and-forward (AF) enabled relaying network for facilitating simultaneous Wireless Transmission of Information and Energy (Wi-TIE) to a destination able to perform both information processing and energy harvesting concurrently. Considering the time switching (TS) and power splitting (PS) based Wi-TIE schemes, we formulate an optimization problem to maximize the overall user data rate while ensuring a minimum harvested power. In this context, we obtain suitable closed form solution and demonstrate through simulation results the Rate-Energy (R-E) trade-off in two different scenarios: (i) with only the relay assisted link, and (ii) with the direct link together with the relay assisted link. [less ▲]

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See detailJoint Wireless Information and Energy Transfer in Cache-assisted Relaying Systems
Gautam, Sumit UL; Vu, Thang Xuan UL; Chatzinotas, Symeon UL et al

Scientific Conference (2018, April 16)

We investigate the performance of time switching (TS) based energy harvesting model for cache-assisted simultaneous wireless transmission of information and energy (Wi-TIE). In the considered system, a ... [more ▼]

We investigate the performance of time switching (TS) based energy harvesting model for cache-assisted simultaneous wireless transmission of information and energy (Wi-TIE). In the considered system, a relay which is equipped with both caching and energy harvesting capabilities helps a source to convey information to a destination. First, we formulate based on the time-switching architecture an optimization problem to maximize the harvested energy, taking into consideration the cache capability and user quality of service requirement. We then solve the formulated problem to obtain closed-form solutions. Finally, we demonstrate the effectiveness of the proposed system via numerical results. [less ▲]

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See detailCache-Aided Millimeter Wave Ad-Hoc Networks
Vuppala, Satyanarayana UL; Vu, Thang Xuan UL; Gautam, Sumit UL et al

Scientific Conference (2018, April 16)

In this paper, we investigate the performance of cache enabled millimeter wave (mmWave) ad-hoc network, where randomly distributed nodes are supported by a cache memory. Specifically, we study the optimal ... [more ▼]

In this paper, we investigate the performance of cache enabled millimeter wave (mmWave) ad-hoc network, where randomly distributed nodes are supported by a cache memory. Specifically, we study the optimal caching placement at the desirable mmWave node using a network model that accounts for the uncertainties in node locations and blockages. We then characterize the average success probability of content delivery. As a desirable side effect, certain factors like the density of nodes and increased antenna gain, can significantly increase the cache hit ratio in mmWave networks. However, a trade-off between the cache hit probability and the average successful content delivery probability with respect to the density of nodes is presented. [less ▲]

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See detailConstructive Interference for Generic Constellations
Haqiqatnejad, Alireza UL; Kayhan, Farbod UL; Ottersten, Björn UL

in IEEE Signal Processing Letters (2018), 25(4), 586-590

In this letter, we investigate optimal and relaxed constructive interference regions (CIR) for the symbol-level precoding (SLP) problem in the downlink of a multiuser multiple-input single-output (MISO ... [more ▼]

In this letter, we investigate optimal and relaxed constructive interference regions (CIR) for the symbol-level precoding (SLP) problem in the downlink of a multiuser multiple-input single-output (MISO) channel.We define two types of CIRs, namely, distance preserving CIR (DPCIR) and union bound CIR (UBCIR) for any given constellation shape and size. We then provide a systematic way to describe these regions as convex sets. Using the definitions of DPCIR and UBCIR, we show that the SLP power minimization problem, minimizing either sum or peak (per-antenna) transmit power, can always be formulated as a convex optimization problem. Our results indicate that these regions allow further reduction of the transmit power compared to the current state of the art without increasing the computational complexity at the transmitter or receiver. [less ▲]

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See detailSymbol-level and Multicast Precoding for Multiuser Multiantenna Downlink: A State-of-the-art, Classification and Challenges
Alodeh, Maha; Spano, Danilo UL; Kalantari, Ashkan et al

in IEEE Communications Surveys and Tutorials (2018)

Precoding has been conventionally considered as an effective means of mitigating or exploiting the interference in the multiantenna downlink channel, where multiple users are simultaneously served with ... [more ▼]

Precoding has been conventionally considered as an effective means of mitigating or exploiting the interference in the multiantenna downlink channel, where multiple users are simultaneously served with independent information over the same channel resources. The early works in this area were focused on transmitting an individual information stream to each user by constructing weighted linear combinations of symbol blocks (codewords). However, more recent works have moved beyond this traditional view by: i) transmitting distinct data streams to groups of users and ii) applying precoding on a symbol-per-symbol basis. In this context, the current survey presents a unified view and classification of precoding techniques with respect to two main axes: i) the switching rate of the precoding weights, leading to the classes of block-level and symbol-level precoding, ii) the number of users that each stream is addressed to, hence unicast, multicast, and broadcast precoding. Furthermore, the classified techniques are compared through representative numerical results to demonstrate their relative performance and uncover fundamental insights. Finally, a list of open theoretical problems and practical challenges are presented to inspire further research in this area. [less ▲]

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See detailCache-Aided Millimeter Wave Ad-Hoc Networks with Contention-Based Content Delivery
Vuppala, Satyanarayana UL; Vu, Thang Xuan UL; Gautam, Sumit UL et al

in IEEE Transactions on Communications (2018)

The narrow-beam operation in millimeter wave (mmWave) networks minimizes the network interference leading to a noise-limited networks in contrast with interference-limited ones. The medium access control ... [more ▼]

The narrow-beam operation in millimeter wave (mmWave) networks minimizes the network interference leading to a noise-limited networks in contrast with interference-limited ones. The medium access control (MAC) layer throughput, and interference management strategies heavily depend on the noise-limited or interference-limited regime. Yet, these regimes are not considered in recent mmWave MAC layer designs, which can potentially have disastrous consequences on the communication performance. In this paper, we investigate the performance of cache-enabled MAC based mmWave ad-hoc networks, where randomly distributed nodes are supported by a cache. The adhoc nodes are modeled as homogenous Poisson Point Processes (PPP). Specifically, we study the optimal content placement (or caching placement) at desirable mmWave nodes using a network model that accounts for uncertainties both in node locations and blockages. We propose a contention-based multimedia delivery protocol to avoid collisions among the concurrent transmissions. Subsequently, only the node with smallest back-off timer amongst its contenders is allowed to transmit. We then characterize the average success probability of content delivery. We also characterize the cache hit ratio probability, and transmission probability of this system under essential factors, such as blockages, node density, path loss and caching parameters. [less ▲]

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See detailSymbol-Level Precoding for the Nonlinear Multiuser MISO Downlink Channel
Spano, Danilo UL; Alodeh, Maha; Chatzinotas, Symeon UL et al

in IEEE Transactions on Signal Processing (2018), 66(5), 1331-1345

This paper investigates the problem of the interference among multiple simultaneous transmissions in the downlink channel of a multiantenna 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 multiantenna wireless system. A symbol-level precoding scheme is considered, in order to exploit the multiuser interference and transform it into useful power at the receiver side, through a joint utilization of the data information and the channel state information. In this context, this paper presents novel strategies that exploit the potential of symbol-level precoding to control the per-antenna instantaneous transmit power. In particular, the power peaks among the transmitting antennas and the instantaneous power imbalances across the different transmitted streams are minimized. These objectives are particularly relevant with respect to the nonlinear amplitude and phase distortions induced by the per-antenna amplifiers, which are important sources of performance degradation in practical systems. More specifically, this paper proposes two different symbol-level precoding approaches. The first approach performs a weighted per-antenna power minimization, under quality-of-service constraints and under a lower bound constraint on the per-antenna transmit power. The second strategy performs a minimization of the spatial peak-to-average power ratio, evaluated among the transmitting antennas. 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 spatial peak-to-average power ratio, spatial dynamic range, and symbol error rate over nonlinear channels. [less ▲]

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See detailPer-antenna Power Minimization in Symbol-level Precoding for the Multi-beam Satellite Downlink
Spano, Danilo UL; Chatzinotas, Symeon UL; Andrenacci, Stefano UL et al

in International Journal of Satellite Communications and Networking (2018)

This paper addresses the problem of multi-user interference in the forward downlink channel of a multi-beam satellite system. A symbol-level precoding scheme is considered, in order to exploit the multi ... [more ▼]

This paper addresses the problem of multi-user interference in the forward downlink channel of a multi-beam satellite system. A symbol-level precoding scheme is considered, in order to exploit the multi-user interference and transform it into useful power at the receiver side, through a joint utilization of the data information and the channel state information. In this context, a per-antenna power minimization scheme is proposed, under Quality-of-Service constraints, for multi-level modulation schemes. The consideration of the power limitations individually for each transmitting RF chain is a central aspect of this work, and it allows to deal with systems using separate per-antenna amplifiers. Moreover, this feature is also particularly relevant for systems suffering non-linear effects of the channel. This is the case of satellite systems, where the non-linear amplifiers should be properly driven in order to reduce the detrimental saturation effect. In the proposed scheme, the transmitted signals are designed in order to reduce the power peaks, while guaranteeing some specific target signal-to-noise ratios at the receivers. Numerical results are presented in order to show the effectiveness of the proposed scheme, which is compared both to the state of the art in symbol-level precoding and to the conventional MMSE precoding approach. [less ▲]

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See detailIMPROVING THE CAPACITY OF VERY DEEP NETWORKS WITH MAXOUT UNITS
Oyedotun, Oyebade UL; Shabayek, Abd El Rahman UL; Aouada, Djamila UL et al

in 2018 IEEE International Conference on Acoustics, Speech and Signal Processing (2018, February 21)

Deep neural networks inherently have large representational power for approximating complex target functions. However, models based on rectified linear units can suffer reduction in representation ... [more ▼]

Deep neural networks inherently have large representational power for approximating complex target functions. However, models based on rectified linear units can suffer reduction in representation capacity due to dead units. Moreover, approximating very deep networks trained with dropout at test time can be more inexact due to the several layers of non-linearities. To address the aforementioned problems, we propose to learn the activation functions of hidden units for very deep networks via maxout. However, maxout units increase the model parameters, and therefore model may suffer from overfitting; we alleviate this problem by employing elastic net regularization. In this paper, we propose very deep networks with maxout units and elastic net regularization and show that the features learned are quite linearly separable. We perform extensive experiments and reach state-of-the-art results on the USPS and MNIST datasets. Particularly, we reach an error rate of 2.19% on the USPS dataset, surpassing the human performance error rate of 2.5% and all previously reported results, including those that employed training data augmentation. On the MNIST dataset, we reach an error rate of 0.36% which is competitive with the state-of-the-art results. [less ▲]

Detailed reference viewed: 254 (25 UL)