http://hdl.handle.net/10993/86 Search this channel search https://orbilu.uni.lu/simple-search http://hdl.handle.net/10993/43992 Title: Extended Adjacency and Scale-dependent Graph Fourier Transform via Diffusion Distances <br/> <br/>Author, co-author: Elias, Vitor R.M.; Alves Martins, Wallace; Werner, Stefan <br/> <br/>Abstract: This paper proposes the augmentation of the adjacency model of networks for graph signal processing. It is assumed that no information about the network is available, apart from the initial adjacency matrix. In the proposed model, additional edges are created according to a Markov relation imposed between nodes. This information is incorporated into the extended-adjacency matrix as a function of the diffusion distance between nodes. The diffusion distance measures similarities between nodes at a certain diffusion scale or time, and is a metric adopted from diffusion maps. Similarly, the proposed extended-adjacency matrix depends on the diffusion scale, which enables the definition of a scale-dependent graph Fourier transform. We conduct theoretical analyses of both the extended adjacency and the corresponding graph Fourier transform and show that different diffusion scales lead to different graph-frequency perspectives. At different scales, the transform discriminates shifted ranges of signal variations across the graph, revealing more information on the graph signal when compared to traditional approaches. The scale-dependent graph Fourier transform is applied for anomaly detection and is shown to outperform the conventional graph Fourier transform. Thu, 06 Aug 2020 16:21:13 GMT http://hdl.handle.net/10993/43991 Title: On the Convergence of Max-Min Fairness Power Allocation in Massive MIMO Systems <br/> <br/>Author, co-author: Chaves, Rafael S.; Cetin, Ediz; Lima, Markus V.S.; Alves Martins, Wallace <br/> <br/>Abstract: Power allocation techniques, among which the max-min fairness power allocation (MMFPA) is one of the most widely used, are essential to guarantee good data throughput for all users in a cell. Recently, an efficient MMFPA algorithm for massive multiple-input multiple-output (MIMO) systems has been proposed. However, this algorithm is susceptible to the initial search interval employed by the underlying bisection search. Even if the optimal point belongs to the initial search interval, this algorithm may fail to converge to such a point. In this paper, we use the Perron-Frobenius theory to explain this issue and provide search intervals that guarantee convergence to the optimal point. Furthermore, we propose the bound test procedure as an efficient way of initializing the search interval. Simulation results corroborate our findings. Thu, 06 Aug 2020 15:16:47 GMT http://hdl.handle.net/10993/43973 Title: Carrier and Power Assignment for Flexible Broadband GEO Satellite Communications System <br/> <br/>Author, co-author: Abdu, Tedros Salih; Lagunas, Eva; Kisseleff, Steven; Chatzinotas, Symeon <br/> <br/>Abstract: Current multi-beam GEO satellite systems operate under a limited frequency reuse configuration and considering uniform power assignment across beams. The latter has been shown to be inefficient in matching the geographic distribution of the traffic demand. In this context, next generation of broadband GEO satellite systems will be equipped with more flexible and reconfigurable payloads, facilitating on-demand resource allocation. In this paper, we consider both carrier and power assignment to match the requested beam demands while minimizing the total transmit power and the total utilized bandwidth. A novel optimization problem is formulated and, given its non-convex structure, we divide the problem into two tractable sub-problems. First, we estimate the number of adjacent frequency carriers required for each beam to satisfy its demand and, subsequently, we optimize the power allocation based on the previously assigned carriers. We validate the proposed method with extensive numerical results, which demonstrate its efficiency with respect to benchmark strategies. Mon, 03 Aug 2020 11:41:44 GMT http://hdl.handle.net/10993/43899 Title: Resource Allocation for Energy Efficiency in OFDMA-Enabled WPCN <br/> <br/>Author, co-author: Nguyen, Tien-Tung; Pham, Quoc-Viet; Nguyen, van Dinh; Lee, Jong-Ho; Kim, Yong-Hwa <br/> <br/>Abstract: This letter considers a wireless powered communication network (WPCN), where an energy-constrained device directly uses harvested energy from a power transfer source to transmit independent signals to multiple Internet of Things (IoT) users using orthogonal frequency division multiple access (OFDMA). Our goal is to maximize the system energy efficiency (EE) by jointly optimizing the duration of energy harvesting (EH), subcarrier and power allocation. The formulated problem is a mixed integer nonlinear programming (MINLP) problem due to the presence of binary assignment variables, and thus it is very challenging to solve it directly. By leveraging Dinkelbach method, a very efficient iterative algorithm with closed-form solutions in each iteration is developed, where its convergence is guaranteed. Numerical results show that the proposed algorithm obtains a fast convergence and outperforms baseline algorithms. Notably, they also reveal that the power source should transmit its maximum allowable power to obtain the optimal EE performance. Mon, 27 Jul 2020 08:03:17 GMT http://hdl.handle.net/10993/43869 Title: Unified Framework for Secrecy Characteristics with Mixture of Gaussian (MoG) Distribution <br/> <br/>Author, co-author: Kong, Long; Chatzinotas, Symeon; Ottersten, Björn <br/> <br/>Abstract: The mixture of Gaussian (MoG) distribution was proposed to model the wireless channels by implementing the completely unsupervised expectation-maximization (EM) learning algorithm. With the high convenience for density estimation applications, the focus of this letter is supposed to investigate the secrecy metrics, including secrecy outage probability (SOP), the lower bound of SOP, the probability of non-zero secrecy capacity (PNZ), and the average secrecy capacity (ASC) from the information-theoretic perspective. The above-mentioned metrics are derived with simple and unified closed-form expressions. The effectiveness of our obtained analytical expressions are successfully examined and compared with Monte-Carlo simulations. One can conclude that this letter provides a simple but effective closed-form secrecy analysis solution exploiting the MoG distribution. Sat, 18 Jul 2020 03:30:03 GMT http://hdl.handle.net/10993/43600 Title: Large Intelligent Surface for Positioning in Millimeter Wave MIMO Systems <br/> <br/>Author, co-author: He, Jiguang; Wymeersch, Henk; Kong, Long; Silven, Olli; Juntti, Markku <br/> <br/>Abstract: Millimeter-wave (mmWave) multiple-input multiple-output (MIMO) system for the fifth generation (5G) cellular communications can also enable single-anchor positioning and object tracking due to its large bandwidth and inherently high angular resolution. In this paper, we introduce the newly invented concept, large intelligent surface (LIS), to mmWave positioning systems, study the theoretical performance bounds (i.e., Cramér-Rao lower bounds) for positioning, and evaluate the impact of the number of LIS elements and the value of phase shifters on the position estimation accuracy compared to the conventional scheme with one direct link and one non-line-of-sight path. It is verified that better performance can be achieved with a LIS from the theoretical analyses and numerical study. Wed, 01 Jul 2020 12:39:43 GMT http://hdl.handle.net/10993/43598 Title: Decision Triggered Data Transmission and Collection in Industrial Internet of Things <br/> <br/>Author, co-author: He, Jiguang; Kong, Long; Frondelius, Tero; Silven, Olli; Juntti, Markku <br/> <br/>Abstract: We propose a decision triggered data transmission and collection (DTDTC) protocol for condition monitoring and anomaly detection in the industrial Internet of things (IIoT). In the IIoT, the collection, processing, encoding, and transmission of the sensor readings are usually not for the reconstruction of the original data but for decision making at the fusion center. By moving the decision making process to the local end devices, the amount of data transmission can be significantly reduced, especially when normal signals with positive decisions dominate in the whole life cycle and the fusion center is only interested in collecting the abnormal data. The proposed concept combines compressive sensing, machine learning, data transmission, and joint decision making. The sensor readings are encoded and transmitted to the fusion center only when abnormal signals with negative decisions are detected. All the abnormal signals from the end devices are gathered at the fusion center for a joint decision with feedback messages forwarded to the local actuators. The advantage of such an approach lies in that it can significantly reduce the volume of data to be transmitted through wireless links. Moreover, the introduction of compressive sensing can further reduce the dimension of data tremendously. An exemplary case, i.e., diesel engine condition monitoring, is provided to validate the effectiveness and efficiency of the proposed scheme compared to the conventional ones. Wed, 01 Jul 2020 12:31:40 GMT http://hdl.handle.net/10993/43568 Title: 5G Cellular and Fixed Satellite Service Spectrum Coexistence in C-Band <br/> <br/>Author, co-author: Lagunas, Eva; Tsinos, Christos; Sharma, Shree Krishna; Chatzinotas, Symeon Thu, 25 Jun 2020 03:30:02 GMT http://hdl.handle.net/10993/43534 Title: Designing MPSK Sequences and Doppler Filter Bank in Cognitive Radar Systems <br/> <br/>Author, co-author: Raei, Ehsan; Alaeekerahroodi, Mohammad; Shankar, Bhavani; Ottersten, Björn <br/> <br/>Abstract: In this paper, we propose an attractive method to jointly design discrete phase radar sequence and receive filter bank with the aim of enhancing Signal to Interference and Noise Ratio (SINR) in a cognitive radar system. Towards this, we consider maximizing the worst case SINR at the output of the filter bank when transmitting M-ary Phase Shift Keying (MPSK) sequences, an exercise hitherto not considered. This maximization results in a max-min optimization problem that is multi-variable and non-convex, where we propose an efficient algorithm based on the Coordinate Descent (CD) framework to address it. The gains demonstrated by the proposed algorithm over the state of the art as well as its discrete phase property render the designed sequences attractive for hardware implementation while enabling efficient utilization of transmit power. Sat, 20 Jun 2020 16:06:02 GMT http://hdl.handle.net/10993/43518 Title: Effective Throughput Analysis of α-η-κ-μ Fading Channels <br/> <br/>Author, co-author: Ai, Yun; Mathur, Aashish; Kong, Long; Cheffena, Michael <br/> <br/>Abstract: The α-η-κ-µ fading model is a very useful instrument to accurately describe various radio wave propagation scenarios. In this paper, we study the effective throughput performance of communication systems over the α-η-κ-µ fading channels. Novel and exact expressions for the effective throughput over α-η-κ-µ channels are derived, and the effective throughput of multiple-input single-output (MISO) and multiple-input multiple-output (MIMO) systems over some widely used small-scale fading models are presented based on the derived results. To obtain more understandings on the impact of physical channel characteristics and system configuration on the effective throughput, closed-form expressions for the asymptotic effective throughput at high signal-to-noise ratio (SNR) regimes are also obtained. The results reveal the underlying connections between different physical channel parameters (e.g., scattering level, phase correlation, channel nonlinearity, multipath clustering, and channel imbalance) and the effective throughput. It is found that the effective throughput improves with the increase of channel nonlinearity and number of multipath clusters, and the high-SNR slope is only dependent on the channel nonlinearity and the number of multipath clusters present in the physical channel. Wed, 17 Jun 2020 12:30:41 GMT http://hdl.handle.net/10993/43430 Title: Cache-aided full-duplex: Delivery time analysis and optimization <br/> <br/>Author, co-author: Vu, Thang Xuan; Trinh, Anh Vu; Chatzinotas, Symeon; Tran, Xuan Nam <br/> <br/>Abstract: Edge caching has received much attention as a promising technique to overcome the stringent latency and data-hungry challenges in the future generation wireless networks. Meanwhile, full-duplex (FD) transmission can improve the spectral efficiency by allowing a node to receive and transmit on the same frequency band simultaneously. In this paper, we investigate the delivery time performance of a cache-aided FD system, in which an edge node, operates in FD mode, serves users via wireless channels and is equipped with a cache memory. Firstly, we derive a closed-form expression for the average delivery time by taking into account the uncertainties of both backhaul and access wireless channels. The derived analysis allows the examination of the impact of the key parameters, e.g., cache size and transmit power. Secondly, a power optimization problem is formulated to minimize the average delivery time. To deal with the non-convexity of the formulated problem, we propose an iterative optimization algorithm based on the bisection method. Finally, numerical results are presented to demonstrate the effectiveness of the proposed algorithm, which can significantly reduce the delivery time compared to the FD reference and the half-duplex counterpart. Sat, 06 Jun 2020 03:30:02 GMT http://hdl.handle.net/10993/43429 Title: MLSE and Spatio-Temporal Interference Rejection Combining with Antenna Arrays <br/> <br/>Author, co-author: Asztély, David; Ottersten, Björn Fri, 05 Jun 2020 21:17:01 GMT http://hdl.handle.net/10993/43428 Title: Blind Subspace Identification of a BPSK Communication Channel <br/> <br/>Author, co-author: Kristensson, Martin; Ottersten, Björn Fri, 05 Jun 2020 21:04:40 GMT http://hdl.handle.net/10993/43427 Title: The Effects of Local Scattering on Direction of Arrival Estimation with MUSIC and ESPRIT <br/> <br/>Author, co-author: Asztély, David; Ottersten, Björn Fri, 05 Jun 2020 21:03:49 GMT http://hdl.handle.net/10993/43426 Title: Analysis of Subspace Fitting Based Methods for Sensor Array Processing <br/> <br/>Author, co-author: Ottersten, Björn; Viberg, M. Fri, 05 Jun 2020 21:01:56 GMT http://hdl.handle.net/10993/43425 Title: A Generalized Array Manifold Model for Local Scattering in Wireless Communications <br/> <br/>Author, co-author: Asztely, David; Ottersten, Björn; Swindlehurst, Andrew Lee <br/> <br/>Commentary: 5 Fri, 05 Jun 2020 20:55:00 GMT http://hdl.handle.net/10993/43424 Title: Power Allocation and Bit Loading for Spatial Multiplexing in MIMO Systems <br/> <br/>Author, co-author: Zhang, Xi; Ottersten, Björn <br/> <br/>Abstract: The power assignment problem is important for Multiple-Input-Multiple-Output (MIMO) systems to achieve high capacity. Although this problem is solved by well-known water filling algorithms, this does not provide an optimal solution if the system is constrained to a fixed raw bit error rate threshold and to discrete modulation s. In this work an approximate approach, called QoS based WF, is proposed to solve the power assignment problem with such constrains. It is shown to outperform quantization of the conventional water filling solution and a well known bit loading algorithm (Chow's algorithm) used in the Digital Subscriber Lines (DSL). Fri, 05 Jun 2020 20:54:13 GMT http://hdl.handle.net/10993/43423 Title: Robust Signal Parameter Estimation in the Presence of Array Perturbations <br/> <br/>Author, co-author: Wahlberg, B.; Ottersten, Björn; Viberg, M. Fri, 05 Jun 2020 20:52:36 GMT http://hdl.handle.net/10993/43422 Title: A Statistical Perspective on State-Space Modeling Using Subspace Methods <br/> <br/>Author, co-author: Viberg, M.; Ottersten, Björn; Wahlberg, B.; Ljung, L. Fri, 05 Jun 2020 20:50:50 GMT http://hdl.handle.net/10993/43421 Title: Full Diversity Detection in MIMO Systems with a Fixed-Complexity Sphere Decoder <br/> <br/>Author, co-author: Jaldén, Joakim; Barbero, Luis G.; Ottersten, Björn; Thompson, John S. Fri, 05 Jun 2020 20:49:50 GMT