1,141 research outputs found
mm-Wave channel estimation with accelerated gradient descent algorithms
No full textAbstract The availability of millimeter wave (mm-Wave) band in conjunction with massive multiple-input-multiple-output (MIMO) technology is expected to boost the data rates of the fifth-generation (5G) cellular systems. However, in order to achieve high spectral efficiencies, an accurate channel estimate is required, which is a challenging task in massive MIMO. By exploiting the small number of paths that characterize the mm-Wave channel, the estimation problem can be solved by compressed-sensing (CS) techniques. In this paper, we propose a novel CS channel estimation method based on the accelerated gradient descent with adaptive restart (AGDAR) algorithm exploiting a ℓ 1-norm approximation of the sparsity constraint. Moreover, a modified re-weighted compressed-sensing (RCS) technique is considered that iterates AGDAR using a weighted version of the ℓ 1-norm term, where weights are adapted at each iteration. We also discuss the impact of cell sectorization and tracking on the channel estimation algorithm. We compare the proposed solutions with existing channel estimations with an extensive simulation campaign on downlink third-generation partnership project (3GPP) channel models
Cluster-head based feedback for simplified time reversal prefiltering in ultra-wideband systems
No full textTime-reversal prefiltering (TRP) technique for impulse radio (IR) ultra wide-band (UWB) systems requires a large amount of feedback to transmit the channel impulse response from the receiver to the transmitter. In this paper, we propose a new feedback design based on vector quantization. We use a machine learning algorithm to cluster the estimated channels into several groups and to select the channel cluster heads (CCHs) for feedback. In particular, CCHs and their labels are recorded at both side of the UWB transceivers and the label of the most similar CCH to the estimated channel is fed back to the transmitter. Finally, the TRP is applied using the feedback CCH. The proposed digital feedback provides three main advantages: (1) it significantly reduces the dedicated bandwidth required for feedback; (2) it considerably improves the speed of transceivers; and, (3) it is robust to noise in the feedback channel since few bytes are required to send the codes that can be heavily error protected. Numerical results on standard UWB channel models are discussed, showing the advantage of the proposed solution
The Killing of Soleimani and International Law
No full textOn 3 January, missiles launched from a United States Reaper drone struck two vehicles leaving Baghdad’s international airport. At least seven people died in the attack, including the commander of Iran’s Quds force, General Qassem Soleimani. On 5 January, Iranian Major General Hossein Dehghan, reported to be the military adviser to Iran’s Supreme Leader, gave an exclusive interview to CNN and said Iran “would retaliate directly against US ‘military sites.’
The Killing of Soleimani and International Law
No full textOn 3 January, missiles launched from a United States Reaper drone struck two vehicles leaving Baghdad’s international airport. At least seven people died in the attack, including the commander of Iran’s Quds force, General Qassem Soleimani. On 5 January, Iranian Major General Hossein Dehghan, reported to be the military adviser to Iran’s Supreme Leader, gave an exclusive interview to CNN and said Iran “would retaliate directly against US ‘military sites.’
Fast Initial Access for mmWave 5G Systems with Hybrid Beamforming Using Online Statistics Learning
No full textStatistical approaches for initial access in mmwave 5G systems
No full textMmWave communication systems overcome high attenuation by using multiple antennas with beamforming at both the transmitter and the receiver. Upon entrance of a user equipment (UE) into a cell, the base station scans the space in order to find the UE, in what is known as initial access (IA) procedure. In this paper, we start from the observation that UEs are more likely to enter from some directions than others, as they typically move along streets, while other movements are impossible due to the presence of obstacles. Moreover, users are entering with a given time statistics. In this context, we propose scanning strategies for IA that take into account the entrance statistics. In particular, we propose two approaches: a memory-less random illumination (MLRI) algorithm and a statistic and memory-based illumination (SMBI) algorithm. The MLRI algorithm scans a random sector in each slot, based on the statistics of sector entrance, without memory. The SMBI algorithm instead scans sectors in a deterministic sequence selected according to the statistics of sector entrance and time of entrance and taking into account the fact that the user has not yet been discovered (thus including memory). We assess the performance of the proposed methods in terms of misdetection and false alarm probability and average discovery tim
Supplemental Material, sj-docx-1-cll-10.1177_09636897211048786 - Improvement of Heart Function After Transplantation of Encapsulated Stem Cells Induced with miR-1/Myocd in Myocardial Infarction Model of Rat
No full textSupplemental Material, sj-docx-1-cll-10.1177_09636897211048786 for Improvement of Heart Function After Transplantation of Encapsulated Stem Cells Induced with miR-1/Myocd in Myocardial Infarction Model of Rat by Samaneh Khazaei, Masoud Soleimani, Seyed Hossein Ahmadi Tafti, Rouhollah Mehdinavaz Aghdam and Zohreh Hojati in Cell Transplantation</p
Statistical approaches for initial access in mmWave 5G systems
No full textWhen a new user enters a cell in a mmWave cellular system, the beamforming directions must be identified to initiate communication, a procedure known as initial access (IA). However, users are more likely to enter from sorne directions than others (eg, along streets), and beamforming directions (eg, those affected by blockage) may never be used. We exploit the unequal distribution of the entrance direction to speed up the IA procedure, exploring more often the directions wherein the probability of finding new users is higher. Two solutions are proposed: a memory-less random illumination (MLRI) algorithm and a statistical and memory-based illumination (SMBI) algorithm. While in MLRI, the direction to be explored is randomly generated according to an optimized distribution, and independent of previously explored directions, in SMBI a precise exploration sequence is designed, thus we take into account previously explored directions. In the analysis, we include the movement of the user within the cell during the IA process, described by a Markov chain whose states correspond to the beamforming directions associated to the user position at a given IA exploration time. We assess the performance of the proposed methods in terms of average discovery time
Weighted PCA for improving Document Image Retrieval System based on keyword spotting accuracy
No full textUltra Wideband and Bluetooth detection based on energy features
No full textDetection, classification, and recognition based on the detection of energy features of Ultra Wide Band (UWB) vs. signals emitted in the Industrial Scientific and Medical (ISM) radio bands, such as Bluetooth, is a challenging issue. This work addressed this issue by analyzing the behavior of UWB versus Bluetooth signals in various noisy environments. The focus was on identifying robust feature extraction algorithms, that would enable encoding UWB and Bluetooth signals with features such as, for example, short time energy, Fast Fourier transform energy, and derivatives of short time energy. Results of experimental analysis showed that with respect to other signals, short-time energy of UWB over small overlapping time windows had acceptable discriminative performance. The different feature selection algorithms were tested with the following classifiers; Support Vector Machine with related kernel methods, Probabilistic Neural Networks, K Nearest Neighborhood, and Naive Bayes were tested in order to select the best option towards detection performance in different noisy conditions. © 2014 IEEE
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