Network densification with deployments of many small base stations (SBSs) is a key enabler technology for the fifth generation (5G) cellular networks, and it is also clearly in conflict with one of the target design r...
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ISBN:
(纸本)9783030419134;9783030419127
Network densification with deployments of many small base stations (SBSs) is a key enabler technology for the fifth generation (5G) cellular networks, and it is also clearly in conflict with one of the target design requirements of 5G systems: a 90% reduction of the power consumption. In order to address this issue, switching off a number of SBSs in periods of low traffic demand has been standardized as an recognized strategy to save energy. But this poses a challenging NP-complete optimization problem to the system designers, which do also have to provide the users with maxima capacity. This is a multi-objective optimization problem that has been tackled with multi-objective evolutionary algorithms (MOEAs). In particular, a problem-specific search operator with problem-domain information has been devised so as to engineer hybrid MOEAs. It is based on promoting solutions that activate SBSs which may serve users with higher data rates, while also deactivating those not serving any user at all. That is, it tries to improve the two problem objectives simultaneously. The resulting hybrid algorithms have shown to reach better approximations to the Pareto fronts than the canonical algorithms over a set of nine scenarios with increasing diversity in SBSs and users.
Quantum annealing offers an appealing route to handle large-scale optimization problems. Existing Quantum Annealing processing units are readily available via cloud platform access for solving Quadratic Unconstrained ...
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Quantum annealing offers an appealing route to handle large-scale optimization problems. Existing Quantum Annealing processing units are readily available via cloud platform access for solving Quadratic Unconstrained Binary Optimization (QUBO) problems. In particular, the novel D-Wave Advantage device has been recently released. Its performance is expected to improve upon the previous state-of-the-art D-Wave 2000Q annealer, due to higher number of qubits and the Pegasus topology. Here, we present a comparative study via an ensemble of Maximum Likelihood (ML) Channel Decoder problems for MIMO scenarios in Centralized Radio Access Network (C-RAN) architectures. The main challenge for exact optimization of ML decoders with ever-increasing demand for higher data rates is the exponential increase of the solution space with problem sizes. Since current 5G solutions mainly use approximate methodologies, Kim et al. leveraged Quantum Annealing for large MIMO problems with Phase Shift Keying and Quadrature Amplitude Modulation scenarios. Here, we extend their work and analyze experiments for more complex modulations and larger MIMO antenna array sizes. By implementing the extended QUBO formulae on the novel annealer architecture, we uncover the limits of state-of-the-art quantum optimization for the massive MIMO ML decoder. We report on the improvements and discuss the uncovered limiting factors learned from the 64-QAM extension. We include the enhanced evaluation of raw annealer sampling via implementation of post-processing methods in the comparative analysis between D-Wave 2000Q and the D-Wave Advantage system.
The use of glide symmetry in radiofrequency devices to introduce dispersive effects has been recently proposed and demonstrated. One of these effects is to control the propagation constant of the structure. Here, we p...
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ISBN:
(纸本)9788890701887
The use of glide symmetry in radiofrequency devices to introduce dispersive effects has been recently proposed and demonstrated. One of these effects is to control the propagation constant of the structure. Here, we propose a mm-wave phase shifter whose elements have a glide-symmetric configuration to achieve a greater phase shift in the same waveguide space than the non-glide-symmetric case. The glide-symmetric phase shifter is implemented in waveguide technology and is formed by rows of metallic pins that produce the desired phase shift. To assess the better performance of the glide-symmetric phase shifter, it is compared to its non-glide-symmetric version whose metallic pins are located only in one of the broad sides of the waveguide. The operating frequency range of the phase shifter is 67 to 75 GHz. Results show a 180 degree phase shift in regard to the reference waveguide without pins, and 50 degrees more than the non-glide-symmetric version.
This document presents the design of an array of helix antennas in axial mode based on higher symmetries. These higher symmetries permit, for a given frequency, the miniaturization of the antenna. Therefore, an array ...
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ISBN:
(纸本)9781728105666
This document presents the design of an array of helix antennas in axial mode based on higher symmetries. These higher symmetries permit, for a given frequency, the miniaturization of the antenna. Therefore, an array formed by this kind of miniaturized antennas presents lower mutual coupling among the constituting antennas. A comparison is made between the performance of antenna arrays formed by conventional and glide-and-twist-symmetrical helix antennas. The results show a decrease in mutual coupling in the glide-and-twist- symmetrical helix array, regarding to the conventional helix array, for the same element spacing. Moreover, better radiation performance is achieved in terms of directivity and gain in the miniaturized helix array.
Evaluating the Torontonian function is a central computational challenge in the simulation of Gaussian Boson Sampling (GBS) with threshold detection. In this work, we propose a recursive algorithm providing a polynomi...
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The use of glide symmetry in radiofrequency devices to introduce dispersive effects has been recently proposed and demonstrated. One of these effects is to control the propagation constant of the structure. Here, we p...
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The use of glide symmetry in radiofrequency devices to introduce dispersive effects has been recently proposed and demonstrated. One of these effects is to control the propagation constant of the structure. Here, we propose a mm-wave phase shifter whose elements have a glide-symmetric configuration to achieve a greater phase shift in the same waveguide space than the non-glide-symmetric case. The glide-symmetric phase shifter is implemented in waveguide technology and is formed by rows of metallic pins that produce the desired phase shift. To assess the better performance of the glide-symmetric phase shifter, it is compared to its non-glide-symmetric version whose metallic pins are located only in one of the broad sides of the waveguide. The operating frequency range of the phase shifter is 67 to 75 GHz. Results show a 180 degree phase shift in regard to the reference waveguide without pins, and 50 degrees more than the non-glide-symmetric version.
The paradigm shift that has to take place in the new 5G networks in order to meet the expected data rates is a huge technological challenge. The use of super dense heterogeneous networks is one of the most promising a...
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This paper is a study of the inhomogeneity reduction for near-field acquisition in high-resolution magnetic resonance imaging (MRI) systems. The acquisition homogeneity in MRI imaging modality is an open issue concern...
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This paper is a study of the inhomogeneity reduction for near-field acquisition in high-resolution magnetic resonance imaging (MRI) systems. The acquisition homogeneity in MRI imaging modality is an open issue concerning the optimal MRI image generation in terms of the RF signal acquisition. The acquisition inhomogeneity is related to the radiation patterns of the receiving antennas and its location in the MRI system, among other relevant aspects. The acquisition inhomogeneity is translated into two main effects: pattern ripples at the outer cylindrical rings and radial inhomogeneity when comparing the center value ( maximum) with the rest of the pattern. To overcome these effects, two strategies are proposed. In the first one, it is proposed to progressively vary the antenna location in the azimuthal array distribution. In the second one, it is proposed to progressively vary the antenna amplitude and phase feeding in the array distribution. To compute a figure of merit of the pattern radial uniformity and the ripples, two metrics are defined in this paper. It is proved that both the progressive modification in the location at each array ring and the variation of the feeding phase of each array ring reduce the pattern ripples and radial inhomogeneity. Optimal values for either the angular rotation or the feeding phase values can be calculated, depending on the particular dimensions of the cylinder that conforms the region of interest.
Energy efficiency is a critical issue for wireless sensor networks (WSNs) as sensor nodes have limited power availability. In order to address this issue, this paper tries to maximize the power efficiency in WSNs by m...
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Energy efficiency is a critical issue for wireless sensor networks (WSNs) as sensor nodes have limited power availability. In order to address this issue, this paper tries to maximize the power efficiency in WSNs by means of the evaluation of WSN node networks and their performance when both clustering and antenna beamforming techniques are applied. In this work, four different scenarios are defined, each one considering different numbers of sensors: 50, 20, 10, five, and two nodes per scenario, and each scenario is randomly generated thirty times in order to statistically validate the results. For each experiment, two different target directions for transmission are taken into consideration in the optimization process (phi = 0 degrees and theta = 45 degrees;phi = 45 degrees, and theta = 45 degrees). Each scenario is evaluated for two different types of antennas, an ideal isotropic antenna and a conventional dipole one. In this set of experiments two types of WSN are evaluated: in the first one, all of the sensors have the same amount of power for communications purposes;in the second one, each sensor has a different amount of power for its communications purposes. The analyzed cases in this document are focused on 2D surface and 3D space for the node location. To the authors' knowledge, this is the first time that beamforming and clustering are simultaneously applied to increase the network lifetime in WSNs.
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