Theoretical analysis of REM-based handover algorithm for heterogeneous networks

© 2013 IEEE. Handover has been a widely studied topic since the beginning of the mobile communications era, but with the advent of another generation, it is worth seeing it with fresh eyes. Data traffic is expected to keep growing as new use cases will coexist under the same umbrella, e.g., vehicle-to-vehicle or massive-machine-type communications. Heterogeneous networks will give way to multi-tiered networks, and mobility management will become challenging once again. Under the current approach, based uniquely on measurements, the number of handovers will soar, so will the signaling. We propose a handover algorithm that employs multidimensional radio-cognitive databases, namely radio environment maps, to predict the best network connection according to the user's trajectory. Radio environment maps have been extensively used in spectrum-sharing scenarios, and recently, some advances in other areas have been supported by them, such as coverage deployment or interference management. We also present a geometric model that translates the 3GPP specifications into geometry and introduce a new framework that can give useful insights into our proposed technique's performance. We validate our framework through Monte Carlo simulations, and the results show that a drastic reduction of at least 10% in the ping-pong handovers can be achieved, thus reducing the signaling needed

Optimal Mode Selection for Full-Duplex Enabled D2D Cognitive Networks

© 2019 IEEE. Full-Duplex (FD) and Device-to-Device (D2D) communications have been recognized as one of the successful solutions of spectrum scarcity in 5G networks. Significant advancements in self-interference-to-power-ratio (SIPR) reduction have paved the way for FD use to double the data rates and reduce the latency. This advantage can now be exploited to optimize dynamic spectrum sharing among different radio access technologies in cognitive networks. However, protecting the primary user communication has been a challenging problem in such coexistence. In this paper, we provide an abstract level analysis of protecting primary users reception based on secondary users FD enabled communication. We also propose optimal mode selection (Half-duplex, Full-duplex, or silent) for secondary D2D users depending on its impact on primary users. Our analysis presents the significant advantage of D2D mode selection in terms of efficient spectrum utilization while protecting the primary user transmission, thus, leading the way for FD enabled D2D setup. Depending on the location and transmit power of D2D users, the induced aggregate interference should not violate the interference threshold of primary users. For this, we characterize the interference from D2D links and derive the probability for successful D2D users for half-duplex and full-duplex modes. The analyses are further supported by theoretical and extensive simulation results

A phased array antenna employing reconfigurable defected microstrip structure (RDMS)

© 2015 IEEE. In this paper, a compact phase-shifting unit based on reconfigurable defected microstrip structure (RDMS) is used to provide controllable phase shift for a 1×4 phased array antenna. The RDMS is made by etching two slots on the microstrip line and loading with PIN diodes. By controlling the working states of the employed PIN diodes, the RDMS is able to provide phase shift. A 1×4 phased array antenna is built employing optimized RDMS. The tested results show that the antenna can work in the frequency band from 5.1-5.4 GHz, and switch its beam to -15°, 0°, and 15° in the H-plane with the average gain of 10 dBi. Compared to our previous work, significantly size reduction of 55% is achieved with similar performance

(E)-3-(Biphenyl-4-yl)-1-(3-bromo­phen­yl)prop-2-en-1-one

In the title compound, C21H15BrO, there are two planar rings connected through a conjugated double bond. As it crystallizes in a non-centrosymmetric space group it can be regarded as a good candidate for non-linear optical applications. The mol­ecule adopts an E configuration and the C—C=C—C torsion angle is 177.1 (4)°. The overall conformation of the compound may be described by the values of dihedral angles between the approximately planar parts. The terminal rings are twisted by an angle of 51.52 (9)°, while the biphenyl part is almost planar, the dihedral angle between the planes of the rings being 4.44 (17)°. The unit cell has one long dimension, above 35 Å, characteristic also of a majority of related compounds. The mol­ecules pack head-to-tail along this direction. C—H⋯π inter­actions are observed in the crystal structure

2-(4-Chloro­phen­oxy)acetohydrazide

In the title compound, C8H9ClN2O2, the two planar fragments, i.e. the chloro­phenyl and C—C(=O)—N groups, are inclined at 14.93 (17)°. In the crystal, relatively weak inter­molecular N—H⋯N, C—H⋯O and N—H⋯O hydrogen bonds connect the mol­ecules into layers. The hydro­phobic parts of mol­ecules stick outside these layers and are connected with the neighbouring layers only by van der Waals contacts and Cl⋯Cl inter­actions [3.406 (2) Å]

Capturing optically important constituents and properties in a marine biogeochemical and ecosystem model

We present a numerical model of the ocean that couples a three-stream radiative transfer component with a marine biogeochemical–ecosystem component in a dynamic three-dimensional physical framework. The radiative transfer component resolves the penetration of spectral irradiance as it is absorbed and scattered within the water column. We explicitly include the effect of several optically important water constituents (different phytoplankton functional types; detrital particles; and coloured dissolved organic matter, CDOM). The model is evaluated against in situ-observed and satellite-derived products. In particular we compare to concurrently measured biogeochemical, ecosystem, and optical data along a meridional transect of the Atlantic Ocean. The simulation captures the patterns and magnitudes of these data, and estimates surface upwelling irradiance analogous to that observed by ocean colour satellite instruments. We find that incorporating the different optically important constituents explicitly and including spectral irradiance was crucial to capture the variability in the depth of the subsurface chlorophyll a (Chl a) maximum. We conduct a series of sensitivity experiments to demonstrate, globally, the relative importance of each of the water constituents, as well as the crucial feedbacks between the light field, the relative fitness of phytoplankton types, and the biogeochemistry of the ocean. CDOM has proportionally more importance at attenuating light at short wavelengths and in more productive waters, phytoplankton absorption is relatively more important at the subsurface Chl a maximum, and water molecules have the greatest contribution when concentrations of other constituents are low, such as in the oligotrophic gyres. Scattering had less effect on attenuation, but since it is important for the amount and type of upwelling irradiance, it is crucial for setting sea surface reflectance. Strikingly, sensitivity experiments in which absorption by any of the optical constituents was increased led to a decrease in the size of the oligotrophic regions of the subtropical gyres: lateral nutrient supplies were enhanced as a result of decreasing high-latitude productivity. This new model that captures bio-optical feedbacks will be important for improving our understanding of the role of light and optical constituents on ocean biogeochemistry, especially in a changing environment. Further, resolving surface upwelling irradiance will make it easier to connect to satellite-derived products in the future

2-Isopropyl-5-methyl­cyclo­hexyl 5-acet­oxy-1,3-oxathiol­ane-2-carboxyl­ate

In the title compound, C16H26O5S, the oxathiol­ane ring adopts an envelope conformation, with the S atom 0.793 (3) Å out of the mean plane of the remaining four atoms. The cyclo­hexane ring of the menthol fragment adopts an almost ideal chair conformation, with all substituents in the equatorial positions. In the crystal, relatively strong, short and linear C—H⋯O hydrogen bonds link the mol­ecules into the chains along [100] direction. The chains are packed into the crystal structure by means of weak dispersive inter­actions. Inter­molecular C—H⋯S inter­actions are also observed

(E)-1-(2,5-Dichloro-3-thien­yl)-3-[4-(dimethyl­amino)phen­yl]prop-2-en-1-one

In the title compound, C15H13Cl2NOS, the benzene and thio­phene rings make a dihedral angle of 10.8 (1)°. The dimethyl­amino substituent and the α,β-unsaturated carbonyl group are almost coplanar with respect to the aromatic ring, forming dihedral angles of 4.73 (3)° and 5.0 (2)°, respectively. In the crystal structure, mol­ecules are connected into two-dimensional layers by weak C—H⋯Cl hydrogen bonds and C—Cl⋯O [Cl⋯O = 3.073 (2) Å] inter­actions. These layers are stacked with short C(meth­yl)–H⋯π contacts betweeen the layers