In this paper, semideterministic multi-input multi-output (MIMO) channel modeling is proposed for a tunnel with two types of cross sections. To be more consistent with the MIMO propagation characteristics of the measured data, ray tracing (RT) is used to simulate the specular components (SCs) and a directed path channel modeling method based on directive scattering model (DSM) is used to simulate the diffuse components (DCs), which has an important contribution in MIMO channel capacity. The performance of the proposed model is compared in terms of delay domain, angle domain, and channel capacity. By analyzing the DSM and the propagation graph based on the Lambertian scattering model (LSM), it was demonstrated that the proposed method is more suitable in terms of comprehensive performance.
The inconsistency of conformal array elements poses a huge challenge to pattern synthesis. Based on convex optimization theory, this paper proposes a novel directivity pattern synthesis method. It can maximize the directivity of dual-polarized conformal arrays with a low dynamic range ratio (DRR). Firstly, the directivity function is presented under a dual-polarized conformal array. Then the pattern synthesis based on maximizing directivity is summarized as a multiconstraint optimization problem. In addition, the DRR constraint is introduced to control the weight range. By using Taylor expansion, the problem is transformed into a convex optimization problem and solved iteratively. Finally, simulation results demonstrate that the proposed method can effectively achieve a good directivity pattern with low sidelobe level (SLL) and low DRR.
Vehicular ad hoc network (VANET) brings an excellent solution to ensure road safety and transportation efficiency in critical environment like tunnel. Particularly, radio link connectivity of vehicle-to-vehicle (V2V) significantly influences the performance of VANETs. The communication range of the radio systems is a random variable in reality due to the channel fading effect. Therefore, the connectivity model between vehicles in realistic environment is a key for accurate evaluation of system performances. In this paper, we study the V2V connectivity performance in the presence of channel randomness for tunnel environment. Firstly, based on channel measurement campaign, empirical path loss (PL) and small-scale fading channel models are established. Secondly, we study the influence of large-scale fading parameters on V2V connectivity. Thirdly, based on real small-scale fading characteristics, we derive the V2V connectivity probability between any two vehicles under Nakagami fading channel for one-dimensional VANET, and give the closed-form of V2V connectivity probability. Finally, we study the influences of various parameters (i.e., Nakagami fading factor, vehicle density, and neighbor order) on V2V connectivity performance. Results show that with the Nakagami fading shape factor increases, the connectivity probability increases. The shadowing fading can improve connectivity in the VANET; the path loss exponent, transmission distance, and signal-to-noise ratio (SNR) threshold have a negative impact on connectivity probability. The transmit power, vehicle density, and path loss threshold value have a positive impact on connectivity.
Direction of arrival (DOA) estimation for non-Gaussian signals using three-level nested array (THL-NA) is investigated in this paper. Motivation from larger consecutive degree of freedom (DOF) and array aperture, the THL-NA is proposed, which can take full advantages of the consecutive coarrays of TL-NA and has the closed-form expression of DOF. Specifically, firstly, the array aperture is expanded by the second order sum coarray (2-SC) of the proposed array, secondly, the nested relationship between subarrays is employed to obtain the difference coarray of 2-SC (2-DCSC), finally, a consecutive virtual array with large array aperture is obtained. Besides, a successive SS-MUSIC algorithm is proposed, which employs the spatial smoothing estimating signal parameter via rotational invariance techniques (SS-ESPRIT) algorithm and partial spectrum searching multiple signal classification (PSS-MUSIC) to obtain initial estimations and fine estimations, respectively, resulting in a better balance between computational complexity and estimation accuracy.
Ismahayati Adam, Muhammad Ramlee Kamarudin, Ali H. Rambe
et al.
This paper analysed the effects of bending on the performance of a textile antenna wherein the antenna under test was made of felt substrate for both industrial, scientific, and medical (ISM) band and WBAN applications at 2.45 GHz. Moreover, the conductive material was used for the patch, and the ground plane used a 0.17 mm Shieldit textile. Meanwhile, the antenna structure was in the form of rectangular, with a line patch in between elements to abate the mutual coupling effect. The measured operating frequency range of the antenna spanned from 2.33 GHz to 2.5 GHz with a gain of 4.7 dBi at 2.45 GHz. In this paper, the antenna robustness was examined by bending the structure on different radii and degrees along both X- and Y-axis. Next, the effects on return loss, bandwidth, isolation, and radiation characteristics were analysed. This paper also discovered that the antenna’s performance remained acceptable as it was deformed, and the measured results agreed well with the simulation.
The aim of this study proposes new system for PT Trakindo as an official agent company (dealer) in Indonesia for Caterpillar products. The company’s operations are the world's largest heavy equipment manufacturer which includes mining industry, oil and gas industry, construction, forestry, agriculture, and power systems. The problem is Procurement of goods and services performed by PT Trakindo Utama currently undergoing a lot of obstacles such as significant cost in finding the right suppliers, bad integration with suppliers, dependence on suppliers, the bill submitted by the supplier can not timely because the billing document incomplete, the use of media such as telephone and so on which may cause considerable cost. The contribution of this research are developing the procurement system design, and web-based services are expected to help anticipate and resolve these problems. This research was conducted using qualitative and case study method, which has the characteristics of exploratory. The results achieved are expected to improve the efficiency and effectiveness of the procurement process at PT Trakindo Utama.
In this paper, we propose a design of two compact and miniaturized RFID epidermal tags in the UHF band for health monitoring applications. The two conceptions of meandered double-loop antennas with T-match configuration, namely, a double-loop antenna with meandered line in the horizontal direction and a double-loop antenna with meandered lines in two directions, are placed at very close distance from the human body. The proposed tags are composed of bio-silicone substrate, to protect the human skin from the electromagnetic waves, and a copper conductor loaded by T-match configuration, to suit the complex impedance of the antenna to that of the chip. We have performed numerical simulations of these conceptions of two tags using the HFSS and CST solvers. Our results show two optimal sizes with a high communication performance, good matching features, and a large read range. We placed afterwards these two optimized tags in an elliptical environment to test their flexibility and examine their performance on different parts of the human body.
Le Ministère de l'Ecologie, du Développement Durable et de l'Energie (MEDDE) s'est doté en 2011 d'un plan d'applications satellitaires. Ce document est la feuille de route de son Pôle de Compétences et d'Innovation « Applications Satellitaires et Télécommunication » (PCI-AST). Parmi différentes missions, le plan fixe pour objectif une montée en compétence des services du ministère dans l'utilisation des technologies satellitaires. Dans ce contexte, le PCI-AST est chargé de démontrer le potentiel des technologies satellitaires pour le ministère, en particulier dans le domaine de l'observation de la terre, puis de diffuser les savoir-faire, méthodologies et outils dans le réseau technique et dans les services déconcentrés.
Les logiciels libres s'implantent progressivement dans les administrations et favorisent l'innovation. En ce sens, l'adoption de l'Orfeo Toolbox comme outil de traitement des images satellites constitue une continuité naturelle. L'outil est utilisé ici comme support à une méthode collaborative impliquant dans une même démarche les porteurs de politiques publiques, les géomaticiens et les télédétecteurs.
Instruments and machines, Applied optics. Photonics
This paper presents a Vlasov antenna with curved cut shape and improved reflector position and geometry suitable for high power microwave applications. The curved shape of the proposed cut totally eliminates the sharp edges and angles present in Vlasov antennas with step and bevel cuts. Furthermore, with the proposed reflector configuration, the wave is radiated in the direction of the axis of the waveguide. A Vlasov antenna, designed for operation at 3 GHz, is used to compare the three cut types. An additional comparison is conducted to validate the concept of the enhanced reflector position, using the bevel-cut antenna and the improved cut. The proposed antenna results in increased antenna gain and in good performance in terms of sidelobe level and half-power beamwidth, with maximum radiation directed toward the axis of the waveguide center.
A wideband dual-polarized coplanar waveguide (CPW) fed antenna integrating a wide stop-band filter is presented. The designed filter is based on a nonuniform defected ground structure (DGS) in order to obtain a wide stop-band and a compact size. This filter is used to reject harmonics and spurious radiation arising from the RF front end. The complete structure (antenna and filter) has been optimized to have a compact size of 0.6×0.6λ02 (λ0 being the free-space wavelength at the lowest operating frequency). The realized antenna operates in the frequency range between 2.7 GHz and 5.9 GHz (bandwidth of about 74%). The isolation between feeding ports is more than 18 dB. The complete structure has a wide stop-band characteristic (103%) for harmonic rejection. The simulated numerical results have been confirmed with measurements.
Mohammad H. Behfar, Toni Björninen, Elham Moradi
et al.
Assessment of intracranial pressure (ICP) is of great importance in management of traumatic brain injuries (TBIs). The existing clinically established ICP measurement methods require catheter insertion in the cranial cavity. This increases the risk of infection and hemorrhage. Thus, noninvasive but accurate techniques are attractive. In this paper, we present two wireless, batteryless, and minimally invasive implantable sensors for continuous ICP monitoring. The implants comprise ultrathin (50 μm) flexible spiral coils connected in parallel to a capacitive microelectromechanical systems (MEMS) pressure sensor. The implantable sensors are inductively coupled to an external on-body reader antenna. The ICP variation can be detected wirelessly through measuring the reader antenna’s input impedance. This paper also proposes novel implant placement to improve the efficiency of the inductive link. In this study, the performance of the proposed telemetry system was evaluated in a hydrostatic pressure measurement setup. The impact of the human tissues on the inductive link was simulated using a 5 mm layer of pig skin. The results from the in vitro measurement proved the capability of our developed sensors to detect ICP variations ranging from 0 to 70 mmHg at 2.5 mmHg intervals.
Target localization in urban sensing can benefit from angle dependency of the pulse shape at a radar receiver antenna. We propose a localization approach that utilizes the embedded directivity in ultra-wideband (UWB) antennas to estimate target positions. A single radar unit sensing operation of indoor targets surrounded by interior walls is considered, where interior wall multipaths are exploited to provide target cross-range. This exploitation assumes resolvability of the multipath components, which is made possible by the virtue of using UWB radar signals. The proposed approach is most attractive when only few multipaths are detectable due to propagation obstructions or owing to low signal-to-noise ratios. Both simulated and experimental data are used to demonstrate the effectiveness of the proposed approach.
The need for effective and efficient telephone billing system in Nigerian telecommunication industries is increasing everyday as a result of the match towards technological advancement. As such, this study tried to investigate the existing telephone billing system used in the various telecommunication industries in Nigeria with a view to improving on them. To accomplish this, the researcher developed comparative analysis for five telecommunication industries in Nigeria. Etisalat Network was chosen as a case study because it is the network that has the best quality of service and has lowest customer tariff with an effective and responsive customer care unit. Interestingly, the billing system of Etisalat network was discovered to have some shortcomings such as customer name, town name and town code. All these parameters are not displayed in the bill after calls. This research has therefore made an attempt to incorporate the three parameters which did not exist in the Etisalat call summary receipt. This task was achieved using Software Engineering Approach and the Program Source Code was developed using Turbo Pascal version 6.0.
This paper presents a low-profile multiband antenna suitable for wireless local area networks (WLANs), using a chip inductor and tuning stub for broadband impedance matching. The proposed antenna is compact 12×10×1 mm3 and covers three bands: 2.4-GHz (2.400–2.484 GHz), 5.2-GHz (5.150–5.350 GHz), and 5.8-GHz (5.725–5.825 GHz). The measured 10-dB bandwidths are 12.0% (2.28–2.57 GHz) in the lower band for 2.4-GHz WLANs and 39.1% (4.81–7.15 GHz) in the upper band for 5 GHz-WLANs. The measured peak gain of the antenna is between 2.7 and 4.39 dBi and the radiation patterns are omnidirectional.
Vincent Savaux, Moïse Djoko-Kouam, Yves Louët
et al.
This paper deals with spectrum sensing in an orthogonal frequency division multiplexing (OFDM) context, allowing an opportunistic user to detect a vacant spectrum resource in a licensed band. The proposed method is based on an iterative algorithm used for the joint estimation of noise variance and frequency selective channel. It can be seen as a second-order detector, since it is performed by means of the minimum mean square error criterion. The main advantage of the proposed algorithm is its capability to perform spectrum sensing, noise variance estimation, and channel estimation in the presence of a signal. Furthermore, the sensing duration is limited to only one OFDM symbol. We theoretically show the convergence of the algorithm, and we derive its analytical detection and false alarm probabilities. Furthermore, we show that the detector is very efficient, even for low SNR values, and is robust against a channel uncertainty.
Different from phased-array radar, frequency diverse array (FDA) radar offers range-dependent beampattern and thus provides new application potentials. But there is a fundamental question: what estimation performance can achieve for an FDA radar? In this paper, we derive FDA radar Cramér-Rao lower bounds (CRLBs) for estimating direction, range (time delay), and velocity (Doppler shift). Two different data models including pre- and postmatched filtering are investigated separately. As the FDA radar has range-angle coupling, we use a simple transmit subaperturing strategy which divides the whole array into two subarrays, each uses a distinct frequency increment. Assuming temporally white Gaussian noise and linear frequency modulated transmit signal, extensive simulation examples are performed. When compared to conventional phased-array radar, FDA can yield better CRLBs for estimating the direction, range, and velocity. Moreover, the impacts of the element number and frequency increment are also analyzed. Simulation results show that the CRLBs decrease with the increase of the elements number and frequency increment.
Le long des côtes, les fonds sableux se déplacent au gré des houles et des courants. Or, les sondages sont irréalisables sur les hauts fonds comme dans les passes d'entrée du Bassin d'Arcachon, qui sont particulièrement dangereuses pour la navigation. Une méthode basée sur l'exploitation de scènes satellites à haute résolution spatiale (Spot) a été mise au point dans le but de reconstruire la morphologie des fonds sous-marins à partir de quelques profils de sondage acoustique. Une corrélation est établie entre les profondeurs et les luminances Spot. Ensuite, si le fond a une couleur constante et si la turbidité est homogène sur la surface à cartographier, la relation est appliquée à l'ensemble des pixels Spot. Les profondeurs sont déduites des luminances de la bande XS1 (500-590 nm). La bande moyen infrarouge (XS4) permet de tracer la limite d'immersion dont le niveau est connu d'après les courbes de marée. Cette méthode permet de fournir une carte de la morphologie sous-marine. La précision absolue est de 0,2 à 0,4 m à proximité du niveau d'émersion et de 1 m au-delà. La profondeur maximale atteinte dépend de la turbidité. Sur les Passes du Bassin d'Arcachon, la "visibilité" Spot XS1 est souvent de 5 à 6 m mais elle peut être de 1 m seulement en hiver et dépasser 15 m en été. Cette surveillance est complétée par des cartes montrant les déplacements des bancs et des passes pour aider la navigation et le balisage des chenaux.
Instruments and machines, Applied optics. Photonics
Other cell interference (OCI) degrades the achievable capacity of downlink multiuser multiple-input multiple-output (MU-MIMO) systems seriously. Among OCI mitigation schemes, methods that sacrifice ξ degrees of freedom to nullify the OCI have been proven to be helpful to improve the cell edge throughput. However, since interference nulling schemes can only improve the signal to interference plus noise ratio (SINR) of ξ users, they are not optimal in terms of average cell throughput, especially for low to medium OCI levels. We explore the question whether it is better to improve the SINR of every user in other cells rather than benefit ξ users. An altruistic precoding method to minimize the sum of generated interference for all of the other cell users is proposed with ξ degrees of freedom being sacrificed. With the altruistic precoding method, we deduce the lower bound on the capacity and solve the multicell user selection problem with a local optimal solution in which only eigenvalues of interfering channels are needed to be shared. Simulation results demonstrate that the proposed method outperforms the existing algorithms at any OCI level. Furthermore, we also analyze the best choice of degrees of freedom used to mitigate OCI through simulation.