1,720,975 research outputs found
Increasing the Capacity of Existing Terrestrial Outdoor Radio Mobile Systems by Means of UAV-HALE Platforms
No full textIn this paper the use of a stratospheric platform as a novel technology for the development of telecommunication applications has been investigated, showing that it can be successfully used as a valid alternative to satellites. More in detail, we employ an unmanned aeronautical vehicle high altitude long endurance (UAV-HALE) platform as a base station for mobile communication systems and we focus the study on the topic of the adaptive antenna array required to provide a higher quality of service all over the cell and to increase the capacity of the system, while keeping at the same time the computational complexity as low as possible, because this is a basic requirement for systems placed on a UAV-HALE platform. In the first part of the paper we show the coverage achievable by the platform, considering constraints related to the geometry of the problem, the propagation environment and the communication system. Then, the architecture of the smart antenna system is considered, by analyzing the direction of arrival (DOA) estimator and the dynamic adaptive beamformer (DAB). The final part of the paper shows experimental results based upon computer simulations. The average error in both azimuth and the elevation angles estimation has been evaluated and the analysis of the results yield to the conclusion that a frequency reuse factor of 3 can be achieved by employing the proposed smart antenna based system as fundamental component of the base station mounted on the stratospheric platfor
Smart Antenna System design for Airborne GSM Base-Stations
No full textA great interest has arisen in the international community for the employ of Unmanned Aeronautical Vehicles High-Altitude Very-Long-Endurance (UAV-HAVE) platforms as a new technology for the development of telecommunication services and remote sensing applications. We consider the use of a stratospheric, solar powered, UAV-HAVE platform, named HELIPLAT, that is currently being designed at the Politecnico di Torino, as a base station for the GSM mobile communication system. We present a study on the on-board smart antenna system, considering the constraints imposed to the payload by the GSM standard, and by the platform technology. The smart antenna system is realized by a direction of arrival (DOA) estimator, based on the PRIME algorithm, whose output is used by an optimum combiner to shape a suitable radiation pattern of the equivalent antenna; so that the interference due to co-channel users and background noise can be reduced and the transmitted power can be directed just towards the users' location. Computer simulations have been performed in order to evaluate the average error in both azimuth and elevation angles estimation. The analysis of the results yield to the conclusion that a frequency reuse factor of 3 can be achieve
HeliNet: A Traffic Monitoring Cost-Effective Solution Integrated with the UMTS System
No full textWe present a traffic monitoring system based on the use of unmanned aerodynamic stratospheric platforms equipped with telecommunication pay-loads integrated with the UMTS system. Each platform is designed to independently detect mobiles on the ground or on the sea surface, and can perform as a collecting node for information signals transmitted by mobiles distributed on a large geographic region. In order to develop a system integrated with the future terrestrial communication infrastructure, the data are organized according to the UMTS standard; since the platform can act also as a UMTS base station to support the terrestrial infrastructure, the integration of the traffic monitoring payload with the third generation standard guarantees the cost-effectiveness of the overall syste
SAM LOST smart antennas-based movable localization system
No full textNowadays, wireless position location of multiple sources attracts considerable interest, not only for military, lawenforcement, and public safety applications, but also in the field of intelligent transportation systems and location-specific commercial services. In this paper, we present a complete, autonomous, and movable-on-demand localization system. It is based on the estimation of the direction of arrival of signals emitted by mobile sources, impinging on an array of sensors placed on board a mobile localization station, represented by any aerial or terrestrial vehicle. The system is especially tailored for wireless users unable to perform self-localization, and its most attractive characteristic is its inherent mobility, which allows a quick employment "on demand," in emergency situations, where other localization infrastructures are not present or are unable to properly operate. Procedures of autolocalization and autoorientation of the localization station, based on a set of emitting sources in known location, are considered as well. The user to be located should only be equipped with a very simple radio transmitter, whose signal can be received and identified by the localization station. Alternatively, in more sophisticated scenarios, the user's equipment can be a personal mobile phone, seamlessly connected with the localization station acting as a temporary base station. The performance of the overall system has been evaluated for a case of code division multiple access (CDMA)-based transceiver via computer simulations, showing that the achievable accuracy for locating the user position can fulfill the Federal Communications Commission (FCC) E-911 standard requirements for emergency calls over reasonably wide coverage area
A Novel Optimum SINR Beamforming in Flat Fading Macrocells
No full textIn the array processing literature several statistically optimum beamformers have been proposed, to cope with the problem of optimal source separation. Optimum signal to interference plus noise power ratio (SINR) beamforming is probably one of the best techniques because it can circumvent most of the drawbacks of other beamforming techniques, but, in many already proposed approaches, the knowledge of the correlation matrices of the desired and the interference signals, is simply assumed. Unfortunately, the estimation might not be easily evaluated in practical scenarios wherein both kind of signals are simultaneously present at the receiver. In this paper we propose a novel direction of arrival (DOA) driven statistically optimum SINR beamformer whose aim is to exploit the inherent structure of the signal space. The beamformer response is optimized in such a way that power contributions of signals belonging to the desired signal subset (DSS) are maximized at the beamformer output, while power contributions of signals belonging to the complementary subset, named the rejected signal subset (RSS) and to the noise are minimized. In addition, a practical way to estimate the correlation matrices of desired and rejected signals is also provided, along with a closed form of the optimum weight vector characterizing the beamformer. This proposed technique yields to a family of SINR optimum beamformers, parameterized by different partitions of the DOA set. Another important feature of our technique is its inherent modularity, that makes it suitable for a parallel hardware implementation, so that real-time applications can be carried ou
Smart Compression System for Remotely Sensed Images Based on Object-Oriented Image Segmentation
No full textIn this paper a method for joint segmentation and compression of remotely sensed images is described. The segmentation task, which is the main topic of this paper, is especially tailored for the identification of Objects Of Interest (OOIs), also called Foreground (FGND) Objects, placed over a non-interesting and homogeneous Background (BGND). These images, collected by satellites or high-altitude platforms, are of particular interest in scientific applications, such as space-borne image analysis, sea observation, regional public services for agriculture, hydrology, fire protection, and so forth. In the case presented here, a suitable compression scheme is then applied to each data stream outcoming from the segmentation block, depending upon its relevance, in order to obtain a selective lossless image compression. Of course, the same segmentation technique can also be a component of many other image processing schemes. An interesting feature of the suggested segmentation method is its versatility and reduced complexity, due to the implementation of the segmentation on the basis of a weighted graph, representing chromatic and morphological features of the regions into which the image is partitioned. The segmentation is based on a step-wise optimization performed with a data-driven decomposition of the image and it is achieved as a region-growing approach based upon the fusion of the best neighbor nodes in the graph. Another important aspect of the proposed technique is its robustness to the variation of represented subjects: neither hypothesis nor restrictions are formulated on the properties of OOIs, because the segmentation procedure identifies the BGND, by using its homogeneity characteristic. Therefore the method can be considered as almost application-independent. Practical applications of the suggested method shown in this paper will demonstrate its effectiveness. Moreover the improvement of Compression Ratio achievable with the proposed technique with respect to classical lossless image compression schemes will be shown on the basis of results obtained on a corpus of images
Elastic Modulus in Large Concrete Structures by a Sequential Hypothesis Testing Procedure applied to Impulse Method Data
No full textAn experimental method denoted as Impulse Method is proposed as a cost-effective non-destructive technique for the on-site evaluation of concrete elastic modulus in existing structures: on the basis of Hertz’s quasi-static theory of elastic impact and with the aid of a simple portable testing equipment, it makes it possible to collect series of local measurements of the elastic modulus in an easyway and in a very short time. A Hypothesis Testing procedure is developed in order to provide a statistical tool for processing the data collected by means of the Impulse Method and assessing the possible occurrence of significant variations in the elastic modulus without exceeding some prescribed error probabilities. It is based on a particular formulation of the renowned sequential probability ratio test and reveals to be optimal with respect to the error probabilities and the required number of observations, thus further improving the time-effectiveness of the Impulse Method. The results of an experimental investigation on different types of plain concrete prove the validity of the Impulse Method in estimating the unknown value of the elastic modulus and attest the effectiveness of the proposed Hypothesis Testing procedure in identifying significant variations in the elastic modulus
Una Procedura di Test di Ipotesi Sequenziale per la Valutazione del Modulo Elastico del Calcestruzzo in Strutture di Grande Estensione
No full textHeliplat: a HALE Platform for Telecommunication and Remote Sensing Applications
No full textthis paper we present preliminary results of a feasibility study of a HALE platform as a base station of a cellular system. In particular we will focus on the topic of the adaptive antenna array required to provide high quality of service all over the macrocell; in fact as it can be seen in Figure 3, because of the high altitude of the base station, the theoretical coverage area can be quite large. While in GSM systems the cell size is limited by maximum propagation delay xed by standard [4], in third generation system (UMTS) based on CDMA techniques the system is interference limited, due to the high number of transmitting user in the area covered by the platform base station. The use of multiuser detection and smart antennas on board is necessary to reduce the interference power on the user bandwidth
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