1,721,021 research outputs found
On the Role of Stratolites as Local Elements of EGNOS and Galileo
No full textThe use of High Altitude Platforms (HAPs) assupport infrastructure for communications is becoming a relevant topic ofinterest for the research activities on future generation systems. In particular, due to their privileged position (stratosphere), these infrastructures are potentially able to yield advantages in the provision of navigation and positioning services: they can exploit the best features of both satellite-based and terrestrial augmentation systems for GlobalNavigation Satellite System (GNSS). Starting from the results presented in [5], in this note it is described how the Stratolite system [2] can be integrated with the EGNOS [6] systemincreasing the overall navigation performances at the user leve
Automatic Object Detection on SAR Images for UAV-HALE Surveillance Systems
No full textThis paper deals with the automatic detection of Objects of Interest (OOIs) in SAR (Synthetic Aperture Radar) still images. A particular scenario in which a Light-SAR is part of the payload for HALE (High Altitude Long Endurance) platform, named Heliplat, currently under development at the Politecnico di Torino. This unmanned, solar powered aeronautical vehicle is especially tailored for operations at altitudes between 15 and 25 Km with a potential endurance of weeks to months. It could provide a wide range of potential applications within telecommunication and remote sensing: in this paper a particular surveillance application, the reconnaissance over sea regions, has been focused
Design and Test-bed Implementation of a Reconfigurable Receiver for Navigation Applications
No full textThe Stratolite concept: Design of a Stratospheric Pseudo-satellite for Galileo
No full textThe development of the Galileo program is currently dealing with the definition of the local elements in order to complete the overall system architecture. The design of original systems, different and improved with respect to the traditional local segments of GPS may enrich Galileo of additional features providing added value to the system. In this paper, we propose a novel local area augmentation system based on the use of stratospheric High Altitude Platforms (HAPs), unmanned aircraft performing long endurance operation at an altitude of about 20 km. Several aeronautical projects developed in different research laboratories around the world demonstrate that the design of a "near eternal airplane" is a feasible task, and that such aircrafts will be delivered in a near future at affordable costs [1][2]. For these reasons HAPs are candidate to host payload for the provision of communications services over large regions, playing the role of very small satellites almost stationary and near to the ground with respect to low Earth orbit spacecrafts. This paper discusses the use of HAPs for the provision of augmentation signals for Galileo (aerial transponder for local differential corrections), and introduces the concept of stratolite (stratospheric-pseudo-satellite), as an aerial pseudo satellite able to provide differential corrections modulated over a satellite-like signal. The main topics of the system concept definition are discussed in order to demonstrate the feasibility of a payload providing navigation services and the expected advantage
A Hybrid Positioning Algorithm for Cellular Radio Networks by using a Common Rake Receiver Architecture
No full textThe development of context-aware services is strongly pushing the integration of positioning capabilities in personal communication terminals, with particular attention to third generation systems (UMTS). On the otlher hand, the synergy between comunication and positioning can be of aid for this latter easing the acquisition and tracking of weak signals, and improving performance. In order to provide the user of reliable positioning solutions a suitable receiver dealing both with navigation and communication signal is reqpired. In this paper, a new hybrid positioning algorithm and a joint receiver structure able to receive and process signals broadcast from both navigation satellite systems and cellular radio networks, is presented, discussing the impact on the joint receive
Integrated NAV/COM digital receivers for indoor performance improvement
No full textIt is well known that in indoor environment performance of GNSS-based positioning are strongly limited by several factors. Acquisition of weak signals is critical, visibility of a sufficient number of satellite is not granted, and the SIS received at the antenna propagates via multiple paths. Indoor signal acquisition can be aided by external elements providing augmentation signals through dedicated links or by means of communication channels (e.g. Assisted GPS). On the other hand several techniques are being developed to integrate positioning capabilities within communication system (namely GSM, UMTS and WLAN), that cannot provide suitable accuracy when performance comparable with the dimension of the building are required. In order to provide the user of reliable positioning solutions, the synergies among different positioning information sources must be exploited, and a suitable receiver dealing both with navigation and communication signal is required. In this paper the implementation of a reconfigurable receiver integrating both navigation and communication capabilities for the specific positioning application is discussed with a particular reference to a project being developed at Politecnico di Torino aiming at the implementation of a digital receiver based on Software Defined Radio (SDR) techniques for GPS and Galile
Multiresolution Acquisition Engine Tailored to the Galileo AltBOC Signals
No full textThis paper discusses possible receiver acquisition strategies tailored to the Alternative Binary Offset Carrier (AltBOC) modulation that will be used by the Galileo system to transmit on the E5 band. In particular the work addresses critical aspects for the acquisition of AltBOC signals, not deeply analyzed in previous works, and an innovative acquisition engine called multiresolution acquisition is proposed. It can be used with coherent dualband AltBOC receiver architectures as an effective solution to the main problems in the transition between the acquisition and the tracking operations (risk of false lock, resolution of the search space and computational burden). Finally, some simulation results are presented and the advantages of the multiresolution acquisition with respect to conventional strategies are discussed in terms of Time To First Fix (TTFF) and implementation complexit
HeliNet: Network of Stratospheric Platforms for Traffic Monitoring, Environmental Surveillance and Broadband Services
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Multiple DLL architecture for multipath recovery in navigation receivers
No full textSmce the Selective Availability was turned off, one of the major error sources in GNSS user positioning is represented by the deleterious superimposition of the same SIS due to obstruction and ground reflections (multipath). Such an ermr component is the most critical in case of urban (or indoor) navigation due to the high density of possible scatterers around the receiver. In this paper, a multiple Delay Lock Loop (DLL) architecture for navigation receivers, which is derived from the philosophy of the RAKE receiver for communication, is proposed. In this sense, it is quite diITerent from common multipath rejection techniques almady proposed, where the multipath is not tracked. Simulation mults of the innovative scheme highlight the increased performance with respect to common multipath rejection techniques
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