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Satellite Communication (satellite + communication)
Selected AbstractsSatellite communications: the contribution of the 5th framework programme and future perspectivesINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 1 2004Bernard Barani Abstract The telecommunication sector is of key importance for the European economy. Digitization, secure broadband access and mobility are expected to shift an ever-growing proportion of the economy on line, thus creating new markets and business opportunities. With the eEurope 2002 and eEurope 2005 initiatives, the European Union has initiated a number of policy actions aiming at favouring the rapid introduction of innovative communication systems, services and applications. Research and development, as supported under the IST programme of the Union, is closely associated to the overall policy picture. The IST programme is notably instrumental in supporting, with a longer-term approach, key policy orientations such as the pervasive introduction of low cost broadband access, introduction of advanced mobile systems, or migration of networks towards the next generation of Internet protocol, IPv6. Satellite communication form an integral part of this diversified communication landscape, and has also been significantly supported under the 5th Framework Programme. Even if the problematic of the satcom industry are to some extent similar to those of the terrestrial players (e.g. catalysing take up of broadband and advanced mobile markets), the strategies followed by the satcom sector differ from those followed by the terrestrial players. This paper review the current technological approaches of the satcom industry, their relevance in the context of the policy goals of the Union, and how they have been supported under the IST programme. It also introduces briefly how co-ordination with ESA work has been achieved, and the perspectives for further support, notably under the now starting 6th Framework Programme. Copyright © 2004 John Wiley & Sons, Ltd. [source] Reliability of capacitive RF MEMS switches at high and low temperaturesINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 4 2004Yong Zhu Abstract Some applications of RF MEMS switches, such as aircraft condition monitoring and distributed satellite communication, present a unique challenge for device design and reliability. This article examines these switches when operational temperatures in the range ,60°C to 100°C are envisioned. The basic operation of a capacitive MEMS switch is described and two tools for examining device reliability, modeling, and on-chip experimentation, are discussed in the case of capacitive MEMS switches. 1D, 2D, and 3D models are presented with emphasis on 3D coupled-field finite-element analysis, including temperature effects. Results and findings from the 3D simulations are reported. In particular, the advantages of employing corrugated membranes in the design of RF MEMS switches are assessed. Their performance in terms of reliability as a function of temperature is quantified. The effects of corrugation on the geometric parameters are discussed in the context of device-design optimization. In order to assess reliability experimentally, the M-test and the membrane deflection experiment (MDE) are reviewed due to their on-chip characteristic and simplicity. Ways in which these experimental/computational methodologies can be combined for identifying material properties and device performance is also highlighted. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 317,328, 2004. [source] EM design of broadband RF multiport toggle switchesINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 4 2004W. Simon Abstract Radio frequency (RF) MEMS is an emerging sub-area of MEMS technology that is revolutionizing RF and microwave applications. RF MEMS devices have a broad range of optional applications in military and commercial wireless communication, and navigation and sensor systems. This article presents the EM design of different multiport toggle switches. Such a multiport switch can be used in the compact designs of switching matrices, routing networks, or phase shifters. One application range is the creation of electronically steerable antenna arrays, which can be used for radar applications and satellite communication. The miniaturized switches are based on the single pole single throw (SPST) toggle switch and, in addition to their small size, they have an increased RF performance regarding losses and operation bandwidth (DC to 50 GHz). A 3D FDTD field solver has been used for the electromagnetic design of all the switches. © 2004 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 329,337, 2004. [source] Design, implementation and verification through a real-time test-bed of a multi-rate CDMA adaptive interference mitigation receiver for satellite communicationINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 1 2003Luca Fanucci Abstract This paper presents the design, the implementation, and the main performance results of a multi-rate code division multiple access (CDMA) interference mitigation receiver for satellite communication. Such activity was performed within a research project supported by the European Space Agency (ESA), whose aim was to demonstrate the suitability of the linear adaptive interference mitigation detector (IMD) named extended complex-valued blind anchored interference-mitigating detector (EC-BAID) for single-user detection of a CDMA signal in third-generation (3G) satellite networks. Such a detector, which exhibits a remarkable robustness to multiple access interference, operates in a blind mode, i.e. it only requires knowledge of the timing of the wanted user's signature code, and is therefore very well suited for integration into handheld user terminals. Experimental results in terms of bit error rate with respect to the theoretical behaviour were derived through a specifically developed test bed. Signal plus multiple access interference generation is performed via a computer-controlled arbitrary waveform generator, followed by frequency up-conversion to the standard intermediate frequency of 70 MHz. Additive white Gaussian noise is then injected with the aid of a precision noise generator. The core of the test bed is a flexible digital receiver prototype featuring the EC-BAID detector plus all functions ancillary to IMD (multi-rate front-end, automatic gain control, code acquisition and tracking, carrier synchronization, etc.). Those functions were implemented through careful mixing of different technologies: field programmable gate arrays (FPGAs) for computing-intensive signal processing functions, digital signal processor (DSP) for housekeeping and monitoring, and application specific integrated circuit (ASIC) for adaptive IMD. The adopted design flow also allows an easy re-use of the prototype architecture to come to an overall integration of the receiver into a single ASIC with modest complexity and power consumption increase with respect to a conventional detector. Copyright © 2003 John Wiley & Sons, Ltd. [source] Classification and design of teledermatology practice: What dermatoses?JOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 8 2009Which technology to apply? Abstract Dermatologists are mostly confined to urban regions and rural population is deprived of specialist care. Teledermatology Practice (TDP) is a solution to overcome this global problem. Tools for TDP includes video conference, store and forward, hybrid, mobile, satellite communication, integration model, nurse-led teledermatology, teledermatology focusing on difficult-to-manage cases, teledermoscopy, and teledermatopathology with combined applications. This article reviews the feasibility studies focusing teledermatology tools and analyses the possible options in designing TDP. Categorizing dermatoses for TDP depends on the purpose and types of technology. The dermatoses presenting from a remote geographic regions requires any of the following approaches (i) only TDP, (b) initial TDP followed by face-to-face, (iii) initial face-to-face followed by TDP and (iv) only face-to-face examination. The technology should suit the dermatoses, meet the purpose, be cost-effective and provide better management with follow-up care. We recommend store and forward as a basic TDP model as most dermatoses are diagnosed and follow-up care is delivered. Leprosy, pigmented skin lesions, leg ulcers, HIV and endemic dermatoses require screening and triage services using mobile teledermatology. Counselling and education require videoconference. Rural dermatology's camps require satellite communication mounted on a vehicle. Objective assessment (vitiligo and leg ulcer) after treatment requires integration model at a tertiary centre. Difficult-to-manage cases require second opinion using hybrid/store and forward TDP. Lower rural centre are provided with mobile/ store and forward teledermatology services. Selected or major community centre should be equipped with hybrid teledermatology and linked to a tertiary centre. This process helps healthcare administration to plan a TDP to cover all dermatoses, utilizing the available health care professional (HCP) and technology with minimum budget investment. Conflicts of interest None declared. [source] Two new ultra-wideband antennas with 3.4/5.5 GHz dual band-notched characteristicsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2009Dan-Hong Bi Abstract This letter presents two ultra-wideband (UWB) antennas with 3.4/5.5 GHz dual-notched bands. The U- and V-slots are used to reject the frequency band (3.3,4.2 GHz) limited by C-band satellite communication and Wimax systems. Another rejection band (5.15,5.825 GHz), limited by IEEE 802.11b or HIPERLAN/2 system, is obtained by using the U/V-slot defected ground structure. Experimental results indicate that these antennas cover the entire UWB for voltage standing wave radio <2, except two notched bands. Moreover, these antennas have omnidirectional radiation patterns in the H-plane and good gain flatness. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2942,2945, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24792 [source] A low-profile broadband 16-mm-diameter post-type monopole antenna ceiling-mounted in a buildingMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2004Yong-Woong Jang Abstract This paper experimentally presents a low-profile broadband post-type monopole antenna. The characteristics of the antenna are highly dependent on the design parameters (Rm, hm, hfl, and Rg). Instead of a wire monopole, the proposed antenna is made of a 16-mm-diameter aluminum post that is ceiling-mounted in a building. This is due to the low-radiation resistance in the usable band. The post-type element is used to enhance the impedance matching. The experimental impedance bandwidth obtained is approximately 67.9% (1.9824,3.5534 GHz) for a VSWR of less than 2.0. The impedance bandwidth covers multiband operations for mobile and satellite communication. We also present the measured radiation patterns and gain characteristics of the proposed antenna. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 395,397, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20150 [source] Review and comparison of tropospheric scintillation prediction models for satellite communicationsINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 4 2006P. Yu Abstract An overview of the origin and characteristics of tropospheric scintillation is presented and a measurement database against which scintillation models are to be tested is described. Maximum likelihood log-normal and gamma distributions are compared with the measured distribution of scintillation intensity. Eleven statistical models of monthly mean scintillation intensity are briefly reviewed and their predictions compared with measurements. RMS error, correlation, percentage error bias, RMS percentage error and percentage error skew are used in a comprehensive comparison of these models. In the context of our measurements, the ITU-R model has the best overall performance. Significant difference in the relative performance of the models is apparent when these results are compared with those from a similar study using data measured in Italy. Copyright © 2006 John Wiley & Sons, Ltd. [source] Interference rejection in non-Gaussian noise for satellite communications using non-linear beamformingINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 1 2003Chang Qing Xu Abstract In this paper, non-linear beamforming based on the method of radial basis functions (RBF) is proposed to combine with constant modulus algorithm (CMA) for interference cancellation in non-Gaussian noise. First, a signal space is constructed from the input array data vectors utilizing RBF. A set of exponential functions is used to transform the Euclidean norm of the input array data vectors into the signal space. Then, CMA is employed to eliminate the interference. Both Gaussian and non-Gaussian noise are considered in the experiment. The numerical results indicate that this scheme is effective and robust in terms of interference cancellation. A deep null can be formed to the direction of interference for both Gaussian and non-Gaussian noise. Furthermore, these results are compared with that of DBF with CMA based on FFT technique, a widely used linear beamforming technique. The comparison shows that a DBF array antenna with CMA based on the method of RBF outperforms its counterpart based on FFT technique. The most interesting result is that the proposed method has a robust interference cancellation performance in non-Gaussian noise whereas the FFT technique fails to do so. This observation can be very useful in satellite communications because that non-Gaussian noise such as atmospheric and man-made noise are often encountered in satellite communications. Copyright © 2003 John Wiley & Sons, Ltd. [source] A low complexity partially adaptive CDMA receiver for downlink mobile satellite communicationsINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 1 2003Gau-Joe Lin Abstract A novel CDMA receiver with enhanced interference suppression is proposed for pilot symbols assisted mobile satellite systems in the presence of frequency offset. The design of the receiver involves the following procedure. First, adaptive correlators are constructed at different fingers, based on the scheme of generalized sidelobe canceller (GSC), to collect the multipath signals and suppress multi-access interference (MAI). In particular, a partially adaptive (PA) realization of the GSC correlators is proposed based on the Krylov subspace technique, leading to an efficient algorithm without the need of complicated matrix computations. Second, pilot symbols assisted frequency offset estimation, channel estimation and RAKE combining give the estimate of signal symbols. Finally, further performance enhancement is achieved by an iterative scheme in which the signal is reconstructed and subtracted from the GSC correlators input, leading to faster convergence of the receiver. The proposed low complexity PA receiver is suitable or the downlink of mobile satellite CDMA systems, and shown to outperform the conventional fully adaptive MMSE receiver by using a small number of pilot symbols. Copyright © 2003 John Wiley & Sons, Ltd. [source] Resource management model and performance evaluation for satellite communicationsINTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 2 2001Axel Jahn Abstract Efficient resource management is mandatory to achieve maximum system capacity for next generation communications systems. Resource management deals with the available spectral band, time, power, and space for a transmission signal. It includes (i) the frequency planning, (ii) the selection of transmit power, and (iii) the assignment of the channels and access nodes to the users. The paper presents a generalized notation as well as graph algorithms for resource management problems. Impairment graphs can be used for frequency planning, whereas flow graphs are suitable for channel access problems. To evaluate the performance of the resource management, service criteria (such as blocking or the carrier to interference ratio C/I) or efficiency criteria (bandwidth requirements) can be derived from the graphs. The resource management techniques are applied to satellite networks with non-geostationary orbits yielding time-variant network topologies. As a simple example, the channel assignment and capacity optimization of the EuroSky Way system are shown. Furthermore, a comparison of fixed, dynamic and hybrid channel allocation schemes (FCA, DCA, HCA) for a typical MEO satellite scenario is given. Satellite diversity and its impact on bandwidth requirement and transmission quality is also examined. Finally, it is shown how spread spectrum systems can be investigated with the presented tools. Copyright © 2001 John Wiley & Sons, Ltd. [source] Triangular planar array of a pyramidal adaptive antenna for satellite communications at 1.7 GHzMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 11 2009J. L. Masa-Campos Abstract Nowadays, satellite communications are basic for the human lifestyle. In this way, a smart, conformal, and multiarray antenna (GEODA) is being developed in order to receive signals from several satellites simultaneously in the 1.7 GHz working band. An adaptive beam system is able to follow the signals from the satellite constellation. The complex structure of the antenna is based in a 3D composition of planar arrays with triangular shape. These arrays are divided into subarrays of three patches (Cells), composing the single control element for the arrays main beam direction management. Fifteen cells (45 radiating elements) compose each triangular array of the GEODA antenna. In this article, a triangular array prototype is implemented and measured. Likewise, an individual characterization of the array components is presented. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2633,2639, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24692 [source] | ||||||||||