The Alphasat Aldo Paraboni propagation experiment: Measurement campaign at the Italian ground stations

Terabit capacity and very high data rates are required for the near‐future broadband satellite communication systems, mainly for multimedia services. The increased capacity can be obtained by using the larger bandwidth available at higher frequency bands, like Ka and Q/V. However, severe detrimental atmospheric effects impair radio waves at these bands, which require the extensive use of fade mitigation techniques, such as link power control, site diversity, or on‐board adaptive power allocation. The Alphasat Aldo Paraboni propagation experiment was designed and supported by the Italian Space Agency, and implemented by the European Space Agency, to better characterize the atmospheric propagation channel at Ka band and Q band, to support the design of future satellite systems. In Italy, 3 ground stations have been installed and are acquiring the Alphasat beacon signals: the 2 ASI main ground stations in Tito Scalo (Southern Italy) and Spino d'Adda (Northern Italy) and the La Sapienza‐FUB station in Roma (Central Italy). The 3 stations cover quite distant locations in Italy, with different climatic characteristics. This paper describes the main features of the experimental setup in the above stations and presents some examples of measurements and results.     

Receiver station in Budapest for Q/V band satellite site diversity and adaptive coding and modulation experiments with Alphasat

The European Space Agency in cooperation with Inmarsat launched the Alphasat communication satellite in 2013, which hosts four technology demonstration payloads. One of them is the Aldo Paraboni payload composed of the Q/V band communication and Ka/Q band propagation experiments. The payload and the communication experiment are funded by the Italian Space Agency. Budapest University of Technology, Hungary in cooperation with Joanneum Research, Austria built a receiver station to conduct site diversity and adaptive coding and modulation experiments over the Q/V band satellite channel. The transmitter/receiver station in Austria and the receiver station in Hungary form a long‐distance diversity system that is used to investigate the capabilities of the adaptive technique under various propagation conditions controlled by the local signal quality at the receiver site in Budapest. This paper provides a detailed overview of the diversity station in Budapest. The operation of the adaptive coding and modulation experiment is illustrated with measurements performed in 2017.     

European research on Ka-band slant path propagation

Europe saw two major initiatives in the mid-1980's to verify the viability of 20-50 GHz frequency bands for high capacity radio transmission. The first was the experimental telecommunication satellite OLYMPUS commissioned by the European Space Agency; the second was the ITALSAT program planned by the Italian Space Agency. Both spacecraft were equipped with highly stable propagation beacon payloads for accurate measurement of propagation conditions. Two international groups of experimenters (OPEX for OLYMPUS and CEPIT for ITALSAT), who had agreed on a set of common procedures for the earth stations' design, experiment management, and comparison of results, carried out the propagation measurements in a collaborative manner. This paper gives a summary of these activities and their results     

Co‐channel interference cancelation at the user terminal in multibeam satellite systems

We study the applicability of soft interference cancelation in the forward link of multibeam satellite systems with focus on mobile terminals. We adopt a standard currently used in commercial satellite systems as a reference. The multibeam satellite antenna radiation diagram has been generated using a physical optics reflector model while a widely adopted channel model has been used for the land mobile satellite channel. The interference pattern has been derived using a system simulator developed by the European Space Agency. Starting from the analysis of the interference pattern, we study the application of a low‐complexity soft interference cancelation scheme for commercial applications. Our results show that, under realistic conditions, a two‐colors frequency reuse scheme can be employed while guaranteeing service availability across the coverage and keeping the complexity at the user terminals relatively low. Copyright © 2015 John Wiley & Sons, Ltd.     

The italsat satellite system

In 1995 the second flight unit of ITALSAT telecommunication satellite will be ary orbit, making operative the ITALSAT telecommunication system after the experimental and preoperational phase performed by ITALSAT F1, which was launched in January 1991 by the Italian Space Agency. A general view of the ITALSAT system is presented with emphasis on the satellite design, the telecommunication mission, the new technologies and the prospects.     

Dynamic link analysis and its in‐orbit verification on a spin‐stabilized satellite mission Eu:CROPIS

In this paper, we present the in‐orbit verification of a dynamic link budget approach for the communication link of the Eu:CROPIS (Euglena and Combined Regenerative Organic‐Food Production in Space) satellite. Because of the high satellite spin rates of up to 30 rpm, the satellite antennas radio frequency beam becomes strongly dynamic, consisting of fast amplitude variations and phase rotations. Both effects degrade the link quality and might lead to an abort of the communication. The paper presents an accurate method of how to simulate these dynamic effects and examines the simulation outputs with real in‐orbit measurements. Both results are compared with each other, and deviations are discussed.     

卫星相干激光通信系统与技术发展

自由空间光通信(Free Space Optical Communication,FSOC)尤其是基于相干体制的卫星激光通信,正逐渐成为突破微波通信瓶颈、建设天地一体化网络、实现高速数据传输的重要手段.总结了欧空局、德国、日本及国内卫星相干激光通信的重要进展,给出了成功验证的相干激光通信系统的激光器、传输速率、多普勒频...     

Metric‐based node synchronization of the Viterbi decoder in satellite applications

Convolutional codes are used in digital communication systems to correct errors that occur during transmission. Their use is now commonplace, particularly in power‐limited satellite and deep space communication systems. Before the decoder can correctly decode the received continuous bit sequence, however, it must establish where codewords begin and end in this sequence. The process of determining codeword boundaries is called node synchronization. In this paper we develop a node synchronization algorithm based on metric difference values with the objectives of simple implementation and reliable performance. Focusing on satellite applications, we consider the constraint length 7, rate ½ convolutional code standardized by the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA); the approach we develop can be extended to other convolutional coding systems. Through simulation, we investigate the statistics of the received sequence, and highlight correlation in the sequence of the decoder metric values. In the light of these observations, we propose a synchronization algorithm, and develop a first‐order analysis of this simple up/down counter framing technique. We recommend framing parameters based on both the analytical results and the expected response of the framing algorithm to correlated metric values. Development of a simple node synchronization algorithm that accommodates correlated metric values has not been reported previously in the literature. Simulation results confirm that reliable node synchronization is possible with this very simple approach. Copyright © 2000 John Wiley & Sons, Ltd.     

Data collection from the Antarctic region through a W‐band low Earth orbit satellite

The DAVID (DAta and Video Interactive Distribution) mission is being carried out in the framework of the Science Small Missions Program of the Italian Space Agency. The mission is aimed at the deployment of two scientific telecommunication experiments through a low Earth orbit (LEO) satellite. The paper will focus on one of these experiments, that will test a satellite system architecture for the exchange of a large amount of data and high definition images through a W‐band link and a Ka‐band inter‐satellite link between the LEO and the ARTEMIS satellite. The proposed architecture, that will explore various innovative aspects, will also allow for the first time the distribution of large volumes of scientific data collected from the Antarctic region and other extremely remote areas of the Earth. The availability of a return link in the envisaged system will also allow interactive control of the various laboratories located in the remote sites. Copyright © 2001 John Wiley & Sons, Ltd.     

RADIO AND NETWORK COMPARISONS FOR MSBN AND GSM SYSTEMS IN A GEOSTATIONARY SATELLITE ENVIRONMENT

One of the most frequently debated issues in satellite communications concerns the comparison between time division multiple access (TDMA) and code division multiple access (CDMA) systems. Although, in our view, a general answer to this problem cannot be found, this paper presents comparisons of two systems utilizing the above-mentioned access techniques, both from a radio and a network point of view. In particular, the mobile satellite business network (MSBN), (a CDMA system currently being developed by the European Space Agency (ESA) for general satellite applications) and the full integrated extension to satellite systems of the global system for mobile communication (GSM) (the well-known frequency division multiplex (FDM)/TDMA pan-European mobile cellular system) are compared by taking, as the reference payload, the L-band land mobile (LLM) satellite (a spot-beam geostationary satellite whose launch should take place at the end of 1997). Reasonable assumptions take into account the fact that, on one hand, the MSBN system is not completely defined and, on the other, the GSM is applied in a context different from the one specified by the European Telecommunication Standard Institute (ETSI). Performance comparisons are carried out in terms of flexibility and number of available channels for the same quality requirements, emitted power levels, propagation environment and interference levels coming from adjacent satellites. It is concluded that MSBN is more flexible than GSM and that, as regards capacity, an advantage of GSM over MSBN is present in the transportable mobile case, whereas, in the vehicular mobile case, MSBN shows an advantage over GSM. © 1996 by John Wiley & Sons, Ltd.     

Optical Communications in Space – a Challenge for Europe

The successful test of a laser communication link between an ESA data-relay satellite and an Earth observation satellite marks a milestone in the development of optical space communications. It is the right moment to look back on more than 20 years of R & D effort in Europe. The paper gives an overview of the optical space communication activities at the European Space Agency (ESA), which have started in summer 1977, when ESA placed the first technology study contract in the domain of intersatellite optical links, and reports on the most recent European systems andhardware technology efforts aimed at the development of small and compact laser terminals for global mobile communication systems and satellite-based data networks.     

The SILEX optical interorbit link experiment

The European Space Agency (ESA) has instigated an in-orbit demonstration project known as SILEX (semiconductor laser intersatellite link experiment) using a pre-operational link between the French SPOT-4 low earth orbit satellite and the ESA Advanced Relay and Technology Mission Satellite (ARTEMIS). Such an optical communication system brings some new and challenging requirements. In particular, the communication beam, which has a divergence of around 6 μrad, must achieve and maintain a very demanding pointing accuracy in the presence of both host satellite vibration and relative satellite motion. The authors provide an overview of the SILEX project and describe a novel pointing mechanism     

Satellite onboard processing for multimedia applications

For future multimedia applications, satellites might play an important role. For broadcast applications satellites are ideally suited to illuminate a large geographical area. However, multimedia applications are interactive, and are therefore a combination of a broadcast mission and a multipoint-to-point mission. The natural question is, can a satellite system compete with the capacity provided by terrestrial cable networks? If the answer is positive, and it shown in this article that it is, a second question arises: what new developments are required to migrate from the state-of-the art satellite technology to such advanced concepts? Taking the example of the European Space Agency's activities in this field, an overview of the required building blocks which make up a complete multimedia communication satellite system are described. Based on this technological overview a discussion of the systems developed by European space industries with support from the European Space Agency is given     

Standardization on performance objectives of satellite systems using adaptive coding and modulation

The radiocommunication part of the International Telecommunication Union (ITU‐R) establishes the standards for wireless communications. Recommendation ITU‐R S.1062 specifies the performance objectives for satellite communication systems providing constant bit rate service. However, this is not applicable to most modern satellite communication systems utilizing adaptive coding and modulation (ACM) schemes to compensate for channel impairments, especially for systems operating in high frequency bands. For this reason, ITU‐R recently developed Recommendation ITU‐R S.2131 that is suitable for satellite systems with ACM. The developed Recommendation provides a method to determine performance objectives for satellite systems using ACM. Two possible objective parameters are presented, including packet error rate and spectral efficiency. This paper presents the standardization process, and the background used to establish new performance objectives. In addition, interpretations of the objectives are given by using estimation results for two different propagation characteristics.     

K波段空间行波管预失真线性化器设计

空间行波管功率放大器在卫星通信系统中具有十分重要的作用,其性能优劣严重影响通信质量,对其线性度提出了苛刻的要求。本文设计了一种单二极管与单pHEMT管相结合的线性化器电路结构,用于改善某K波段空间行波管的线性度。仿真结果表明,在行波管的工作频带范围内均能在一定程度上改善系统的增益和相移的非线性特性,提高线性度。     

The impact of satellite altitude on the performance of LEOS based communication systems

Low earth orbit satellite (LEOS) systems promise to provide global communication, including voice and data services from Iridium and high capacity broadband services from Teledesic. In design of LEOS systems, the choice of satellite altitude is an important consideration, which has a significant impact on system performance. Among the factors affected by satellite altitude choice are system capacity, user‐to‐user delay, power system design and communication services that can be offered. This paper analyzes the effects of satellite altitude on quality of service, frequency reusability and power system sizing. It is found that a choice of low altitude has a positive impact on system capacity and power system requirements. As a consequence, satellite mass and launch cost can be reduced for satellites in lower orbits due to the lower power requirements. In terms of user‐to‐user delay, the results are in favor of medium altitudes, while very high altitudes are not a good choice relative to these measures. This revised version was published online in June 2006 with corrections to the Cover Date.     

VLSI implementation of a signal recognition and code acquisitionalgorithm for CDMA packet receivers

The widespread application of direct-sequence spread-spectrum code division multiple access (DS/SS-CDMA) to wireless communication systems asks for ever faster and more reliable real-time signal processing operations to be performed by highly integrated and low-power consumption digital receivers. One of the most critical signal processing tasks to be performed by the DS/SS-CDMA receiver is signal presence detection and code epoch estimation. This paper deals with the design and realization of an application-specific integrated-circuit (ASIC) for fast signal recognition and code acquisition (SR/CA) in packet DS/SS-CDMA receivers operating in a satellite or terrestrial radio network. In particular, we show how a parallel acquisition circuit can be effectively implemented on a single-chip with a 1.0-μm CMOS technology according to the specifications of the ARCANET Ku-band CDMA VSAT satellite network sponsored by the European Space Agency (ESA). It is shown that the ASIC performance closely follows analytical predictions     

Euro Space Agency opens '02 with a bang

This paper presents an overview of European Space Agency (ESA) projects due for the year 2002. These include the launch of the Envisat Earth observation satellite, the Insat 3C telecommunications satellite and an International Space Station mission     

Satellitenkommunikationssysteme und ihre anwendung

For more than 20 years advanced satellite communications methods and systems have been investigated and developed at the Department of Communications and Wave Propagation (INW) and the Institute of Applied Systems Technology (IAS). Data communications systems for computer networking, video and audio dissemination were designed, tested and improved, using powerful modulation, coding and multiple access techniques. The following contribution presents an overview of the properties of satellites and key projects which have been carried out under contracts by European Space Agency and the European Union.