Three‐year fade and inter‐fade duration statistics from the Q‐band Alphasat propagation experiment in Madrid

Propagation campaigns are carried out at different frequencies and geographical areas to characterize the slant‐path propagation channel. One of the objectives of the Alphasat Propagation Experiment is to evaluate the performance of satellite links that operate in the Q/V band. Since March 2014, the copolar level of the Alphasat Q‐band beacon signal has been measured at Universidad Politécnica de Madrid, Spain. The fade dynamics—fade and inter‐fade durations—results for three complete years (March 2014 to February 2017) of measurements are presented in this paper. Moreover, the experimental setup and receiver characteristics are described in detail. The collected data (with a mean availability of 97%) can be used to evaluate the atmospheric propagation impairments with a very good degree of accuracy. The probability of occurrence and the fraction of time of fade duration for an average‐year have been compared with the ITU‐R and CRC models with moderate agreement. For this reason, a modeling effort has been made leading to the conclusion that there is room for improvement in the models.     

Twelve years of rain attenuation statistics of Earth–space propagation experiment at Ka band in Toulouse

Since 2009, ONERA has been running Ka band propagation experiments in Toulouse (France, latitude 43.57°N, longitude 1.47°E). A rain gauge was also deployed on site to collect rainfall rate measurements concurrently to beacon data. Since April 2011, the beacon receiver has been recording the 20.2 GHz (vertical polarisation) Astra 3B beacon signal along a slant path of 35.1° of elevation angle. All years of the experiment had excellent data availability, hence giving 12 years of data at Ka band. First, the propagation experiment and the data processing methodology are described. Second, a statistical analysis of rain attenuation and rainfall rate is conducted. Comparisons are then performed with the prediction methods of Recommendations ITU-R P.837-7 (rainfall rate), P.618-13 (rain attenuation) and P.678-3 (variability of propagation phenomena).     

A discrete‐components millimeter‐wave satellite beacon receiver for Q‐band propagation experiment

Ever increasing bandwidth requirements in satellite communications continuously push the frequency limits. Q‐ band (33 – 50 GHz) is the next frequency band to be populated; however, at these frequencies, the Earth's troposphere (weather) profoundly alters the radio propagation conditions. Therefore, in order to properly plan radio links, accurate statistical models of radio channels are necessary. These statistical models are built upon empirical data, ie, measurements, which are furthermore used to design appropriate Propagation Impairment Mitigation Techniques. The Q‐ band lacks such data, hence the statistical models are inadequate. To address this problem, we propose a cost‐effective, easy to replicate Q‐ band beacon receiver to leverage the Alphasat propagation campaign. We present a step‐by‐step implementation process of the receiver's fundamental part, a Low‐Noise Block, which translates input 39.402 GHz signal into 162 MHz output signal with a conversion gain of 52 dB. The receiver furthermore utilizes software define radio for signal processing and other data manipulation. Here, we describe the receiver implementations in great details, supplementing the crucial parts with laboratory validation results. Finally, we show 2 example datasets, showing usual data obtained during heavy showers and on a quiet day, respectively.     

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.     

Time diversity evaluation for attenuation mitigation method using attenuation data in Thailand and Japan

In order to support future satellite broadcasting and communication in the Ka band and above, the time diversity method provides a novel attenuation mitigation technique for maintaining satellite service availability at levels between 99.9 and 99.99%. In this paper, the time diversity method is analyzed using various time delays from between 1 min and 1 h in an effort to mitigate convective rain attenuation by using various beacon signal transmission delays. For comparison purposes, receiver beacon data from Japan and Thailand are presented to highlight tropical and non‐tropical zone regional differences, and the International Telecommunications Union (ITU) R P.618‐12 standard is used for scaling up the Thaicom beacon frequencies from 12.57 and 12.59 GHz in the Ku band to 19.45 GHz, which is the Ka band frequency used by Japan's communication satellite (CS) beacon. We found that the time diversity method is very useful for mitigating the effects of rain attenuation. Copyright © 2016 John Wiley & Sons, Ltd.     

Calibration procedure of a microwave total-power radiometer

A total-power radiometer built in combination with a beacon receiver is being used for low-level attenuation measurements. This experimental receiver was built to measure atmospheric propagation impairments, using the ITALSAT satellite 50 GHz signal. The radiometer is mainly used to provide the reference level for the beacon measurements. Its precision should be better than ±3 K, for low attenuation levels, in order to have 0.1 dB accuracy in the attenuation measurements. A suitable calibration procedure is described     

NASA's alphasat propagation terminals: Milan,Italy, and Edinburgh,Scotland

Since May of 2014, NASA's Glenn Research Center has operated measurement campaigns for the Alphasat Aldo Paraboni Propagation Experiment alongside the European community of propagation experimenters. Presently, three NASA stations have been deployed to distinct climatological regions across Europe. NASA's participation in the campaign began in 2014 through a collaborative effort with the Politecnico di Milano (POLIMI) to jointly operate a 20/40 GHz ground terminal at the POLIMI campus in Milan, Italy. Subsequently, a single‐channel 40 GHz terminal was deployed to Edinburgh, Scotland in March 2016 in collaboration with Heriot‐Watt University (HWU). A third terminal was deployed to NASA's Madrid Deep Space Communications Complex (MDSCC) in March 2017 with NASA'S Jet Propulsion Laboratory (JPL), also observing the 40 GHz beacon. In addition, a fourth station is planned for deployment to Andøya, Norway by early 2019 in collaboration with the Norwegian Defence Research Establishment (FFI). This paper will detail the design and results of the two most established terminals, Milan and Edinburgh, which together comprise 11 station years of propagation measurements.     

Austrian satellite ground station for the Alphasat Q/V band experiments

The bandwidth demand in radio communications is increasing every year, not only in the terrestrial domain, but also in the satellite domain. The Ku Band is already at its capacity limit and the higher Ka Band is filling rapidly and will reach its capacity limit in the years to come. From both the research and commercial point of view it is important to explore the next frontier for satellite communication, which is the Q/V band. In radio communication it is not only a simple up-scaling of the frequency to achieve the same gain with smaller antennas as with bigger antennas in lower bands, but it is the challenge to handle the different wave propagation properties of these higher bands. In Q/V band the atmospheric attenuations are changing quicker than in lower bands (up to 3 dB/s) and the scintillation caused by gas density changes are in the region of 1 Hz with amplitudes of up to 2 dB. The newly developed ground station in Graz will now help to answer basic research questions in the exploration of the Q/V band. The questions are for instance: Which fade mitigation technique is the best to operate a modem via the Q/V band channel or which averaging times shall be used to have the highest availability with the lowest required margins. Joanneum Research will investigate the optimal operation of this channel together with researchers from the University of Rome Tor Vergata and in the wave propagation domain together with the Politecnico di Milano. The first part of the paper describes the ground station design for the communication experiments to be operated over the Q/V band communication transponder of Alphasat, called Aldo Paraboni payload. In addition to the Q/V band Ground Station, in the frame of ESA’s ARTES-5 programme, a beacon receiver was designed and manufactured, for measurement of the Ka/Q band beacon signals provided by the Alphasat Technological Demonstration Payload 5 as well. This receiver measures co-polar and cross-polar signal at Ka and Q band with one antenna feed and provides a perfect measure of the actual signal quality.     

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.     

An estimation of S/N degradation at millimeter waves during rain events

The use of Ka Band (20/30 GHz) for future satellite communications has been addressed. The exploitation of Ka band with a bandwidth of 2500 MHz seems to represent the largest significant achievement in satellite communications potential, so far. The problems associated with the use of this frequency band such as attenuation and receiver noise temperature (floor) variation with rain has been addressed. The receiver noise floor variation with rain has so far been ignored. Therefore, in view of propagation and noise study over this Ka Band, both signal attenuation and receiver noise floor variations with rain rate are estimated using dual frequency radiometers operating at 22.235 and 31.4 GHz over a tropical station, Calcutta, India.     

Satellite site diversity: Results of a radiometer experiment at 13 and 18 GHz

Joint attenuation statistics for a model site-diversity satellite system which would operate at 18 and 30 GHz were gathered in a radiometer experiment conducted at sites near Atlanta, GA, and Denver, CO. The receiver is of the classic Dicke radiometer type, monitoring sky-noise power at 13.6 and 17.8 GHz. Scaling provides the means to derive 30 GHz performance. The experiment, which commenced in May 1973, provides an expedient means of acquiring essential rain attenuation statistics without the use of active signal sources, such as a satellite beacon. This article describes the experiment and presents the results, including representative data samples from the 1½A year measurement period. Based on these measurements, a model satellite system operating during, the measuring period in Atlanta, at 18 and 30 GHz with 8 and 18 dB fade margins, respectively, would require 14-mi site diversity to insure no more than 0.005 percent propagation outage. During the same time period, site diversity was found unnecessary to satisfy this objective with operation in Denver.     

Observed frequency scaling of amplitude scintillation at 20, 40, and 50 GHz

This paper presents an analysis of instantaneous frequency scaling of scintillation using propagation data recorded during a three month period (May-July 1997) at Sparsholt UK from the ITALSAT satellite beacons at frequencies 18.7, 39.6, and 49.5 GHz. Variations in the height of turbulence within reasonable limits were found to have a negligible effect on the scaling ratios. Furthermore, the exponent in the power law dependence of scintillation intensity on signal frequency was found to be on average 27% smaller than the theoretical value of 7/12 and to exhibit a slight diurnal effect. It is shown that this behavior can be partly accounted for by receiver thermal noise contribution to the measured signal variance. Ascribing the minimum observed short-term variance in each beacon to thermal noise and excluding this contribution yielded a higher exponent, which was nevertheless 15% below the theoretical value.     

The Alphasat Aldo Paraboni scientific and communication experiments at Ka and Q/V bands in Austria

The use of higher frequencies for satellite multimedia communication systems calls for research of the atmospheric propagation effects at these bands (rain, cloud and gaseous attenuation, scintillation, and depolarization). Alphasat was successfully launched on 25 July 2013. This largest and most powerful European telecommunication satellite carries, besides a commercial payload belonging to the mobile satellite communication provider Inmarsat, several Technology Demonstration Payloads (TDPs) from ESA. One of them is the Aldo Paraboni payload (TDP5) for Q/V‐band communication and Ka/Q‐band propagation experiments. These experiments explore future applications in satellite communication and measure how the Earth's atmosphere affects the propagation of electromagnetic waves. Under ESA contract, JOANNEUM RESEARCH designed, developed, and operates a Q/V‐band communication ground station and a Ka/Q‐band propagation terminal. The experimental site is equipped with ancillary equipment including a multifrequency radiometer profiler, a 2D video disdrometer (2DVD), and meteorological stations. This paper reports on the experimental setup, data processing, and obtained results.     

Potential interference and rain attenuation at 21.4–22 GHz downlink broadcasting satellite signals

World Radio Conference WRC-1992 has allocated the frequency band 21.4–22.0?GHz to regions 1 and 3 to be utilised to carry direct broadcasting satellite (DBS) services. This high-frequency band is more susceptible to rain attenuation, leading to degradation of the signal quality. Moreover, this frequency band is assigned to two different services, i.e. satellite broadcasting and fixed mobile services at the same regions; hence, the impact of intersystem interference in a depredated signal is a critical issue in the DBS receiver. In this study, the effects of rain attenuation on the DBS downlink signals as well as the impact of the potential interference on the reception quality will be estimated. An interference scenario will be introduced to investigate the system performance in both propagation mechanisms of clear-sky and rain conditions.     

Assessment of spatial and temporal properties of Ka/Q band earth‐space radio channel across Europe using Alphasat Aldo Paraboni payload

The upcoming migration of satellite services to higher bands, namely, the Ka‐ and Q/V‐bands, offers many advantages in terms of bandwidth and system capacity. However, it poses challenges as propagation effects introduced by the various atmospheric phenomena are particularly pronounced in these bands and can become a serious constraint in terms of system reliability and performance. This paper presents the goals, organisation, and preliminary results of an ongoing large‐scale European coordinated propagation campaign using the Alphasat Aldo Paraboni Ka/Q band signal payload on satellite, performed by a wide scientific consortium in the framework of a European Space Agency (ESA) project. The main objective of this activity is the experimental characterisation of the spatial and temporal correlation over Europe of the radio channel at Ka and Q band for future modelling activities and to collect data for development and testing of fading mitigation techniques.     

信标信号频谱在接收机跟踪性能分析上的应用

接收机锁定卫星信标后,经过二次或三次变频将C频段信标转变为70 MHz中频,然后通过解调单元从中频中提取误差信号。通过分析比较信标信号、L频段频率、70 MHz中频信号频谱使跟踪系统的性能指标层次化,从信标频谱中提取有用信息,全面判断数字接收机跟踪性能,对单脉冲跟踪体制下的接收机故障排查具有一定的指导意义。     

Precipitation attenuation studies based on measurements of ATS-6 20/30-GHz beacon signals at Clarksburg, MD

COMSAT Laboratories participated in the millimeter wavelength propagation experiment under NASA contract NAS5- 20740, performing measurements of the 20/30-GHz ATS-6 satellite beacon signals and auxiliary measurements such as radiometric sky temperature and minute precipitation at Clarksburg, MD. These measurements were intended to broaden the data base required to advance the understanding of the propagation characteristics of the earth-satellite path at frequencies over 10 GHz. A correlation is established between direct measurement of attenuation of the signal radiated from the satellite and the indirect measurement of attenuation by auxiliary ground-based equipment. The indirectly derived statistics agreed reasonably well or can be reconciled with earlier published results and may therefore be used as a basis for estimating long-term cumulative attenuation statistics.