Tropospheric Scintillation Research Articles

On the applicability of some existing tropospheric scintillation prediction models for Ikeja and Abuja, Nigeria

Tropospheric scintillation which causes rapid fluctuation of signal due to the turbulence in the atmosphere is of significance in satellite link budget design. Existing models that predict the intensity of scintillation such as Karasawa, International Telecommunication Union Radiocommunication (ITU-R) Sector, Otung, Van de Kamp and Ortgies are not appropriate for predicting scintillation intensity (SI) in Nigeria due to localization of the models to particular regions. The monthly average air temperature and relative humidity for Ikeja and Abuja, Nigeria, retrieved from the Nigerian Meteorological Centre data bank were used for the investigation. An elevation angle of 5° was used as look angle, antenna diameter of 0.3 m, 40 GHz and 45 GHz frequencies were considered in this study. The existing scintillation model values were then compared with the measured values for the two locations to determine the best performance model. The SI results at 40 GHz and 45 GHz were obtained for each of the existing models. It could be deduced from the results obtained that orgies model values were the most closet to the measured values. Therefore, Orgies-N model was the most appropriate for SI prediction in Ikeja and Abuja.

The Effect of Tropospheric Scintillation on Microwave Frequencies for GSM System in The Iraqi Atmosphere

Several papers have been published recently on the effects of scintillation on microwave propagation in standard atmospheres. Most of them have analyzed theoretically the influence of various parameters on the propagation, but barely a few researchers were able to extract the results from the model relying on microwave links in a nonstandard atmosphere. A method is proposed to predict the tropospheric scintillation on the space path of Earth for both standard and nonstandard atmospheres using the frequency range (20-38) GHz which is used in the Global System for Mobile (GSM). This method can be applied to the different atmospheric conditions in different regions. This work studied the effects of various parameters, such as antenna diameter, meteorological elements t (average temperature), H (relative humidity), and water vapor pressure and frequency, on the scintillation magnitude of GSM bands in Basrah and Baghdad.

Scintillation Effects of Ka-band Frequency on Satellite Application

The satellite communication system is currently congested because of the high demand for data transmission. The Ka-band is a greater range band that can help to solve the issue. However, Ka-band is severely impacted by scintillation at its high frequency. One of the transmitting impairments is scintillation, a sudden fluctuation in the amplitude of the signal and electromagnetic waves, that generates signal attenuation and degradation. In the presence of rain and even under clear skies, scintillation affects the output of Ka-Band. The scintillation prediction model has mostly been evaluated and applied in countries with four-season climates. The objective of this study was to evaluate the Ka-band scintillation data and compare the findings with other existing scintillation models to validate the outcome. For data of one year (2016) at the Ka-Band frequency of 20.2 GHz, this research focused on analysing the tropospheric scintillation from the satellite data. The experimental data from MEASAT 5 were analysed to see the effect of tropospheric scintillation under clear-sky conditions using a dish antenna with a diameter of 7.3 metres and an elevation angle of 68.8°. The satellite signal measurement samples were gathered and filtered using MATLAB to provide clear-sky scintillation. Next, the obtained raw data was converted into readable data. The data was then plotted, and the experimental data was compared to the other models of scintillation. It was essential to evaluate the outcome of the comparison and address which model was most appropriate for tropical climates. Moreover, this project’s cutoff frequency was 0.023Hz, which was computed from the average cut-off frequencies of 12 months in 2016.

Analysis of tropospheric scintillation in Ku-band in Malaysian tropical climate

This research is the continuation from the previous paper which has been published. The focus of this paper is to analyse the tropospheric scintillation which consists of both fades and enhancements and the worst-month of scintillation fades and enhancements. This analysis is then compared against the six scintillation prediction models, namely Karasawa, ITU-R, Van de Kamp, Otung, Anthony-Mandeep and Nadirah-Rafiqul. The result shows that both measured scintillation fades and enhancements are 0.50 dB and 0.48 dB at 0.01% of time. Whereas the other six scintillation models have the following reading for the scintillation amplitude (both fades and enhancements) respectively: 0.44 dB and 0.36 dB (Karasawa), 0.42 dB (ITU-R only for fades but not enhancements), 0.23 dB for both (Van De Kamp), 0.70 dB and 0.68 dB (Anthony & Mandeep) and 0.38 dB and 0.33 dB (Nadirah & Rafiqul) at 0.01% of time. Otung has the highest scintillation fades and enhancements with values of 1.29 dB and 0.67 dB respectively. On the other hand, the measured worst-month of both scintillation fades and enhancements have the highest amplitude at 0.01% of time, which are 0.88 dB and 0.90 dB if compared to the annual cumulative distribution function (CDF), which yield 0.50 dB and 0.48 dB respectively. The month of February 2016 is declared to be the worst-month because it has the highest values for the scintillation fades and enhancements. Furthermore, the percentage fractional error and Root Mean Square (RMS) error are shown. Particularly at 0.01% of time, Van de Kamp has the highest fractional error for both scintillation fades and enhancements which are 100.8% and 100% respectively. Similarly, the same for RMS errors for both scintillation fades and enhancements with the values of 78.3% and 65.3% respectively. Whereas the other models have higher values for both percentage fractional error and RMS error except for Karasawa with the values of 11.6% and 17.2% for fades and enhancements respectively. Thus, this model is suitable to be used in Malaysia.

Prediction of Tropospheric Amplitude Scintillation for Accurate Design of Earth-Space Communication Link over Akure, Nigeria

Prediction of Tropospheric Amplitude Scintillation for Accurate Design of Earth-Space Communication Link over Akure, Nigeria

Distribution of tropospheric amplitude scintillation on Ku-Band earth-space link over a tropical station

Distribution of tropospheric amplitude scintillation on Ku-Band earth-space link over a tropical station

Development and performance evaluation of tropospheric scintillation model on Ku-band satellite link over Akure, Nigeria

Existing amplitude scintillation prediction models often perform less satisfactorily when deployed outside the regions where they were formulated. This necessitates the need to evaluate the performance of scintillation models developed in one region using data data from other regions while documenting their relative errors. Due to its variation with elevation angle, frequency, other link parameters and meteorological factors, we employed three years (January 2016 to December 2018) of concurrently measured satellite radio beacons and tropospheric weather parameters to develop a location-based amplitude scintillation prediction model over the Earth-space path of Akure (7.17oN, 5.18oE), South-western Nigeria. The satellite beacon measurement used Tektronix Y400 NetTek Analyzer at 1 s integration time while meteorological parameters, namely; temperature, pressure and relative humidity were measured using Davis Vantage Vue weather station at 1 min integration time. Comparative study of the model’s performance with nine (9) existing scintillation prediction models indicates that the best and worst performing models, in terms of root mean square error (RMSE), are the Statistical Temperature and Refractivity (STN) and direct physical and statistical prediction (DPSP) models with values 11.48 and 51.03 respectively. Also, worst month analysis indicates that April, with respective enhancement and fade values of 0.88 and 0.90 dB for 0.01% exceedance, is the overall worst calendar month for amplitude scintillation.

Study of tropospheric scintillation effects in Ku-band frequency for satellite communication system

Scintillation is a rapid fluctuation of an electromagnetic waves in terms of phase and amplitude due to a small-scale inconsistency in the transmission path (or paths) with time. Scintillation exists continuously throughout a day whether during raining or clear sky conditions. The raw signal data need to exclude other propagations factors that include signal fluctuations to further understand the scintillation studies. This paper presents the analysis of tropospheric scintillation data from January 2016 till December 2016 at Ku-band frequency of 12.202 GHz beacon signal. The experimental data from MEASAT 3B were collected and analyzed to see the effect of tropospheric scintillation. The elevation angle of the dish antenna is 77.45o. The highlighted objectives are to analyze the scintillation data at Ku-band, and to compare and validate the results with other scintillation models. The result shows that the stipulated scintillation analysis has higher amplitude, which is 0.73 dB compared to other scintillation analysis which has lower scintillation amplitude: 0.45 dB (Karasawa), 0.42 dB (ITU-R), 0.4 dB (Nadirah & Rafiqul), 0.42 dB (Van De Kamp) and 0.11 dB (Anthony & Mandeep).

Optimising models for prediction of tropospheric scintillation on satellite links

A phenomenon that also causes impairment in the received signal strength of the RF signal in satellite links operating at frequencies above 10 GHz, especially in those systems that operate at higher frequencies with small fade margins, is the tropospheric scintillation that occurs in the lower layer of the troposphere. In order to estimate the intensity, i.e. the variance between the scintillation amplitude fluctuations, there are several models in the literature, whose accuracy depends on the locality in which the models are implemented. In this Letter, new models are developed for the prediction of tropospheric scintillation that adjusts to localities in Spain, specifically Madrid city, based on measurements of the aforementioned phenomenon reported from Spain and the bios-inspired technique Cuckoo Search (CS). The results obtained, evaluated in terms of the root mean square error, were totally satisfactory, being the most outstanding cases the improved versions of the Ortgies-T, Statistical Temperature and Humidity 2 and Statistical Temperature and Refractivity 2 models.

Kalman Filter-based Robust Closed-loop Carrier Tracking of Airborne GNSS Radio-Occultation Signals.

GNSS radio occultation (RO) signals have been demonstrated as a viable means to retrieve atmospheric profiles. Current GNSS-RO observations rely on open-loop (OL) processing of the signals, especially for signals propagating through the lower troposphere. The reason is that GNSS signals at low elevations are adversely affected by multipath effects due to propagation through lower troposphere structures and reflections and scattering from the Earth surface. The low-elevation RO signals are characterized by deep and fast amplitude fading and rapid signal carrier phase fluctuations, collectively referred to as signal scintillation. The conventional phase-lock loop (PLL) may lose lock of these signals. While OL tracking is known for its robustness, its accuracy is determined by the climatological models used to create the reference for the GNSS signal carrier tracking loop. The wide bandwidth typically associated with OL tracking also introduces large errors in signal parameters estimations. In this paper, we present an adaptive Kalman filter-based closed-loop (KFC) tracking method, which takes into consideration the tropospheric scintillation, platform vibration, and real-time C/N0 estimation of the RO signals. The KFC method has comparable robustness with and improved accuracy over the OL tracking, which are demonstrated through comparison using real GPS RO data collected on an airborne platform. Analysis of the excess Doppler estimation, retrieved bending angles and impact parameters also confirms the improved performances of the proposed algorithm over OL tracking.

Diurnal Behaviour of Tropospheric Scintillations at Ka band Frequencies for Indian Climate Conditions

In this to study the diurnal behavior of scintillations at ka band frequencies for Indian tropical climate conditions. Scintillations are the most significant important propagation impairment at ka band frequency. To minimize this effect need to study the complete behavior of scintillations. Because the scintillations are vary with respect time(day and night),the metrological parameters temperature and relative humidity are more effected on the scintillation variations.

Generalized Multifrequency GPS Carrier Tracking Architecture: Design and Performance Analysis

This article presents a generalized multifrequency carrier tracking architecture applicable to multifrequency global navigation satellite system receivers operating in frequency-selective fading environments. This architecture unifies a conventional single-frequency-independent tracking (ST) mode, which only operates on measurements from a single carrier, a multifrequency joint tracking (JT) mode, which linearly combines measurements from multiple carriers, and a multifrequency optimal tracking (OT) mode, which incorporates signal intensity in multicarrier combinations via an aggregate Kalman filter. The analytical closed-form expressions of the tracking error variance for the ST, JT, and OT modes are derived for theoretical analysis and comparison. Their tracking performances are evaluated and quantified using a simulated triple-frequency GPS signal with varying combinations of signal strengths. To have a fair assessment in real-world scenarios, real data collected during strong ionospheric, tropospheric scintillations, and multipath reflections and scattering are also used for performance evaluations in ST, JT, and OT modes.

Characterization of concurrent ku band tropospheric scintillation and rain attenuation in Malaysia

<span>Tropospheric scintillation in satellite communication systems operating at frequencies over 10 GHz is a significant impairment, especially in tropical regions, as attenuation affects scintillation dramatically. This work concentrates on tropospheric scintillation in equatorial Johor Bahru, Malaysia, based on a one-year Ku-band propagation measurement study utilising a direct broadcast receiver and an automatic weather station. This study aimed to investigate the relationship between wet scintillation and rain attenuation using experimental measurements. The power spectral analysis has been carried out to determine required cut-off frequency of filtering to separate out rain attenuation and scintillation effects. The results can provide significant information on the fluctuations of wet scintillation at Ku-band earth space link in tropical regions.</span>

Tropospheric Scintillation with Rain Attenuation of Ku Band at Tropical Region

Tropospheric scintillation can become a significant impairment in satellite communication systems, especially in tropical regions with frequencies higher than 10 GHz, the attenuation is dramatically affecting the scintillation. This work concentrates on those aspects in equatorial Johor Bahru, Malaysia, based on a one-year Ku-band propagation measurement campaign, utilizing the equipment of Direct Broadcast Receiver (DBR) and Automatic Weather Station (AWS). This study investigates the relationship between wet scintillation and rain attenuation using experimental measurement and concentrate on the probability density function (PDF) of different scintillation parameters. From the results, it is concluded that wet scintillation intensity increases with rain attenuation. Thus, the relationship can be phrased by linear equations or power-law. The PDFs of wet scintillation intensity, adapted to a given rain attenuation level, are found lognormally distributed, leading to selection of method for determining the relation between conditional PDFs and rain attenuation.

Modification of ITU-R Parameters to Improve the Prediction of Tropospheric Scintillation for Tropical Regions

Scintillation is the rapid fluctuation of the received signal. It is caused by the variation in the refractivity structure of the atmosphere profile. This phenomenon leads to the signal degradation and is significant in low fade margin links and at low elevation angles. So, analyzing the scintillation intensity and its statistics are vital for a system designer to design an efficient system for the satellite communication link. This paper presents the methodology to extract the scintillation intensity from the raw beacon signal and comparison of ITU-R scintillation prediction model with the measured results to test its acceptability over tropical region. When compared with measured results, ITU-R model overestimates the scintillation fade. Hence the parameters of the time percentage factor are modified to obtain near fit to the measured results.

Analysis and comparison of tropospheric scintillation prediction models at Covenant University

Knowledge of tropospheric scintillation is an important phenomenon in the design of satellite communication system. One year (January 2015-December 2015) scintillation data extracted from Astra 2E/2F/2G Satellite link measurement installed at Covenant University, Ota (Lat: 6.7 oN, Long: 3.23 oE) southwest Nigeria, at an elevation angle of 59.9o and a frequency of 12.245 GHz was used in this study. The analysis and the result were compared with some reputable scintillation prediction models so as to obtain best performance model for Ota region. From the result, it was discovered that the Karasawa model gives the lowest percentage error rate for both fade and enhancement of about 0.57% at 0.1 percentage of time and 6.93% at 0.01 percentage of time respectively and therefore was best found fit for the prediction of propagation impairment for the region. However, the model should be tested further using higher frequency band such as Ka and V bands to confirm the accuracy of the model. The information provided in this study will help in fade margin for antenna sizing and performance needed for satellite communication link in the region.

Experimental analysis and comparison of tropospheric scintillation prediction models using eutelsat-36b satellite in a tropical Nigeria

Knowledge on clear-air effects is of paramount importance to proper link budgeting for optimum communication systems design performances. In this paper, one-year (January - December 2013) tropospheric scintillation data are extracted from the EUTELSAT-36B Ku-band satellite measurements installed at Akure (Lat: 7.17 oN, Long: 5.18 oE, Alt: 358 m) for statistical analysis and the result compared with some established troposphere scintillation models in order to obtain the best prediction model performance for this region. The result shows that even in the absence of rain, tropospheric scintillation shows a strong seasonal effect in this region up to amplitude above 0.92 dB. The scintillation intensity fits better to gamma distribution at a high scintillation level taken into consideration the local meteorological parameters. Models comparison with experimental data also shows that the Karasawa model with the lowest percentage error of about 7% was found to be best fit for predicting propagation impairment relating to be fading at a Ku band frequency in this region. The overall results will provide information on scintillation margin needed for sizing antennas and amplifiers for reliable performance and the average bit-error probability on a scintillation-degraded digital satellite link in this region.

Analysis of non-rainy attenuation on earth-space path in Ota, Southwest Nigeria

Propagation effects due to atmospheric gases and tropospheric scintillation requires accurate modelling in the design of satellite communication systems. The combination of the two attenuation phenomena was observed within the period of August 2014 to December 2015. The result of this paper presents the on-going observation and data analysis of non-rainy attenuation on earth-space path in Ota, Southwest Nigeria. Results of clear-sky attenuation vary between 0 dBm and 4.85 dBm in January and February 2015 respectively. While a value of 4.23 dBm and 4.75 dBm were observed in October 2014 and 2015 respectively. The results will be useful for satellite communication system design and will be submitted to ITU-R Study group 3 Databank.

Channel Measurements, Characterization, and Modeling for Land Mobile Satellite Terminals in Tropical Regions at Ku-band

Severe tropical weather dynamics impairments on the earth-sky signal quality at the Ku-band relative to temperate weather increase the demand for land mobile satellite (LMS) channel characterization and modeling specific to tropical regions. Variation in weather dynamics decreases the accuracy of the existing LMS channel models if applied to the tropics. This paper presents a tropical weather-aware LMS channel model that can be applied at areas with diverse atmospheric (rain, clouds, and tropospheric scintillation) and mobility impairments. The proposed tropical-LMS channel (TRO-LMSC) model is designed based on actual experimental measurements conducted in a tropical area. The TRO-LMSC model involves multipath design, mobility model, rain impairment model, cloud impairment model, tropospheric scintillation model, and link budget module (LBM). The proposed model shows improved channel modeling accuracy and comprehensiveness with relatively less root mean square error (rmse), compared with existing models. Consequently, this improvement enhances the identification of the type and performance of the fade mitigation technique, the management of available communication resources, and the reliability and efficiency of the communication services.

The Normalized Differential Spectral Sensitivity Approach Applied to the Retrieval of Tropospheric Water Vapor Fields Using a Constellation of Corotating LEO Satellites

The use of the normalized differential spectral attenuation (NDSA) approach in the microwaves and (later) in the millimeter waves has been recently introduced to retrieve information about integrated water vapor (IWV) content from attenuation measurements along microwave links between two low Earth orbit (LEO) satellites. NDSA was originally proposed for a configuration of two counter-rotating satellites, to achieve vertical profiles of water vapor (WV) from IWV measurements. In this paper, we analyze the exploitability of the NDSA approach in the case of a constellation of corotating LEO satellites in order to estimate the WV content in a 2-D field lying in the orbital plane of the satellites. The WV retrieval is formalized as the solution of an inverse problem. Simulation results are presented in order to demonstrate the feasibility of the proposed approach: a complete acquisition system composed of transmitting and receiving LEO satellites, including tropospheric scintillation effects, has been modeled, and the reconstruction of 2-D maps of the atmospheric WV from multiple IWV measurements is shown.