Performance of time diversity technique in heavy rain region (original) (raw)
Related papers
International Journal of Electrical and Computer Engineering (IJECE), 2018
This paper reports a study on mitigation of propagation impairments on Earth-space communication links. The study uses time diversity as a technique for mitigating rain propagation impairment in order to rectify rain fade. Rain attenuation time series along earth-to-satellite link were measured for two years period at 12.255 GHz in Malaysia. The time diversity technique was applied on measured rain fade to investigate the level of possible improvement in system. Time diversity gain from measured one-minute rain attenuation for two years period was estimated and significant improvement was observed with different delays of time. These findings will be utilized as a useful tool for link designers to apply time diversity as a rain fade mitigation technique in Earth-satellite communications systems. 1. INTRODUCTION Due to the high demands on higher frequency range, the International Telecommunication Union (ITU) released recently a new broadcasting bands operating at 21.4-22 GHz for region 1 and region 3 [1]. Tropical countries such as Malaysia that is located in ITU region 3 experience many of heavy rain events during the year. This will cause a huge attenuation to the satellite signal during the raining events [2]. In order to mitigate the signal degradation, either a large fade margin should be included in the transmission system or a mitigation technique should be applied. It is not a practical way to include a large fade margin in link budget. Thus, using a mitigation technique is more significant to overcome the signal strength degradation. Several fade mitigation techniques have been proposed in the open literature to handle the signal attenuation during rain in tropical region. Techniques such as power control [3], site diversity [4], [5] frequency diversity [6], [7] and time diversity [8] show a promising result. However, the time diversity technique considered the most attractive in terms of implementation cost and efficiency for non real time satellite applications. The main drawback of time diversity technique is that it is not applicable for real time applications. However, using this technique will significantly eliminate the rain attenuation and compensate the satellite signal. Considering that, the same signal needs to be delivered again in a better channel conditions than the first signal. Therefore, a propagation mid-term prediction model is required to accurately
Performance of SatCom systems implementing time diversity in equatorial Malaysia
2014
Time diversity is one of the advanced diversity techniques that aim to mitigate propagation impairments for satellite communication systems operating above 10 GHz. In this work, we exploit three years of one-minute integrated rain rate data collected at Kuala Lumpur to simulate rain attenuation time series at 12 GHz using the Stratiform-Convective Synthetic Storm Technique (SC-SST). The performance of time diversity is statistically evaluated as a function of the retransmission delay. The predicted joint probability distributions of attenuation were found to agree with those derived from rain attenuation time series on a link to the MEASAT satellite. The diversity gain, calculated as a function of retransmission delay for different system availability levels, demonstrate the effectiveness of time diversity in improving the Quality of Service (QoS) in this heavy rain region. Although further tests in other sites are necessary, this work points out that the SC-SST and local one-minute integrated point rain rate time series can be combined to reliably infer the performance of time diversity when no satellite-based measurements are available.
The purpose of this paper is to show how the complementary probability distribution of rain attenuation is drastically changed in the lower rain attenuation range by applying linear combining techniques, namely, equal-gain combining and the maximal-ratio combining, discussed in the historical paper by Brennan in 1959. These combing techniques can also be applied to the Automatic Repeat Request techniques. Defined the instantaneous processing gain and the equivalent attenuation in the 3 cases, we show examples of time series of the various parameters, based on the experimental rain attenuation time series recorded with the ITALSAT 18.7 GHz beacon, in a 37.8°slant path in Spino d'Adda (Italy). Then, we report long-term complementary probability distribution functions of the instantaneous gain and equivalent attenuation, by simulating rain attenuation time series at 19.7 and 39.4 GHz, path elevation angle 35.5°, with the Synthetic Storm Technique, using on-site measured rain rate time series of 10 years, by simulating the ALPHASAT link at Spino d'Adda. Similar results are also found at different frequencies and elevation angles in Tampa (Advanced Communications Technology Satellite, ACTS result test), the Isle of Guam, and Prague. The main conclusions are as follows: (1) As expected, the instantaneous time diversity gain can be large when the delay time is large and rain attenuation is large; (2) scintillation affects time diversity links as the direct links; (3) equal-gain and maximal-ratio combining can add up to 3 dB to the selection diversity gain when the time diversity gain is very small; and (4) equal-gain and maximal-ratio combining reduce the fraction of time of rain attenuation in an average year to a value less than the probability of exceeding 3 dB in the link without diversity.
Radar simulation and physical modeling of time diversity satellite systems
Radio Science, 2009
1] Satellite telecommunication systems that make use of frequencies higher than 10 GHz can experience strong attenuation due to rain. One of the countermeasures that can be adopted is time diversity. In this paper the performance of the time diversity technique is investigated through both radar simulation and modeling. We first exploit an extensive database of radar maps of precipitation collected in northern Italy to generate synthetic time series of attenuation; the performance of the time diversity technique is evaluated for different frequencies and elevation angles. The same analysis is then performed using the ExCell attenuation prediction model, whose input parameters are elevation, frequency and polarization of the Earth terminal, and the ''effective'' rainfall rate. The model-predicted diversity gain is found to agree well with that obtained through radar simulation, demonstrating that the performance of the time diversity technique can be evaluated from the time series of rain rate, acquired by a rain gauge. Citation: Capsoni, C., M. D'Amico, and R. Nebuloni (2009), Radar simulation and physical modeling of time diversity satellite systems, Radio Sci., 44, RS4009,
International Journal of Satellite Communications and Networking, 2007
The aim of this paper is to present recent developments in terms of propagation time-series synthesizers, carried out in the framework of the ESA study 16865/03/NL/EC 'Development of propagation models for telecommunication satellite systems' (ONERA Final Report RF 4/07757/DEMR, 2004). The paper is composed of three parts: a review of the initial requirements related to propagation time series for system performance simulation, a description of a collection of rain attenuation time-series synthesizers and of their related input parameters, and a comparative analysis of the output characteristics of these time-series synthesizers as compared with experimental data collected during the OLYMPUS and ITALSAT propagation experiments.
SAIEE Africa Research Journal, 2018
In this work, measured subtropical rain attenuation was compared with rain attenuation generated theoretically by the Synthetic Storm Technique (SST). The rain attenuation data was obtained from a Ku-band satellite TV link collocated at the site of a rain rate measurement system in Durban, South Africa (2887S, 3098E). A mathematical model developed from the measurement campaign was used to generate measured data for four years of rainfall. Annual cumulative distribution functions of SST prediction results are compared with the results of the measurementbased model. The results show SST to be a fair approximation of actual measurements. This was established by error analysis carried out to compare the error margins in SST prediction and the error margins in the in-force ITU-R prediction method. While the SST approach was shown to conform slightly less accurately to measurements than the ITU-R model, it still yields highly acceptable results in the 0 to 11 dB margin in which the said link experiences most of the measured attenuation before total channel squelching occurs.
Diversity gain for rain attenuation over Earth-space path at a tropical location
Advances in Space Research, 2016
The present study proposes a technique by which the diversity gain can be estimated for a site utilizing the propagation data obtained at a single station. The technique is crucial in estimating diversity parameters in the absence of multi-station data. The rain decay parameter, as defined in the Simple Attenuation Model (SAM), is used to derive the rain rate and consequently rain attenuation at different distances from the single receiving site. The tropical location has been found to experience a wide variability of rain features during different periods of the year causing strong seasonal variations in the diversity gain. A comparison of the diversity gain obtained from the present propagation data and the ITU-R model indicates the necessity of modifying the model parameters of the ITU-R model. The modified model incorporates the seasonal variation and exhibits better prediction capability than the ITU-R model as related to the tropical location.
International Journal of Satellite Communications and Networking, 2009
To compensate propagation impairments on Earth-space communication links, a specific fade mitigation technique to make up for rain propagation impairments is studied in this paper: the time diversity. This process consists in sending the information when the propagation channel allows to get it through. Here the time diversity technique is applied to different experimental attenuation time series collected in Europe: Spino d'Adda (Italy), Louvain-la-Neuve and Lessive (Belgium). These propagation measurements have been collected from 12 to 50 GHz and the performance of time diversity technique is assessed from the generation of time diversity statistics conditioned to the time delay. A prediction method of these statistics is also described. The proposed model relies on the time correlation of the attenuation time series. The model is validated and its accuracy analysed in terms of prediction error calculated using the different databases.
IEEE Access
The Ka-band is modifying the mode of legacy communication towards versatile satellite-oriented systems with the beam-spot capability and a high-throughput architecture to provide twice the capability of classic Fixed Satellite Service (FSS) satellites, thus significantly reducing the cost per bit. Given this background, the contribution of precipitation rate and Ka-band downpour attenuation are expected to improve statistical models for effect prediction. The International Telecommunication Union (ITU) and local researchers are working tirelessly to determine the best prediction model for tropical climates. However, persistent and continuous efforts are required because currently available models do not perform well. The current prediction model for large datasets exhibits a certain deviation. Direct beacon measurement has been compared with an available prediction model that analyses rain effects in tropical regions. Theoretically, the size of the antenna and its gain influence the performance of the receiving signal. Size and availability are two factors which cause degradation and outage in the receiving signal. The majority of extant studies focus on a single antenna with a diameter lesser than 2.4m. Theoretically, antennas with a smaller diameter possess a smaller margin in comparison with antennas with larger diameters. This condition could affect the prediction model when the high attenuation causes a rapid outage in a small antenna and lead to the unavailability of measurement results. To study such effects and provide a good recommendation, the current work measures the beacon attenuation data at two locations, namely, Bukit Jalil (Kuala Lumpur) and Cyberjaya (Selangor). The locations are approximately 15 km apart and have antennas from 0.65m to 31.1m in sizes. Analyses using an available prediction model revealed that ITU-R P.618 provides the lowest RMS value of 14.37 with regards to rainfall rate on two selected samples in Malaysia. High-accuracy prediction can be achieved through the contribution of this study, and comparative data can be obtained for future research. This study is an encouraging step towards a highly comprehensive and accurate prediction of tropospheric impairments in Ka-band satellite communications in the tropical region. ⁞ INDEX TERMS ITU, Rain attenuation, Ka-band satellite communication.
Diurnal variation of slant path Ka-band rain attenuation at four tropical locations in India
Indian Journal of Radio & Space Physics, 2013
Rain attenuation is very severe at Ka and higher frequencies especially in tropical regions. The conventional fade mitigation techniques are not be able to mitigate this severe fade and hence, suitable diversity technique is required for this purpose. In this paper, rain characteristics and slant path rain attenuation at 30 GHz using synthetic storm technique has been presented. Three years of high resolution rain rate data obtained from disdrometer at four tropical and equatorial locations in India have been utilized. The results indicate that the fade margin requirement is very high (above 50 dB at 30 GHz) for 99.99% link availability for these locations. However, the diurnal analysis shows that in most of the places, the rain occurrence is much less in morning/early-morning hours and therefore, the fade margin requirement will be considerably lower (around 30 dB at 30 GHz) in the morning hours compared to the afternoon hours. The result indicates the suitability of using selective time period for high link availability data communication over the locations studied.