CCIR Model Research Articles

Robust least square modelling for selected daytime ionospheric parameters using geomagnetic observations at low latitudes

The east–west electric field and the characterized horizontal configuration of the geomagnetic fields around the equatorial region cause electron redistribution in the ionospheric bottomside F- region. This electric field E in turn causes the flow of current in a narrow band around this region called Equatorial Electrojet (EEJ) current. The paper discusses the robust least square modelling approach for modelling some selected ionospheric profile parameters below the maximum height of the F2 layer from the computed EEJ values at Jicamarca station (12°S, 76.9 °W) in the Southern American sector and Ilorin (8.50°N, 4.68°E) in the West African sector. The modelled parameters are the maximum electron density, NmF2, the maximum height, hmF2 and the thickness parameter, B0 of the F2- layer which were then compared with the recent ionospheric international standard model (IRI-2016). The proposed new model for ionospheric parameters based on ground-based magnetic field data at specific locations improved the model fit for hmF2 with RMSE value ∼ 30 km, an improvement to the IRI hmF2 model options. In addition, the derived NmF2 model performs poorly as compared to the IRI URSI and CCIR model options for NmF2. The model was however able to reproduce the temporal changes in the NmF2, for example, the semi-annual variation in the observational NmF2 value. The specific local features that were not fully reproduced in the IRI B0 model options can be seen in the derived model.

An Analytical Analysis of Path Loss Models for Mobile Cellular Wireless Communications

The paper deals with thestudy based on the comparative analysis of radio propagation models for mobile cellular wireless communication of global system for mobile at frequencies 0.9 GHz and 1.8 GHz, respectively. Thepath loss propagation models arevitaltool for planning the wireless network as well as designed to predict path loss in a meticulous environment . Various propagation models: Free-space model, CCIR (ITU-R) model, Hata model, Ericson model, and Stanford University Interim (SUI) model have been studied and examinedthrough analytically from the base station (BS) to mobile station (MS) and vice versa followed by respective simulation performance evaluation by using Matlab simulator. The observed data is collected at the operating frequency of 0.9 GHz from various environments (high density region and low density region) using the spectrum analyzer and path loss comparisonis shownfor different model.

The Research on the Simulation of VHF Radio Broadcasting Loss

VHF radio is a crucial part of the communication system in the battlefield. Since that the paper has adopted the idea of hierarchical modelling, and aiming at building up a simulation model of VHF radio accordingly, which is described with CCIR model, and the elevation data is presented with topographical map. Finally, the battlefield simulation of VHF radio is implemented with OMNET++. The result of simulation validated the credibility of the method, which would provide the simulation of battlefield in complicated electro-magnetic environment with new practical approaches.

3-D ionospheric tomography from dense GNSS observations based on an improved two-step iterative algorithm

Computerized ionospheric tomography (CIT) can image 3-D ionospheric variations from ground Global Navigation Satellite System (GNSS) observations. However, due to the sparse and inhomogeneous ground GNSS observations, the prior information from the empirical models (e.g., IRI-2012 and NeQuick 2) have to be used, which affect the reconstructed results in the CIT, particularly the peak parameters of the F2 layer, namely foF2 and M(3000)F2. In this paper, an improved two-step CIT algorithm is developed to image the ionospheric electron density (IED) distribution up to 2000 km over Japan using dense GNSS Earth Observation Network (GEONET) observations operated by the Geospatial Information Authority (GSI) of Japan. Firstly, we update the IRI-2012 using the ground-based GNSS observations. The NeQuick-2 is used to provide the vertical ionospheric profile, and foF2 and M(3000)F2 derived from CCIR model in NeQuick 2 are improved by the B-spline modeling methods. Secondly, the updated IRI-2012 is input as a prior value and the multiplicative algebraic reconstruction technique (MART) is implemented to reconstruct the IED distribution. The reconstructed results are validated by the simulation and observation results from ground-based GNSS, GNSS Radio Occultation (GNSS-RO) observations and ionosonde measurements. The results demonstrate the feasibility and superiority of our new method. The standard deviations of TEC residual errors from the updated NeQuick 2 are at least 20% less than those from the original NeQuick 2 model, and the updated NeQuick 2 has better performance for the ionospheric correction.

Characterisation of Propagation Loss for a 3G Cellular Network in a Crowded Market Area Using CCIR Model

In this paper, the propagation loss for 1800 MHz cellular network in a crowded market is studied and characterized using the Comit´e International des Radio-Communication, (CCIR) propagation loss model. Empirical measurement of the received signal strength in the market was conducted using CellMapper android app installed on Samsung Galaxy S4 phone. The CCIR model was configured with three different percentages of covered areas (PB). The model was optimized using the root means square error (RMSE) method and also by tuning the PB value. The un-tuned CCIR model gave an RMSE value of 9.23 dB which is above the acceptable upper limit of 6 dB for propagation loss prediction models. On the other hand, the PB-tuned CCIR model gave the best prediction result with an RMSE value of 2.177 dB and prediction accuracy of 98.11 % which is better than the performance of all the RMSE-tuned CCIR models. The results showed that apart from using an RMSE value to tune the CCIR propagation loss model, adjustment of some other key parameters of the model can as well provide a better prediction performance. However, the choice of the parameter to be tuned depends on the specific nature of the case study area.

Comparative Study of Least Square Methods for Tuning CCIR Pathloss Model

Comparative study of two least square methods for tuning CCIR pathloss model is presented. The first model tuning approach is implemented by the addition or subtraction of the root mean square error (RMSE) based on whether the sum of errors is positive or negative. The second method is implemented by addition of a composition function of the residue to the original CCIR model pathloss prediction. The study is based on field measurement carried out in a suburban area for a GSM network in the 1800 MHz frequency band. The results show that the untuned CCIR model has a root mean square error (RMSE) of 17.33 dB and prediction accuracy of 85.33%. On the other hand, the pathloss predicted by the RMSE tuned CCIR model has RMSE of 4.09dB and prediction accuracy of 96.82% while the pathloss predicted by the composition function tuned CCIR model has RME of 2.15 dB and prediction accuracy of 98.39%. In all, both methods are effective in minimizing the error to within the acceptable value of less than 7 dB. However, the composition function approach has better pathloss prediction performance with smaller RMSE and higher prediction accuracy than the RMSE-based approach.

Equatorial predictions from a new neural network based global foF2 model

A new neural network (NN) based global empirical model for the foF2 parameter, which represents the peak ionospheric electron density, has been developed using extended temporal and spatial geophysical relevant inputs. It has been proposed that this new model be considered as a suitable replacement for the International Union of Radio Science (URSI) and International Radio Consultative Committee (CCIR) model options currently used within the International Reference Ionosphere (IRI) model for the purpose of F2 peak electron density predictions. The most recent version of the model has incorporated data from 135 global ionospheric stations including a number of equatorial stations. This paper concentrates on the ability of this new model to predict foF2 for the equatorial sector, an area that has been identified as problematic within the current IRI peak prediction setup. The improvement in the predictions of the foF2 parameter by the new model as compared to the URSI and CCIR model options of the IRI is demonstrated and the requirement for additional foF2 data from the equatorial zone for the purpose of global modeling of foF2 is highlighted in this paper.

Comparative study of ionospheric characteristic parameters obtained by DPS-4 digisonde with IRI2000 for low latitude station in China

Data of f oF2, h mF2, B0 and B1 with half hourly interval resolution, which are scaled and deduced from ionograms recorded by DPS-4 digisonde at the low latitude station Hainan, China for the time period of March–August 2002, are analyzed for the diurnal and seasonal variation behavior of the ionosphere using the calculated monthly medians. Comparisons between the observational result and that of the International Reference Ionosphere model (IRI2000) are made. Our present study showed that: (1) For f oF2, both CCIR and URSI choices in the IRI model produced reasonably good result during daytime hours, but they underestimated f oF2 value for nighttime hours and in some cases also in the afternoon hours. (2) For the peak height h mF2, when the CCIR model for M(3000)F2 is chosen, IRI model results are in a poor agreement with observations, especially during hours spanning from afternoon to pre-sunrise; When the measured M(3000)F2 value is used as the F2 peak input, the IRI-produced h mF2 has a much better agreement with the observed value than when the CCIR model for M(3000)F2 is used. With the measured M(3000)F2, IRI can reproduce quite well the observed features such as the three peaks occurring in the pre-sunrise, near local noon and in the evening hours. However, it still underestimates the observed value during nighttime hours. (3) The bottomside F2 layer thickness parameter B0 given by B0-Gulyaeva choice in IRI2000 is generally in a better agreement with observations than when the newly updated B0-Table choice is used.

Equatorial F2-layer peak height and correlation with vertical ion drift and M(3000)F2

Ionosonde data recorded at Korhogo, Côte-d'Ivoire (Latitude +9.3; Longitude −5.4, Dip −0.67) during a year of low solar activity (1995) were used to investigate ways of improving the representation of equatorial F2 peak height (hmF2) in the International Reference Ionosphere (IRI). For this purpose we have studied the correlation between hmF2 and the equatorial F region vertical drift as given by the model of Scherliess and Fejer (1999). The positive correlation found during nighttime could be helpful in representing the post-sunset peak of hmF2 that is currently not represented by IRI. We have also investigated the reliability of the CCIR model for the propagation factor M(3000)F2 model since the IRI hmF2 model is based on the strong anti-correlation between hmF2 and M(3000)F2. Overall the CCIR model represents the diurnal variation of M(3000)F2 quite well but does not represent small-scale features. With the M(3000)F2 values deduced from the Korhogo ionograms as input, the IRI hmF2 model provides an excellent representation of the observed diurnal structure including the post-sunset peak.

Equatorial F2-peak parameters in the IRI model

We have used measurements of an ionosonde station near the magnetic equator in Ouagadougou, Burkina Faso to evaluate the ability of the International Reference Ionosphere (IRI) model to correctly represent ionospheric F2 peak parameters in this region. The data represent conditions of high and low solar activity. Comparing the URSI and CCIR option for the F2 plasma frequency, foF2, we find that for low solar activity both options agree quite well with the ionosonde foF2 values and overall the CCIR maps show a slightly better fit. During high solar activity discrepancies are found during nighttime and the URSI maps providing the overall better fit. The measured F2 peak height values, hmF2, are compared on one hand with IRI predictions that are obtained based on the CCIR model for the propagation factor M(3000)F2 and on the other hand with the ionosonde-measured M(3000)F2 values. As expected using the measured values results in more accurate predictions. It is important to note that with the measured M(3000)F2 values IRI predicts the characteristics post-sunset that is seen in the measurements but not in the IRI predictions with the CCIR-M(3000)F2 model.

A single-station prediction model as a source of additional screen-points for PRIME model

The aim of this paper is to present a possible improvement to the global map of the f0F2 parameter obtained using statistical or any other model, by adding to it the additional screen points. The proposed method is illustrated by combining the CCIR model and a set of single points data. The comparison of the pure global CCIR model and CCIR model modified by the additional screen-points with measurements for different seasons and different solar activity is presented. The results show significant improvement of the f0F2 map.

Monthly median f0F2 and M(3000)F2 ionospheric model over Europe

Monthly median f0F2 and M(3000)F2 ionospheric model, MQMF2, based on the multiquadric (MQ) method of spatial interpolation and a new ionospheric index MF2 describes the monthly median f0F2 and M(3000)F2 over Europe for any UT moment, month and level of solar activity. The multiquadric method allows a surface to be drawn strictly over a given set of points unlike many other currently used ionosphere mapping methods. A non-linear dependence of f0F2 and M(3000)F2 on solar activity level (expressed by MF2 index) is used to establish local models for each ionosonde station. Observations on 28 ionosondes for f0F2 and 19 for M(3000)F2 over 10-30 years were used for model derivation. The MQMF provides better accuracy than the CCIR model in retrospective mode over Europe. Long-term f0F2 prediction with the help of MF2 index for the rising part of solar cycle 22 is shown to provide better prediction accuracy than the CCIR model based on sunspot number R12. MQMF2 is implemented as a code for PC AT-386/387 or compatible, providing tables, plots and maps.

A discrepancy in the International Radio Consultative Committee report 322‐3 radio noise model: The probable cause

The cause of a discrepancy in the CCIR Report 322‐3 (International Radio Consultative Committee (CCIR), 1988) radio noise model is reported. The basis for this discrepancy results from the procedure used to prepare the measured noise data for the determination of a global numerical representation of the 1‐MHz data. In the development of the model, correction factors to an older CCIR model were determined for each measurement site. These corrections were interpolated for each time block and season to a grid of 100 latitude points by 84 longitude points. The correction factors at each grid point were then added to corresponding values for the older CCIR model, and finally, the resulting data for each time block and season were numerically mapped. Nineteen locations were used in the final model. Four sites used in the original CCIR model were not used. As either no correction factors were obtained for these locations or a correction factor of zero was used to maintain the status quo, the interpolation algorithm produced erroneous values near these four sites in determining the 100‐by‐84 grid of correction factors. For Bill, Wyoming, the result is not too serious; but for the other three sites at some seasons and time of day, the error is serious. For Thule, Greenland; for Ibadan, Nigeria; and for Byrd Station, Antarctica; the maximum and minimum errors were 10.1 and −10.8 dB; 12.5 and −1.5 dB; and 12.0 and 3.0 dB, respectively. Examination of the geographical extent of these errors reveals that the error is not confined to the measurement location but in fact can be very large. This geographical enhancement of the error is most serious during June, July, and August and least serious during December, January, and February. The error as a function of frequency was found to be diurnally dependent, being more serious during the daytime hours. The absence of the data locations as nodes in the interpolation affected the accuracy of the interpolation itself. The CCIR Report 322‐3 atmospheric noise model should be used with caution, especially for locations in the northern and southern high latitudes, the Arabian Peninsula, northern Africa, and the Mid‐Atlantic Ocean areas.

HF atmospheric noise levels in the Canadian Arctic

Since the 1970s there has been some doubt as to the accuracy of the CCIR Report 322 atmospheric noise predictions in the Canadian Arctic. The only Arctic station used in the original (1963) development of these predictions was Thule, and its data were always contaminated by significant levels of local man-made noise. The 1988 revision of CCIR Report 322 excluded the Thule data and included data from the former Soviet Union. In the present study, measurements were made at Nanisivik, North West Territories (NWT) during two summers, at two time periods (0800-1200 Local Standard Time (LST) and 2000-2400 LST) from 3 to 20 MHz. The results presented show that the measured levels are about 10 dB below the 1988 revised CCIR model predictions, which have been adopted by the International Telecommunications Union (ITU) in 1990. >

A gamma distribution of raindrop sizes and its application to Singapore's tropical environment

The use of a gamma distribution of raindrop sizes in the calculation of microwave rain attenuation is gaining acceptance. A method of calculating the general gamma distribution of raindrop sizes based on the rain attenuation relation aRb has been developed in this article using the measured microwave attenuation data with respect to the rain rates. The method, which has been tested using the CCIR model, overcomes the common problems of instability and does not suffer from the possibility of multiple solutions. The parameters of the gamma distribution suitable for the moderate climatic region are computed from the calculated attenuation data provided by CCIR model. Comparison of the calculated results with the data from the CCIR model shows that the method provides the ideal modeling of raindrop size distribution (DSD). As an application, the two-year experimental data recorded in Singapore have been used to obtain another set of parameters of the gamma DSD function for the tropical region. © 1994 John Wiley & Sons, Inc.

Rain fades on low elevation angle Earth-satellite paths: comparative assessment of the Austin, Texas, 11.2 GHz experiment

Only a few years of rain attenuation data for Earth-space paths are available for low elevation angle paths, and these show a consistent tendency by the CCIR fade prediction model to underpredict rain fades. The authors contribute to the database four years of 11.2 GHz measurements, taken on a 5.8 degrees elevation path in Austin, Texas, USA and assess higher than predicted fade results with respect to earlier measurements and the CCIR model. At the fiducial 0.01 percent of time, the rain fall rate was 73 mm/h and the attenuation exceeded the 25 dB measurement fade margin. It is found that the monthly variability of rain fall rates and decibel fades follows a normal distribution. Durations of rainfall and fades are classified into events, episodes, interevent gaps (longer than 4.2 h), and interepisode gaps (shorter than 4.2 h). Rainfall interevent gaps and event durations, as well as fade event, episode, and gap durations are log-normally distributed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The application of a bistatic intersystem interference model to radio systems co‐ordination and satellite systems optimization

AbstractThis paper presents results from a new theoretical model to estimate bistatic rain scatter interference between terrestrial radio relay systems and earth‐satellite systems operating at the same frequency. The current model used by the CCIR was developed in the early 1970s when system packing density was low and the large earth‐station antennas allowed the consideration of narrow beam approximations. This resulted in a small common volume of intersection of the two beams and large circular contours. The recent increase in microwave communications traffic and the improvements in technology have meant that very small aperture terminals (VSATs) can be employed, and hence the model must allow for the consideration of sidelobes, low gain antennas and non‐uniform rain cells intersecting much larger common volumes. Aspects of the new model are discussed and different assumptions made by the CCIR model are examined. Results from the new model show that the contours are smaller and non‐circular and result in much smaller co‐ordination areas.

High elevation angle propagation results, applied to a statistical model and an enhanced empirical model

The results of a recent narrowband propagation experiment at high elevation angles have been further analysed to determine fit coefficients for the model proposed by Lutz et al. Results for the suburban and wooded environmental categories for elevation angles greater than 60° are reported. An empirical model for L and S bands covering elevation angles from 20 to 80° has been developed. The model combines the empirical roadside shadowing model, and the empirical fading model derived from the results of a narrowband propagation campaign, and improves the existing CCIR model.

Application of the expansion into empirical orthogonal functions to ionospheric characteristics

Representation of empirical models of ionospheric characteristics in terms of empirical orthogonal functions (EOF), as proposed by DVINSKIKH /1/, has been applied to the critical frequencies, foF2, and the peak heights, hmF2, of the F2 layer in the International Reference Ionosphere (IRI) and in ionospheric prediction models. Using the expansion coefficients given by DVINSKIKH, a comparison is made with the CCIR atlas. No significant differences to the CCIR model and to vertical sounding data of the Northern hemisphere are found. As compared to the calculation of the CCIR atlas, use of the EDF expansion leads to considerable saving of computer time, the number of necessary expansion coefficients being reduced by a factor of about 40.

The relationship of raindrop-size distribution to attenuations experience at 50, 80, 140, and 240 GHz

Millimeter-wave rain attenuation measurements have been made at 50.4, 81.8, 140.7, and 245.5 GHz on a terrestrial path of 0.81 km. On the basis of these experimental results, a comparison between the model of specific attenuation currently adopted by the International Radio Consultative Committee (CCIR) and that based on the raindrop-size distribution derived from our previous propagation experiments at 11.5, 34.5, and 81.8 GHz is made. For the Japanese climate, it is found that the CCIR model underestimates the rain attenuation at frequencies above 80 GHz and that our specific attenuation model is effective for the prediction of rain attenuation in the whole millimeter-wave region.