Papers by Adekunle Adediji
Wireless Personal Communications, 2014
Surface radio refractivity studies are being carried out in Akure, (7.15 • N, 5.12 • E) SouthWest... more Surface radio refractivity studies are being carried out in Akure, (7.15 • N, 5.12 • E) SouthWestern Nigeria, by in-situ measurement of atmospheric pressure, temperature, and relative humidity using Wireless Weather Station (Integrated Sensor Suit, ISS). Five years of measurement (January, 2007-December, 2011) were used to compute the surface radio refractivity and its diurnal, daily, seasonal and yearly variations are analyzed. The results were then used to compute radio horizon distance (R DH) and examine the field strength (FSV) variability. Results obtained show that the surface radio refractivity, N s , varies with the time of the day as well as the seasons of the year. High values of N s were recorded in the morning and evening hours while the values were minima around 1,500 h local time. An average value of surface radio refractivity of 364.74 N-units was obtained for this location. The annual maximum mean of FSV is 15.24 dB and the minimum is 2.20 dB. This implies that the output of a receiving antenna in Akure may generally be subject to variations not less than 2 dB in a year, but can be as high as 15 dB.
The influence of primary radio climatology parameters on radio refractive index over the African region: a 30-year satellite study
Journal of Physics: Conference Series, 2021
In the lower part of the atmospheric boundary layer, structure of the radio refractive index play... more In the lower part of the atmospheric boundary layer, structure of the radio refractive index plays a vital role when planning and designing microwave communication link. The effects of primary radio climatic parameters on radio wave propagation at UHF and microwave frequencies are crucial in studying radio refractive index. 1951 to 1980 satellite data has been used to investigate the mean values of both the primary radio climatic variables and surface radio refractive index over the Africa. The mean value of water vapor pressure, temperature and pressure ranges from 3-23 mbar, 284-302 K and 800-1000 mbar respectively across Africa. The high values of water vapor pressure around the Coastal and Rainforest reduce towards the Savanna and Steppe region (semi-arid). The mean variation value of surface refractivity over Africa ranges from 160 - 340 N-units. The refractivity values in larger part of the savanna range between 250 – 280 N-units.
Statistical Analysis of Atmospheric Parameters, Noise Temperature and Digital Terrestrial Television Signal Strength Over JOS Metropolis, Plateau State, Nigeria
SSRN Electronic Journal, 2021
Daytime hourly values of the critical frequency of the ionospheric E-layer, ƒoE, obtained at Ouag... more Daytime hourly values of the critical frequency of the ionospheric E-layer, ƒoE, obtained at Ouagadougou Ionospheric Observatory (12.4°N, 1.5°W) in Burkina Faso, West Africa, an equatorial station, during the solar cycle 22 (1985 – 1995) have been used to develop a model based on solar zenith angle through cosχ index factor using the relation ƒoE = a (cosχ), The average value of the diurnal cosχ index, n, at Ouagadougou was found to be 0.30 for both low and high solar activity. The model was tested with ƒoE data from Korhogo (9.3°N, 5.4°W) in Cote-d’Ivoire, another equatorial station, and there is good agreement between the model and observations. The validity of the ƒoE model was also compared with predicted values by IRI-2012 model and good agreement has been observed. The percentage difference, when ƒoE observed compared with IRI-2012 model, was found to be within ±10% for both equinoxes and solstices for the two levels of solar activity.
Correlation Between NAO and Radio Refractive Index Over Africa
Patterns and Mechanisms of Climate, Paleoclimate and Paleoenvironmental Changes from Low-Latitude Regions, 2019
The pathway of a propagated radio waves is partly determined by the refractive index of the atmos... more The pathway of a propagated radio waves is partly determined by the refractive index of the atmosphere through which the waves traverse. The radio refractive index is in turn governed by the variations in the meteorological parameters while the Northern Atlantic Oscillation (NAO) has been found to influence temperature and precipitation patterns. This study investigated the correlation between NAO and radio refractive index over Africa using 30 years data of daily meteorological parameters and NAO, spanning from 1981 to 2010. Rainforest and Desert climate recorded the highest (>290 N-units) and the lowest (<200 N-units) radio refractive index, respectively. The correlation is observed to be generally weak (−0.2 to 0.2).
High-capacity satellite systems are specially designed to provide several gigahertz-allotted spec... more High-capacity satellite systems are specially designed to provide several gigahertz-allotted spectra for multiple spot beams. The reliability of the communication links at high frequencies is often subjected to rain attenuation. In addition to rain attenuation, rain-induced cross-polarization is an important factor for dual-polarization microwave radio communication systems operating at such frequencies. Dual-polarized communication systems adopting frequency reuse usually encounter interference due to a change of transmission energy from one polarization state to another. Signal degradation as a result of some degree of noise causes reduction in the quality of signal between the two orthogonal channels—cross-polarization discrimination (XPD). Therefore, this study assesses the level of degradation due to interference on dual-polarized communication systems for millimeter wave’s band over some selected locations in Nigeria using 5 years (2008–2012) data collected at tropical data ac...
A Preliminary result of the measurement of radio meteorological parameters for the profiling of r... more A Preliminary result of the measurement of radio meteorological parameters for the profiling of radio refractivity over Akure, Nigeria, is presented. One year (January-December 2018) data of temperature, pressure, and relative humidity were collected for ground surface and heights of 50, 100, 150, and 200 m respectively from the ongoing measurement of the parameters by Communication Physics Research Group of the Federal University of Technology, Akure, Nigeria. From the data collected, radio refractivity, N were computed, and correlation of N with temperature was evaluated. Results showed that the mean value of surface refractivity obtained during this period of study is 365 N-units while that at the elevated altitudes are: 362, 359, 357, and 354 N-units respectively. It was also deduced that radio refractivity decrease with an increase in height, and its values were generally higher during the rainy season (April October) than in the dry season months (November -March). Correlation...
Bulletin of the American Physical Society, 2016
Development and performance evaluation of tropospheric scintillation model on Ku-band satellite link over Akure, Nigeria
Advances in Space Research, 2021
Abstract Existing amplitude scintillation prediction models often perform less satisfactorily whe... more Abstract 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 those 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 (7.17 oN, 5.18 oE), South-western Nigeria. The satellite beacon measurement used Tektronix Y400 NetTek Analyzer at 1 second integration time while meteorological parameters, namely; temperature, pressure and relative humidity were measured using Davis Vantage Vue weather station at 1 minute 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.
International Journal of Physical Sciences, 2020
Rain-induced depolarization impairments have been a constraint on the effective use of satellite ... more Rain-induced depolarization impairments have been a constraint on the effective use of satellite communication systems at millimetre wave band especially in the tropical regions like Nigeria. This region often experiences high and varying degree of rainfall intensity accompanied with large raindrops due to distortion of raindrops when dual orthogonal polarization is employed to double the channel capacity without increasing the bandwidth. This paper examines the performance of five cross polarization discrimination (XPD) models at millimetre wavelengths over ten (10) different locations in Nigeria using five years climatological data acquired from Tropospheric Observatory Data Acquisition Network (TRODAN) of the Centre for Atmospheric Research (CAR). The performance of five different XPD models namely: recent ITU-R 618-15, old ITU-R-722, SIM, CHU and DHW were tested based on the level of estimated interference due to tropospheric effects. The results revealed that at Ku-band uplink/downlink frequencies (10/14 GHz), the unwanted signals will completely overshadow the copolarized signal between 0.001 and 0.018% of time for the new ITU-R model at Jos, Yola, Sokoto and Nsukka. However, at fade level between 8.93 and 11.08 dB, the crosstalk is prevalent at the receiving station. Though, the recent ITU-R model received wider acceptance, the performance in this study is ranked the lowest while SIM model displayed the best performance. The study therefore recommends, SIM model as the most preferred model to be adopted in estimating depolarization in this region. However, further experimental data for validation is suggested to substantiate this assertion.
Heliyon, 2020
This study investigated the propagation curves and coverage areas of some Digital Terrestrial Tel... more This study investigated the propagation curves and coverage areas of some Digital Terrestrial Television Broadcast Stations (DTTBS) over four climatic zones of coastal (Lagos), tropical rain forest (Akure), Sudan Savannah (Kaduna) and Sahel Savannah (Katsina) cities of Nigeria. Measurement of the Received Signal Strength (RSS) was carried out along different routes with each of the DTTBS as reference points. Measurements of RSS were carried out using two specified antenna receiver heights of 1.5 and 3.0 m for each data point. The GPS receiver was used to measure the geographic coordinates, elevation and Line of Sight (LOS) of data points along the routes in a drive test. Measurement was done during dry and wet season months at 1 km interval up to about 20 km in each of the selected routes covering a period of three years (2016-2018). Mean data were obtained and used to generate the propagation curves and the coverage areas over the study locations. Generally, results revealed that RSS undulates with LOS separation distance from DTTBS in all routes irrespective of seasons and routes. Particularly, RSS reduces to about half of its base station's value at about 8 and 12 km LOS from the DTTBS in Akure and Katsina respectively while, it reduces to about half of its base station's value at about 6 km from the DTTBS in Lagos and Kaduna. The implication of this is that higher coverage areas were obtained in suburban compared to urban cities. In addition, radial maps showing coverage areas and their grades useful for networking purposes were generated. Television White Spaces (TVWS) for secondary users were also proposed. For networking purposes and spatial arrangements of DTTBS that will ensure optimum coverage over the study locations, DTTBS can be sited at 8.0 and 13.5 km (LOS) interval from each other in urban and sub urban cities respectively. The overall results will enable system engineers to know the appropriate distance(s) and locations to site additional DTTBS for networking purposes and prepare power budget for optimum coverage area and good quality of services for terrestrial digital channels.
Physical Science International Journal, 2019
In this study, four years in-situ measurements of atmospheric parameters (pressure, temperature a... more In this study, four years in-situ measurements of atmospheric parameters (pressure, temperature and relative humidity) were carried out. The measurement was by placing an automatic weather station at five different heights: ground surface, 50, 100, 150 and 200 m respectively on a 220 m Nigeria Television Authority TV tower in Akure, South Western Nigeria. The four years Data collected (January 2007 to December 2009 and January to December 2011) were used to compute radio refractivity and its gradient. The local effect of a location/ region cannot but looked into when designing effective radio link, hence the diurnal, seasonal and annual variations of the radio refractivity gradient were studied. Results showed that refractivity gradient steadily increases inthe hour of 8:30 and 9:30 to 18:00 during dry season throughout the years investigated, and decreases two hours in the rainy season than the dry season. The record shows that at 50 m altitude, the maximum and minimum values are 1...
Asian Journal of Physical and Chemical Sciences, 2019
In this study, results of the variation of maximum and minimum radio horizon distance derived fro... more In this study, results of the variation of maximum and minimum radio horizon distance derived from the computation of surface refractivity through measurement of temperature, relative humidity and pressureacrosssevenlocations((Akure (7.15°N, 5.12°E), Lagos (6.30°N, 3.20°E), Abuja (7.10°N, 9.25°E), Jos (9.50°N, 8.50°E), Makurdi (7.30°N,8.53°E), Port-Harcourt(4.20°N,7.00°E), and Nsukka (6.90°N,7.67°E)) in Nigeria are presented. Two years (Jan., 2011–Dec., 2012) archived data as provided by Tropospheric Data Acquisition Network (TRODAN) of the Centre for Atmospheric Research Anyigba, Kogi State were utilized for the study. Results showed that the values of surface refractivity (Ns) were low during the dry season months and high during the wet season months and also there was high value of NS at the coastal areas compared with the inland areas. It was also deduced that the mean value of NS for Abuja, Akure, Jos, Lagos, Markurdi, Nsukka and Port-Harcourt is 355, 362, 303, 391, 375, 361 a...
Journal of Microwave Power and Electromagnetic Energy, 2014
In-situ measurement of radio climatological parameters of pressure, temperature and relative humi... more In-situ measurement of radio climatological parameters of pressure, temperature and relative humidity to investigate anomalous propagation conditions in the first 100-m altitude in a tropical location are presented in this study. The analysis has been based on the dependence of average value of radio refractivity, N, on different times of the day along the year. The results of the analysis was used to determine the vertical radio refractivity gradient and k-factor over this region, which is useful for the determination of optimum performance of digital terrestrial point to point links. The results showed that N-values for the wet months were higher than in the dry months, and it also decreases with increasing altitude. It was also found that maximum values of N averaged over the month occurred at 6:00 h local time, and the minimum N values occurred at 18:00 h. The maximum variation between maximum and minimum N-value over 50 m altitude was 34.07 N-units in the month of September, while maximum variation between maximum and minimum N-value over 100 m height was 54.00 N-units during the month of December. Results of the minimum values of k-factor averaged over the month occurred at 18:00 h local time, and the maximum values averaged over the month occurred at 6:00 h during the year 2012 is analyzed. It was also observed that k-factor is low in the dry months (Jan-Mar and Nov-Dec) while the values rise during the wet months. Overall, results show that propagation in this region is mostly super-refractive.
Theoretical and Applied Climatology, 2015
The use of solar energy for power generation and other uses is on the increase. This demand neces... more The use of solar energy for power generation and other uses is on the increase. This demand necessitate a better understanding of the underlying dynamics for better prediction. Nonlinear dynamics and its associated tools readily lend itself for such analysis. In this paper, nonlinearity in solar radiation data is tested using recurrence plot (RP) and recurrence quantification analysis (RQA) in a tropical station. The data used was obtained from an ongoing campaign at the Federal University of Technology, Akure, Southwestern Nigeria using an Integrated Sensor Suite (Vantage2 Pro). Half hourly and daily values were tested for each month of the year. Both were found to be nonlinear. The dry months of the year exhibit higher chaoticity compared to the wet months of the year. The daily average values were found to be mildly chaotic. Using RQA, features due to external effects such as harmattan and intertropical discontinuity (ITD) on solar radiation data were uniquely identified.
In the VHF band (30 MHz-300 MHz), radio propagation is usually by space waves, which consist of d... more In the VHF band (30 MHz-300 MHz), radio propagation is usually by space waves, which consist of direct wave and ground-reflected wave. These radio signals are affected by the electrical parameters of the ground, curvature of the earth surface, height of the antenna above earth’s surface and weather conditions in the troposphere. The electric field strength of radio signals decreases with increase in distance from the transmitting antenna. In this work, measurement of electric field strength of Frequency Modulated (FM) radio signals from Crystal FM, Minna, on 91.2 MHz and Power FM, Bida, on 100.5 MHz in Niger State Nigeria, was carried out in all the 25 Local Government Areas of the state. A Digital Signal Level Meter, GE-5499, covering the signal range of 30-120 dBµV, was used to measure the signals. The longitude, latitude, altitude and also distance from the reference point (i.e., location of the transmitting antenna) were measured at every location using a handheld Global Positio...
Chaos in radio refractivity over Akure, South‐Western Nigeria
Journal of Atmospheric and Solar-Terrestrial Physics
Measurements of atmospheric pressure, temperature and relative humidity were made in Akure (7.15 ... more Measurements of atmospheric pressure, temperature and relative humidity were made in Akure (7.15 o N, 5.12 o E), South Western Nigeria using Wireless weather stations positioned at different height levels beginning from the ground surface and at intervals of 50 m to an altitude of 200 m on a TV tower. From the data collected, radio refractivity, its gradient and effective earth radius factor (k-factor) was calculated. The results show that refractivity values were generally high during the rainy season and decrease with increasing altitude. The average refractivity gradient is-52.8 N/km and the average value of k-factor is 1.51 for the two years of this report.
Nigeria Journal of Pure and Applied Physics, 2005
Predicting radio refractivity using a stochastic model
2014 XXXIth URSI General Assembly and Scientific Symposium (URSI GASS), 2014
ABSTRACT The radio refractivity of the atmosphere is a very important variable in radio communica... more ABSTRACT The radio refractivity of the atmosphere is a very important variable in radio communication. This paper attempts to model the radio refractivity over a tropical station (Akure, Southwestern Nigeria) with the aim of predicting future values. Atmospheric variables (temperature, pressure and relative humidity) were obtained over a period of eighteen months using a Davis Pro weather station. Differencing of the data was carried out to ensure stationarity. Suitable lags were obtained using the Box-Jenkins approach. Based on the model parameters, predictions were made. The predictions were found to be good for a period of about 11 days into the future.
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Papers by Adekunle Adediji