Faculty of Basic and Applied Sciences
Permanent URI for this facultyhttps://ir.uat.edu.ng/home/handle/123456789/8
Browse
9 results
Search Results
Item Machine learning-based models for forecasting radio refractivity over the coastal area of South Africa(Learning Gate, 2025-02-04) Yusuf Babatunde Lawal1*, Pius Adewale Owolawi2, Chunling Tu3, Etienne Van Wyk4, Joseph Sunday Ojo5Surface refractivity is a crucial parameter that determines the bending of radio signals as they propagate within the troposphere. It is greatly influenced by the atmospheric weather conditions and changes rapidly, especially in the coastal areas. This research utilized 50 years (1974-2023) surface temperature, pressure, and humidity data from six coastal stations in South Africa to forecast radio refractivity in the Mediterranean climate. Five machine learning models: Gated Recurrent Unit (GRU), Light Gradient Boosting Machine (LightGBM), Long-Short Term Memory (LSTM), Prophet, and Random Forest were trained for future prediction of surface refractivity at any coastal area in South Africa. The stations latitude, longitude, altitude, surface refractivity and date were applied as the input parameters to train the models. The models were optimized through the randomized searchCV hyperparameter tuning to improve their efficiency. The LightGBM outperformed other models with RMSE and adjusted determination coefficients of 1.67 and 0.96, respectively. The model is recommended for future prediction of surface refractivity needed for the improvement of point-to-point wireless communication, terrestrial radio and television transmissions, and mobile communication networks in the coastal sub-tropical regions.Item Investigation of Point Refractivity Gradient and Geoclimatic Factor at 70 m Altitude in Yenagoa, Nigeria(Nigerian Society of Physical Sciences, 2023-03-05) Y. B. Lawala,∗, E. T. OmotosoThe quality of services provided via Inter-Terrestrial radio communication links such as GSM networks, Wide Area Network (WAN), Radio and TV broadcasts is largely influenced by some meteorological parameters such as temperature, pressure and humidity. Proper knowledge of these parameters, specifically at microwave antenna heights (about 70m) is important in order to maintain an effective line-of-sight (LOS) link even during the worst weather conditions. The geoclimatic factor is an important quantity that must be considered in the design of terrestrial links for effective wireless communication. This work utilized satellite data from the European Center for Medium-Range Weather Forecasts (ECMWF) to compute the point refractivity gradient and geoclimatic factor for Yenagoa and its environs. The research was necessitated by the paucity of research on this subject matter for Yenegoa. The results of the research show that point refractivity gradient and geoclimatic factor in the study area vary with season. The average point refractivity gradient and geoclimatic factor at 70 m above the ground level are:136.433 N-unit/Km and 6.638633E-05 respectively. This implies that radiowaves propagating in this region at the said altitude is most likely to be super refractive in both rain and clear air atmospheric conditions. Rain or worst condition refers to the period when atmospheric components such as hydrometeor, lithometeor, aerosol have significant effects on propagated radio signals. Clear-air conditions means when maximum possible signal is received such that the most threatening atmospheric components (rain drops) have negligible effects on propagated signal. The results will be useful for radio engineers in the design and configuration of inter-terrestrial microwave links in Yenagoa and Its environs for optimum quality of serviceItem Impact of Rain Heights on Rain-Induced Attenuation for Communication Systems Operating at Ka and V Bands in Pretoria, South Africa(IEEE, 2025-12-12) Yusuf Babatunde Lawal, Pius A. Owolawi, Chunling Tu, Etienne A. van Wyk and Joseph Sunday OjoWireless communication networks, such as 5G networks, inter-terrestrial, and earth-space links, transmit radio signals at high-frequency bands. However, the signal quality of radio communication systems operating at frequencies above 10 GHz in tropical and subtropical regions is often degraded due to rain induced attenuation. Rain rate and rain height are the most influential meteorological parameters determining the level of attenuation. This research investigates the effects of seasonal variations in rain height on rain-induced attenuation and its impact on radio links operating at typical downlink and uplink frequencies in the Ka (30/20 GHz) and V (40/50 GHz) bands in Pretoria, South Africa. The research revealed that maximum rain heights experienced in the summer resulted in the worst rain-induced attenuation at all frequencies. The estimated attenuations would assist to determining the minimum fade margins required to achieve 99.9%, 99.99% and 99.999% signal availability annually at these frequencies in the study location. The results are expected to serve as a database for future planning of high-frequency link budgets.Item Geoclimatic characterization and latitudinal dependence of rain heights over Nigeria(IOP Publishing, 2021-04-06) Y. B. Lawal, J. S. Ojo, S. E. Falodun and E. O. OlurotimiAttenuation due to rain remains the most severe threat to terrestrial and satellite communication links in the tropics. Rain height is a precipitation parameter that plays important role in the determination of rain-induced attenuation. In this paper, a statistical study was carried out to establish the relationship between rain height and earth station latitude using rain heights derived from Zero Degree Isotherm Height (ZDIH) data retrieved from Global Precipitation Measurement (GPM). A strong positive correlation of 0.83 propelled the attempt to model equations for the estimation of rain height based on latitude. The research recommends a polynomial function of order 3 which has the best coefficient of determination (0.8). The annual mean values of rain heights were also computed and recommended for each of the four geo climatic zones in Nigeria.Item Development of a Microcontroller Based Heat Index Meter(JOST, 2023-04-07) Lawal, Y.B.The research focuses on the development of a heat index meter using microcontroller technology. A DHT22 thermo-hygrometer sensor was employed to measure ambient temp and relative humidity simultaneously. The analogue values of these parameters were fed into Arduino Uno Microcontroller which is the heart of the developed meter. The microcontroller has been programmed to compute the heat index using an embedded equation. The microcontroller is interfaced with a 16 by 2 Liquid Crystal Display (LCD) to display the measured temperature, relative humidity as well as the computed heat index. The developed instrument performed satisfactorily during testing and evaluation. It is therefore recommended for measurement and monitoring of heat index.Item Design and Construction of a Two Channel Microcontroller Based Remote Control for Switching Electrical Appliances(ABUAD, 2020-04-14) Mobolaji Aduramo SODUNKE, Adeyemi Idris OLATEJU, Yusuf Babatunde LAWAL, Joseph Ogheneruemu ODIETE, Taiwo Titus ABATAN, Waliu Olayemi MUFUTAUThis paper presents the design and development of a microcontroller-based system that can switch off and on Electrical appliances or wall sockets at user’s will remotely. This research is aimed at increasing the accessibility as well as response rate to prevent appliances from damage due to transient, intermittent and fluctuations in power supply. This system uses a wireless telemetry technique through an infra-Red (IR) transmitter and receiver to control the switching state of home and laboratory/industrial electrical or electronic devices. The entire circuit is built around ATMEGA-328P microcontroller which was programmed to interpret digital signal sent from the IR transmitter (remote control) to the IR receiver. As the microcontroller receives a real time signal from the IR transmitter through the IR receiver module, a command is sent to the relay switching unit which activates or deactivates the channel(s) based on the software code embedded in the microcontroller. The normally open (N/O) and normally closed (N/C) terminals of the relay are connected to the live terminals of AC sockets for automation. The Liquid Crystal Display (LCD) displays the status of the sockets in any of the two channels (points) as instructed by the microcontroller. The system is cost effective, durable and versatile as it can be applied to any devices connected to electrical socket outlet.Item DESIGN AND CONSTRUCTION OF A DARK-ACTIVATED EMERGENCY MAINS FAILURE TORCH(GVU Science, 2023-08-02) Dada, J. B.1* and Lawal, Y. B.This paper presents the design and construction of a dark-activated emergency mains failure (DAEMF) torch mounted on a printed circuit board (PCB). The battery-powered torch called a DAEMF is intended to automatically light up a home and its surroundings in the dark, but it will turn off if it detects the presence of a power source, even if the lighting system is not on. The charging, switching, and lighting sections comprise the three main sections. During the dark period, the switching circuit was switched ON by a voltage of 1.7 volts, and a current of 0.006 mA measured across the light-dependent resistor (LDR) at the switching section. The charging section uses a linear Integrated Circuit (IC) LM 317 as the main electronic component to charge the battery with about 0.65A load current. The high-voltage transformer (HVT) at the lighting unit inverts and converts a 12 Volts direct current (DC) to approximately 100 Volts alternating current (AC) to drive the 6 watts 12 volts fluorescent tube in the lighting section to illuminate the household and its surrounding for 10.5 hours of continuous useItem Comparative Analysis of Surface Refractivity Variations in the Sahel and Coastal Zones of Nigeria(Science Publishing Group, 2023-04-03) Yusuf Babatunde Lawal, Joseph Babatunde DadaVariation in Surface Refractivity N is largely influenced by changes in some meteorological parameters such as air temperature, relative humidity, and pressure. These parameters are more accurate when measured locally due to their temporal and spatial variations. The research studies and verifies the contributions of the dry and wet term components of surface radio refractivity. The research focuses on the comparison of surface refractivity variations in two geoclimatic zones of Nigeria. The study reveals that the Sahel and Coastal zones have dissimilar distinct weather conditions and consequently diverse variational pattern of their surface refractivities diurnally and seasonally. The diurnal values of surface refractivity vary moderately on typical sunny days with average values of about 345-391 N-units and 275-314 N-units in the Coastal and Sahel respectively. Wider daily variations were observed during the rainy season in both geoclimatic zones due to frequent rainfalls, especially in the Coastal Stations. The average daily refractivity in the Coastal and Sahel during the rainy seasons are 339-390 and 311-384 N-units respectively. Analysis of the results obtained indicates that the annual mean of the ITU-R recommendation underestimates surface refractivity by 11-15% across the coastal stations and by 5-10% across the Sahel zone. The derived values for each station would be useful for radio engineers in the design and optimization of terrestrial radio links.Item Analysis of Cross-Polarization Discrimination Due to Rain for Earth–Space Satellite Links Operating at Millimetre-Wave Frequencies in Pretoria, South Africa(MDPI, 2025-06-16) Yusuf Babatunde Lawal, Pius Adewale Owolawi and Joseph Sunday OjoThis study investigates the impact of rain-induced attenuation on cross polarization discrimination (XPD) in Earth–space satellite links operating at millimeter wave frequencies in Pretoria, South Africa. The traditional method of computing XPD employs a constant annual mean rain height and annual mean co-polar attenuation (CPA) over a certain location. This research utilized seasonal rain height data obtained from a recent study and the latest ITU-R P.618-14 guidelines, to compute and analyze XPD variations across six selected frequencies (11.7 GHz to 35 GHz) for different percentages of time exceedance in Pretoria. The study reveals significant seasonal dependencies of rain heights, with XPD reaching its maximum during winter due to lower rain height, and lower rain-induced attenuation and its minimum during summer, characterized by intense convective rainfall and maximum rain height. FFor instance, the estimated XPD for a 35 GHz signal at 0.01% of the time in the summer, spring, winter, and autumn are 13, 14, 15, and 14 dB, respectively. This implies that radio signals suffer severe attenuation caused by low XPD in the summer. The relationship between CPA and XPD highlights the need for increased XPD margins at higher frequencies to mitigate signal degradation caused by rain depolarization. Practical recommendations include the adoption of adaptive modulation and coding schemes to maintain link reliability during adverse weather conditions, particularly in summer. This research highlights the significance of incorpo-rating frequency-dependent parameters and rain height variability in XPD estimation to enhance the design of satellite communication systems, ensuring optimized performance and reliable operation in a tropical climate.