المؤلفون: Igwe, K.C.¹ (AUTHOR) k.igwe@futminna.edu.ng, Oyedum, O.D.¹ (AUTHOR) onyedidavid@futminna.edu.ng, Ajewole, M.O.² (AUTHOR) oludare.ajewole@futa.edu.ng, Aibinu, A.M.³ (AUTHOR) abiodun.aibinu@futminna.edu.ng

المصدر: Journal of Atmospheric & Solar-Terrestrial Physics. Jul2019, Vol. 188, p52-61. 10p.

مصطلحات موضوعية: *TELECOMMUNICATION satellites, *RADIO wave propagation, *PREDICTION models, *COMMUNICATION models, *RAINFALL

مصطلحات جغرافية: NIGERIA

مستخلص: Abstract Propagation of radio waves between terrestrial and earth-space links at frequencies above 10 GHz are adversely affected by weather, especially rain. Rain-induced attenuation is an important propagation effect that has to be considered in satellite communication system design. Prediction of rain attenuation for earth-space links in North Central Nigeria at Ku and Ka bands is investigated using five rain attenuation models: The ITU-R P.618 model, Bryant model, Garcia-Lopez model, Svjatogor model and Simple attenuation model (SAM). The main objective is to determine the optimal rain attenuation prediction models for satellite communication in this region. 33 years (1983–2015) daily rainfall data obtained from the Nigerian Meteorological Agency (NIMET) were used. Three elevation angles were considered: 55° 42.5° and 23°. The results obtained showed that the ITU-R P.618, Garcia-Lopez and Bryant models performed best in this region. Also, attenuation ranged from 14 dB to 16 dB at 55° elevation angle, 15 dB–16 dB at 42.5° elevation angle and 20 dB–22 dB at 23° elevation angle for exceedance time percentage of 0.01% at Ku-band in all the stations. For the Ka-band, attenuation varied between 33 dB and 37 dB at 55° elevation angle, 33 dB and 37 dB at 42.5° elevation angle and between 42 dB and 48 dB at 23° elevation angle for same 0.01% exceedance time percentage. From the values of rain attenuation predicted for 0.01% time exceedance, availability of signal is possible at 42.5° and 55° elevation angles but impossible at 23° elevation angle at Ku-band. At Ka-band, the predicted rain attenuation values for 0.01% time exceedance have shown that availability of signal is impossible at all three elevation angles, which implies total signal fade out during such rainfall events in the region. Highlights • Five rain attenuation models were used in predicting rain attenuation for earth-space links. • The ITU-R P.618, Garcia-Lopez and Bryant attenuation models performed satisfactorily. • Signal availability is possible at 42.5° and 55° elevation angles but impossible at 23° for the Ku-band. [ABSTRACT FROM AUTHOR]

المؤلفون: Yusuf, Najib, Ekpe, O. E., Said, Rabia S., Ayantunji, B. G., Umahi, A. E.

المصدر: Meteorology & Atmospheric Physics; Jun2020, Vol. 132 Issue 3, p327-340, 14p

مصطلحات موضوعية: AUTOMATIC meteorological stations, RADIO wave propagation, ATMOSPHERE, WATER

مصطلحات جغرافية: LAGOS (Nigeria), NIGERIA

مستخلص: The seasonal and diurnal trends of surface refractivity were derived using International Telecommunication Union Radio assembly model (ITU-R P.453-13) in two locations of entirely different vegetation characteristics in Nigeria. Atmospheric refractivity is a function of temperature, pressure as well as humidity. These meteorological variables were applied to the model to compute the refractivity parameter. Atmospheric refraction or refractivity is a key component in radio wave propagation. Real-time measurement data from a network of ground-based automatic weather station (AWS) installed at 3 m height were used and the monthly trends of surface refractivity at both stations (Lagos and Anyigba) were derived; the trends showed a month-to-month variability signifying the dynamic nature of the Earth's atmosphere. The monthly trends in both stations show high refractivity values in the rainy months and low refractivity values in the dry months. A drop in refractivity value was observed in Lagos in the month of August, due to the cessation in rainfall as a result of a phenomenon referred to as August break. The diurnal variations were also determined and results obtained showed that the lowest refractivity value in the dry season observed in Lagos is higher than the highest refractivity value in rainy season observed in Anyigba. This is attributed to the fact that Lagos is located along the coast of the South Atlantic Ocean, therefore, the monsoon has a direct influence on its atmosphere, while Anyigba is an inland station with a mixture of savannah vegetation. Overall, the diurnal variations show high values in the morning and evening hours and low values in the afternoon hours in both seasons in Anyigba, while in Lagos we observed a surprising result, such as a rise in refractivity value at pre-noon and a post-noon drop. This unacquainted observation is probably due to excessive precipitation in the area caused by the influence of massive emissions from the South Atlantic Ocean, these emissions are mainly a result of the trapped heat due to warming of surface water. [ABSTRACT FROM AUTHOR]

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المؤلفون: Falodun, S.¹ besfal@yahoo.com, Okeke, P.²

المصدر: Theoretical & Applied Climatology. Jul2013, Vol. 113 Issue 1-2, p127-135. 9p. 2 Color Photographs, 1 Diagram, 1 Chart, 9 Graphs, 2 Maps.

مصطلحات موضوعية: *RADIO wave propagation, *SPACE sciences, *CLIMATIC zones, *TELECOMMUNICATION systems, *COMMUNICATION

مصطلحات جغرافية: NIGERIA

مستخلص: International conferences on frequency coordination have, in recent years, required new information on radiowave propagation in tropical regions and, in particular, on propagation in Africa. The International Telecommunications Union (ITU-R) initiated 'radio-wave propagation measurement campaign' in some African countries some years back. However, none of the ITU-initiated experiments were mounted in Nigeria, and hence, there is lack of adequate understanding of the propagation mechanisms associated with this region of the tropics. The Centre for Basic Space Science (CBSS) of NASRDA has therefore embarked on propagation data collection from the different climatic zones of Nigeria (namely Coastal, Guinea Savannah, Midland, and Sahelian) with the aim of making propagation data available to the ITU, for design and prediction purposes in order to ensure a qualitative and effective communication system in Nigeria. This paper focuses on the current status of propagation data from Nigeria (collected by CBSS), identifying other parameters that still need to be obtained. The centre has deployed weather stations to different locations in the country for refractivity measurements in clear atmosphere, at the ground surface and at an altitude of 100 m, being the average height of communication mast in Nigeria. Other equipments deployed are Micro Rain Radar and Nigerian Environmental and Climatic Observing Program equipments. Some of the locations of the measurement stations are Nsukka (7.4° E, 6.9° N), Akure (5.12° E, 7.15° N), Minna (6.5° E, 9.6° N), Sokoto (5.25° E, 13.08° N), Jos (8.9° E, 9.86° N), and Lagos (3.35° E, 6.6° N). The results obtained from the data analysis have shown that the refractivity values vary with climatic zones and seasons of the year. Also, the occurrence probability of abnormal propagation events, such as super refraction, sub-refraction, and ducting, depends on the location as well as the local time. We have also attempted to identify and calculate the most important propagation factors and associated data, such as k factor, that are relevant in considerations of propagation in tropical regions like Nigeria. [ABSTRACT FROM AUTHOR]

المؤلفون: Osita, Ibe, Nymphas, E. F.

المصدر: Meteorology & Atmospheric Physics; Apr2019, Vol. 131 Issue 2, p251-261, 11p

مصطلحات موضوعية: RADIO wave propagation, RAINFALL, RADIO engineering, RADIO waves

مصطلحات جغرافية: NIGERIA

مستخلص: Radio waves especially at the millimeter-wave band are known to be attenuated by rain. Radio engineers and designers need to be able to predict the time of the day when radio signal will be attenuated so as to provide measures to mitigate this effect. This is achieved by characterizing the rainfall intensity for a particular region of interest into worst month and worst hour of the day. This paper characterized rainfall in Nigeria into worst year, worst month, and worst hour. It is shown that for the period of study, 2008 and 2009 are the worst years, while September is the most frequent worst month in most of the stations. The evening time (LT) is the worst hours of the day in virtually all the stations. [ABSTRACT FROM AUTHOR]

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المؤلفون: Adediji, A.T. kadediji@futa.edu.ng, Ajewole, M.O.¹

المصدر: Journal of Atmospheric & Solar-Terrestrial Physics. Apr2010, Vol. 72 Issue 5/6, p550-555. 6p.

مصطلحات موضوعية: *RADIO wave propagation, *MICROWAVES, *ATMOSPHERIC radio refractivity, *REFRACTIVE index, *HUMIDITY, *ATMOSPHERIC pressure, *ATMOSPHERIC temperature

مصطلحات جغرافية: NIGERIA

مستخلص: Abstract: Anomalous propagation (Anaprop) of microwave radiation is known to be caused by several meteorological conditions. In this study, radio refractive index and modified refractivity gradient were computed using the results of measurements of atmospheric pressure, temperature and relative humidity made in Akure (7.15 ° N, 5.12 ° E), South Western Nigeria using Davis 6162 Wireless Vantage Pro2 weather stations (Integrated Sensor Suite, ISS) positioned at five different height levels beginning from the ground surface and at intervals of 50m from the ground to a height of 200m on a tower/mast owned by the Nigeria Television Authority (NTA) located at Iju in Akure north local government area of Ondo state but which is no longer being used. The study utilized one year of data measured between January and December 2008. From the results, the modified refractivity was calculated and found to increase with increasing altitude. The values were observed to be generally high during the rainy periods and generally low during the dry periods. The study also revealed that for microwave propagation in this geographic zone, the propagation condition is mostly super-refractive. [Copyright &y& Elsevier]

المؤلفون: Faruk, N., Ayeni, A. A., Adediran, Y. A.

المصدر: Nigerian Journal of Technology; Jul2013, Vol. 32 Issue 2, p253-265, 13p

مصطلحات موضوعية: STANDARD deviations, PATH analysis (Statistics), RADIO wave propagation

مصطلحات جغرافية: ILORIN (Nigeria), NIGERIA

مستخلص: Path loss exponent, standard deviation and building penetration loss are used in all distance path loss models. Once these data are known for an environment, coverage planning and propagation analysis could be done easily. Many countries across the world, such as Japan, United Kingdom, Germany, and the USA have already published their propagation data, mostly, the path loss exponent for their various cities. However in Nigeria, these data are not available. In this work, measurements were conducted at 203.25 MHz and 583.25 MHz frequencies along ten routes in Ilorin City in Kwara State of Nigeria. Least squares regression method is used to fit the measured data with log-normal propagation path loss model to characterize the path loss parameters. Results of the experiment indicate that the path loss exponent for Ilorin City varies from 1.4 to 4.94 with an average value of 2.80. The work further investigates the behaviour of the TV signals in the same environment in terms of standard deviation and building penetration loss across the routes, and some selected building structures. [ABSTRACT FROM AUTHOR]

: Copyright of Nigerian Journal of Technology is the property of University of Nigeria, Faculty of Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Usman, A. U., Okereke, O. U., Omizegba, E. E.

المصدر: IUP Journal of Telecommunications; 2011, Vol. 3 Issue 4, p7-17, 11p, 2 Diagrams, 4 Charts, 3 Graphs

مصطلحات موضوعية: GSM communications, MOBILE communication systems, TELECOMMUNICATION systems, RADIO wave propagation

مصطلحات جغرافية: BAUCHI (Nigeria), NIGERIA

مستخلص: This paper presents a comprehensive set of propagation measurements taken at 900/1800 MHz in Bauchi, Nigeria, to validate the applicability of some popularly used empirical models for mobile network design in the environment. The results show that the Egli and Hata suburban models provide close predictions for base stations, BS1, BS3 and BS4, thus supporting the use of these two models for future network design or system expansion in suburban areas of Bauchi town and other environments with similar features. However, BS2 typifies an open area as the Hata open area model gave the best prediction with absolute mean error (μ), standard deviation (σ) and root mean square error (rmse) values of 5.6 dB, 4.8 dB and 7.25 dB respectively at 900MHz and 7.7 dB, 6.5 dB and 10.10 dB at 1800MHz. [ABSTRACT FROM AUTHOR]

: Copyright of IUP Journal of Telecommunications is the property of IUP Publications and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Semire, F. A., Raji, T. I.

المصدر: Journal of Telecommunications & Information Technology; 2011, Vol. 2011 Issue 2, p85-89, 5p

مصطلحات موضوعية: RAINFALL, MICROWAVES, CLIMATOLOGY, INFORMATION technology, ARTIFICIAL satellites, BROADBAND communication systems, RADIO wave propagation

مصطلحات جغرافية: OGBOMOSO (Nigeria), NIGERIA

المؤلفون: Azubogu, A. C. O., Onoh, G. N., Idigo, V. E., Ohaneme, C. O.

المصدر: IUP Journal of Science & Technology; Jun2011, Vol. 7 Issue 2, p45-54, 10p, 3 Charts, 2 Graphs

مصطلحات موضوعية: RADIO wave propagation, MOBILE communication systems, SUBURBS, RADIO & literature, FM radio receivers

مصطلحات جغرافية: AWKA (Nigeria), NIGERIA

مستخلص: A number of empirical propagation prediction models for mobile radio communication systems are available in the literature. However, the accuracy of these models suffers when they are used in an environment other than that for which they have been developed. In this research work, a set of propagation measurements taken at 800 MHz band in the suburban city of Awka, Nigeria is used to develop path loss prediction model for suburban environment. Hata and COST-231 Hata models which are widely used for path loss prediction in GSM and CDMA systems are compared with the results of the developed model. The results of this research assist mobile cellular network designers in carrying out accurate analysis and design, deployment and management of their networks. [ABSTRACT FROM AUTHOR]

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المؤلفون: Ojo, J. S., Ajewole, M. O., Emiliani, L. D.

المصدر: IEEE Antennas & Propagation Magazine; Oct2009, Vol. 51 Issue 5, p82-89, 8p

مصطلحات موضوعية: ATTENUATION (Physics), RADIO wave propagation, MICROWAVES, SYSTEMS design, DISTRIBUTION (Probability theory), RADIO transmitter-receivers, STATISTICS

مصطلحات جغرافية: NIGERIA

مستخلص: Rain attenuation is the dominant propagation impairment for high-frequency microwave systems. System design therefore requires the knowledge of the one-minute integrated-rain-rate cumulative distribution function over the coverage area in order to determine the appropriate transmitter and receiver characteristics. This paper presents a set of rain-rate contour maps, useful for link and network power sizing in Nigeria. They were developed using a combination of first-order rain-rate statistical methods: the Moupfouma-Martin model for rain-rate prediction in tropical regions, and the Rice-Holmberg model. [ABSTRACT FROM AUTHOR]

: Copyright of IEEE Antennas & Propagation Magazine is the property of IEEE and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)