Scholarly works

Permanent URI for this collectionhttps://repository.ui.edu.ng/handle/123456789/420

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Author: search.filters.author.Osita, I.Start date: 2020

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    Worst month rain rate characterization for line-of-sight link performance in tropical locations
    (2021) Osita, I.; Nymphas,E.F.
    Communication equipment operating in the 30 to 300GHz frequencies avails large bandwidth and high speed data transmission but suffers greatly from attenuation by rain. The design of radio communication equipment has been based on predicted rain rate from the International Telecommunication Union-Radio (ITU-R) recommendations. This equipment fails in the tropics due to the differences in tropical and temperate rainfall structure on which the ITU-R recommendation is based. Five minutes rainfall data from two tropical locations in Nigeria – Jos (9.93 oN, 8.89oE, 1280 m) and Minna (9.61 oN, 6.56 oE, 223 m) were analysed. The 1- minute and ITU-R predicted rain rate (RR) were obtained with the Lavergnat and Gole model and MatLab rain rate statistics respectively while the logarithmic scale was used to convert the RR to exceedance time percentages (0.001 to 1%). The two parameter conversion factors, Q1 and β were generated with the ITU-R P. 841-6 recommendation; these were compared with the conversion factors recommended by ITU-R for global rain rate application. The results showed that at 0.01% exceedance, the ITU-R predicted rain rate for Jos and Minna were 87.1mm/hr and 91.6mm/hr respectively while the estimated rain rate from these locations were 84.5mm/hr and 110.0mm/hr respectively. The ITU-R conversion factor for the computation of the mean annual worst month from mean annual rain rate percentage exceedence were Q1 = 2.83 and β = - 0.15 while these parameters at Jos is, Q1 = 3.17 and β = - 0.19 and at Minna, Q1 = 3.12 and β = - 0.18. The results showed that there is a very strong relationship between the distribution of rain rate in the worst month and the annual rain rate distribution with coefficient of determination of 0.9994 and 0.9984 respectively. Thus for optimum link design budgeting, the modified values of Q and β should be adopted in these locations in order to enhance radio equipment performance in Nigeria.
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    Characterization of tropical rainfall structure for some selected locations in Nigeria
    (2021) Osita, I.; Nymphas,E.F.
    Rainfall rate for any location is required for rain attenuation modeling for the region of interest. The characteristics of tropical rainfall structure in Nigeria have been investigated. The data was collected from the Tropical Data Acquisition network (TRODAN) set up by the Center for Atmospheric Research (CAR) in Nigeria. The rainfall rates were measured at 5-minutes integration time. The results were then compared with those predicted by the ITU-R model, and those from other tropical locations. The results revealed that the ITU-R model performs best only in the Southern Guinea Savannah (SGS) region of the country. In other geographical locations, the ITU-R model either under-estimates or over-estimates rainfall rates. The Cumulative Distribution Functions (CDFs) at the 0.01% time of exceedence showed that the percentage difference in the measured rain rate and the ITU-R estimates varied from a minimum of 4.89% in SGS to a maximum of 22.93% in the Derived Savannah (DS). At the 0.001% of time, these differences varied from a minimum of 11.90% to a maximum of 38.80% in these respective regions. These results and others from the tropics suggest the need for the modification of the ITU-R model for predicting rain attenuation in the tropical region to take into account the peculiar characteristics of rainfall in the region.
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    Determination of rainfall attenuation at millimeter wave band for the design of 5g and higher bandwidth radio equipment for terrestrial paths in the tropical region
    (2020) Osita, I.; Nymphas, E. F.
    Millimeter Wave (mmW) radio systems operating at 30 to 300GHz band provides higher bandwidth, frequency reuse and communications security. With the available wide bandwidth, millimeter wave equipment is capable of achieving 10 Gbps full duplex capacities. The mean annual 1-minute RR (mm/hr) ranged from 87.25 in the coastal region to 51.0mm/hr in semi-arid region. The ITU-R predicted RR ranged from 109.10mm/hr in the coast to 91.90mm/hr in the semi-arid region. The ITU-R overestimated the rain rate by 23.83% in the semi-arid region while at the coastal region, it was over-estimated by 12.47%. The highest value of specific attenuation (R g) at horizontal polarization (Hp) and vertical polarization (Vp) for the two regions occurred at 120 and 150GHz MWFs and R P g H > R P g V. The clear signal band at 20km Path length were estimated to be 40 and 45GHz across the regions, while the predicted value by ITU-R is also 40GHz. However, the ITU-R over predicted the value of attenuation at this frequency band by 13.16% and 35.29% at the coastal and semi-arid locations respectively. included 150GHz which overlaps with 45GHz band. The path attenuation across the regions at 40GHZ ranged from 112.58dB to 164.14dB while at 45GHZ, it ranged from 122.02dB to 175.57.45dB. The range of the ITU predicted value of path attenuation at 40GHz and 45GHz were 170.20dB to 192.18dB and 181.83 dB to 204.43dB respectively.