Pius A. Owolawi

Effect of Rainfall on Millimeter Wavelength Radio in Gough and Marion Islands

With the increasing in spectrum occupancy and demand for high bandwidth for evolution of complex radio access network, the need to explore the advantages of millimetric wave band has become imperative. The advantages of the band are: large spectrum availability, high frequency re-used potential, small antenna and equipment size. In this paper, a new-hybrid approach is used to convert rainfall from five-minute integration time to one-minute integration time for the calculation of rain attenuation. The paper also provides information on cumulative distributions, seasonal variability, and worst month of rainfall rate for the islands. Consequently, relationship between average year (AY) and average worst month (AWM) are obtained.

Optical Spatial Modulation with Diversity Combiner in Dual-Hops Amplify-and-Forward Relay Systems Over Atmospheric Impairments

In this paper, we analyzed a dual-hop optical spatial modulation channel state information-assisted amplified and forward (AF) relay system with spatial diversity combiner under the influence of gamma-gamma atmospheric turbulence induced fading and pointing error impairments. Maximum ratio combiner (MRC) and equal gain combiner (EGC) with heterodyne detection are considered at the destination as mitigation tools to improve the system error performance. The statistical characteristics of AF relay in terms of moment generating function (MGF), probability density function and cumulative density function are derived for both impairments. Based on these expressions, the average pairwise error probability for each of the combiners under study is determined and the average bit error rate (ABER) for the system is given by using union bounding technique. By utilizing the derived ABER expressions, the effective capacity for the considered system is then obtained. The effect of turbulence strength ranging from weak to strong levels and pointing errors in terms of beam width and jitter displacement are studied. The numerical results obtained show that the more the turbulence strength and/or pointing error increases, the more the error rate and effective capacity of the system deteriorates. Under the same conditions, the results confirmed that MRC system offers an optimal performance compared with EGC.

Hybrid power systems for GSM and 4G base stations in South Africa

This paper aims to address the use of hybrid renewable energy sources to supply power to the base station, hence to enhance the minimum Operational Expenditure (OPEX) and alleviate the effect of Greenhouse Gas (GHG) which are detrimental to the environment and human health at large. Using Hybrid Optimization Model for Electric Renewable (HOMER) software for simulation and optimization, we discovered that we can reduce the carbon emission by over 87.47%, and the total fossil fuel consumption by over 10,400 litres annually. Hence, it is safe to conclude that the existing (diesel-only) system for powering the Base Station (BS) though, has the least initial capital cost, in the end, it has the highest Net Present Cost (NPC) and cost of energy per kilowatt over the life span of the BS.

Modeling freezing height level for satellite link communication: Durban, South Africa

In the design process of Earth-space link telecommunication systems at higher frequencies, the precise estimation of attenuation due to rain which depends on rain height is important. This study examines two statistical distribution models for freezing height level over Durban, South Africa, using 5 years data and then studied the monthly, seasonal and annual variations using the parameters estimated by the maximum likelihood of the distributions. Three statistical goodness of fit were also used to determine the performance evaluation of the distributions. It was observed that 3-Parameter Dagum (Dagum) distribution performs better over the next most suitable distribution (3-Parameter Log-logistic) for the modeling of freezing height level over Durban with improvement of 0.94% in Bias error, 0.48% Root Mean Square Error (RMSE) and 7.43% Kolmogorov-Smirnov test (K-S test). Also, the location, shape and scale parameters for the distributions show a wider variation.

A comparison between mathematical tools for analyzing FSO systems over Gamma-Gamma atmospheric channel

Atmospheric turbulence induce-fading is one of the major link impairments that degrade the performance of Free Space Optical (FSO) communication systems. In this paper, the authors present the performance difference between the Meijer-G function and infinite Power Series expansion as mathematical tools for analyzing the performance of FSO system over Gamma-Gamma atmospheric turbulence. The Probability Distribution Function (PDF) for the Gamma-Gamma channel is obtained in terms of Meijer-G function and infinite power series expansion. Thus, the Average Bit Error Rate (ABER) and outage probability close-form expressions of a Subcarrier Intensity Modulation (SIM) that employed Bipolar Phase-Shift Keying (BPSK) are then derived using the statistical channel PDF. Under the same atmospheric conditions, the results show that both analyses offer the same performance but power series expansion analysis yield the best computational running time than the Meijer-G analysis. It is also deduced that Meijer-G close-form expression does not reveal insight into the system design compare to the power series approach but offers a traceable close-form result for the two performance metrics as compared to the Power Series Expansion.

Performance analysis of Block Error Rate for SIM-FSO system with spatial diversity over Gamma-Gamma fading and pointing error channel

Atmospheric turbulence and pointing error impairments are the major detriment challenges that degrade the FSO system performance. In this paper, we presented the performance analysis of Block Error Rate (BLER) of Subcarrier Intensity Modulation (SIM) in FSO system over atmospheric turbulence and pointing error channel with the spatial diversity as mitigation tools at the receiving end. The channel Probability Distribution Function (PDF) for the Maximum Ratio Combiner (MRC) and Equal Gain Combiner (EGC) were derived using power series expansion based approach. Utilizing the channel PDF, the BLER close form expressions for each under studied combiner were obtained. The obtained numerical results confirmed that the channel impairments and increase in number of block lengths significantly deteriorate the system performance. It is also demonstrated from the results that the combining technique greatly improved the system BLER performance as the link range increases with the MRC outperformed the EGC.