Papers by Hisham Muhammed
ELEKTRIKA- Journal of Electrical Engineering
This paper presents a novel approach to the modelling of electrical energy demand forecasting, ba... more This paper presents a novel approach to the modelling of electrical energy demand forecasting, based on the Quasi-Moment-Method (QMM). The technique, using historical energy consumption/demand data, essentially calibrates nominated ‘base’ models (in this case, nominal Harvey and Autoregressive models) to provide significantly better performing models. In addition to the novelty of the use of QMM, the paper identifies hitherto unreported singularities of the generic Harvey / logistic model, through which a simple, but remarkably pivotal modification is proposed, prior to the model’s use as base model in QMM calibration schemes. The treatment of the ‘Harvey singularities’ informed a similar and equally significant modification of the Autoregressive model utilized in the paper. For the purposes of validation and performance evaluation, computational results due to the QMM models are compared with corresponding results reported in three different journal publications, which utilized the...
International Journal on Communications Antenna and Propagation (IRECAP), 2021
This paper develops and comprehensively evaluates a very simple and remarkably efficient method, ... more This paper develops and comprehensively evaluates a very simple and remarkably efficient method, here referred to as the Quasi-Moment-Method (QMM), as a tool for the calibration of basic (classical) pathloss models, in various radiowave propagation scenarios. After a succinct description of the characterizing features of the method, the paper presents computational results involving comparisons with published data concerning Minimum Mean Square Error (MMSE) optimization, Adaptive Neuro-Fuzzy Inference System (ANFIS) pathloss modeling, and (for an indoor case), a dual-slope reference model. The results reveal that the QMM remarkably outperforms the MMSE-optimized and modified single-slope, close-in reference models, when evaluated in terms of the statistical measures of Root Mean Square Error (RMSE), Mean Prediction Error (MPE), and Standard Deviation Error (SDE). Computational results due to the QMM also compare favorably (and better, with some performance metrics) with published corresponding results available from the literature, in which heuristic (ANFIS and Artificial Neural Network (ANN)) as well as geospatial (Kriging) models were utilized. A number of inherent properties of the real, symmetric ‘model calibration matrices’ associated with QMM process are identified in the paper, as offering interesting possibilities for further investigations involving eigenvalues and corresponding eigenvectors.
International Journal of Computer Applications, 2021
This paper systematically examines the response to QuasiMoment-Method (QMM) calibration, of the b... more This paper systematically examines the response to QuasiMoment-Method (QMM) calibration, of the basic COST231Walfisch-Ikegami, ITUR-Walfisch-Ikegami, and WalfischBertoni models. First, it is demonstrated that the component parameters of the models are suitable candidates for use as expansion/testing functions with QMM pathloss model calibration schemes; and thereafter, the basic models are subjected to calibration, using measurement data available in the open literature. Computational results reveal that the COST231-Walfisch-Ikegami and ITU-Walfisch-Ikegami models have virtually identical QMM-calibration root mean square error (RMSE) responses; and that the Walfisch-Bertoni model has better RMSE responses than both of them. A particular attribute revealed by the simulation results is that all QMM-calibrated ‘Walfisch-type’ basic models have excellent mean prediction error (MPE) metrics (in general, less than 0.001dB). In addition to pathloss prediction profiles, the paper also prese...
Nigerian Journal of Technology, 2021
This paper introduces the Quasi-Moment-Method (QMM) as a novel radiowave propagation pathloss mod... more This paper introduces the Quasi-Moment-Method (QMM) as a novel radiowave propagation pathloss model calibration tool, and evaluates its performance, using field measurement data from different cellular mobile communication network sites in Benin City, Nigeria. The QMM recognizes the suitability of component parameters of existing basic models for the definition of ‘expansion’ and ‘testing functions’ in a Galerkin approach, and simulations were carried out with the use of a FORTRAN program developed by the authors, supported by matrix inversion in the MATLAB environment. Computational results reveal that in terms of both Root Mean Square (RMS) and Mean Prediction (MP) errors, QMM-calibrated models performed much better than an ‘optimum’ model reported for the NIFOR (Benin City), by a recent publication. As a matter of fact, the QMM-calibrated COST231 (rural area) model recorded reductions in RMS error of between 31.5% and 71% compared with corresponding metrics due to the aforementio...
This paper develops exact expressions for the radiation field integrals of a single-wound bi-elli... more This paper develops exact expressions for the radiation field integrals of a single-wound bi-elliptical toroidal helical antenna, based on the vector magnetic potential approach. Using the conventional thin-wire approximation in which current flow is constrained along the wire's axis, a vector-potential integral is developed for the problem in terms of the unknown current distribution and physical attributes of the wire antenna, with the integrals' integrands expressed in matrix format. Entries into these integrand matrices lend themselves into certain physical interpretations, which facilitate a number of conclusions concerning the physics of the problem. For example, it becomes readily discernible that the antenna's radiation field admits description as a sum of two expressions; one deriving from the main loop, and the other associ-ated with the poloidal loops of the antenna. These same conclusions were arrived at from the results of the empirical investigations report...
In this presentation, we develop an analytical model, using the electric field integral equation ... more In this presentation, we develop an analytical model, using the electric field integral equation (EFIE) approach, for a folded zigzag thin-wire antenna, with the geometry of a circular-loop. Following a treatment described elsewhere [1], for the bi-elliptical toroidal helical antenna, the kernel of the integral expression for the magnetic vector potential for the problem is derived in a matrix format, through which distinct contributions to the radiation field by the circular-loop geometry and the zigzag emerge. The computational results obtained for some input characteristics and the far-zone fields, for an assumed uniform current distribution, indicate that choice of number of zigzag sections pro-vides the important possibilities of varying antenna's electrical length and controlling pattern directivity. Similar conclusions were arrived at by Zainud-Deen et al. [2], who investigated the performance features of zigzag antennas for portable radio equipment.
Journal of Communication and Information Systems
Investigations in this paper focus on establishing the uniqueness properties of the Quasi-Moment-... more Investigations in this paper focus on establishing the uniqueness properties of the Quasi-Moment-Method (QMM) solution to the problem of calibrating nominal radiowave propagation pathloss prediction models. Nominal (basic) prediction models utilized for the investigations, were first subjected to QMM calibrations with measurements from three different propagation scenarios. Then, the nominal models were recast in forms suitable for Singular Value Decomposition (SVD) calibration before being calibrated with both the SVD and QMM algorithms. The prediction performances of the calibrated models as evaluated in terms of Root Mean Square Prediction Error (RMSE), Mean Prediction Error (MPE), and Grey Relational Grade-Mean Absolute Percentage Error (GRG-MAPE) very clearly indicate that the uniqueness of QMMcalibrations of basic pathloss models is more readily observable, when the basic models are recast in forms specific to SVD calibration. In the representative case of calibration with indoorto-outdoor measurements, RMSE values were recorded for QMM-calibrated nominal models as 5.2639dB for the ECC33 model, and 5.3218dB for the other nominal models. Corresponding metrics for the alternative (rearranged) nominal models emerged as 5.2663dB for the ECC33 model and 5.2591dB for the other models. A similar general trend featured in the GRG-MAPE metrics, which for both SVD and QMM calibrations of all the alternative models, was recorded as 0.9131, but differed slightly (between 0.9138 and 0.9196) for the QMM calibration of the nominal models. The slight differences between these metrics (due to computational round-off approximations) confirm that when the components of basic models are linearly independent, the QMM solution is unique. Planning for wireless communications network deployment may consequently select any basic model of choice for QMM-calibration, and hence, identify relative contributions to pathloss by the model's component parts.
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Papers by Hisham Muhammed