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Ray-tracing propagation models for urban microcellular environments become time consuming as the validation of higher order of ray interactions presents a significant computational overhead. This letter presents a time efficient ray validation algorithm for ray-tracing models. The model presented in this letter uses a pre-computed database of building faces that are completely or partially visible to each face and vertical edge of all the buildings in the radio environment. This database is used to readily validate the ray-segments between the transmitter and receiver. The validation results show considerable time saving over previous models.

The problem of computing 2D EM wave scattering from rough surfaces is addressed using an integral equation formulation discretised using the method of moments. Successive Symmetric Over-Relaxation (SSOR) is applied to the governing matrix equations along with eigenvalue deflation which is de- signed to separately account for the effect of those eigenvectors of the iteration matrix that have eigenvalues greater than 1. Numerical results are presented applying the method to a variety of scattering profiles and examining the resultant convergence performance.

There has been a great deal of interest in radio channel modeling for upcoming vehicular and device-to-device 5G applications. Site-specific models for such mobile transmitter scenarios become time-consuming as the visibility computations need to be independently performed for each transmitter location. This paper presents an efficient ray-tracing algorithm for a mobile transmitter radiating in an urban environment. The model presented uses a precomputed database of intravisibility of walls and edges in the environment. A visibility table that contains a list of walls and edges visible to multiple transmitters along a linear trajectory is computed for the given order of ray interaction. The walls and edges visible at a given location along the transmitter route are then readily determined using the visibility table thereby accelerating the ray-tracing algorithm. The validation results show considerable time-saving over unaccelerated ray tracing.

A full-wave indoor propagation model based on the two-dimensional (2D) volume electric field integral equation (VEFIE) is presented. The model is discretised with the method of moments (MoM). The linear system arising from the MoM discretisation is solved with an iterative solver accelerated by using the fast Fourier transform and a reduced operator. The 2D VEFIE is validated against the analytical Mie series solution for scattering from a dielectric cylinder before being applied to a typical indoor propagation environment and compared against measurements. It is also compared against current popular empirical models and ray tracing. The ability of the frequency domain VEFIE method to produce time domain information is demonstrated with an investigation of numerical considerations that must be made.

This paper presents an efficient technique to identify surfaces which are visible to a mobile transmitter in outdoor environments with moving scatterers. The presence of moving scatterers or a mobile transmitter in a propagation environment makes the radio channel modelling very challenging as visibility computations need to be repeatedly performed in a changing scenario. This makes the pre-processing overhead unfeasible for ray-tracing based propagation prediction models. The algorithm described in this paper first computes the static visibility table for the mobile transmitter assuming that the environment is static. Then the effects of moving scatterers are modelled to compute the so-called dynamic visibility table. Both the static and dynamic visibility tables are used along with information about the scatterers’ location to validate the rays arriving at the receiver. Validation results show a considerable reduction in run times.

A robust and accurate iterative algorithm is proposed for the solution of electromagnetic wave scattering from 1-D layered rough surfaces. The forward–backward method (FBM) has been applied extensively for solving electromagnetic scattering from single-layer rough surfaces due to its rapid convergence rate. Nevertheless, the performance of the FBM deteriorates, as it is applied to layered random rough surface problems. The proposed method greatly improves the convergence rate of the FBM by applying a residual minimization step. The computational cost of the minimization step and the forward–backward sweeps is expedited by using the spectral acceleration. In this communication, the proposed algorithm is applied as a solution to the problem of electromagnetic wave scattering from layered rough surfaces. Numerical results are presented to demonstrate the better convergence properties of the proposed method as compared with the standard FBM. In addition, the proposed method is shown to be more robust than the FBM, especially as the distance between interfaces decreases. The computational complexity of the proposed algorithm is also presented and discussed.

The potential of microbial processes for removal of major nutrients (e.g., N, P) and inorganic cations (e.g., Ca2+, Mg2+, and Fe2+) from hydroponic systems was investigated. Microbial consortium- and axenic culture-based experiments were conducted in a waste nutrient solution (WNS). A microbial consortium grown in the WNS and selected microalgae species of Paracercomonas saepenatans were inoculated in two different synthetic media (Bold's Basal Medium (BBM) and synthetic WNS) in batch systems, and the microbial growth characteristics and the rate and extent of nutrient removal were determined for each system. No toxicity or growth inhibition was observed during microbial growth in either media. Both the waste-nutrient-grown microbial consortium and Paracercomonas saepenatans can be grown effectively in BBM and WNS, and both remove most ions from both media (e.g.,>99% removal of NO3- and 41-100% removal of PO43-) within 16days. Significant nutrient removal was observed during the growth phase of the microbial communities (4-10days period), indicating major nutrient utilization for microbial growth as well as chemical mineral precipitation. Furthermore, MINEQL+4.6 modeling showed higher PO43- removal in WNS during microbial growth (compared to BBM) due to precipitation of phosphate minerals (e.g., hydroxyapatite, vivianite). The dominant microbial species in both systems were also identified. DNA sequencing showed that Vorticella (58%) and Scenedesmus (33%) in WNS and Scenedesmus (89%) in BBM were the predominant species. This study demonstrates the potential application of microbial consortium (predominantly algae and protozoan)-based treatment techniques for hydroponic systems.

This paper presents an efficient ray tracing algorithm for propagation prediction in urban environments. The work presented in this paper builds upon previous work in which the maximum coverage area where rays can propagate after interaction with a wall or vertical edge is described by a lit polygon. The shadow regions formed by buildings within the lit polygon are described by shadow polygons. In this paper, the lit polygons of images are mapped to a coarse grid superimposed over the coverage area. This mapping reduces the active image tree significantly for a given receiver point to accelerate the ray finding process. The algorithm also presents an efficient method of quickly determining the valid ray segments for a mobile receiver moving along a linear trajectory. The validation results show considerable computation time reduction with good agreement between the simulated and measured data for propagation prediction in large urban environments.

Future wireless nanosensor networks are envisioned to operate in the THz band, due to the tiny size of the network components. Among the diverse range of applications that such networks promise, high-resolution plant monitoring systems are the categories which can benefit from the size and high sensitivity of nanosensor devices and also the high bandwidth provided by them. However, communications at the THz frequency band, especially within a hybrid channel like plant foliage, undergo peculiar types of attenuation and distortion. These phenomena, which can challenge the feasibility of the aforementioned applications, need to be addressed/modeled precisely. Therefore, in this paper, we propose the first THz path-loss model within a plant environment. In addition, we provide a simplified model of plant structure as well as a model for the probability of successful transmissions between nanosensors and microscale receivers mounted on the plant stem. The introduced models consider the limited capability of THz radiation to propagate through plant leaves, and also the high free-space path-loss as the main sources of signal loss in the network communications. Furthermore, these models can be customized based on the structural characteristics of a plant, e.g., leaves size and distribution, to account for a variety of plant species. Finally, the performance of communications based on the provided models is evaluated for different network scenarios.

The forward-backward method (FBM) is well-known for its robust convergence when applied to solve one rough interface problems. Challenges arise with the presence of multiple rough surfaces, resulting in a poor performance of the FBM. The improved forward-backward method with multiple correction vectors is proposed to enhance the convergence rate of the FBM. This is achieved by applying a residual minimisation step at the end of every iteration. In this paper, the application of the proposed method to exponential correlation surfaces is investigated. Numerical results are presented to demonstrate the accuracy and the efficiency of the proposed method as compared to the FBM.

The phase interplay between overlapping electric and magnetic dipoles of equal amplitude generated by exclusively alldielectric structures presents an intriguing paradigm in the manipulation of electromagnetic energy. Here, we offer a holistic implementation by proposing an additive manufacturing route and associated design principles that enable the programming and fabrication of synthetic multi-material microstructures. In turn, we compose, manufacture and experimentally validate the first demonstrable 3d printed all-dielectric electromagnetic broadband absorbers that point the way to circumventing the technical limitations of conventional metal-dielectric absorber configurations. One of the key innovations is to judicially distribute a dispersive soft matter with a high-dielectric constant, such as water, in a low-dielectric matrix to enhance wave absorption at a reduced length scale. In part, these results extend the promise of additive manufacturing and illustrate the power of topology optimisation to create carefully crafted magnetic and electric responses that are sure to find new applications across the electromagnetic spectrum.

An efficient method is proposed for computing electromagnetic wave propagation over lossy terrain profiles using a coupled surface integral equation formulation. The proposed method uses a set of basis functions, which can produce a linear system with much fewer unknowns than that created using pulse basis functions. In addition, the matrix entries can be computed very rapidly using precomputed tabulated values. The method improves upon the original tabulated interaction method (TIM) by extending it to lossy profiles, allowing for back-scatter and by introducing increased accuracy for near-field interactions. The complexity and numerical analysis demonstrates that the proposed method has an extremely low computational complexity and storage requirement. Moreover, the accuracy of the proposed method is demonstrated by comparing the pathloss against numerically precise solutions and measured data.

This paper proposes extending the forward scattering based Tabulated Interaction Method (TIM) for computing electromagnetic wave propagation over terrain profiles to one incorporating backscattering. The proposed method uses a common set of basis functions in conjunction with a “matching technique” to produce a linear system with much fewer unknowns than that created using pulse basis functions and therefore provides a very efficient and accurate method. The original TIM is shown to be a special case of the proposed method whereby the lower triangular portion of the reduced system is retained and solved. The proposed method is compared with the recently proposed Characteristic Basis Function Method with which it shares several features. The complexity and numerical analysis demonstrates that the proposed method has an extremely low computational complexity and storage.

In this paper a full wave propagation model based on the volume electric field integral equation (VEFIE) is applied to the problem of indoor propagation modelling. The two dimensional form of the VEFIE is used. It is discretised using the method of moments and solved with an iterative solver. The model is validated against indoor measurements and a good agreement is achieved. It is shown how the VEFIE can predict information about the propagation channel in the frequency and time domains. It is also demonstrated how the VEFIE can be used to produce angle of arrival information in indoor environments.

This paper presents an efficient ray-tracing acceleration technique for a mobile receiver in urban environments. The entry and exit points of lit polygon of images and the associated shadow polygons along the receiver route are predetermined to produce a database of relative location of polygons intersection along the route. The ray-tracing is accelerated as the geometrical test for ray validation is replaced by a simple distance comparison check. The validation results show considerable computation time reduction for propagation prediction in large urban environments.

This paper presents a new approach to compute the image tree of given order of ray interaction for ray-tracing. The intra-visibility of walls and vertical edges along with their angular position in the visibility region is computed. The image tree is readily created as the angular information is used to determine if a wall or vertical edge lies within an image illumination zone. Validation results show a considerable reduction in run times for image tree computations. The elimination of a recursive visibility algorithm for image tree creation is a first step towards efficient ray-tracing in mobile transmitter scenarios such as in vehicular networks.

New developments in energy efficient wireless communications systems and indoor location and tracking algorithms have created a greater demand for accurate propagation models. In this paper a frequency domain full wave propagation model is used to produce accurate power delay profile information. The propagation model is based on the volume electric field integral equation (VEFIE). The VEFIE is solved in two dimensions at a number of frequencies and the fourier transform is applied to convert the frequency domain data to the time domain. The generated PDP is compared against the well known theory of geometrical optics and a very good agreement is achieved. The effects of finite bandwidth and resolution on the PDPs are also investigated.

[EN] This paper presents a curriculum design approach for a Masters Programme in Telecommunications Management based on demand data obtained from surveying the needs of potential students of the proposed programme. Through online surveys disseminated at telecom companies in Jordan, it was possible to measure the demand for such a programme and to determine the required programme contents and specifications. The curriculum design is based on definition of programme outcomes and on using a house of quality approach (HOQ) to determine the list of courses required in the programme. Surveyed competencies are mapped to a long list of proposed courses in a HOQ in order to determine the importance of each of these courses. A final list of core and elective courses is then developed considering the contribution to programme outcomes and the academic standards., This work has been funded with support from the European Commission through Tempus Program, Project Number 511074. This publication reflects only the views of the authors, and the Commission cannot be held responsible for any use which may be made of the information contained therein.

An efficient and accurate iterative method is proposed for computing electromagnetic (EM) scattering from 1-D dielectric rough surfaces. The communication improves the convergence of forward backward method, applying it to the problem of 2D wave scattering from random lossy rough surfaces using a coupled surface integral equation formulation. A matrix splitting technique is introduced to reduce the number of matrix-vector multiplications required by the correction step and Spectral Acceleration (SA) is applied to reduce the computational complexity of each matrix-vector product from O(N2) to O(N). The proposed method is called the improved forward backward method with spectral acceleration (IFBM-SA). The numerical analysis demonstrates that IFBM-SA has a higher convergence rate than FBM-SA and a recent technique which is used as a reference method. Moreover, IFBM-SA is more robust than the reference method and has smaller storage requirements meaning that it can readily scale to larger problems. In addition an eigenvalue based analysis is provided illustrating how the improvement step works.

This article presents the methodology and results of the curriculum review of the Masters of Science programme in Wireless Communications offered by the Telecommunications Engineering Department at Yarmouk University in Jordan. The review is based on expert opinion collected through questionnaires and meetings about the programme and focuses on two main aspects: the first is relevance of the programme to the needs of local and regional telecommunications industry and the second is comparability to similar programmes in the EU. Through an extensive analysis of the collected data, a set of recommendations for improvement of the existing curriculum was developed. These recommendations were then used to redesign the curriculum with regard to contents, teaching methodology and assessment.

Most of the existing student response systems, such as clickers, have limited input capabilities, typically only offering students a multiple-choice selection. In some instances, students can input a numerical or textual response. However, mathematical equations, diagrams, etc. are all beyond the capabilities of such systems. This paper proposes and presents a novel multi-platform smart device-based student response system, called UniDoodle, that allows for a more generic and flexible input. This system consists of a student application that allows for freeform input through sketching capabilities, a lecturer application that allows easy viewing of multiple sketch-based responses and a cloud-based service for co-ordinating between these two applications. In essence, students can now respond to a question posed by the lecturer using sketches and, hence, mathematical equations, circuit diagrams, graphs, etc. are all possible on the UniDoodle system. In addition, the lecturer can now gain a richer and more useful insight to the students’ understanding of the relevant material. This paper also evaluates the UniDoodle system in a large class of first year Engineering Mathematics students. Details of the UniDoodle system, the evaluation process and the feedback obtained are all presented within.

A hybrid model for the efficient and accurate computation of 3D indoor propagation is presented. The model is based on the volume electric field integral equation. Two 2D simulations with 3D components are performed and their results averaged to produce an accurate approximation for the total electric field. Numerical results are presented demonstrating the improved computational efficiency of the model. It's accuracy is also compared against a full 3D simulation and a very good agreement is achieved.

This paper presents an efficient pre-processing technique for fast ray-object intersection test. The visibility region of the images are described by lit polygons. The visible buildings within the lit polygons, that form the shadow regions, are represented by the dark polygons. This representation ensures that only a few validation checks are required for the ray-object intersection test. Validation results show a significant acceleration in the ray calculation times in urban areas.

This paper presents a comparison between a volume electric field integral equation (VEFIE) modelling approach and ray tracing for the purposes of indoor propagation modelling. Focus is drawn to the inclusion of multiple internal interactions in the computation of reflections and transmissions in ray tracing. Results are presented for lossless and lossy materials. It is found that including multiple internal reflections improves the agreement between the ray tracing model and the VEFIE for reflections from a slab whilst there is a negligible improvement when considering transmissions through the slab. It is shown that when considering reflections from a slab it is more beneficial to consider internal interactions over diffraction but for transmissions through the slab other electromagnetic phenomenon are of more benefit than internal interactions.

An efficient iterative method is proposed for computing the electromagnetic fields scattered from a one dimensional (1D) flat surface. The new iterative method is based on a similar implementation to the Conjugate Gradient Fast Fourier Transform (CG-FFT), where acceleration of the matrix-vector multiplications is achieved using fast Fourier transforms (FFT). However, the iterative method proposed is not based on Krylov subspace expansions and is shown to converge faster than GMRES-FFT and CGNE-FFT while maintaining the computational complexity and memory usage of those methods. Analysis is presented deriving an explicit convergence criterion.

An improved implementation of a post-detection packet combining scheme, which is especially applicable to low power, resource-constrained sensor networks, is developed and practically implemented on popular off-the-shelf wireless motes. The algorithm can be used as part of protocols such as cooperative communications and hybrid-ARQ schemes which have been shown to be of major benefit for wireless communications. Using the packet combining implementation developed in this paper more than an 85% reduction in energy costs are possible over previous, similar approaches. Both simulated and practical experiments are developed in which packet combining is shown to offer up to approximately 2.5dB reduction in the required Signal-to-Noise Ratio (SNR) for a desired Packet Error Rate (PER). This is a welcome result as complex schemes, such as maximal-ratio combining, are not implementable on many of the resource constrained devices under consideration.

This communication presents an improved forward backward technique for the solution of electromagnetic wave scattering problems. The forward backward method displays rapid convergence when the eigenvalues of the associated iteration matrix are small. Conversely when the eigenvalues are large it displays poorer convergence. The hybridized method presented in this communication helps to circumvent the poor convergence of the forward backward method in the latter case by introducing an optimally sized correction in the approximate direction of the eigenvector associated with the iteration matrix's dominant eigenvalue. Numerical results are presented in order to demonstrate the convergence of the improved forward backward method.

Ray-tracing is an established technique for modelling wireless propagation over a large area in an e-cient manner. Existing frequency domain ray tracing simulators incur severe computational burden when extended to model an Ultra-Wideband (UWB) channel of several Giga-Hertz. We propose an acceleration algorithm that improves the e-ciency of such simulators by approximating the frequency domain response of individual ray at a reduced set of frequency points. Result show time savings up to 75% with a maximum relative error in the region of 0.8%.

The paper describes a reduced forward operator for solving electromagnetic scattering problems using a volume integral equation in conjunction with a conjugate gradient fast Fourier transform scheme. The reduction is obtained by decoupling of the interaction between the locations in the spatial computational domain at which there is non-zero contrast and those positions at which there is zero contrast. The decoupling is achieved by multiplication of the kernel by a diagonal matrix whose entries reflect the presence or absence of contrast at the associated point. Analysis supported by numerical experiments shows that the conjugate gradient algorithm applied to the reduced system converges more rapidly than when it is applied to the original system.

A novel technique is proposed to greatly enhance the convergence property of stationary iterative solvers applied for the solution of scattering from two-dimensional random rough surfaces. The proposed method extends the standard improvement step to enable the use of multiple correction vectors, leading to a significantly improved convergence rate of stationary iterative methods with negligible increases in computational complexity. Spectral acceleration technique is also applied to reduce a computational burden and storage requirements. Numerical results are shown to demonstrate the advantages of the proposed technique.