Improved Resource Allocation for TV White Space Network Based on Modified Firefly Algorithm

There is continued increased demand for dynamic spectrum access of TV White Spaces (TVWS) due to growing need for wireless broadband. Some of the use cases such as cellular (2G/3G/4G/5G) access to TVWS may have a high density of users that want to make use of TVWS. When there is a high density of secondary users (SUs) in a TVWS network, there is possibility of high interference among SUs that exceeds the desired threshold and also harmful interference to primary users (PUs). Optimization of resource allocation (power and spectrum allocation) is therefore necessary so as to protect PUs against harmful interference and to reduce the level of interference among SUs. Existing resource allocation optimization algorithms for a TVWS network ignore adjacent channel interference, interference among SUs or apply greedy algorithms which result in sub-optimal resource allocation. In this paper we propose an improved resource allocation algorithm based on continuous-binary firefly algorithm. Simulation is done using Matlab. Simulation results show that the proposed algorithm improves the SU sum throughput and SU signal to interference noise(SINR) ratio in the secondary network

Optimal Control of Transmission Power Management in Wireless Backbone Mesh Networks

International audienceno abstrac

Beam steering for circular switched parasitic arrays using a combinational approach

In this paper we present a method of electronic beam steering for circular switched parasitic array (SPA) antennas. In circular SPA antennas, one achieves azimuth beam steering by open-circuiting and short-circuiting different parasitic elements, usually with only one parasitic element open-circuited at a time. For the SPA antenna with few parasitic elements, this results in low azimuth beam steering resolution. In the proposed method, we iterate through different combinations of parasitic elements and the possible switch states of the lumped impedance loads connected to the parasitic elements. Our method aims to increase the azimuth beam steering resolution of the circular SPA antennas. The method is verified using a combination of simulation (using both MATLAB and WIPL-D) and a SPA antenna prototype implementation. The MATLAB code uses the induced EMF method, while the WIPL-D uses the Methods of Moment (MoM) for solving the antenna impedances. The three sets of results (simulations and measurement) match very well at 2.4 GHz. The results indicate the availability of more options (different loading configurations) for electronic beam switching that can be adopted to improve the beam steering resolution of circular SPA antennas

The 11th International Conference on Emerging Ubiquitous Systems and Pervasive Networks ( EUSPN 2020)

The potential of IoT in contributing towards sustainable economic development in Sub-Saharan Africa (SSA) through digital transformation and effective service delivery is widely accepted. However, the unreliability/unavailability of connectivity and power grid infrastructure as well as the unaffordability of the overall system hinders the implementation of a multi-layered IoT architecture for rural societal services in SSA. In this work, affordable IoT architecture that operates without reliance on broadband connectivity and power grid is developed. The architecture employs energy harvesting system and performs data processing, actuation decisions and network management locally by integrating a customized low-cost computationally capable device with the gateway. The sharing of this device among the water resource and quality management, healthcare and agriculture applications further reduces the overall system cost. The evaluation of LPWAN technologies reveals that LoRaWAN has lower cost with added benefits of adaptive data rate and largest community support while providing comparable performance and communication range with the other technologies. The relevant results of the analysis is communicated to end-users’ mobile device via 2G/3G GPRS. Hence, the proposed IoT architecture enables the implementation of IoT systems for improving efficiency in three key application areas at low cost.</p

The 11th International Conference on Emerging Ubiquitous Systems and Pervasive Networks (EUSPN 2020)

 Ensuring food security has become a challenge in Sub-Saharan Africa (SSA) due to combined effects of climate change, high population growth, and relying on rainfed farming. Governments are establishing shared irrigation infrastructure for smallholder farmers as part of the solutions for food security. However, the irrigated farms often failed to achieve the expected crop yield. This is partly due to lack of water management system in the irrigation infrastructure. In this work, IoT-based irrigation management system is proposed after investigating problems of irrigated farmlands in three SSA countries, Ethiopia, Kenya, and South Africa as case studies. Resource-efficient IoT architecture is developed that monitors soil, microclimate and water parameters and performs appropriate irrigation management. Indigenous farming and expert knowledge, regional weather information, crop and soil specific characteristics are also provided to the system for informed-decision making and efficient operation of the irrigation management system. In SSA, broadband connectivity and cloud services are either unavailable or expensive. To tackle these limitations, data processing, network management and irrigation decisions and communication to the farmers are carried out locally, without the involvement of any back-end servers. Furthermore, the use of green energy sources and resource-aware intelligent data analysis algorithm is studied. The intelligent data analysis helps to discover new knowledge that support further development of agricultural expert knowledge. The proposed IoT-based irrigation management system is expected to contribute towards long term and sustainable high crop yield with minimum resource consumption and impact to the biodiversity around the case farmlands.</p

Developing an optimal academic workload distribution model: a case study of an academic department at a university of technology in South Africa

The recent surge in demand for higher education has witnessed an increased number of students and the evolution of newer courses in Higher Education Institutions (HEIs) globally. This phenomenon has further precipitated the development of more efficient mechanisms for educational quality assurance with more student and outcome oriented. Academic work is notoriously difficult to quantify, but the rationale for managing academic workload is pillared on accountability required of the HEIs by stakeholders. Studies show that existing workload models in practice are not optimal and cannot guarantee fair, equitable, transparent and consistent distribution of academic work. This study aims to determine a mathematically optimal aggregate academic workload distribution (AAWLD) model in a case study department at a university of technology in South Africa. The aim was achieved by developing a low complex mathematical optimisation model numerically solved using Matrix Laboratory (MATLAB)TM software. Empirical data was collected using a developed on online survey questionnaire. Data from the empirical study from a population number (N = 161) and sample size (n = 63) as well as from the institutional academic workload norms were utilised to moderate the performance of the optimal AAWLD model. Further statistical tests were conducted using STATA and word cloud analyses tool to establish the statistically significant differences among the academic post levels with regard to their level of agreements on academic workload distribution preferences. Results showed that the developed optimal AAWLD model yielded optimal values of the academic workload commitments in a fair, equitable, transparent and consistent manner. The results also showed that developing an optimal AAWLD model is a catalyst for an improved job productivity and satisfaction among academics in a UoT context

Le contrôle de pouvoir dynamique dans la radio de colonne vertébrale fait concorder des réseaux : une approche décentralisée

The remarkable evolution of wireless networks into the next generation to provide ubiquitous and seamless broadband applications has recently triggered the emergence of Wireless Mesh Networks (WMNs). The WMNs comprise stationary Wireless Mesh Routers (WMRs) forming Wireless Backbone Mesh Networks (WBMNs) and mobile Wireless Mesh Clients (WMCs) forming the WMN access. While WMCs are limited in function and radio resources, the WMRs are expected to support heavy duty applications : that is, WMRs have gateway and bridge functions to integrate WMNs with other networks such as the Internet, cellular, IEEE 802.11, IEEE 802.15, IEEE 802.16, sensor networks, et cetera. Consequently, WMRs are constructed from fast switching radios or multiple radio devices operating on multiple frequency channels. WMRs are expected to be self-organized, self-configured and constitute a reliable and robust WBMN which needs to sustain high traffic volumes and long “online” time. However, meeting such stringent service expectations requires the development of decentralized dynamic transmission power control (DTPC) approaches. This thesis addresses the DTPC problem for both single and multiple channel WBMNs. For single channel networks, the problem is formulated as the minimization of both the link-centric and network-centric convex cost function. In order to solve this issue, multiple access transmission aware (MATA) models and algorithms are proposed. For multi-radio multi-channel (MRMC) WBMNs, the network is modelled as sets of unified channel graphs (UCGs), each consisting of interconnected active network users communicating on the same frequency channel. For each UCG set, the minimization of stochastic quadratic cost functions are developed subject to the dynamic Link State Information (LSI) equations from all UCGs. An energy-efficient multi-radio unification protocol (PMMUP) is then suggested at the Link-Layer (LL). Predictive estimation algorithms based on this protocol are proposed to solve such objective functions. To address transmission energy and packet instabilities, and interference across multiple channels, singularly-perturbed weakly-coupled (SPWC) control problems are formulated. In order to solve the SPWC transmission power control problem, a generalized higher-order recursive algorithm (HORA) that obtains the Riccati Stabilizing Solutions to the control problem is developed. The performance behaviours of the proposed models and algorithms are evaluated both analytically and through computer simulations. Several simulations are performed on a large number of randomly generated topologies. Simulation and analytical results confirm the efficacy of the proposed algorithms compared to the most recently studied techniquesL'évolution importante des réseaux sans fil tend à fournir les supports nécessaires aux applications ubiquitaires émergentes dans les réseaux Mesh sans fil. Les réseaux mesh comprennent des nœuds stationnaires qui remplissent la fonction de routage et appelés routeurs Mesh sans fil (WMR) et qui consitutent le réseau backbone sans fil (WBMN) ainsi que des nœuds clients mesh sans fil (WMCs). Alors que les WMCs sont limités en termes de fonctions et de resources radio, les WMRS fournissent des fonctions de pont et de passerelle afin de connecter les réseaux WMNs aux autres réseaux comme les réseaux cellulaires, les réseaux IEEE 802.11, les réseaux IEEE 802.16, ou tout simplement à Internet. Par conséquent, les réseaux WMRs sont construits à partir sur la base d'équipement radio de communication rapide et/ou multi-radio et multi-canaux. Les routeurs WMRs sont supposes être auto-organisés, auto-configurés et constituant un réseau WNMN robuste ce qui nécessite de soutenir des volumes importants de trafic de données et sur de longues périodes. Cependant, répondre à attentes élevées en termes de services nécessite le développement d'approches décentralisés pour le control dynamique des puissances de transmission (DTPC). La présente thèse se focalise sur le problème DTPC pour les deux cas de réseaux; utilisant un canal de communication et multicanaux. Pour les réseaux exploitant un seul canal, le problème est formulé en termes de problème d'optimisation où l'objectif est de minimiser en même temps des critères convexes associés aux liens et aux réseaux. Afin de résoudre ce problème, des modèles et des algorithmes, appelés MATA (multiple access transmission aware), ont été proposés. Pour les réseaux WBMNs utilisant des systèmes multi-radio et multi-canaux (MRMC), le réseau est modélisé par un ensemble de graphes appelés UCGs (unified channel graphs), chacun consistant les utilisateurs connectés au point d'accès en utilisant le même canal fréquentiel. Pour chaque ensemble UCG, le problème à résoudre un problème quadratique et stochastique soumis aux contraintes des états des liens dynamiques LSI (Link State Information) de tous les UCGs. Le protocole PMMUP, mutli-radio et minimisant la consummation énegétique, est propose au niveau de la couche liaison. Algorithmes d'estimation prédictive base sur ce protocol sont proposes pour résoudre les problèmes d'optimisation associés aux UGCs. Les problèmes énergétiques, les instabilités des queues et les interférences, sont formulés en termes de problèmes de commande optimale couplée, appelés SPWC (singularly-perturbed weakly-coupled). Pour résoudre les problèmes SPWC caractérisant le problème de commande optimal des energies de transmission, l'algorithme HORA (aeneralized higher-order recursive algorithm) qui permet d'obtenir les solutions stables pour les équations de Riccati a été développé. Les performes des modèles et algorithmes proposés dans le cadre de la présente thèse ont été évalués tant sur le plan théorique qu'en simulation. Différentes simulations ont été effectuées sur un large ensemble de topologies réseaux générés aléatoirement. Les résultats de simulation et analytiques Simulation confirment l'efficacité des algorithmes proposés par rapport à la majorité des techniques existante

Joint Full- and Half-Duplex Communication Strategy for MIMO Interference Channels

Although a full-duplex (FD) communication in K-links MIMO systems suffers from both self-interference and interuser interference, the bidirectional exchange of information between nodes on each of the K-links in FD significantly enhances the capacity of the wireless channel. On the other hand, a half-duplex (HD) communication is not affected by self-interference but faces the interuser interference. In order to take full advantages of the FD and HD communication modes, this article proposes a joint full- and half-duplex (FuHaDu) communication strategy for MIMO interference channels whereby K MIMO links capacity is enhanced, while both self-interference and interuser interference are reduced. Specifically, the proposed joint FuHaDu model is based on Rosen’s gradient projection method for maximising the weighted sum rate (WSR) of optimal transmitter and receiver filters. The computer simulation results show that the joint FuHaDu strategy enhances the spectral efficiency when compared to the purely HD and FD conventional approaches. The results further reveal that channel capacity doubles as the number of antennas is increased from 2×2 to 4×4. The most significant capacity performance is noted with the 4×3 MIMO configuration for the HD, FD, and FuHaDu strategies