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Item Towards affordable broadband communication: a quantitative assessment of TV white space in Tanzania(Springer Nature, 2017) Matogoro, Jabhera; Mvungi, Nerey H.; Justinian, Anatory; Karandikar, Abhay; Singh, JaspreetA quantitative assessment of TV White Space in Tanzania was conducted to assess the level of spectrum utilization as well as a key milestone towards the use of white space for affordable broadband communication. Two approaches have been used; pollution and protection viewpoints and experimental spectrum measurements based on energy detection principle. The study focused on 470–694 MHz UHF spectrum band which is used for digital terrestrial television in Tanzania. It was found that, more than 120 MHz is available as white space in various locations in Tanzania when pollution and protection view point was used and about 184 MHz are available as white space in Dodoma urban using experimental spectrum measurements and almost 100% of the available frequencies are not used in Dodoma rural. Both approaches revealed that there is low spectrum utilization and therefore presents a best case towards development of dynamic spectrum access technologies in TanzaniaItem Investigation of radio propagation characteristics in UHF band over straight and circular paths in central Tanzania(IEEE, 2021) Matogoro, Jabhera; Mfupe, Luzango; Mvungi, Nerei; Anatory, JustinianA study was conducted to investigate radio propagation characteristics in ultra-high frequency (UHF) bands over straight and circular paths in central Tanzania. The received signal power values (in dBm) were collected using a spectrum analyzer in straight and circular paths. The collected values were further converted to path loss values and validated against those computed from theoretical formulas of ITU-R P.452-16, ITU-R P.1812-4, Hata and Longley-Rice models. The study used the experimental spectrum measurements approach and Pearson’s correlation coefficient (PCC) to determine the best-fit propagation model for the UHF spectrum band allocated for digital terrestrial television (DTT) in central Tanzania. The DTT spectrum band ranges from 470 – 694 MHz in Tanzania after successfully migrating from analogue to digital broadcasting. The study found a significant difference between measured path loss values and those computed from theoretical formulas. The Hata and Longley-Rice models had a better convergence with reality for most of the fixed locations. The accuracy of the empirical propagation model plays a critical role in the optimal planning of the television white space (TVWS) network and contributes to efficient spectrum utilization.Item Dendritic cell algorithm enhancement using fuzzy inference system for network intrusion detection(IEEE, 2019) Elisa, Noe; Yang, Longzhi; Fu, Xin; Naik, NitinDendritic cell algorithm (DCA) is an immune-inspired classification algorithm which is developed for the purpose of anomaly detection in computer networks. The DCA uses a weighted function in its context detection phase to process three categories of input signals including safe, danger and pathogenic associated molecular pattern to three output context values termed as co-stimulatory, mature and semi-mature, which are then used to perform classification. The weighted function used by the DCA requires either manually pre-defined weights usually provided by the immunologists, or empirically derived weights from the training dataset. Neither of these is sufficiently flexible to work with different datasets to produce optimum classification result. To address such limitation, this work proposes an approach for computing the three output context values of the DCA by employing the recently proposed TSK+ fuzzy inference system, such that the weights are always optimal for the provided data set regarding a specific application. The proposed approach was validated and evaluated by applying it to the two popular datasets KDD99 and UNSW NB15. The results from the experiments demonstrate that, the proposed approach outperforms the conventional DCA in terms of classification accuracy.Item Short-term load forecasting for improved service restoration in electrical power systems: A case of Tanzania(IEEE, 2020) Mwifunyi, Rukia J.; Kissaka, Mussa M.; Mvungi, Nerey H.Reliable operation of the power system and efficient utilization of its resources requires load demand forecasting in a wide range of time leads, from minutes to several days. Underestimation of load demand forces the power system to operate in a vulnerable region to the disturbance. In the Tanzanian electrical power distribution network, peak hour load demand values are used during service restoration resulting in prolonged load shedding. This study aims at developing a short-term load forecasting model to be used during service restoration for improved service reliability. Several methods have been devised for short-term load forecasting including conventional statistical approaches and data-driven approaches. Data-driven approaches perform well in load forecasting due to its ability in learning features for the dataset with nonlinear characteristics like load demand dataset. The study has adopted an experimental design approach in developing the short-term load foresting model using six years datasets from 2014 to 2019 with twenty minutes resolution from the Tanzania power distribution network. A total of 141,749 datasets were used and three deep learning models namely Long Short-Term Memory (LSTM), Recurrent Neural Network (RNN) and Gated Recurrent Unit (GRU) were used during the experiments. It has been observed that the LSTM outperforms the RNN and GRU with forecasting accuracy of 96.43%. The future work will be the development of a distributed algorithm for service restoration considering stochastic nature of load demand using developed forecasting load model.Item Agents based service restoration in electrical secondary distribution network(IEEE Xplore, 2019) Mwifunyi, Rukia J.; Mvungi, Nerey H.; Kissaka, Mussa M.Service Restoration (SR) is one of the fundamental functionalities of distribution management system during the fault management process. Several approaches have been devised to solve the SR problem on the distribution network including centralized and distributed approaches. Most of the existing studies focused on the service restoration in the medium voltage network with very few focusing on the Secondary Distribution Network (SDN). In most countries including Tanzania, the service restoration is accomplished manually through relying on operational experiences, rated capacity of the transformers and peak hour demand for decision making. This study aimed at designing a distributed algorithm based on the multiagent system for SR in the SDN. The study has been conducted through intensive literature review together with focus group discussion with key stakeholders from the utility company, study visits to the Tanzania SDN in Dar es Salaam region and interviews with the technical people. SDN with three transformers rated at 315kVA, 200kVA and 100kVA have been chosen as the pilot site for designing the distributed algorithm. The designed algorithm includes designing of multiagent system, objective functions to be optimized and design for the equipment specifications and power system network topology to support SR. Four agents namely, Control Agent, Grid Agent, Load Agent and Switch Agent have been found to be optimal for the SR process. The designed restoration process mainly focuses on load transfer to the nearby transformer and load shedding. The future work will focus on the real implementation of the designed algorithm and consideration of the integration of the renewable distributed generations.Item Automated recommendation of software refactorings based on feature requests(IEEE, 2019) Nyamawe, Ally S.; Liu, Hui; Niu, Nan; Umer, Qasim; Niu, ZhendongDuring software evolution, developers often receive new requirements expressed as feature requests. To implement the requested features, developers have to perform necessary modifications (refactorings) to prepare for new adaptation that accommodates the new requirements. Software refactoring is a well-known technique that has been extensively used to improve software quality such as maintainability and extensibility. However, it is often challenging to determine which kind of refactorings should be applied. Consequently, several approaches based on various heuristics have been proposed to recommend refactorings. However, there is still lack of automated support to recommend refactorings given a feature request. To this end, in this paper, we propose a novel approach that recommends refactorings based on the history of the previously requested features and applied refactorings. First, we exploit the state of-the-art refactoring detection tools to identify the previous refactorings applied to implement the past feature requests. Second, we train a machine classifier with the history data of the feature requests and refactorings applied on the commits that implemented the corresponding feature requests. The machine classifier is then used to predict refactorings for new feature requests. We evaluate the proposed approach on the dataset of 43 open source Java projects and the results suggest that the proposed approach can accurately recommend refactorings (average precision 73%).Item Re-visiting design-after-design: Reflecting implementation mediators connectedness in distributed participatory design activities(ACM Press, 2014) Shidende, Nima Herman; Mörtberg, ChristinaThis paper aims at an extended understanding of the design facilitators' role, here implementation mediators, in participatory design practices. In reflecting connectedness between use and design in a distributed open source software design practice, a particular focus is devoted to the implementation mediator’s interaction between local users, global software developers, and local designers who are geographically distributed, possess different technological skills, and different work experiences. The implementation mediators’ insights are useful in the design of large information systems that involve distributed actors. A maternal and child health setting in Tanzania was the case in this study. An ethnographic study involving interactions with global developers and participative activities in local health practices were conducted. In addition, mediators connected local and global designers to configure a computer system for a particular context; configured participation, involving health workers in designing practices. We present the role of the implementation mediators and its related participatory activities by using the notion of design-after-design. We also highlight the challenges which could face implementation mediators in distributed participatory design activities.Item Complex adaptive notch filters for frequency estimation of three-phase power systems(Institute of Electictrical and Electronics Engineers, 2013) Nishimura, Shotaro; Mvuma, Aloys; Hinamoto, TakaoThis paper presents a new technique for adaptive estimation of the frequency of unbalanced three-phase power systems using complex coefficient first-order notch filters. The input complex sinusoid is given by a sum of sequences with positive and negative frequencies. The analytical expression of a estimation error oscillation introduced by the sequence with negative frequency has been derived. Closed form expression for frequency tracking error has been also derived for a complex linear chirp signal. Computer simulation results are presented to validate the analysis.Item Numerical estimation of electric field radiation behaviour for BPLC system(International Conference on Electronics and Power Engineering, 2013) Naiman, S.; Kissaka, M. M.; Hamad, O. F.; Anatory, J.Radiation on BPLC caused by presence of high frequency communicating signal is discussed in this paper. The paper presents the derived mathematical model express electric field radiation behavior of BPLC system. The model was developed using the combined numerical method of moment (MOM) and transmission line transient (TLT) method utilizing maxwell integral equation to predict the radiation over the line. The mathematical model was validated using CST commercial software and results show that there is a good agreement in terms of radiation pattern in time and frequency domain. Other tests such as variation on the observation distance (3m, 7m and 10m) from line and connected load (0Ω to infinity) both shows good conformity.Item Tracking properties of complex adaptive notch filter for detection of multiple real sinusoids(Institute of Electictrical and Electronics Engineers, 2013) Nishimura, Shotaro; Mvuma, Aloys; Hinamoto, TakaoThis paper presents a new realization of adaptive notch filter based on a cascade of adaptive IIR notch filters using complex coefficient first-order notch filters. The input is multiple real linear chirp signals embedded in a white Gaussian noise. Closed-form expression for frequency tracking mean square error (MSE) is given. Optimum step size parameter and notch bandwidth coefficient that minimize the tracking MSE are also derived. Computer simulation results are presented to validate the analysis.