Joseph Chuma | Botswana International University of Science & Technology (original) (raw)

Papers by Joseph Chuma

Proceedings of the 19th IFAC World Congress, 2014

A prototype rotary valve engine has been built from a conventional single piston generator. In th... more A prototype rotary valve engine has been built from a conventional single piston generator. In this study, an engine control unit, ECU, is designed, tested and implemented for the purpose of carrying out the primary engine functions of sparking, fuelling and valve events control. The rotary valve engine has no camshaft, therefore, only a crankshaft (optical) sensor is required. The controller has also the advantage of turning the engine in either direction, removing the need for a reverse gear. Full control over valve events, together with crank motion independent sparking, removes the need for a throttle valve and a mechanical starter. With the valve turning freely, no feedback sensing is necessary. The proposed ECU has been designed, successfully tested and implemented on ALTERA's UP1 prototyping board. The FPGA programmable device used is the EPM7064SLC44-5.

Electronics and Communications in Japan (Part II: Electronics), 2006

In this paper, a new equivalent circuit representation for the electromagnetic field coupling bet... more In this paper, a new equivalent circuit representation for the electromagnetic field coupling between distributedline resonators is discussed. Based on this circuit, the coupling coefficient is defined. In this definition, the coupling coefficient between resonators takes a positive, negative, or zero value. Hence, this equivalent circuit representation is useful in the design of multipole filters with poles in the stopband, in which positive and negative coupling are needed. Based on this definition, the design of an elliptic function four-pole bandpass filter is carried out with the Sonnet em simulator and the effectiveness of the approach is discussed.

In this paper, the low-loss coaxial probe fed microwave cavity filter is presented. The filter ha... more In this paper, the low-loss coaxial probe fed microwave cavity filter is presented. The filter has recently shown great performance improvement in its selectivity and S-parameter response, but the rate of signal to noise ratio due to spurious modes in the pass band is significantly too high to ignore. A 2nd order band pass filter is investigated and its S-parameter response analysed by employing improved dielectric-loaded cavity resonators. The design is based on a low pass Chebyshev prototype at 1 dB insertion loss and 10 dB return loss. An efficient analytical method for reducing the spurious bandwidth of the filter is also devised to improve the filter response. The results shows that the filter, on its single mode operation state, provides increased selectivity and a significant amount of Q values are achieved to reduce the transmission losses.

Iet Communications, Apr 1, 2020

We investigate physical layer security design, which employs random linear network coding with op... more We investigate physical layer security design, which employs random linear network coding with opportunistic relaying and jamming to exploit the secrecy benefit of both source and relay transmissions. The proposed scheme requires the source to transmit artificial noise along with a confidential message. Moreover, in order to further improve the dynamical behaviour of the network against an eavesdropping attack, aggregated power controlled transmissions with optimal power allocation strategy is considered. The network security is accurately characterized by the probability that the eavesdropper will manage to intercept a sufficient number of coded packets to partially or fully recover the confidential message.

Journal of Computer Science, Jul 1, 2017

Network traffic model and analysis provides the average load, bandwidth requirements and the diff... more Network traffic model and analysis provides the average load, bandwidth requirements and the different application of the available bandwidth for a particular network, in addition to several other details of the network. This paper presents mathematical model used for modelling real world problems using Botswana International University of Science and technology (BIUST) network traffic as a case. Sophisticated analysis of data is done to model the BIUST network with the succor of statistics, as it implies the collection and interpretation of data through mathematical processes called stochastic processes. From the attained results, the model and estimation of packet traffic distribution for BIUST Network based on Pareto distribution, it was perceived that about 20% of the users had about 80% of the bandwidth consumed.

Botswana Journal of Technology, Mar 4, 2010

Advances in mobile technology, due to the rapid growth of mobile wireless systems, coupled with s... more Advances in mobile technology, due to the rapid growth of mobile wireless systems, coupled with stringent selectivity requirements, have led to the need for smaller and lighter high quality filters. The slotted cylindrical ring resonator is one resonator considered promising in the development of high quality compact filters for mobile communication systems due to its small size and medium to high Q-factor [1]. In this paper the Transmission Line Modeling method is used to determine the effects of using a high dielectric constant material on the size and coupling constant of the resonator. Modeling and simulations are done using Microstripes, a commercial TLM field solver from Flomerics. The paper shows that by placing a high dielectric constant material in the resonator gap the resonant size is decreased and the coupling improved. Keywords: Slotted cylindrical ring resonator, resonant frequency, electric coupling, magnetic coupling, Transmission line modeling

IEEE Access, 2022

This treatise presents a framework for the optimisation of a colour-based optical spatial modulat... more This treatise presents a framework for the optimisation of a colour-based optical spatial modulation for visible light communication (VLC). The focus is particularly on the conflicting interests between illuminance and signal transmission. The system under consideration is configured with a non-lineof-sight (NLoS) model, based on the joint use of colour shift keying (CSK) and optical spatial modulation (OSM) with intensity modulation and direct detection (IM/DD). With the adaptation of the aforementioned optical techniques and convex optimisation, the design and development of a colour-based optical wireless system is carried out. Firstly, an optimisation problem with the intention of minimising the total luminous intensities of the light emitting diode (LED) arrays subject to the transmitting LED array's optical power budget, minimum required illuminance level, LED-user channel conditions and latency intolerant users' (LITUs) quality-of-service (QoS) target constraints is defined. Secondly, a coordinated algorithm for the selection of a transmitting LED array, maintenance of a particular illuminance and signal-to-interferenceplus noise ratio (SINR) levels during symbol transmission is designed. Lastly, through computer simulations, a numerical analysis is carried out to demonstrate and evaluate the performance of the algorithm. During the transmission of all symbols, the proposed framework is capable of satisfying the SINR target for LITUs while reducing the optical power by approximately 20% to 25% and 20% to 75% for transmitting and non-transmitting LED arrays, respectively. Additionally, provided that the required illuminance level is specified within the standardised levels of 300 lux to 1500 lux, the proposed system can provide adequate illuminance as per the users' requirement at all points where either a LITU or a latency tolerant user (LTU) is located at any given instance. However, fair SINR levels are not guaranteed at the points where the LTUs are positioned. On the other hand, the algorithm disposes low illuminance levels ranging from 100 lux to 250 lux at locations towards the room boundaries where there are no users. The proposed system is able to achieve data rates of 5 Mbps to 25 Mbps using commercially-off-the-shelf LEDs.

This paper proposes a system for remotely monitoring the behavior of a vehicle. It monitors a veh... more This paper proposes a system for remotely monitoring the behavior of a vehicle. It monitors a vehicle in terms of four parameters which are engine temperature, rotational speed of the crankshaft and as well as the frequency and amplitude due to the vibration of the vehicle engine. These parameters can be used to trace malfunctions leading to abnormalities in the parameters. Diagnostics data are sent to the vehicle owner and it's mechanic through the Cloud. The owner of the vehicle and the mechanic can visualize the data on their smart phones. A Liquid Crystal Display screen on the dashboard also shows the values of the parameters being continuously measured. An application was created for the system to allow for visualization of diagnostics data, manual scanning of the vehicle and determination of it's location. The system has stored threshold values for the parameters being monitored. If a threshold value is exceeded, the system sends a notification to the owner and the mechanic. Four Internet of Things protocols are used to send data. These are General Packet Radio Service, Wireless Fidelity, Bluetooth and Zigbee. The system architecture allows vehicles to serve as relays for each other in some situations. The relay actions are achieved by Bluetooth and Zigbee. The system was simulated in Proteus professional software and it was found to be operational. A prototype was also constructed and tested, and proved to be functional. The application could also receive notifications accordingly.

Journal of Engineering and Applied Sciences, 2018

IOP conference series, Mar 1, 2016

The effects of conductor disc in a dielectric loaded combline resonator on its spurious performan... more The effects of conductor disc in a dielectric loaded combline resonator on its spurious performance, unloaded quality factor (Qu), and coupling coefficients are analysed using a commercial electromagnetic software package CST Microwave Studio (CST MWS). The disc improves the spurious free band but simultaneously deteriorates the Qu. The presence of the disc substantially improves the electric coupling by a factor of 1.891 for an aperture opening of 12 mm, while it has insignificant effect on the magnetic coupling.

IEEE Access

Procedia Manufacturing

Variable valve timing (VVT) enables the valve events to vary with RPM for optimum engine performa... more Variable valve timing (VVT) enables the valve events to vary with RPM for optimum engine performance. It alters the timing on the camshaft using pneumatic, hydraulic or electromechanical means. The Cameless Stepping Valve system uses software controlled valve events. Here, VVT is achieved by advancing/retarding valve events using only the direction of the piston and interpolated virtual angles on the flywheel. The engine model used has an optimum RPM of 24000, which translates to a period of 2.5mS. A 1 0 angle increment on the flywheel corresponds to 6.9µS. As a result, a retardation/advance of 1 0 would mean that the valve will open/close 6.9µS after the current/previous TDC. A 9bit real-time digital counter was triggered to count the calculated angles at every Otto Cycle so that advance/retard is updated at every RPM. In this project, it was demonstrated that valve event control is possible using interpolation of virtual angles on the flywheel, replacing a multi-tooth timing wheel. The proposed technique is more accurate and robust.

2017 IEEE Radio and Antenna Days of the Indian Ocean (RADIO), 2017

The effect of thickness of a hollow post in a combline resonator on the resonant frequency, coupl... more The effect of thickness of a hollow post in a combline resonator on the resonant frequency, coupling coefficients and spurious performance are analysed. It is shown that both the electric and magnetic couplings are not significantly affected by the size of the thickness of the hollow post, whereas the resonant frequency and spurious free band both change. When the thickness of the hollow post reduces the spurious free band deteriorates while the resonant frequency increases.

Green Internet of Things Sensor Networks, 2020

IoT opportunities and application domains are endless and equally have shortcomings that need to ... more IoT opportunities and application domains are endless and equally have shortcomings that need to be addressed. This section broadens the open research areas that need to be further investigated to address the challenges in IoT networks. We highlight potential future directions and futuristic applications that can help alleviate these challenges. Although the application of IoT has been widely adopted, an extensive research effort still needs to be done in this direction. This chapter aims to further discuss and collate future work direction in the area of IoT sensor networks to give insights to researchers for areas that still need investigation in wireless IoT sensor networks. Open research areas in IoT sensor networks include hardware security, lack of lightweight cryptographic algorithms, lack of trust management systems, lack of lightweight, secure routing protocols, and anti-malware solutions. Future challenges have been exposed in this chapter, with the hope of encouraging fur...

The proliferation of the Internet has birthed the emergence of the Internet of Things (IoT), whic... more The proliferation of the Internet has birthed the emergence of the Internet of Things (IoT), which is rapidly evolving and already taking strides as a universal solution to connected things. IoT transforms devices to be smart, to deliver exceptional services, and to transform everyday settings. The rapid evolution of IoT has brought along many benefits. However, IoT has also brought about ambiguity and several security concerns to IoT adopters. Security issues are the most critical challenges that need to be addressed in promoting the adoption and development of IoT systems. Addressing these challenges using a layered approach has not been adequately addressed. Several studies have proposed solutions to address security issues. Nevertheless, they have failed to propose an appropriate layered security approach or framework that addresses the majority of the security issues using a cross-layered approach. The aim of this work is to highlight security issues and challenges and provide ...

Due to the advances in technology, growth of IoT, and the numerous advantages that come with havi... more Due to the advances in technology, growth of IoT, and the numerous advantages that come with having connected devices, almost any device can be made into a smart IoT device, even a simple day-to-day home appliance. Limitations of what can be made into a smart IoT device are based on the cost and practicality of the device. Examples of smart IoT devices that can be found in a building include smart light bulbs, smart kettles, smart switches, smart refrigerators, and many more. In this chapter, we report on the design and implementation of smart IoT devices and applications through the solving of an example problem of adding security and access control to a building’s main electricity. Through this chapter, one will become familiar with the design process of making smart IoT devices. Each section in this chapter shows the methods and procedures undertaken to design the smart IoT devices used to solve the given example problem. This includes the problem definition, aim, and objectives....