Secure Precise Clock Synchronization for Interconnected Body Area Networks

Secure time synchronization is a paramount service for wireless sensor networks (WSNs) constituted by multiple interconnected body area networks (BANs). We propose a novel approach to securely and efficiently synchronize nodes at BAN level and/or WSN level. Each BAN develops its own notion of time. To this effect, the nodes of a BAN synchronize with their BAN controller node. Moreover, controller nodes of different BANs cooperate to agree on a WSN global and/or to transfer UTC time. To reduce the number of exchanged synchronization messages, we use an environmental-aware time prediction algorithm. The performance analysis in this paper shows that our approach exhibits very advanced security, accuracy, precision, and low-energy trade-off. For comparable precision, our proposal outstands related clock synchronization protocols in energy efficiency and risk of attacks. These results are based on computations

Visual and Camera Sensors

This book includes 13 papers published in Special Issue ("Visual and Camera Sensors") of the journal Sensors. The goal of this Special Issue was to invite high-quality, state-of-the-art research papers dealing with challenging issues in visual and camera sensors

The effects of network factors on the performance of 3G UMTS applications

Includes bibliographical references (leaves 139-148).3G is the wireless network technology expected to allow wireless applications to perform on par with wired applications. However 3G has factors which limit its performance. These factors include both device factors such as small screens, limited battery power and life, as well as network factors such as high delay networks and low bandwidths. This thesis investigates the following: how network factors affect the performance of 3G UMTS applications; which network factors have the most significant impact on a specific application; whether there are any minimum requirements needed for an application. Eight popular 3G applications were investigated: FTP, email, MMS, SMS, HTTP web browsing, broadcast media, video calling and streaming media

Object Tracking

Object tracking consists in estimation of trajectory of moving objects in the sequence of images. Automation of the computer object tracking is a difficult task. Dynamics of multiple parameters changes representing features and motion of the objects, and temporary partial or full occlusion of the tracked objects have to be considered. This monograph presents the development of object tracking algorithms, methods and systems. Both, state of the art of object tracking methods and also the new trends in research are described in this book. Fourteen chapters are split into two sections. Section 1 presents new theoretical ideas whereas Section 2 presents real-life applications. Despite the variety of topics contained in this monograph it constitutes a consisted knowledge in the field of computer object tracking. The intention of editor was to follow up the very quick progress in the developing of methods as well as extension of the application

Voice over IP

The area that this thesis covers is Voice over IP (or IP Telephony as it is sometimes called) over Private networks and not over the Internet. There is a distinction to be made between the two even though the term is loosely applied to both. IP Telephony over Private Networks involve calls made over private WANs using IP telephony protocols while IP Telephony over the Internet involve calls made over the public Internet using IP telephony protocols. Since the network is private, service is reliable because the network owner can control how resources are allocated to various applications, such as telephony services. The public Internet on the other hand is a public, largely unmanaged network that offers no reliable service guarantee. Calls placed over the Internet can be low in quality, but given the low price, some find this solution attractive. What started off as an Internet Revolution with free phone calls being offered to the general public using their multimedia computers has turned into a telecommunication revolution where enterprises are beginning to converge their data and voice networks into one network. In retrospect, an enterprise\u27s data networks are being leveraged for telephony. The communication industry has come full circle. Earlier in the decade data was being transmitted over the public voice networks and now voice is just another application which is/will be run over the enterprises existing data networks. We shall see in this thesis the problems that are encountered while sending Voice over Data networks using the underlying IP Protocol and the corrective steps taken by the Industry to resolve these multitudes of issues. Paul M. Zam who is collaborating in this Joint Thesis/project on VoIP will substantiate this theoretical research with his practical findings. On reading this paper the reader will gain an insight in the issues revolving the implementation of VoIP in an enterprises private network as well the technical data, which sheds more light on the same. Thus the premise of this joint thesis/project is to analyze the current status of the technology and present a business case scenario where an organization will be able to use this information

Agent-based modelling of paratransit as an intelligent complex adaptive system to improve efficiency

Thesis (PhD)--Stellenbosch University, 2021.ENGLISH ABSTRACT: Urban residents in Sub-Saharan Africa (SSA) face mobility challenges that limit theiraccess to jobs, services, markets, and socioeconomic opportunities. In most SSA cities,public transport is predominantly provided by the inefficient paratransit system – a flex-ible mode of passenger transport consisting of privately-owned, low-capacity unscheduledminibuses and motorcycle taxis. There is growing interest among city authorities andurban transport researchers in addressing the inefficiency problem associated with para-transit. Several approaches, such as complete overhaul to bus rapid transit (BRT), andphased banning of paratransit from the cities have previously been proposed and con-comitant implementation projects started. However, most of such projects have eitherfailed to take off, or they have stalled. This is likely because of the huge capital invest-ment required, the unique social and cultural dynamics associated with “third world”countries, and urban sprawl due to poor city planning. This study departs from the com-mon perspective held by several researchers and city authorities who view paratransit as“chaotic”, thus, the justification for its total overhaul and banning. Instead, this studyaims to leverage the beneficial aspects of existing paratransit – such as flexibility, demand-responsiveness and near-ubiquitous coverage – with the elusive objective of achieving amore efficient paratransit state as a result.Through theoretical modelling, field study and experimental approaches, this studyaimed to improve the efficiency of minibus taxis paratransit systems. The theoretical mod-elling work involved modelling paratransit systems as complex adaptive systems (CAS)and developing an agent-based model (ABM) for minibus taxi operations in an organically-evolved paratransit setting. The field study involved an in-depth investigation of minibustaxi operations in Kampala’s paratransit system, and collection and analysis of minibustaxi movement data that was used to validate the agent-based model. The experimen-tal approaches involved three separate simulation experiments, simulating the minibustaxi transportation dynamics with varying levels of agents’ intelligence and situational awareness. Machine learning methods, such as random forests and convolutional neuralnetworks were used to train agents in the subsequent simulation experiment to improvetheir intelligence during decision making. At each stage, several efficiency metrics’ valuessuch as passenger waiting time and minibus taxi occupancy were collected. The resultsfrom the experiments showed that there was an improvement in the overall efficiency ofthe minibus taxi paratransit system. For instance, the average passenger waiting time re-duced from 1.2 hours to 30 minutes, indicating a 55% improvement. Whereas the averageminibus taxi occupancy increased from 42% to 51%, indicating a 21% improvement. Ac-cordingly, we concluded that improving the micro-level agents’ intelligence and situationalawareness, results in an overall increase in the efficiency of the paratransit system.To the transportation researchers, we recommend further work on using ABM toinclude other modes of paratransit transport such as the three-wheeled rickshaws andmotorcycle taxis (boda bodas). To the city authorities, we recommend the integration ofsmart mobility and ICT applications into the paratransit ecosystem to support journeyplanning, booking, scheduling, and fare collection.AFRIKAANSE OPSOMMING: Stedelike inwoners in Afrika Suid van die Sahara (SSA) word gekonfronteer met mo-biliteitsuitdagings wat hul toegang tot werk, dienste, markte en sosio-ekonomiese geleen-thede beperk. In die meeste SSA-stede word openbare vervoer oorheersend aangebieddeur die ondoeltreffende paratransit-stelsel -’n buigsame manier van passasiersvervoerwat bestaan uit private lae-volume busse en huur-motorfietse. Daar is toenemende be-langstelling onder stadsowerhede en navorsers van stedelike vervoer om die ondoeltref-fendheidsprobleem so eie aan paratransit. Verskeie benaderings, soos byvoorbeeld dievolledige opknapping van busvervoer (BRT) en ’n gefaseerde verbod op paratransit instede, is voorheen voorgestel en verwante implementeringsprojekte is van stapel gestuur.Die meeste van hierdie projekte het egter nie daarin geslaag om te begin nie, of hulleis gestaak. Dit is waarskynlik as gevolg van die groot kapitaalinvestering wat benodigword, die unieke sosiale en kulturele dinamika wat verband hou met lande van die ”derdewˆereld” en stedelike uitbreiding as gevolg van swak stadsbeplanning.Hierdie studie wyk af van die algemene perspektief wat deur verskeie navorsers en stad-sowerhede gehou word, wat paratransit as “chaoties” beskou, en dus van die regverdigingvir die totale opknapping en verbod daarvan. In plaas daarvan beoog hierdie studie omdie voordelige aspekte van paratransit te versterk - soos buigsaamheid, aanvraagresponsi-witeit en byna alomteenwoordige dekking - met die hoop om ’n doeltreffender paratransit-staat as gevolg daarvan te bewerkstellig.Deur middel van teoretiese modellering, veldstudies? en eksperimentele benaderings,het hierdie studie ten doel gehad om die doeltreffendheid van minibustaxi-paratransitstelselste verbeter. Die teoretiese modelleringswerk behels die modellering van paratransitstelselsas komplekse aanpasbare stelsels (CAS) en die ontwikkeling van ’n agent-gebaseerde model(ABM) vir minibustaxibedrywighede in ’n organies-ontwikkelde paratransit-omgewing.Die veldstudie behels ’n diepgaande ondersoek na minibustaxibedrywighede in Kampala se paratransit-stelsel, en versameling en ontleding van minibustaxibewegingsdata wat ge-bruik is om die agent-gebaseerde model te bekragtig. Die eksperimentele benaderings hetdrie afsonderlike simulasie-eksperimente behels, wat die minibustaxi-vervoerdinamika metverskillende vlakke van agente se intelligensie en situasiebewustheid simuleer. Masjienleer-metodes soos ewekansige woude en evolusionˆere neurale netwerke is gebruik om agente indie daaropvolgende simulasie-eksperiment op te lei om hul intelligensie tydens besluitnem-ing te verbeter. In elke stadium is verskeie waardes vir doeltreffendheid soos die passasier-swagtyd en die besetting van minibustaxi’s versamel. Die resultate van die eksperimentehet getoon dat die algehele doeltreffendheid van die minibus-paratransitstelsel verbeterhet. Byvoorbeeld, die gemiddelde passasierwagtyd verminder van 1,2 uur tot 30 minute,wat dui op ’n 55% verbetering. Terwyl die gemiddelde besetting van minibustaxi van 42%tot 51% gestyg het, wat dui op ’n verbetering van 21%.Gevolglik het ons tot die gevolgtrekking gekom dat die verbetering van die intelligensieen situasiebewustheid van die mikrovlakagente tot ’n algehele toename in die doeltreffend-heid van die paratransitstelsel lei.Vir die vervoernavorser beveel ons verdere ABM-werk aan om ander maniere vanparatransit-vervoer soos die driewiel-riksja’s en motorfiets-taxi’s (boda bodas) in te sluit.Aan die stadsowerhede beveel ons die integrasie van slim mobiliteit- en IKT-toepassingsaan in die paratransit-ekosisteem om reisbeplanning, bespreking, skedulering en tariefin-vordering te ondersteun.Doctora