Device-to-device communication has been suggested as a complement to traditional cellular networks as a means of offloading cellular traffic. In this thesis we explore a solution for device-to-device communication based on opportunistic content distribution in a content-centric network. Communication opportunities arise as mobile nodes roam around in an area and occasionally enter in direct communication range with one another. We consider a node to be a pedestrian equipped with a mobile device and explore the properties of opportunistic communication in the context of content dissemination in urban areas. The contributions of this thesis lie in three areas. We first study human mobility as one of the main enablers of opportunistic communication. We introduce traces collected from a realistic pedestrian mobility simulator and demonstrate that the performance of opportunistic networks is not very sensitive to the accurate estimation of the probability distributions of mobility parameters. However, capturing the space in which mobility occurs may be of high importance. Secondly, we design and implement a middleware for opportunistic content-centric networking, and we evaluate it via a small-scale testbed, as well as through extensive simulations. We conclude that energy-saving mechanisms should be part of the middleware design, while caching should be considered only as an add-on feature. Thirdly, we present and evaluate three different energy-saving mechanisms in the context of opportunistic networking: a dual-radio architecture, an asynchronous duty-cycling scheme, and an energy-aware algorithm which takes into account node selfishness. We evaluate our proposals analytically and via simulations. We demonstrate that when a critical mass of participants is available, the performance of the opportunistic network is comparable to downloading contents directly via the cellular network in terms of energy consumption while offloading large traffic volumes from the operator. / <p>QC 20151120</p>

Thesis (MBA (Business Management))--Stellenbosch University, 2008. / ENGLISH ABSTRACT: The world today is facing many energy challenges such as power outages experienced internationally and in South Africa. The demand for energy is constantly increasing and is creating environmental problems such as climate change, which is presently a major concern to society. This study is an attempt to establish how energy saving mechanisms such as the elimination of non-essential power can add economic value within the mining industry. This paper examines the effect of non-essential power and how it could assist companies to reduce their energy consumption, aid local power utilities in a crisis and maintain normal production levels. This research report was based on an investigation for power saving opportunities at a mining company during a power crisis. The paper looks at energy efficiency and the barriers to the adoption of energy savings. Companies in general do not have a structured way of addressing non-essential power saving. Companies are not aware of the value such initiatives could have on corporate responsibility and sustainable reporting. The benefits of energy efficiency and nonessential power on the triple bottom line are not clearly documented in literature. When comparing the impact of non-essential power on the triple bottom line, it became obvious that further research is required in order to prove whether it influences the social aspect. The impact of power generation on the global environment has not been clearly calculated and linked to the value of saving power. The literature review highlighted that companies are focusing on long-term initiatives instead of smaller initiatives, which requires less effort. During the investigation of the mining company, it was found that not much effort was made during the design stages in separating the electrical circuits from non-essential and essential power. The author concludes that switching off non-essential power held economic and environmental benefits for the mining company. The author therefore concludes that switching off non-essential power impacts positively on the economic and environmental part of the triple bottom line. It was found that the elimination of non-essential power is easy to implement with minimum investment and effort. Furthermore, the savings from these initiatives could easily be measured to calculate the return on the investment. / AFRIKAANSE OPSOMMING: Ons kry deesdae al meer te doen met uitdagings soos internasionale en plaaslike kragonderbrekings in die energiebedryf. Die aanvraag vir energie verhoog deurlopend en veroorsaak omgewingsprobleme soos klimaatsveranderinge, wat ‘n groot bekommernis is vir die samelewing. In hierdie studie word gepoog om vas te stel hoe energie besparings meganismes soos die eliminering van nie-noodsaaklike krag ekonomiese waarde kan voeg tot die mynboubedryf. Die uitwerking wat nie-noodsaaklike krag het en hoe dit maatskappye kan help om kragverbruik te verlaag terwyl produksievlakke steeds gehandhaaf word, is hier ondersoek. Plaaslike kragvoorsieners kan ook baat vind hierby in krisistye. Hierdie navorsingsverslag is gebaseer op ‘n ondersoek van krag besparings geleenthede by ‘n mynmaatskappy gedurende ‘n krisistydperk van kragonderbrekings. Die verslag kyk na die doetreffendheid van energieverbruik, asook na die hindernisse wat ondervind word in die inwerkingstelling van energie besparings inisiatiewe. Maatskappye het in die algemeen nie ‘n gestruktureerde metode om die probleem rakende nie-noodsaaklike krag aan te spreek nie. Hulle is nie bewus van die nut wat sulke inisiatiewe kan hê op korporatiewe verantwoordelikheid en volhoubare verslaggewing nie. Die voordele wat energiebesparing en die eliminering van nie-noodsaaklike krag op die ekonomie, gemeenskap en omgewing het, word nie duidelik geboekstaaf nie. Verdere navorsing moet gedoen word om die impak van energiedoeltreffendheid en nie-noodsaaklike krag op die sosiale aspek te bewys. Die uitwerking wat kragopwekking op die globale omgewing het is nog nie bereken en verbind met die waarde daarvan op kragbesparing nie. Die verslag beklemtoon dat maatskappye fokus op langtermyn inisiatiewe in plaas daarvan om te kyk na kleiner inisiatiewe wat minder moeite en tyd sal verg. Die ondersoek by die mynmaatskappy het getoon dat daar nie klem geplaas is op die onderskeiding tussen nie-noodsaaklike en noodsaaklike krag met die installering van die elektriese stroombane tydens die ontwerpstadium nie. Daar is gevind dat die afskakeling van nie-noodsaaklike krag ekonomiese en omgewingsvoordele vir die maatskappy inhou. Daar is tot die slotsom gekom dat die afskakeling van nie-noodsaaklike krag in die algemeen dus ‘n voordelige uitwerking het op die ekonomie en omgewing. Dit is maklik om te implementeer met minimum moeite en belegging. Die besparings deur middel van hierdie inisiatiewe kan ook maklik gemeet word om die opbrengs op die belegging te bereken.