Proximity as a Service via Cellular Network-Assisted Mobile Device-to-Device

PhD ThesisThe research progress of communication has brought a lot of novel technologies to meet the multi-dimensional demands such as pervasive connection, low delay and high bandwidth. Device-to-Device (D2D) communication is a way to no longer treat the User Equipment (UEs) as a terminal, but rather as a part of the network for service provisioning. This thesis decouples UEs into service providers (helpers) and service requesters. By collaboration among proximal devices, with the coordination of cellular networks, some local tasks can be achieved, such as coverage extension, computation o oading, mobile crowdsourcing and mobile crowdsensing. This thesis proposes a generic framework Proximity as a Service (PaaS) for increasing the coverage with demands of service continuity. As one of the use cases, the optimal helper selection algorithm of PaaS for increasing the service coverage with demands of service continuity is called ContAct based Proximity (CAP). Mainly, fruitful contact information (e.g., contact duration, frequency, and interval) is captured, and is used to handle ubiquitous proximal services through the optimal selection of helpers. The nature of PaaS is evaluated under the Helsinki city scenario, with movement model of Points Of Interest (POI) and with critical factors in uencing the service demands (e.g., success ratio, disruption duration and frequency). Simulation results show the advantage of CAP, in both success ratio and continuity of the service (outputs). Based on this perspective, metrics such as service success ratio and continuity as a service evaluation of the PaaS are evaluated using the statistical theory of the Design Of Experiments (DOE). DOE is used as there are many dimensions to the state space (access tolerance, selected helper number, helper access limit, and transmit range) that can in uence the results. A key contribution of this work is that it brings rigorous statistical experiment design methods into the research into mobile computing. Results further reveal the influence of four factors (inputs), e.g., service tolerance, number of helpers allocated, the number of concurrent devices supported by each helper and transmit range. Based on this perspective, metrics such as service success ratio and continuity are evaluated using DOE. The results show that transmit range is the most dominant factor. The number of selected helpers is the second most dominant factor. Since di erent factors have di erent regression levels, a uni ed 4 level full factorial experiment and a cubic multiple regression analysis have been carried out. All the interactions and the corresponding coe cients have been found. This work is the rst one to evaluate LTE-Direct and WiFi-Direct in an opportunistic proximity service. The contribution of the results for industry is to guide how many users need to cooperate to enable mobile computing and for academia. This reveals the facts that: 1, in some cases, the improvement of spectrum e ciency brought by D2D is not important; 2, nodal density and the resources used in D2D air-interfaces are important in the eld of mobile computing. This work built a methodology to study the D2D networks with a di erent perspective (PaaS)

Predicting lorawan behavior. How machine learning can help

Large scale deployments of Internet of Things (IoT) networks are becoming reality. From a technology perspective, a lot of information related to device parameters, channel states, network and application data are stored in databases and can be used for an extensive analysis to improve the functionality of IoT systems in terms of network performance and user services. LoRaWAN (Long Range Wide Area Network) is one of the emerging IoT technologies, with a simple protocol based on LoRa modulation. In this work, we discuss how machine learning approaches can be used to improve network performance (and if and how they can help). To this aim, we describe a methodology to process LoRaWAN packets and apply a machine learning pipeline to: (i) perform device profiling, and (ii) predict the inter-arrival of IoT packets. This latter analysis is very related to the channel and network usage and can be leveraged in the future for system performance enhancements. Our analysis mainly focuses on the use of k-means, Long Short-Term Memory Neural Networks and Decision Trees. We test these approaches on a real large-scale LoRaWAN network where the overall captured traffic is stored in a proprietary database. Our study shows how profiling techniques enable a machine learning prediction algorithm even when training is not possible because of high error rates perceived by some devices. In this challenging case, the prediction of the inter-arrival time of packets has an error of about 3.5% for 77% of real sequence cases

Predicting lorawan behavior. How machine learning can help

Large scale deployments of Internet of Things (IoT) networks are becoming reality. From a technology perspective, a lot of information related to device parameters, channel states, network and application data are stored in databases and can be used for an extensive analysis to improve the functionality of IoT systems in terms of network performance and user services. LoRaWAN (Long Range Wide Area Network) is one of the emerging IoT technologies, with a simple protocol based on LoRa modulation. In this work, we discuss how machine learning approaches can be used to improve network performance (and if and how they can help). To this aim, we describe a methodology to process LoRaWAN packets and apply a machine learning pipeline to: (i) perform device profiling, and (ii) predict the inter-arrival of IoT packets. This latter analysis is very related to the channel and network usage and can be leveraged in the future for system performance enhancements. Our analysis mainly focuses on the use of k-means, Long Short-Term Memory Neural Networks and Decision Trees. We test these approaches on a real large-scale LoRaWAN network where the overall captured traffic is stored in a proprietary database. Our study shows how profiling techniques enable a machine learning prediction algorithm even when training is not possible because of high error rates perceived by some devices. In this challenging case, the prediction of the inter-arrival time of packets has an error of about 3.5% for 77% of real sequence cases

General dynamics of the physical-chemical systems in mammals

Biodynamic regulator chain models for physical chemical systems in mammal

A Meta-Analysis Of Resource Pulse-Consumer Interactions

Resource Pulses are infrequent, large-magnitude, and short-duration events of increased resource availability. They include a diverse set of extreme events in a wide range of ecosystems, but identifying general patterns among the diversity of pulsed resource phenomena in nature remains an important challenge. Here we present a meta-analysis of resource pulse-consumer interactions that addresses four key questions: (1) Which characteristics of pulsed resources best predict their effects on consumers? (2) Which characteristics of consumers best predict their responses to resource pulses? (3) How do the effects of resource Pulses differ in different ecosystems? (4) What are the indirect effects of resource pulses in communities\u27? To investigate these questions, we built a data set of diverse Pulsed resource-consumer interactions from around the world, developed metrics to compare the effects of resource pulses across disparate systems, and conducted multilevel regression analyses to examine the manner in which variation in the characteristics of resource pulse-consumer interactions affects important aspects Of Consumer responses. Resource pulse magnitude, resource trophic level, resource Pulse duration, ecosystem type and subtype, consumer response mechanisms, and consumer body mass were found to be key. explanatory factors predicting the magnitude, duration, and timing of consumer responses. Larger consumers showed more persistent responses to resource pulses, and reproductive responses were more persistent than aggregative responses. Aquatic systems showed shorter temporal lags between peaks of resource availability and consumer response compared to terrestrial systems, and temporal lags were also shorter for smaller consumers compared to larger consumers. The magnitude of consumer responses relative to their resource pulses was generally smaller for the direct consumers of primary resource pulses, compared to consumers at greater trophic distances from the initial resource pulse. In specific systems, this data set showed both attenuating and amplifying indirect effects. We consider the mechanistic processes behind these patterns and their implications for the ecology of resource pulses

INNOVATION ON THE VENDOR SIDE - ANALYZING THE EFFECTS OF INNOVATION INITIATIVES ON OUTSOURCING PROVIDERS\u27 PERFORMANCE

‘Innovation through outsourcing’ describes a firm’s strategy to receive innovation by outsourcing IT or IT-intensive processes to more competent and innovative service providers who, in turn, do not only operate their activities but also improve and innovate for or on behalf of their clients. This strategy has gathered some attention by recent research, though it has almost only examined the client perspective, yet. We contribute to this sub-field of IT outsourcing/BPO research by analyzing vendors’ strategies to improve their innovation capability and thus to be more innovative for their clients. Based on a longitudinal global dataset of 136 outsourcing vendors, we analyze which innovation-enabling initiatives are related to superior firm performance (in terms of revenue growth). We find that particularly employee-involving initiatives are promising: outsourcing vendors that have implemented, e.g., idea/innovation platforms that support employee-driven innovation, receive above-average revenue growth

HIV prevalence estimates and their use in regression models: cautionary evidence from Zimbabwe and studies of the relationship between armed conflict and HIV

Includes abstract.Includes bibliographical references.This dissertation makes two central arguments. The first is that regressions on country-level HIV prevalence are compromised by the fact that the HIV data used are estimates and not empirical data points. The HIV prevalence rates published by UNAIDS are estimates derived from epidemiological modelling (using EPP and Spectrum) in which data from antenatal clinics (sometimes supplemented by population survey data) are translated into adult HIV prevalence estimates

Processes underlying the fine-scale partitioning and niche diversification in a guild of coral reef damselfishes

A major goal of ecology is to explain the mechanisms that drive species distributions and ecological partitioning along gradients in the natural environment. The distributions and coexistence of ecologically similar animals may depend on the degree of niche diversification and competitive interactions within and among species. The extent of ecological partitioning in guilds of coral reef fishes was hotly debated in the 1980s, and despite 4 decades of research, the issue remains unresolved. In particular, the link between niche partitioning and agonistic interactions together have received little attention. In the thesis I investigated finescale species distributions, resource use (e.g., habitat and food), and competition in a guild of 7 territorial damselfish species in Kimbe Bay, Papua New Guinea. Common generalisations about the ecological function of territorial damselfish and associated interactions with important roving herbivorous fishes were also investigated. Using ecological surveys, laboratory-based analytical methods, observational studies, and manipulative field experiments, this thesis addresses novel questions about the ecology and functional role of territorial damselfish and the resulting community effects. Competition over resources is recognised to play a primary role in the structure of coral reef fish communities. The distribution of ecologically similar species may depend on the degree to which traditional niche mechanisms operate alongside competitive dynamics. In Chapter 2 these effects were examined by investigating fine-scale species distributions, microhabitat use, and aggression among territorial damselfishes. I documented patterns of habitat partitioning across the 3 reef zones – reef flat, reef crest, and reef slope – with distinct patterns of distribution within these zones at extremely fine scales (1 − 2 m). Distinct differences between neighbouring species in the microhabitat use selected were also observed. Furthermore, aggression elicited by neighbouring species was significantly higher for all species, compared with non-adjacent species. This chapter revealed a fine level of spatial partitioning among reef zones and microhabitats in this guild of damselfish, which was likely maintained by agonistic interactions among neighbouring species. While Chapter 2 found that neighbouring damselfish constrain their microhabitat use to facilitate the co-habitation of reef zones, microhabitat selectivity alone was insufficient to explain the distinct zonation and limited distributional overlap. I hypothesised that in this highly partitioned ecological community, where there are intense agonistic interactions for resources, ecologically neighbouring territorial damselfish may also partition food resources. Other studies had previously quantified diet contributions for the study species, but no isotopic analysis had been conducted for territorial damselfish to date to specifically target pelagic-based food sources. In Chapter 3 I quantified the trophic niches of the territorial damselfish guild through the use of stable isotopes (δ¹³C and δ¹⁵N). Adjacent species on the reef flat, reef crest, and reef slope exhibited high to intermediate trophic niche partitioning when examining pelagic versus reef-based dietary sources, with two species previously described as benthic herbivores actually exhibiting pelagic feeding. Findings of Chapter 3 indicate that diet choice reinforces the patterns of spatial partitioning and coexistence among ecologically similar species. In addition, evidence of planktivorous pelagic feeding adds to the growing view that interspecific differences among similar species are lost when categorizing species into broad functional classifications. In Chapter 4 the direct and indirect effects of interference competition on resource partitioning were measured. The previous chapters found that microhabitat selectivity and dietary diversification facilitated the co-habitation of reef zones among the territorial damselfish guild. Additionally, evidence suggested that interspecific aggression helped maintain the distributional boundaries between neighbouring species. However, an experimental removal of a dominant competitor was necessary to understand if interference competition is present and if subordinate distributional shifts would occur. I employed an observational experiment and a large-scale removal experiment (220 m²) to examine the intensity of agonistic interactions among species and the extent to which the most abundant species influenced the distribution and abundance of neighbouring and non-neighbouring species in the guild. The findings indicated that the distinct distribution patterns among the reef crest species were linked to levels of interspecific agonistic behaviour. The competitive release following the removal of a superior competitor resulted in comprehensive direct and indirect effects, with the subordinate neighbour shifting into the newly available space, followed by successive shifts in species responding to the change in the distributions of their immediate neighbours. Through a novel multi-species large-scale experiment, Chapter 4 provides the conclusive evidence that distributions and the coexistence of the territorial damselfish guild are a result of niche diversification and competitive interactions within and among species. Chapter 5 broadens the thesis by investigating the common perception that all territorial damselfish negatively influence overall reef function and roving herbivorous fishes. Similar to Chapter 2 where generalisations about the guild's diet were questioned, here I challenged the paradigm that intermediate-sized territorial damselfishes have a negative influence on surgeonfish, parrotfish, and rabbitfish abundance and foraging behaviour. To test this, I conducted experimental removals (220 m²) of the most abundant territorial damselfish to examine its impact on roving herbivores and the benthic community structure. The overall relative abundance (MaxN) of roving herbivores was not influenced by the removal. No changes in foraging patterns were observed for parrotfish, the family that received the highest rate of agonistic interactions, and rabbitfish. Instead, the removal resulted in a significant decrease in surgeonfish feeding, suggesting the territorial damselfish species altered foraging patterns indirectly through territorial maintenance and not aggression. The results indicate that all territorial damselfishes do not have a negative impact on all roving herbivores and instead may enhance surgeonfish foraging indirectly through the removal of sediment. The generalisation that territorial damselfish reduce foraging rates of roving herbivores may not be applicable in all systems or for all species. In summary, this thesis investigated the mechanisms that drive species distributions and ecological partitioning along gradients in the natural environment as a precursor to the long-term ecological changes on coral reefs. It first established fine-scale partitioning in a guild of competing fishes on a high-diversity coral reef. Second, the research showed that microhabitat selectivity and dietary diversification facilitates the co-habitation of reef zones, and that interspecific aggression maintains the distributional boundaries between neighbouring species. In order to demonstrate how competitive interactions and resource partitioning influence species coexistence in a complex ecosystem a large-scale field experiment was conducted. The results demonstrate that when exploring coexistence in reef fish communities, the more traditional niche mechanisms operate alongside direct and indirect competitive dynamics, and within highly diverse systems these ecological processes are magnified. Moreover, the thesis highlights the importance of challenging common generalisations and paradigms. By examining the functional role of territorial damselfishes this research provides evidence of novel dietary diversification and demonstrates the complexity of territorial damselfish and roving herbivore interactions