Congestion Control and Routing over Challenged Networks

This dissertation is a study on the design and analysis of novel, optimal routing and rate control algorithms in wireless, mobile communication networks. Congestion control and routing algorithms upto now have been designed and optimized for wired or wireless mesh networks. In those networks, optimal algorithms (optimal in the sense that either the throughput is maximized or delay is minimized, or the network operation cost is minimized) can be engineered based on the classic time scale decomposition assumption that the dynamics of the network are either fast enough so that these algorithms essentially see the average or slow enough that any changes can be tracked to allow the algorithms to adapt over time. However, as technological advancements enable integration of ever more mobile nodes into communication networks, any rate control or routing algorithms based, for example, on averaging out the capacity of the wireless mobile link or tracking the instantaneous capacity will perform poorly. The common element in our solution to engineering efficient routing and rate control algorithms for mobile wireless networks is to make the wireless mobile links seem as if they are wired or wireless links to all but few nodes that directly see the mobile links (either the mobiles or nodes that can transmit to or receive from the mobiles) through an appropriate use of queuing structures at these selected nodes. This approach allows us to design end-to-end rate control or routing algorithms for wireless mobile networks so that neither averaging nor instantaneous tracking is necessary

On exploiting priority relation graph for reliable multi-path communication in mobile social networks

© 2018 Elsevier Inc. A mobile social network (MSN) consists of certain amount of mobile users with social characteristics, and it provides data delivery concerning social relationships between mobile users. In MSN, ordinary people contact each other more frequently if they have more social features in common. In this paper, we apply a new topology structure–priority relation graph (PRG) to evaluate the data delivery routing in MSN on the system-level. By using the natural order of nodes’ representation, the diameter, the regular degree and the multi-path technology, we determine the priority relation graph-based social feature routing (PRG-SFR) algorithm to find disjointed multi-paths in MSN. Here, the multi-path technology can be exploited for ensuring that, between each pair of sender and receiver, the important information can be delivered through a highly reliable path. Then we calculate the tolerant ability of ‘faults’ and estimate the availability of MSN on the theoretical level. Finally, we analyze the efficiency of PRG-SFR algorithm from the numerical standpoint in terms of fault tolerance, forwarding number, transmission time and delivery rate. Moreover, we make comparisons between PRG-SFR algorithm and certain state-of-the-art technologies

Hybrid routing in delay tolerant networks

This work addresses the integration of today\\u27s infrastructure-based networks with infrastructure-less networks. The resulting Hybrid Routing System allows for communication over both network types and can help to overcome cost, communication, and overload problems. Mobility aspect resulting from infrastructure-less networks are analyzed and analytical models developed. For development and deployment of the Hybrid Routing System an overlay-based framework is presented

Hybrid Routing in Delay Tolerant Networks

This work addresses the integration of today\u27s infrastructure-based networks with infrastructure-less networks. The resulting Hybrid Routing System allows for communication over both network types and can help to overcome cost, communication, and overload problems. Mobility aspect resulting from infrastructure-less networks are analyzed and analytical models developed. For development and deployment of the Hybrid Routing System an overlay-based framework is presented

PROBABILISTIC APPROACH TO WATER, SEDIMENT, AND NUTRIENT CONNECTIVITY FOR ADVANCING WATERSHED MODELLING

The goal of this dissertation is to represent the spatial and temporal domains of water, sediment, and nutrient flux and pathways within fluvial and watershed settings. To complete this goal, we integrate connectivity theory into watershed model structures to simulate water, sediment, and nutrient movement at the fundamental unit they occur. Fluvial-based sediment and nutrient flux is an important driver of global sediment and nutrient budgets, and the quantification of which serves as an ongoing challenge to limnologists, engineers, and watershed managers. Watershed models have been richly developed over the past century, but are currently restrained by problems related to omission of physical transport and detachment processes as well ambiguous representation of active non-point sources and their transport pathways. To overcome limitations such as these, geomorphologists introduced connectivity theory, which has garnered popularity from watershed managers and modelers due perhaps to its ability to explain the non-linearity of system response and explicitly detail non-point sources, sinks, and transport pathways. Connectivity is defined herein as, “the integrated transfer of material from source to sink facilitated by the continuum of material generation, loss, and transport in three dimensions and through time.” Connectivity theory has matured such that we now have a holistic view of phenomena controlling connectivity, however, the connectivity community has not yet adopted a unified conceptual framework with the goal of connectivity quantification. Existing connectivity models have varying approaches to quantify connectivity such as: (1) index-based connectivity assessments; (2) effective catchment area estimation; and (3) network-based connectivity simulations. While these models often adequately represent the structural connections of landscape elements, few frameworks are able to represent the variability of connectivity from dynamic hydrologic forcings. We argue that explicit coupling of watershed models with a unified connectivity framework will help to improve the basis of watershed modelling in physics while avoiding problems that current watershed models possess: namely due to spatial and temporal lumping and empirical estimations of non-point source generation and fate. This dissertation seeks to fulfill this objective through of six studies that advance formulation of the tenets of connectivity including the magnitude, extent, timing, and continuity of connectivity with respect to water, sediment, and nutrients

MediaSync: Handbook on Multimedia Synchronization

This book provides an approachable overview of the most recent advances in the fascinating field of media synchronization (mediasync), gathering contributions from the most representative and influential experts. Understanding the challenges of this field in the current multi-sensory, multi-device, and multi-protocol world is not an easy task. The book revisits the foundations of mediasync, including theoretical frameworks and models, highlights ongoing research efforts, like hybrid broadband broadcast (HBB) delivery and users' perception modeling (i.e., Quality of Experience or QoE), and paves the way for the future (e.g., towards the deployment of multi-sensory and ultra-realistic experiences). Although many advances around mediasync have been devised and deployed, this area of research is getting renewed attention to overcome remaining challenges in the next-generation (heterogeneous and ubiquitous) media ecosystem. Given the significant advances in this research area, its current relevance and the multiple disciplines it involves, the availability of a reference book on mediasync becomes necessary. This book fills the gap in this context. In particular, it addresses key aspects and reviews the most relevant contributions within the mediasync research space, from different perspectives. Mediasync: Handbook on Multimedia Synchronization is the perfect companion for scholars and practitioners that want to acquire strong knowledge about this research area, and also approach the challenges behind ensuring the best mediated experiences, by providing the adequate synchronization between the media elements that constitute these experiences

Runoff generation over seasonally-frozen ground: trends, patterns, and processes

Understanding and modeling runoff generation over seasonally-frozen hillslopes is a major challenge in hydrology. On the Canadian Prairies, snowmelt drives up to 80% of annual runoff, but the hydrological regime is vulnerable to changing precipitation states, snowpack persistence, snowmelt timing and rates, and frozen ground states. Our ability to understand and predict water partitioning and availability is being challenged by a lack of hillslope-scale climate-runoff observations, the presence of multiple interacting controls, and occurrence of spatial and temporal nonlinearity in runoff responses. I undertook long-term analyses of a 52-year dataset (1962-2013) of climate, snow cover, soil water content, and runoff from three 5 ha hillslopes in Saskatchewan. The aim was to determine how recent changes in climate have impacted upon hillslope rainfall- and snowmelt-runoff, and to unscramble the hierarchy of controls on hillslope snowmelt-runoff generation. These analyses then provided a multi-decadal contextual backdrop to an intensive field campaign that I led during the 2014 snowmelt season. I measured the spatial patterns of controls on runoff to assess the mechanisms behind connectivity and threshold delivery of snowmelt over frozen ground. There are three main conclusions from this research. First, differences between frozen and unfrozen soil infiltrabilities caused contrasting long-term snowmelt- and rainfall-runoff trends: no statistically significant changes were observed for rainfall-runoff amounts, but snowmelt-runoff showed statistically significant decreases over the 52-year record. Second, snowmelt-runoff was driven by hierarchical and condition-dependent controls related to snowfall, snow cover, antecedent soil moisture, and melt season dynamics. Third, for an individual melt season, filling and spilling of micro- and meso-depressions by snowmelt over frozen ground was the driver of hillslope connectivity and runoff delivery. Through a coupled analysis of trends, hierarchies and patterns, this research has advanced our understanding of runoff generation over seasonally-frozen ground. The long-term decrease in spring soil water recharge and snowmelt-runoff is a threat to dryland crop production and economic prosperity in farming. These findings have implications for modeling these threats by guiding new empirical frameworks for lumped hillslope runoff based on what we found in our long terms analysis and identifying what micro- and meso-scale features are important to now include in our process-based distributed snowmelt models