Exploiting Mobile Social Networks from Temporal Perspective:A Survey

With the popularity of smart mobile devices, information exchange between users has become more and more frequent, and Mobile Social Networks (MSNs) have attracted significant attention in many research areas. Nowadays, discovering social relationships among people, as well as detecting the evolution of community have become hotly discussed topics in MSNs. One of the major features of MSNs is that the network topology changes over time. Therefore, it is not accurate to depict the social relationships of people based on a static network. In this paper, we present a survey of this emerging field from a temporal perspective. The state-of-the-art research of MSNs is reviewed with focus on four aspects: social property, time-varying graph, temporal social property, and temporal social properties-based applications. Some important open issues with respect to MSNs are discussed

Structure and topology of transcriptional regulatory networks and their applications in bio-inspired networking

Biological networks carry out vital functions necessary for sustenance despite environmental adversities. Transcriptional Regulatory Network (TRN) is one such biological network that is formed due to the interaction between proteins, called Transcription Factors (TFs), and segments of DNA, called genes. TRNs are known to exhibit functional robustness in the face of perturbation or mutation: a property that is proven to be a result of its underlying network topology. In this thesis, we first propose a three-tier topological characterization of TRN to analyze the interplay between the significant graph-theoretic properties of TRNs such as scale-free out-degree distribution, low graph density, small world property and the abundance of subgraphs called motifs. Specifically, we pinpoint the role of a certain three-node motif, called Feed Forward Loop (FFL) motif in topological robustness as well as information spread in TRNs. With the understanding of the TRN topology, we explore its potential use in design of fault-tolerant communication topologies. To this end, we first propose an edge rewiring mechanism that remedies the vulnerability of TRNs to the failure of well-connected nodes, called hubs, while preserving its other significant graph-theoretic properties. We apply the rewired TRN topologies in the design of wireless sensor networks that are less vulnerable to targeted node failure. Similarly, we apply the TRN topology to address the issues of robustness and energy-efficiency in the following networking paradigms: robust yet energy-efficient delay tolerant network for post disaster scenarios, energy-efficient data-collection framework for smart city applications and a data transfer framework deployed over a fog computing platform for collaborative sensing --Abstract, page iii

車両・無人航空機を活用した災害時情報共有のためのDTNプロトコル

電気通信大学202

Modelos, Algoritmos y Protocolos para Redes de Comunicaciones Tolerantes a Interrupciones con Alto Grado de Predecibilidad

Tesis (DCI)--FCEFN-UNC, 2019La industria de las comunicaciones satelitales ha mostrado un avance limitado en las últimas décadas en comparación con la evolución de las redes terrestres tales como Internet. La razón principal consiste en que el entorno espacial es radicalmente diferente al terrestre, lo cual impacta considerablemente en la estabilidad de las conexiones y en el hecho de que los protocolos de comunicación utilizados en Tierra resulten inadecuados y/o ineficientes cuando se tratan de adaptar al espacio. Sin embargo, recientemente, y producto de un esfuerzo conjunto de diferentes agencias espaciales (NASA, ESA, CONAE, etc), se ha comenzado a estudiar y experimentar con estrategias de comunicaciones en red que son capaces de tolerar retardos e interrupciones mediante un cambio paradigmático en la forma de realizar dichas comunicaciones. En particular, se ha propuesto una arquitectura de protocolos llamada Delay/Disruption Tolerant Networking (DTN), y que dada la predecibilidad de las trayectorias satelitales, permite aprovechar un plande contactos compuesto por las oportunidades de comunicación en el futuro, lo que permite a los satélites tomar decisiones eficientes sobre cómo y cuándo transmitir el tráfico generado o recibido desde otros satélites. En los últimos años, se han llevado a cabo numerosos avances en la implementación de DTN y se han realizado experimentos en órbita que avalan el potencial beneficio de esta arquitectura. Además, se ha estudiado el problema del diseño del plan de contactos que constituye el proceso de configurar y elegir apropiadamente las oportunidades de comunicación con el objetivo de optimizar el rendimiento y realizar una adecuada gestión de los limitados recursos que se disponen en este tipo de redes. Sin embargo, esta arquitectura se encuentra aún en una etapa de maduración y son numerosos los desafíos que deben ser superados. En particular, en esta tesis se pone el foco en el problema de la congestión que ocurre cuando la planificación referida a la utilización de los recursos no resulta apropiada. Básicamente, se proponen mecanismos que actúan, por un lado, sobre el algoritmo de enrutamiento ejecutado de manera distribuida por los satélites de la red, y por otro, sobre el diseño automático del plan de contactos. Adicionalmente, se realizan aportes referidos a los problemas de incertidumbre y de escalabilidad e integración de la red. De esta manera, en esta investigación contribuimos con enfoques originales en los que se aprovecha la predictibilidad de las comunicaciones satelitales para proveer mecanismos de gestión y toma de decisiones de manera automatizada, solucionando de esta forma problemas cuya complejidad aumenta drásticamente con la cantidad de satélites y tiempos de evaluación. Cabe destacar además, que si bien los aportes realizados pueden ser utilizados de forma general en la arquitectura DTN, los mismos encuentran aplicación dentro del Plan Espacial Argentino, ya que esta arquitectura resulta particularmente adecuada para ser aplicada en las nuevas misiones satelitales distribuidas que propone CONAE para la observación terrestre. Por lo tanto, los aportes brindados en esta tesis tienen alcance hacia protocolos desarrollados mediante colaboraciones internacionales y podrían además ser utilizados en nuestro país para resolver desafíos de interés local

Energy efficiency in wireless communication

This era would probably be recognized as the information age, hence as a paramount milestone in the progress of mankind, by the future historians. One of the most significant achievements of this age is, making it possible to transmit and receive information effectively and reliably via wireless radio technology. The demand of wireless communication is increasing in a never-resting pace, imposing bigger challenge not only on service providers but also on innovators and researches to innovate out-of-the-box technologies. These challenges include faster data communication over seamless, reliable and cost effective wireless networks, utilizing the limited physical radio resources as well as considering the environmental impact caused by the increasing energy consumption. The ever-expanding wireless communication infrastructure is withdrawing higher energy than ever, raising the need for finding more efficient systems. The challenge of developing efficient wireless systems can be addressed on several levels, starting from device electronics, up to the network-level architecture and protocols. The anticipated gains of achieving such efficiency is the key feature of extending mobile devices' battery life and reducing environmental and economic impacts of wireless communication infrastructure. Therefore energy efficient designs are urgently needed from both environmental and economic aspects of wireless networks. In this research, we explore the field of energy efficiency in MAC and Physical layers of wireless networks in order to enhance the performance and reliability of future wireless networks as well as to reduce its environmental footprint. In the first part of this research, we analyse the energy efficiency of two mostly used modulation techniques, namely MQAM and MFSK, for short range wireless transmissions, up to a few $100$s of meters, and propose optimum rate adaptation to minimize the energy dissipation during transmissions. Energy consumed for transmitting the data over a distance to maintain a prescribed error probability together with the circuit energy have been considered in our work. We provide novel results for optimal rate adaptation for improved energy efficiency. Our results indicate that the energy efficiency can be significantly improved by performing optimal rate adaptation given the radio and channel parameters, and furthermore we identify the maximum distance where optimal rate adaptation can be performed beyond which the optimum rate then becomes the same as the minimum data rate. In the second part of this research, we propose energy efficient algorithm for cellular base stations. In cellular networks, the base stations are the most energy consuming parts, which consume approximately $60-80\%$ of the total energy. Hence control and optimization of energy consumption at base stations should be at the heart of any green radio engineering scheme. Sleep mode implementation in base stations has proven to be a very good approach for the energy efficiency of cellular BSs. Therefore, we have proposed a novel strategy for improving energy efficiency on ternary state transceivers for cellular BSs. We consider transceivers that are capable of switching between sleep, stand-by and active modes whenever required. We have modelled these ternary state transceivers as a three-state Markov model and have presented an algorithm based on Markov model to intelligently switch among the states of the transceivers based on the offered traffic whilst maintaining a prescribed minimum rate per user. We consider a typical macro BS with state changeable transceivers and our results show that it is possible to improve the energy efficiency of the BS by approximately $40\%$ using the proposed MDP based algorithm. In the third part of this research, we propose energy efficient algorithm for aerial base stations. Recently aerial base stations are investigated to provide wireless coverage to terrestrial radio terminals. The advantages of using aerial platforms in providing wireless coverage are many including larger coverage in remote areas, better line-of-sight conditions etc. Energy is a scarce resource for aerial base stations, hence the wise management of energy is quite beneficial for the aerial network. In this context, we study the means of reducing the total energy consumption by designing and implementing an energy efficient aerial base station. Sleep mode implementation in base stations (BSs) has proven to be a very good approach for improving the energy efficiency; therefore we propose a novel strategy for further improving energy efficiency by considering ternary state transceivers of aerial base stations. Using the three state model we propose a Markovian Decision process (MDP) based algorithm to switch between the states for improving the energy efficiency of the aerial base station. The MDP based approach intelligently switches between the states of the transceivers based on the offered traffic whilst maintaining a prescribed minimum channel rate per user. Our simulation results show that there is a around $40\%$ gain in the energy efficiency when using our proposed MDP algorithm together with the three-state transceiver model for the base station compared to the always active mode. We have also shown the energy-delay trade-off in order to design an efficient aerial base station. In the final part of our work, we propose a novel energy efficient handover algorithm, based on Markov decision process (MDP) for the two-tier LTE network, towards reducing power transmissions at the mobile terminal side. The proposed policy is LTE backward-compatible, as it can be employed by suitably adapting a prescribed SNR target and standard LTE measurements. Simulation results reveal that compared to the widely adopted policy based on strongest cell and another energy efficient policy, our proposed policy can greatly reduce the power consumption at the LTE mobile terminals. Most of our works presented in this dissertation has been published in conference proceeding and some of them are currently undergoing a review process for journals. These publications will be highlighted and identified at the end of the first chapter of this dissertation