15 research outputs found
Advanced Location-Based Technologies and Services
Since the publication of the first edition in 2004, advances in mobile devices, positioning sensors, WiFi fingerprinting, and wireless communications, among others, have paved the way for developing new and advanced location-based services (LBSs). This second edition provides up-to-date information on LBSs, including WiFi fingerprinting, mobile computing, geospatial clouds, geospatial data mining, location privacy, and location-based social networking. It also includes new chapters on application areas such as LBSs for public health, indoor navigation, and advertising. In addition, the chapter on remote sensing has been revised to address advancements
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On SIP Server Clusters and the Migration to Cloud Computing Platforms
This thesis looks in depth at telephony server clusters, the modern switchboards at the core of a packet-based telephony service. The most widely used de facto standard protocols for telecommunications are the Session Initiation Protocol (SIP) and the Real Time Protocol (RTP). SIP is a signaling protocol used to establish, maintain, and tear down communication channel between two or more parties. RTP is a media delivery protocol that allows packets to carry digitized voice, video, or text.
SIP telephony server clusters that provide communications services, such as an emergency calling service, must be scalable and highly available. We evaluate existing commercial and open source telephony server clusters to see how they differ in scalability and high availability.
We also investigate how a scalable SIP server cluster can be built on a cloud computing platform. Elasticity of resources is an attractive property for SIP server clusters because it allows the cluster to grow or shrink organically based on traffic load. However, simply deploying existing clusters to cloud computing platforms is not good enough to take full advantage of elasticity. We explore the design and implementation of clusters that scale in real-time. The database tier of our cluster was modified to use a scalable key-value store so that both the SIP proxy tier and the database tier can scale separately. Load monitoring and reactive threshold-based scaling logic is presented and evaluated.
Server clusters also need to reduce processing latency. Otherwise, subscribers experience low quality of service such as delayed call establishment, dropped calls, and inadequate media quality. Cloud computing platforms do not guarantee latency on virtual machines due to resource contention on the same physical host. These extra latencies from resource contention are temporary in nature. Therefore, we propose and evaluate a mechanism that temporarily distributes more incoming calls to responsive SIP proxies, based on measurements of the processing delay in proxies.
Availability of SIP server clusters is also a challenge on platforms where a node may fail anytime. We investigated how single component failures in a cluster can lead to a complete system outage. We found that for single component failures, simply having redundant components of the same type are enough to mask those failures. However, for client-facing components, smarter clients and DNS resolvers are necessary.
Throughout the thesis, a prototype SIP proxy cluster is re-used, with variations in the architecture or configuration, to demonstrate and address issues mentioned above. This allows us to tie all of our approaches for different issues into one coherent system that is dynamically scalable, is responsive despite latency varations of virtual machines, and is tolerant of single component failures in cloud platforms
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Modeling and Analysis of Next Generation 9-1-1 Emergency Medical Dispatch Protocols
Emergency Medical Dispatch Protocols are guidelines that a 9-1-1 dispatcher uses to evaluate the nature of emergency, resources to send and the nature of help provided to the 9-1-1 caller. The current Dispatch Protocols are based on voice only call. But the Next Generation 9-1-1 (NG9-1-1) architecture will allow multimedia emergency calls. In this thesis I analyze and model the Emergency Medical Dispatch Protocols for NG9-1-1 architecture. I have identified various technical aspects to improve the NG9-1-1 Dispatch Protocols. The devices (smartphone) at the caller end have advanced to a point where they can be used to send and receive video, pictures and text. There are sensors embedded in them that can be used for initial diagnosis of the injured person. There is a need to improve the human computer (smartphone) interface to take advantage of technology so that callers can easily make use of various features available to them. The dispatchers at the 9-1-1 call center can make use of these new protocols to improve the quality and the response time. They will have capability of multiple media streams to interact with the caller and the first responders.The specific contributions in this thesis include developing applications that use smartphone sensors. The CPR application uses the smartphone to help administer effective CPR even if the person is not trained. The application makes the CPR process closed loop, i.e., the person who administers the CPR as well as the 9-1-1 operator receive feedback and prompt from the application about the correctness of the CPR. The breathing application analyzes the quality of breathing of the affected person and automatically sends the information to the 9-1-1 operator. In order to improve the Human Computer Interface at the caller and the operator end, I have analyzed Fitts law and extended it so that it can be used to improve the instructions given to a caller. In emergency situations, the caller may be physically or cognitively impaired. This may happen either because the caller is the injured person, or because the caller is a close relative or friend of the injured person. Using EEG waves, I have analyzed and developed a mathematical model of a person's cognitive impairment. Finally, I have developed a mathematical model of the response time of a 9-1-1 call and analyzed the factors that can be improved to reduce the response time. In this regard, another application, I have developed, allows the 9-1-1 operator to remotely control the media features of a caller's smartphone. This is needed in case the caller is unable to operate the multimedia features of the smartphone. For example, the caller may not know how to zoom in the smartphone camera.All these building blocks come together in the development of an efficient NG9-1-1 Emergency Medical Dispatch protocols. I have provided a sample of these protocols, using the existing Emergency Dispatch Protocols used in the state of New Jersey. The new protocols will have fewer questions and more visual prompts to evaluate the nature of the emergency
A mobile toolkit and customised location server for the creation of cross-referencing location-based services
Although there are several Software Development kits and Application Programming Interfaces for client-side location-based services development, they mostly involve the creation of self-referencing location-based services. Self-referencing location-based services include services such as geocoding, reverse geocoding, route management and navigation which focus on satisfying the location-based requirements of a single mobile device. There is a lack of open-source Software Development Kits for the development of client-side location-based services that are cross-referencing. Cross-referencing location-based services are designed for the sharing of location information amongst different entities on a given network. This project was undertaken to assemble, through incremental prototyping, a client-side Java Micro Edition location-based services Software Development Kit and a Mobicents location server to aid mobile network operators and developers alike in the quick creation of the transport and privacy protection of cross-referencing location-based applications on Session Initiation Protocol bearer networks. The privacy of the location information is protected using geolocation policies. Developers do not need to have an understanding of Session Initiation Protocol event signaling specifications or of the XML Configuration Access Protocol to use the tools that we put together. The developed tools are later consolidated using two sample applications, the friend-finder and child-tracker services. Developer guidelines are also provided, to aid in using the provided tools
A mobile toolkit and customised location server for the creation of cross-referencing location-based services
Although there are several Software Development kits and Application Programming Interfaces for client-side location-based services development, they mostly involve the creation of self-referencing location-based services. Self-referencing location-based services include services such as geocoding, reverse geocoding, route management and navigation which focus on satisfying the location-based requirements of a single mobile device. There is a lack of open-source Software Development Kits for the development of client-side location-based services that are cross-referencing. Cross-referencing location-based services are designed for the sharing of location information amongst different entities on a given network. This project was undertaken to assemble, through incremental prototyping, a client-side Java Micro Edition location-based services Software Development Kit and a Mobicents location server to aid mobile network operators and developers alike in the quick creation of the transport and privacy protection of cross-referencing location-based applications on Session Initiation Protocol bearer networks. The privacy of the location information is protected using geolocation policies. Developers do not need to have an understanding of Session Initiation Protocol event signaling specifications or of the XML Configuration Access Protocol to use the tools that we put together. The developed tools are later consolidated using two sample applications, the friend-finder and child-tracker services. Developer guidelines are also provided, to aid in using the provided tools
Contribution to the improvement of the performance of wireless mesh networks providing real time services
Nowadays, people expectations for ubiquitous connectivity is continuously growing. Cities are now moving towards the smart city paradigm. Electricity companies aims to become part of smart grids. Internet is no longer exclusive for humans, we now assume the Internet of everything. We consider that Wireless Mesh Networks (WMNs) have a set of valuable features that will make it an important part of such environments. WMNs can also be use in less favored areas thanks to their low-cost deployment. This is socially relevant since it facilitates the digital divide reduction and could help to improve the population quality of life. Research and industry have been working these years in open or proprietary mesh solutions. Standardization efforts and real deployments establish a solid starting point.We expect that WMNs will be a supporting part for an unlimited number of new applications from a variety of fields: community networking, intelligent transportation systems, health systems, public safety, disaster management, advanced metering, etc. For all these cases, the growing needs of users for real-time and multimedia information is currently evident. On this basis, this thesis proposes a set of contributions to improve the performance of an application service of such type and to promote the better use of two critical resources (memory and energy) of WMNs.For the offered service, this work focuses on a Video on Demand (VoD) system. One of the requirements of this system is the high capacity support. This is mainly achieved by distributing the video contents among various distribution points which in turn consist of several video servers. Each client request that arrives to such video server cluster must be handled by a specific server in a way that the load is balanced. For such task, this thesis proposes a mechanism to appropriately select a specific video server such that the transfer time at the cluster could be minimized.On the other hand, mesh routers that creates the mesh backbone are equipped with multiple interfaces from different technologies and channel types. An important resource is the amount of memory intended for buffers. The quality of service perceived by the users are largely affected by the size of such buffers. This is because important network performance parameters such as packet loss probability, delay, and channel utilization are highly affected by the buffer sizes. An efficient use of memory for buffering, in addition to facilitate the mesh devices scalability, also prevents the problems associated with excessively large buffers. Most of the current works associate the buffer sizing problem with the dynamics of TCP congestion control mechanism. Since this work focuses on real time services, in which the use of TCP is unfeasible, this thesis proposes a dynamic buffer sizing mechanism mainly dedicated for such real time flows. The approach is based on the maximum entropy principle and allows that each device be able to dynamically self-configure its buffers to achieve more efficient memory utilization. The proper performance of the proposal has been extensively evaluated in wired and wireless interfaces. Classical infrastructure-based wireless and multi-hop mesh interfaces have been considered. Finally, when the WMN is built by the interconnection of user hand-helds, energy is a limited and scarce resource, and therefore any approach to optimize its use is valuable. For this case, this thesis proposes a topology control mechanism based on centrality metrics. The main idea is that, instead of having all the devices executing routing functionalities, just a subset of nodes are selected for this task. We evaluate different centralities, form both centralized and distributed perspectives. In addition to the common random mobility models we include the analysis of the proposal with a socially-aware mobility model that generates networks with a community structure.Actualmente las expectativas de las personas de una conectividad ubicua están creciendo. Las ciudades están trabajando para alcanzar el paradigma de ciudades inteligentes. Internet ha dejado de ser exclusivo de las personas y ahora se asume el Internet de todo. Las redes inalámbricas de malla (WMNs) poseen un valioso conjunto de características que las harán parte importante de tales entornos. Las WMNs pueden utilizarse en zonas menos favorecidas debido a su despliegue económico. Esto es socialmente relevante ya que facilita la reducción de la brecha digital y puede ayudar a mejorar la calidad de vida de la población. Los esfuerzos de estandarización y los despliegues de redes reales establecen un punto de partida sólido.Se espera entonces, que las WMNs den soporte a un número importante de nuevas aplicaciones y servicios, de una variedad de campos: redes comunitarias, sistemas de transporte inteligente, sistemas de salud y seguridad, operaciones de rescate y de emergencia, etc. En todos estos casos, es evidente la necesidad de disponer de información multimedia y en tiempo real. En base a estos precedentes, esta tesis propone un conjunto de contribuciones para mejorar el funcionamiento de un servicio de este tipo y promover un uso eficiente de dos recursos críticos (memoria y energía) de las WMNs.Para el servicio ofrecido, este trabajo se centra en un sistema de video bajo demanda. Uno de los requisitos de estos sistemas es el de soportar capacidades elevadas. Esto se consigue principalmente distribuyendo los contenidos de video entre diferentes puntos de distribución, los cuales a su vez están formados por varios servidores. Cada solicitud de un cliente que llega a dicho conjunto de servidores debe ser manejada por un servidor específico, de tal forma que la carga sea balanceada. Para esta tarea, esta tesis propone un mecanismo que selecciona apropiadamente un servidor de tal manera que el tiempo de transferencia del sistema sea minimizado.Por su parte, los enrutadores de malla que crean la red troncal están equipados con múltiples interfaces de diferentes tecnologías y tipos de canal. Un recurso muy importante para éstos es la memoria destinada a sus colas. La calidad de servicio percibida por los usuarios está altamente influenciada por el tamaño de las colas. Esto porque parámetros importantes del rendimiento de la red como la probabilidad de pérdida de paquetes, el retardo, y la utilización del canal se ven afectados por dicho tamaño. Un uso eficiente de tal memoria, a más de facilitar la escalabilidad de los equipos, también evita los problemas asociados a colas muy largas. La mayoría de los trabajos actuales asocian el problema de dimensionamiento de las colas con la dinámica del mecanismo de control de congestión de TCP. Debido a que este trabajo se enfoca en servicios en tiempo real, en los cuales no es factible usar TCP, esta tesis propone un mecanismo de dimensionamiento dinámico de colas dedicado principalmente a flujos en tiempo real. La propuesta está basada en el principio de máxima entropía y permite que los dispositivos sean capaces de auto-configurar sus colas y así lograr un uso más eficiente de la memoria. Finalmente, cuando la WMN se construye a través de la interconexión de los dispositivos portátiles, la energía es un recurso limitado y escaso, y cualquier propuesta para optimizar su uso es muy valorada. Para esto, esta tesis propone un mecanismo de control de topología basado en métricas de centralidad. La idea principal es que en lugar de que todos los dispositivos realicen funciones de enrutamiento, solo un subconjunto de nodos es seleccionado para esta tarea. Se evalúan diferentes métricas, desde una perspectiva centralizada y otra distribuida. A más de los modelos aleatorios clásicos de movilidad, se incluye el análisis de la propuesta con modelos de movilidad basados en información social que toman en cuenta el comportamiento humano y generan redes con una clara estructura de comunidade