COMPUTER NETWORKS

Author: GARCÍA SÁNCHEZ ANTONIO JAVIER.
Year: 2005.
University: POLITÉCNICA DE CARTAGENA [www.upct.es].
Place of defense: ESCUELA TÉCNICA SUPERIOR DE INGENIEROS DE TELECOMUNICACIÓN.
Place of preparation: ESCUELA TÉCNICA SUPERIOR DE INGENIEROS DE TELECOMUNICACIÓN.

Summary: Today, telecommunications networks are made up of complex environments with a lot of equipment and technologies diverse nature that characterize as heterogeneous systems. The integration of different operating systems, network technologies and programming languages is a problem that mucos researchers have tried and middleware technologies allow resolved. The middleware is a software layer between the application and ordered the transport layer that enables the programmer to isolate itself from palicaciones the underlying operating system, protocol stack and hardware devices. Within the various middleware, CORBA is the greater flexibility offered both in the quantity of programming languages it supports as in the number of operating systems that can be applied. Multimedia applications take on a special significance because of the amount of resources they require. In particular, it highlights the uncompressed video applications. These are needed in various fields of work (military, medical, industrial, etc.), which coupled with improved bandwidth of existing networks (especially local), allowing these applications can be integrated with other reach multimedia services of interest. This dissertation presents a study on the appropriateness of using a middware as ACE + TAO in widespread use among service Audio / Video Streaming. The study provides the ability to validate this distribution of CORBA and its multimedia service, allowing the definition of the conditions of service use A / V streaming. At present, the development of applications using multimedia service A / V streaming approved for OMG CORBA is unique. Therefore, this dissertation is proposed to design a new architecture that provides the creation of a service A / V streaming on the NET platform. The evaluation of this service provides a comparative picture between the two working environments, and CORBA. NET platform. A key aspect is the study of the limitations offered pr service A / V streaming and do not allow greater flexibility in their use or adapt to many of the needs of developers of multimedia applications. It is proposed to remedy these shortcomings with the design of an extension of service A / V streaming, providing some of the features previously lacked. A service widely used within CORBA is the Service Notifications. This service offers several features highlighting including asynchronous communication between clients and servers and filtering messages. The ability to adapt to the service of search algorithms decentralized, open a new field of action within peer-to-peer applications. In this dissertation is also proposing a new service using the CORBA Notification Service, for the development of peer-to-peer applications in heterogeneous work environments.

Author: GARCÍA SÁNCHEZ FELIPE.
Year: 2005.
University: POLITÉCNICA DE CARTAGENA [www.upct.es].
Place of defense: ESCUELA TÉCNICA SUPERIOR DE INGENIRÍA DE TELECOMUNICACIÓN.
Place of preparation: ESCUELA TÉCNICA SUPERIOR DE INGENIERÍA DE TELECOMUNICACIÓN.

Summary: The development of integrated applications in heterogeneous systems (consisting of different operating systems, network technologies and programming languages), has been the subject of intense study in software engineering over the last decade. The problems associated with this reality, is addressed through an additional software layer, between the transport layer and the application. The middleware layer. This layer offers significant advantages to application programmers, which are released details relatiovs the computer where the application is running (eg Sistma opoerativo), and network communications (eg protocols, network technologies), and only have to worry about the relationship with this new intermediate level. Among the proposed middleware COBRA is perhaps the most widely used. CORBA has interfaces to a large number of programming languages, and versions compativles for different operating systems. However, the problems are most acute when it comes to multimedia applications and streams audio and / or video. The transmission of this type of traffic has a number of special requirements in terms of delays, bandwidth, etc., that make traditional communications middleware are not valid. The CORBA specification of the service A / V streaming, is specifically designed to facilitate the development of such applications. This thesis is focused on this specification, studying and identifying their limitations in certain application environments. As a result, a proposed extension to the service A / V streaming, it is designed to address the shortfalls. One of the environments where they had studied the application of this service A / V streaming, has been to wireless networks. In addition to the direct application of the existing specifications to wireless media. Doctoral dissertation This brings the design of a new service that allows extend funcionalmiento service A / V streaming to wireless environments, providing applications in the middle radiated mobility. The new service is not based on existing specifications lasa (called Wireless Access and Terminal Mobility), and resolves the process of interconnection to the wired network in an efficient manner. In addition, among other features, allows for the transmission of asynchronous events, something much needed in wireless environments, mobility applications that can be source or destination of the stream A / V system networking allowing retrieve information that is critical having lost in the process.

Author: SÁNCHEZ LAGUNA JUAN ANTONIO.
Year: 2006.
University: MURCIA [www.um.es].
Place of defense: FACULTAD DE INFORMATICA - UNIVERSIDAD DE MURCIA.
Place of preparation: FACULTAD DE INFORMÁTICA.

Summary: At present, wireless sensor networks (WSN) enjoy tremendous interest on the part of not only the scientific community but also the business community. This is due in part to recent advances in miniaturization, packing and cost reduction in the manufacture of electronic components. Thanks to them, it is now possible to deploy WSN real composite potentially thousands of sensor nodes and low-cost all applications that, in their day were designed to take advantage of the characteristics of WSNs, begin and develop. These include the monitoring of large areas of natural complex or restricted access, environmental monitoring, early detection of outbreaks of fires in wooded areas, and so on. Most of these applications make use of the so-called group communications. They send messages between a source and destination many, many sources and a destination or many sources and many destinations. Such communications could be carried out efficiently using multicast routing protocols, which would facilitate the development of applications in WSNs. The development of multicast routing protocols for WSNs presents great challenges. The WSNs are characterized by having a topology changing due to the sensors that make up are not always active. These cycles of activity / inactivity Responding to name duty-cycle, are designed to reduce the energy consumption of sensors. The sensors typically have limited energy resources and it is desirable to reduce their energy consumption to a minimum. Moreover, its computing power is very low due to the hardware used in its construction, which makes routing protocols developed for WSNs be simple in terms of computabilidad. These factors, coupled with the fact that the sensors on WSNs generally do not have a mechanism for addressing such as IP routing protocols to prevent reuse classics designed to Ad-Hoc networks. These protocols, which normally make use of the flood, involving excessive overhead for WSNs by the amount of messages involved in them. A new class of routing algorithms based on coordinates is developing in the field of WSN, due in part to not suffer from these problems. We named geographic routing algorithms, based decision making routing only on the positions of the nodes. Given the need for group communications in WSNs in this thesis has dealt with the design of multicast routing algorithms that allow a WSN offer natively group communications to applications that are being developed at present. As a secondary objective, and bearing in mind the limited energy resources at their disposal sensors, it has sought to make the algorithms designed with a reduced energy consumption. Thus, after conducting an evaluation of the various proposals and select as its starting point the geographical unicast routing algorithms, being scalable and fully distributed, have proposed two geographic multicast routing algorithms: GMR and LEMA. The first has been designed to reduce the total bandwidth necessary to send a message to a group of recipients. By reducing the total number of messages sent is achieved by reducing energy because transmissions account for the largest percentage of energy consumed by a node. Simulations have been performed to evaluate the performance of the algorithm and the results have been compared with those of the main existing proposal so far in the literature, PBM ((em Possition Bassed Multicast Routing)). The results obtained by GMR match or improve the PBM with the addition of a GMR you 8 Jan c c48 oste computational lower than PBM and unlike the latter does not need to be parameterized. Unlike GMR, in the design of the protocol SLOGAN models have been used in the network have been taken into account transmission errors inherent in wireless communications as well as the ability to adjust the transmitting power they possess most of the current sensors. Prior to designing SLOGAN and with the aim of using it in the same, has been designed and evaluated satisfactorily LOSR, a technique to reduce energy, which is applicable to any geographical unicast routing algorithm and SUMMER, a metric estimation of energy consumption on network models considering potential losses and use of retransmissions. LOSR optimizes each decision algorithm which applies to reducing energy consumption to a minimum. To do so, once a node has selected its next leap, using only local information, determines the most efficient in terms of energy consumption between the current node and the next jump. Then, using source routing, forces the message to follow this path locally optimal. SLOGAN used LOSR to reduce energy multicast tree branches. Using metrics as SUMMER to find the shortest path in LOSR, is achieved taking into account the probability of error in the decisions taken by selecting the links and more likely to succeed and less consumption is estimated to have. This behavior raises the percentage of messages delivered end-to-end. Lastly, SLOGAN uses a variation of the MST heuristics to make decisions branching. The heuristic is applied individually by each node participant multicast routing. Using only the position of the destinations included in the message header, a node is able to decide what is more convenient, ramificar or continue on the same branch. The result is a multicast tree very similar to that obtained by applying the same heuristics so centralized. Simulations have been performed to evaluate the performance of SLOGAN. Because so far do not exist in the literature other geographic multicast routing algorithms, the results have been compared with those obtained by the major algorithms centralized. The multicast trees constructed by SLOGAN have a lower power consumption that built by these algorithms, plus the percentage of delivery is higher.