Catálogo de publicaciones - libros

In this paper we present a fast, a reconfigurable and scalable priority active queue managemnt (AQM) to be used in high-performance switches supporting fine-grained quality of service (QoS) guarantees. Priority queues are used to implement highest-priority-first scheduling policies. Our hardware architecture is based on a new data structure called priority circular linked list (P-CLL). This data structure enables the reconfiguration of the AQM. In addition, the architecture have to scale very well to a large number of priority levels and to large queue sizes. In this respect, we will give a detailed description of our proposed new data structure, the associated algorithms and the adequate hardware implementation.

Due to resource constraints and dynamic topology of Mobile Ad Hoc Networks (MANETs), supporting Quality of Service (QoS) in MANETs is a challenging task. Although lots of research have been done on supporting QoS in the Internet and other networks, they are not suitable for the MANET environment. This paper provides a brief review of the current researches on QoS support in MANETs and proposes a new model for enhancing QoS support in MANETs. Through extensive simulation, we observe and analyze the performance of the network in terms of throughput and average delay. A thorough investigation of the performance of higher and lower priority traffic is made under different traffic loads and mobility scenarios. The simulation results show an improvement of the performance of our QoS model as compared to SWAN[7].

The requirements of today’s telecommunication systems to support high bandwidth and added flexibility brought about the expansion of Asynchronous Transfer Mode (ATM) as a new method of high-speed data transmission. Various analytical and simulation methods may be used to estimate the performance of ATM switches. Analytical methods considerably limit the range of parameters to be evaluated due to extensive formulae used and time consuming iterations. They are not as effective for large networks because of excessive computations that do not scale linearly with network size. One the other hand, simulation-based methods allow determining a bigger range of performance parameters in a shorter amount of time even for large networks. A simulation model, however, is more elaborate in terms of implementation. Instead of using formulae to obtain results, it has to operate software or hardware modules requiring a certain amount of effort to create. In this work simulation is accomplished by utilizing the ATM library – an object oriented software tool, which uses “software chips” for building ATM switches. The distinguishing feature of this approach is cut-through routing realized on the bit level abstraction treating ATM protocol data units, called cells, as groups of 424 bits. The arrival events of cells to the system are not instantaneous contrary to commonly used methods of simulation that consider cells as instant messages. The simulation was run for basic multistage interconnection network types with varying source arrival rate and buffer sizes producing a set of graphs of cell delays, throughput, cell loss probability, and queue sizes. The techniques of rearranging and sorting were considered in the simulation. The results indicate that better performance is always achieved by bringing additional stages of elements to the switching system.

This paper describes the laws of the telecommunications industry in terms of the Weibull and Gompertz functions. The laws and regulations of the industry are presented and analyzed from this perspective. The results show that the regulations fail according to the Gompertz functions.

The aim of this study was to assess the acceptability of a new mobile service; namely hot spot game playing. The more specific objectives were to reveal current mobile phone and new mobile phone service usage, and to relate this to domain-specific innovativeness as well as to willingness to pay. Moreover, to study how a service like this will affect current general consumer behavior. Subjects were female and male volunteers living in the city of Lulea in the northern part of Sweden recruited from the Website www.testplats.com. The results show that the subjects had good knowledge about both mobile telephony and game playing which imply that the knowledge barrier should not be too high to overcome and, hence, the actual adoption of the new service should be promising. However, due to the somewhat immature technologies used, this was not realized in this study. Though, the study in itself seemed to have had an impact on shopping behavior and gave valuable insights to further elaborate upon regarding acceptability of new mobile phone services

From the requirement of shipping enterprises’ communication, this paper presents a solution of safety telecommunication between ocean ships and land station and introduces the structure of system and the method of realization. It also designs a protocol based on satellite data communication and discusses some key technique in realization process.

In this paper, we propose a scheduler based architecture to provide QoS support in IEEE 802.11. Our architecture extends Cali’s dynamic p-persistent 802.11 by providing multiple traffic classes while using separate parameters for QoS and channel access functionalities. We used a weight-based fair scheduler to obtain throughput service differentiation at the node level. Compared to 802.11 EDCF, the scheduler-based architecture gives accurate throughput differentiation and easy tuning. We present the performance results of our scheme using nodes with symmetric traffic flows. The simulation results show that the scheduler based scheme consistently achieves the desired throughput service differentiation among traffic classes, better channel access latencies, incurs very little overhead, and gives higher system throughput than EDCF.

It is often useful to move network models between different network design, simulation and topology discovery tools in order to obtain different view of the network. Unfortunately, these tools are not compatible to each other and cannot be used together directly. This paper presents a tool, Network Design and Simulation Environment (NeDaSE) of version v2.0, developed for the purpose of integrating such different types of tools. Some experiments have been illustrated using topology generation tool BRITE, analytical tool Delite, simulation tool ns-2 and wireless simulator Glomosim. A network description language LNMet-X has been used for the implementation.

Modern high-bandwidth and open networks are a good medium for digital content distribution. However, digital content distribution over open networks can raise an all set of different issues related to piracy and intellectual propriety infringements and circumventions. Therefore, in order to avoid and overcome such issues, a good content security mechanism must be placed online to control and manage how the content access is processed. There are some actual discussions and initiatives going on to provide such controlling mechanisms, but perhaps one of the most highlighted is Digital Rights Management (DRM). Nevertheless, current DRM solutions, although solving part of the problem, most of the times end up adding an additional problem – interoperability. This paper will provide a description of a method and a system that is currently developing a new approach to the DRM interoperability issue. The method, which is described on the paper is part of a DRM system implementation whose description will also be provided here, and is based on the introduction of a middleware layer between the content rendering applications and the rights and content suppliers.