Showing papers by "Francisco J. González-Castaño published in 2007"

Base technologies for vehicular networking applications: review and case studies

Abstract: In this paper, we review the state of the art of two key hardware technologies that support vehicular applications: on-board embedded systems and wireless sensor networks (WSN) We focus on pre-competitive or state-of-the-art hardware, and illustrate its use with two case studies: on-line navigation assistance and data collection in a mobile WSN In the first case (based on a joint collaboration within project FUNCMOV PGIDIT05TIC00501CT, Xunta de Galicia, Spain), we describe our development experience with automotive embedded systems In the second case, we analyze the feasibility of wake-up schema to gather data from highly dispersed sensor nodes The goal of the paper is to offer a perspective on the current possibilities of these hardware systems

On the Implementation of a Multi-Reader Radio Frequency Identification (RFID) Architecture

Abstract: Radio Frequency Identification (RFID) systems are one of the enabling technologies for the ubiquitous computing paradigm. At the moment, the EPCglobal organization leads the development of industry-driven standards for this field and has settled the EPC "Gen 2" as a reference standard. In this paper, we analyze the anti-collision procedure of EPC "Gen 2" to find the time needed to identify a population of tags, by means of the finite Markov-chain of the system. In addition, a UHF multi-reader prototype based on time division multiple access (TDMA) scheme is evaluated in this work. In this TDMA scheme, the reader time-slot duration is allocated according to the computations obtained from our analytical study. The main conclusions derived from this implementation are summarized in this work.

A Survey and Perspective on NVoD Systems for Satellite Networks

Abstract: In this paper, we review different architectures for near video-on-demand (NVoD) systems on satellite networks. In many scenarios, satellites are the only available option for content distribution. On the other hand, video-on-demand (VoD) has been a topic of intense research in the past. The main problem of VoD systems is that their bandwidth requirements do not scale well with user requests. For this reason, VoD is only feasible under some constraints. In general, NVoD systems are an approximation of VoD ones. In them, downloads do not necessarily start when the request arrives, but some time later. By doing so, it is possible to bound the total required bandwidth at the cost of introducing some delay in content download.

Enhanced parallel iterative schedulers for IBWR optical packet switches

Abstract: In this paper we propose an enhanced parallel iterative scheduler for IBWR synchronous slotted OPS switches in SCWP mode. It obtains a maximal matching of packet demands without resource conflicts. The analytical and numerical results are highly competitive regarding previous work.

Decoupled parallel hierarchical matching schedulers

Abstract: The load balanced Birkhoffvon Neumann switch is an elegant VOQ architecture with two outstanding characteristics: (i) it has a computational cost of O(1) iterations and (ii) input controllers do no...

Quantitative assessment of the benefits of RFID technology for libraries: a trans-European study

Abstract: Large libraries are complex organizations. Radiofrequency identification (RFID) technologies allow the deployment of advanced services like re-shelving assistance. A number of commercial solutions for libraries have recently appeared, but so far there was a lack of objective assessments of the real benefits of RFID. In this paper we present the results of the validation that was funded by the EU in the framework of the LIBER-IMMS eTENproject. The validation was performed in libraries with different profiles, in three EU countries.

Nonlinear Optimization of IEEE 802.11 Mesh Networks

Abstract: In this paper, we propose a novel optimization model to plan IEEE 802.11 broadband access networks. From a formal point of view, it is a mixed integer non-linear optimization model that considers both co-channel and inter-channel interference in the same compact formulation. It may serve as a planning tool by itself or to provide a performance bound to validate simpler planning models such as those in [3].

Support Vector Machine Detection of Peer-to-Peer Traffic in High-Performance Routers with Packet Sampling

Abstract: In this paper, we explore the possibilities of support vector machines to identify peer-to-peer (p2p) traffic in high-performance routers with packet sampling. Commercial networks limit user access bandwidth -either physically or logically-. However, in research networks there are no individualbandwidth restrictions, since this would interfere with research tasks. User behavior in research networks has changed radically with the advent of p2p multimedia file transfers: many users take advantage of the huge bandwidth (e.g. compared to domestic DSL access) to exchange movies and the like. This behavior may have a deep impact on research network utilization. Consequently, in the framework of the MOLDEIP project, we have proposed to apply support vector machine detection to identify those activities in high-performance research network routers. Due to their high port rates, those routers cannot extract the headers of all the packets that traverse them, but only a sample. The results in this paper suggest that support vector machine detection of p2p traffic in high-performance routers with packet sampling is highly successful and outperforms recent approaches like [1].

Decoupled parallel hierarchical matching schedulers: Research Articles

Abstract: The load balanced Birkhoff–von Neumann switch is an elegant VOQ architecture with two outstanding characteristics: (i) it has a computational cost of O(1) iterations and (ii) input controllers do not exchange information (as a result, it allows decoupled implementations with a low power density). The load balancing stage guarantees stability under a broad class of traffic patterns. It may alter packet sequence, but this can be solved with appropriate packet selection strategies.The average packet delay caused by previous maximal size matching algorithms, such as iSLIP, RDSRR, or PHM is noticeably lower than that of a Birkhoff–von Neumann switch, especially for low and medium loads. However, they need tightly coupled VOQ controllers, which implies higher power density. For example, this makes difficult to apply those algorithms to optical switching architectures. Moreover, they require O(log2 N) iterations to converge, and this computational cost may be unacceptable for the slot lengths in optical packet switches.In this paper, we propose a family of decoupled Parallel Hierarchical Matching (PHM) VOQ controllers (DPHM). They outperform the Birkhoff–von Neumann scheduler, which can be viewed as a member of the family (in fact, the simplest one). DPHM schedulers have a computational cost of O(1) iterations and, unlike last generation maximal size matching algorithms, they allow a low input controller interconnection complexity (low power density switch implementation). Copyright © 2006 John Wiley & Sons, Ltd.

Decoupling Maximal Size Matching Schedulers for Scalable Electro-Optical Switches

Abstract: In this paper we propose a novel scaling approach that combines the advantages of the fully decoupled Birkhoff-von Neumann architecture and the low latency of maximal size matching (MSM) schedulers, to meet the highly demanding performance requirements of electro-optical switches. We identify a sufficient condition for the stability of a decoupled MSM scheduler. The particular case of decoupled iSLIP is studied.

Emulating Access Grid features at web endpoints

Abstract: In this paper we present a system that captures and processes streams from Access Grid virtual rooms (venues) and distributes them to web endpoints. Its distinctive advantage is the emulation of Access Grid features using standard web clients. The system includes a toolset to handle audio and video contents, demultiplex the different sources, transcode them to adequate formats and store the resulting multimedia streams in repositories in real-time. A specialized server delivers those streams to standard web browsers that synchronize them, emulating typical Access Grid features like multiple windows or dynamic video selection. Web browsers can compose multiple independent streams, providing the appearance of Access Grid presentations. This paper presents the design principles, the system architecture and our current implementation in detail.

Load balanced distributed schedulers for WASPNET Optical packet switches maintaining packet order

Abstract: Previously the author's (Lopez-Bravo et al., 2007) proposed the Load Balanced WASPNET Scheduler (LBWS), a novel scheduling approach for WASPNET optical packet switching (OPS) nodes. Unlike the original WASPNET description, LBWS is fully distributed and its computational cost is independent from switch size. Since it predicts packet delays at packet ingress based on a deterministic evolution of the switch configuration, it is not necessary to emulate RAM memories. However, LBWS does not maintain the packet sequence. In this paper we present the LBWS algorithm with packet ordering (OLBWS), the first step to prevent mis-sequencing in a LBWS scheduler. We show that despite the algorithm simplicity a reasonable throughput can be achieved.

BlueSS: Extending VoIP Chat Applications with Symbian Cordless Terminals

Abstract: Internet telephony has become extremely popular in the last years, specially after the Skype [1] launch in 2003. Currently, Skype has over six million on-line users. In the meanwhile, traditional text-oriented Internet chat and VoIP are converging. The top messaging applications offer VoIP services [2]. In this context, social relations and entertainment are a powerful driving force, especially among young people. There is a clear link with the explosion of SMS messaging, boosted by the extension of cellular telephony: in 2003 Europe had 0.8 cell phones per inhabitant. Countries like Sweden or Luxembourg have reached a 100% penetration [3]. It is not surprising that cell phones and VoIP technologies are also converging. This is our main motivation. We present BlueSS, an open source Symbian [4] application that turns a Nokia phone into a wireless extension of a Skype PC client.

Support Vector Machine Detection of Peer-to-Peer Traffic in High-Performance Routers with Packet Sampling: Nonlinear Kernel Approach

Abstract: In this paper, we apply nonlinear support vector machines to identify peer-to-peer (p2p) traffic in high-performance routers with packet sampling Due to their high port rates, those routers cannot extract the headers of all the packets that traverse them, but only a sample The results in this paper suggest that nonlinear support vector machines are highly successful and outperform recent approaches like [1,2]