Case Study: Installing RFID Systems in Supermarkets

Radio frequency identification technology (RFID) is considered as the reference technology for wireless identification and item traceability. Supermarkets are one of those scenarios where the RFID potential can be harnessed. In theory, RFID in supermarkets shows several advantages compared with traditional barcode systems, offering real‐time inventory, stock control, cash queues, among others. In practice, its massive and global implementation is still being delayed due to the high quantity of factors that degrade the RFID system performance in these scenarios, causing uncontrolled items and identification losses and, at the end, economical losses. Some works in the scientific literature studied a single or a set of problems related to RFID performance, mostly focused on a specific communication layer: antennas and hardware design, interferences at physical layer, medium access control (MAC) protocols, security issues, or middleware challenges. However, there are no works describing in depth the set of factors affecting RFID performance in a specific scenario and contemplating the entire communication layer stack. The first challenge of this chapter is to provide a complete analysis of those physical and environmental factors, hardware and software limitations, and standard and regulation restrictions that have a direct impact on the RFID system performance in supermarkets. This analysis is addressed by communication layers, paying attention to the point of view of providers, supermarket companies, and final customers. Some of the most feasible and influential research works that address individual problems are also enumerated. Finally, taking the results extracted from this study, this chapter provides a Guide of Good Practices (GGPs), giving a global vision for addressing a successful RFID implementation project, useful for researchers, developers, and installers

Fair bandwidth allocation algorithm for PONS based on network utility maximization

Network utility maximization (NUM) models have been successfully applied to address multiple resource- allocation problems in communication networks. This paper explores, for the first time to our knowledge, their application to modeling the bandwidth-allocation problem in passive optical networks (PONs) and long-reach PONs. Using the NUM model, we propose the FEx-DBA (fair excess-dynamic bandwidth allocation) algorithm, a new DBA scheme to allow a fair and efficient allocation of the upstream channel capacity. The NUM framework provides the mathematical support to formally define the fairness concept in the resource allocation and the guidelines to devise FEx-DBA. A simulation study is conducted, whereby FEx-DBA is compared to a state-of-the-art proposal. We show that FEx-DBA (i) provides bandwidth guarantees to the users according to the service level agreement (SLA) contracted and fairly distributes the excess bandwidths among them; (ii) has a stable response and fast convergence when traffic or SLAs change, avoiding the oscillations appearing in other proposals; (iii) improves average delay and jitter measures; and (iv) only depends on a reduced set of parameters, which can be easily tuned.This work has been funded by Spanish Ministry of Science and Innovation (TEC2014-53071-C3-2-P and TEC2015-71932-REDT)

Effects of baby-adult interaction on baby's learning of aquatic skills in an aquatic program: a sociocultural approach

Based on a sociocultural approach, the article aims to explore the role played by the baby-adult interaction on the acquisition of baby's water motor skills in a baby swimming program. With a direct and intrasubject observation (n = 4) and an ad hoc category system, a quantitative approach research with a quasiexperimental design was designed. The interactions were recorded in video, every two weeks, and during the four months of the aquatic program. The results describe the educational context of the interaction according to the categories, and describe the improvement of the babie’s water motor skills. These results allow us to suggest which conditions of the interaction favour the water motor skills learning of the babies.A través de uma abordagem sociocultural, o artigo pretende explorar o papel desempenhado pela interação bebê-adulto na aquisição de habilidades motoras aquáticas do bebê, no âmbito de um programa educacional. Com base em uma observação direta e intrassujeita (n = 4) e na criação de um sistema de categorias ad hoc, foi desenvolvida uma pesquisa de abordagem quantitativa com delineamento quase-experimental. As interações foram gravadas em vídeo, quinzenalmente e durante os quatro meses do programa aquático. Os resultados descrevem o contexto educacional da interação de acordo com as categorias de análise e a melhoria das habilidades aquáticas em bebês. Esses resultados nos permitem sugerir quais condições da interação favorecem o aprendizado das habilidades aquáticas dos bebêsMediante un enfoque sociocultural, el artículo se propone explorar el papel que juega la interacción bebéadulto sobre la adquisición de las destrezas motrices acuáticas del bebé en el marco de un programa educativo. Basándose en una observación directa e intrasujeto (n = 4) y la creación de un sistema de categorías ad hoc, se diseñado una investigación de aproximación cuantitativa y con un diseño cuasi experimental. Se registraron las interacciones en video, quincenalmente y durante los cuatro meses del programa acuático. Los resultados describen el contexto educativo de la interacción conforme a las categorías de análisis y la mejora de las destrezas acuáticas en los bebés. Estos resultados permiten sugerir qué condiciones de la interacción favorecen el aprendizaje de las destrezas acuáticas de los bebés

W2LAN: Protocol that transforms a 802.11 Mobile Ad-Hoc Network (MANET) into an Ethernet LAN

ABSTRACT To overcome the partial visibility problem that Mobile Ad-Hoc Networks (MANET) exhibit [1] data link-level (level 2 OSI) routing protocols must be considered. Examples of protocols in use are the Ad Hoc On-Demand Distance Vector (AODV) [2] routing protocol -reactiveand the Destination-Sequenced Distance Vector (DSDV) [3] routing protocol -proactive-, and reviews of other routing protocols are available i

Polymer microfibers obtained using porous silicon templates

The deposition of specific materials into ordered pores arranged in a regular lattice allows the fabrication of ordered fiber arrays. Porous silicon is an attractive candidate for use as a template because the porosity and pore size can be tuned. Polymer microfibers using macroporous silicon with various pore depths as template system is reported here. The method entails vacuum infiltration of a polymer solution into the pores of the template. Two different types of polymer were selected in order to obtain ordered arrays of fibers made from Poly(methyl) methacrylate) or Poly(dimethylsiloxane). Microtubes were obtained when we used a silicon membrane as a template, whereas microfibers were obtained when we used a silicon template with pores opened only at one end.Peer ReviewedPostprint (published version

Polymer microfibers obtained using porous silicon templates

The deposition of specific materials into ordered pores arranged in a regular lattice allows the fabrication of ordered fiber arrays. Porous silicon is an attractive candidate for use as a template because the porosity and pore size can be tuned. Polymer microfibers using macroporous silicon with various pore depths as template system is reported here. The method entails vacuum infiltration of a polymer solution into the pores of the template. Two different types of polymer were selected in order to obtain ordered arrays of fibers made from Poly(methyl) methacrylate) or Poly(dimethylsiloxane). Microtubes were obtained when we used a silicon membrane as a template, whereas microfibers were obtained when we used a silicon template with pores opened only at one end.Peer Reviewe