Finding the sweet spot for frame aggregation in 802.11 WLANs

This letter proposes an algorithm for the dynamic tuning of the maximum size of aggregated frames in 802.11 WLANs. Traffic flows with opposed requirements may coexist in these networks: traditional services as web browsing or file download that need high throughput, and services with real-time requirements that need low latency. The proposed algorithm allows the network manager to find an optimal balance (i.e. the ''sweet spot'' between throughput and latency: a ''delay budget'' can be assigned to real-time flows, with the objective of keeping the latency as close as possible to that budget, while penalizing the throughput of traditional services as little as possible. © 1997-2012 IEEE

IoTsafe, Decoupling Security from Applications for a Safer IoT

The use of robust security solutions is a must for the Internet of Things (IoT) devices and their applications: regulators in different countries are creating frameworks for certifying those devices with an acceptable security level. However, even for already certified devices, security protocols have to be updated when a breach is found or a certain version becomes obsolete. Many approaches for securing IoT applications are nowadays based on the integration of a security layer [e.g., using transport layer security, (TLS)], but this may result in difficulties when upgrading the security algorithms, as the whole application has to be updated. This fact may shorten the life of IoT devices. As a way to overcome these difficulties, this paper presents IoTsafe, a novel approach relying on secure socket shell (SSH), a feasible alternative to secure communications in IoT applications based on hypertext transfer protocol (HTTP and HTTP/2). In order to illustrate its advantages, a comparison between the traditional approach (HTTP with TLS) and our scheme (HTTP with SSH) is performed over low-power wireless personal area networks (6loWPAN) through 802.15.4 interfaces. The results show that the proposed approach not only provides a more robust and easy-To-update solution, but it also brings an improvement to the overall performance in terms of goodput and energy consumption. Core server stress tests are also presented, and the server performance is also analyzed in terms of RAM consumption and escalation strategies

Can a Wi-Fi WLAN support a first person shooter?

In corporate and commercial environments, the deployment of a set of coordinated Wi-Fi APs is becoming a common solution to provide Internet coverage to moving users. In these scenarios, real-time services as online games can also be present. This paper presents a set of experiments developed in a test scenario where an end device moves between different APs while generating game traffic. A WLAN solution based on virtual APs is used, in order to make the handoffs transparent for Layer 3. The results show that it is possible to maintain an acceptable level of subjective quality during the handoff. At the same time, it is set clear that the fact of having a gamer in an AP could be taken into account by radio resource management algorithms, in order to provide a better quality

Attention to Wi-Fi Diversity: Resource Management in WLANs with Heterogeneous APs

Many home networks integrate a small number (typically 2-4) of Wi-Fi Access Points (APs), with heterogeneous characteristics: different 802.11 variants, capabilities and security schemes. This paper proposes the consideration of these specific characteristics in order to improve the management of network resources. Three use cases are presented in order to showcase the potential benefits. By the use of a user-space AP, which works in coordination with a controller, the network is able to assign each connected station to the AP that best fits with its characteristics. The system also manages security, avoiding the need of adding specific elements for authentication, encryption or decryption. Extensions are proposed to an existing protocol that defines the communication between the AP and the controller, in order to communicate and store the specific characteristics of each AP and end device. This includes new association and handoff schemes that do not introduce any additional delay. The system has been implemented in a real environment, and a battery of tests has been run using three hardware platforms of different characteristics. The results show that handoffs between bands are possible, and estimate the processing delays, the Round-Trip Time and the handoff delay, which is small enough in order not to produce any significant disruption to the user (10-50 ms). Finally, the scenarios of interest have been replicated in a simulation environment, showing that significant benefits can be achieved if the specific characteristics of each AP and station are considered

Leveraging on Digital Signage Networks to Bring Connectivity IOT Devices

The number of Internet-connected devices exceeds the world’s population by more than three times and this figure is expected to be doubled within the next five years. The Internet of Things is a concept that describes this trend and outlines certain aspects of design and functionality that new devices should incorporate for a successful integration into the Internet. In this respect, Digital Signage networks traditionally used for audiovisual media, accomplish many of the characteristics of the Internet of Things devices: interoperability, mobility, scalability and ubiquity, both in terms of access and control of devices and regarding the information they generate. This paper raises the power to employ a proposed Digital Signage network as a substrate to connect other types of devices that can benefit from the advantages of this kind of networks. For that aim, the main problems for this integration are discussed, mainly those related to the bidirectional tunneling scheme used in the proposed Digital Signage solution. The effects of this tunneling approach are analyzed in scenarios with bandwidth constraints, and different solutions are proposed. Tunneling performance in mobility is improved, to increase the amount of Internet of Things devices and applications that can benefit from this type of network. El número de dispositivos conectados a Internet supera actualmente a la población mundial por más de tres veces y se espera que esta cifra se duplique en los próximos cinco años. El Internet de las Cosas es un concepto que describe esta tendencia y perfila ciertos aspectos de diseño y funcionalidad que los nuevos dispositivos deben incorporar para lograr una integración exitosa en Internet. En este sentido, las redes digital signage utilizadas tradicionalmente para los medios de comunicación audiovisual cumplen muchas de las características requeridas en el contexto del Internet de las Cosas: interoperabilidad, movilidad, escalabilidad y ubicuidad; relativas tanto al acceso y control de dispositivos como a la información que estos generan. En este trabajo se plantea el poder de emplear la red digital signage propuesta como sustrato para poder conectar otros tipos de dispositivos para que así puedan aprovechar las ventajas de estas redes. Para ese fin, se discuten los principales problemas existentes en esta integración, prestando especial atención al esquema de túnel bidireccional utilizado en la solución digital signage propuesta. Los efectos de este enfoque de tunelación se analizan en escenarios con limitaciones de ancho de banda y se proponen diferentes soluciones. Con ello se consigue mejorar el rendimiento del túnel en movilidad, facilitando la integración de más dispositivos al Internet de las Cosas al permitir que puedan integrarse en este tipo de redes

Integrin-Specific Mechanoresponses to Compression and Extension Probed by Cylindrical Flat-Ended AFM Tips in Lung Cells

Cells from lung and other tissues are subjected to forces of opposing directions that are largely transmitted through integrin-mediated adhesions. How cells respond to force bidirectionality remains ill defined. To address this question, we nanofabricated flat-ended cylindrical Atomic Force Microscopy (AFM) tips with ∼1 µm2 cross-section area. Tips were uncoated or coated with either integrin-specific (RGD) or non-specific (RGE/BSA) molecules, brought into contact with lung epithelial cells or fibroblasts for 30 s to form focal adhesion precursors, and used to probe cell resistance to deformation in compression and extension. We found that cell resistance to compression was globally higher than to extension regardless of the tip coating. In contrast, both tip-cell adhesion strength and resistance to compression and extension were the highest when probed at integrin-specific adhesions. These integrin-specific mechanoresponses required an intact actin cytoskeleton, and were dependent on tyrosine phosphatases and Ca2+ signaling. Cell asymmetric mechanoresponse to compression and extension remained after 5 minutes of tip-cell adhesion, revealing that asymmetric resistance to force directionality is an intrinsic property of lung cells, as in most soft tissues. Our findings provide new insights on how lung cells probe the mechanochemical properties of the microenvironment, an important process for migration, repair and tissue homeostasis

The PSE-ID-CATEGO system

draft-saldana-tsvwg-tcmtf-04 This document describes a method to improve the bandwidth utilization of network paths that carry multiple streams in parallel sharing a common path. The method combines standard protocols that provide compression, multiplexing, and tunneling over a network path for the purpose of reducing the bandwidth used when multiple streams are carried over that path. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is a

Avances en regulacion natural de la fertilidad

Centro de Informacion y Documentacion Cientifica (CINDOC). C/Joaquin Costa, 22. 28002 Madrid. SPAIN / CINDOC - Centro de Informaciòn y Documentaciòn CientìficaSIGLEESSpai

Vegetable consumption and carotenoids in plasma and adipose tissue in Malaga, Spain

Objective: To study relationships between habitual dietary intake, adipose tissue concentrations of alpha-carotene; beta carotene and lycopene, and plasma concentrations of alpha- and beta-carotene. Design: Cross-sectional study including assessment of food habits by a food frequency questionnaire and 48-hour recall and determination of carotenoid concentrations in adipose tissue and plasma. Subjects: 51 women (mean age of 62 years) from the control group of the European Community Multicentre. Study on Antioxidants, Myocardial Infarction, and Breast Cancer (EURAMIC), Malaga, Spain. Results: In adipose tissue, beta-carotene was correlated with consumption of green pepper (r = 0.36; p <0.05) and lycopene with total fruit/vegetable intake (r = 0.28; p <0.05), green pepper (r = 0.31;