New algorithm for distributed frequency assignments in IEEE 802.11

The continuous growth of IEEE 802.11 wireless local area networks (WLAN) brings the benefit of a high speed wireless access to packet networks, such as Internet. But it also entails the successive appearance of new unresolved problems. One of these problems consists in the degradation of the performance observed by the users when there is a great number of radio networks coexisting in the same area. In densely populated zones it is not strange to find WLANs of different nature (private, public, etc.) sharing a scarce resource as it is the radio spectrum. This problem can be mitigated with an appropriate channel allocation. In this paper we present an algorithm for the frequency assignment problem (FAP) in IEEE 802.11, based on classical graph colouring but adding the objective of reducing interferences among overlapping cells, and thus improving the global throughput performance. An accurate evaluation of interferences is obtained not only measuring power levels, but also being aware of traffic load. Important performance improvements have been observed on a real scenario

Despliegue de WLANs en exteriores : desarrollo de una herramienta para la toma de medidas georeferenciadas

Peer Reviewe

Redes celulares 4G basadas en Mobile IPV6 con soporte de nodos durmientes

Este artículo describe el protocolo Mobile IPv6 que permite la movilidad de nodos e ntre redes sin pérdida de conecti vidad y que podría ser uno de los pil ares de la denomi nada 4G de redes celulares. Además se desc ribe las modifi cacio nes teóricas y prácti cas, a partir de una implementación en código abierto de Mobile IPv6, para que este protocolo soporte de nodos móviles durmie ntes, nodos que para ahorrar batería desacti van periódi camente su interfaz radi o c uando no la necesitan. Todo e llo probado sobre un maqueta IPv6.Peer Reviewe

Despliegue de una WLAN en la EPSC

Peer Reviewe

Despliegue de una WLAN en la EPSC

Peer Reviewe

Despliegue de WLANs en exteriores : desarrollo de una herramienta para la toma de medidas georeferenciadas

Peer Reviewe

Evaluation of receiver-feedback techniques for fragmentation over LPWANs

© 2021 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other worksThe Internet Engineering Task Force (IETF) has standardized a new framework for IPv6 support over Low Power Wide Area Networks (LPWANs), called Static Context Header Compression and Fragmentation (SCHC). SCHC includes acknowledgment (ACK)-based mechanisms for reliable fragmented packet transmission. For the latter, SCHC defines a Receiver-Feedback Technique (RFT), called Compressed Bitmap (CB), by which a receiver reports to the sender whether the fragments carrying a packet have been received or not. Such information is carried as ACK payload. Considering the extraordinary frame size and message rate constraints of LPWANs, ACK payload size becomes crucial. In this paper, we compare the performance of CB with that of several alternative RFTs, namely List of Lost Fragments (LLF), List of Deltas (LoD), and Uncompressed Bitmap (UB), where the latter is used as a benchmark. We evaluate the considered RFTs in terms of ACK size, number of Layer 2 (L2) frames needed to carry an ACK, and ACK Time on Air. Our analysis shows that the use of RFTs different from CB offers significant performance improvement in many scenarios. Furthermore, we provide guidance on which RFT should be used for different packet sizes, error rates and error patterns.This research is funded in part by the ERDF and the Spanish Government through project TEC2016-79988-P and project PID2019-106808RA-I00, AEI/FEDER, EU.Peer ReviewedPostprint (author's final draft

The SF12 well in LoRaWAN: problem and end-device-based solutions

© 2021 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/)LoRaWAN has become a popular technology for the Internet of Things (IoT) device connectivity. One of the expected properties of LoRaWAN is high network scalability. However, LoRaWAN network performance may be compromised when even a relatively small number of devices use link-layer reliability. After failed frame delivery, such devices typically tend to reduce their physical layer bit rate by increasing their spreading factor (SF). This reaction increases channel utilization, which may further degrade network performance, even into congestion collapse. When this problem arises, all the devices performing reliable frame transmission end up using SF12 (i.e., the highest SF in LoRaWAN). In this paper, we identify and characterize the described network condition, which we call the SF12 Well, in a range of scenarios and by means of extensive simulations. The results show that by using alternative SF-management techniques it is possible to avoid the problem, while achieving a packet delivery ratio increase of up to a factor of 4.7.Postprint (published version

Seguretat i Administració de Xarxes. Verificació del funcionament d’SSH

Cas pràctic2022/202