Evaluation of IEEE 802.11 coexistence in WLAN deployments

This is a pre-print of an article published in Wireless Networks. The final authenticated version is available online at: https://doi.org/10.1007/s11276-017-1540-z.Wi-Fi has become a successful technology since the publication of its first WLAN standard due to continuous advances and updates while remaining always backwards compatible. Backwards compatibility among subsequent standards is an important feature in order to take advantage of previous equipment when publishing a new amendment. At present, IEEE 802.11b support is still mandatory to obtain the Wi-Fi certification. However, there are several harmful effects of allowing old legacy IEEE 802.11b transmissions in modern WLAN deployments. Lower throughput per device is obtained at slow rates, but also the effect known as performance anomaly, which nearly leads to starvation of fast stations, has to be taken into account. Finally, backwards compatibility mechanisms pose an important penalty in throughput performance for newer specifications. This paper presents a thorough analysis of the current state of IEEE 802.11, comparing coverage range and throughput performance among subsequent amendments, and focusing on the drawbacks and benefits of including protection mechanisms.Peer ReviewedPostprint (author's final draft

Informe bibliomètric bimestral Campus Baix Llobregat. Base de dades Scopus. Maig-juny 2017

Informe bibliomètric bimestral Campus Baix Llobregat. Base de dades Scopus. Data de la cerca 28/06/2017Postprint (author's final draft

Informe mensual d'articles publicats. Campus Baix Llobregat. Base de dades Scopus. Febrer i març 2019

Informe bibliomètric mensual Campus Baix Llobregat. Base de dades Scopus. Febrer i març 2019Postprint (published version

Wireless local area network management frame denial- of-service attack detection and mitigation schemes

Wireless Local Area Networks (WLAN) are increasingly deployed and in widespread use worldwide due to its convenience and low cost. However, due to the broadcasting and the shared nature of the wireless medium, WLANs are vulnerable to a myriad of attacks. Although there have been concerted efforts to improve the security of wireless networks over the past years, some attacks remain inevitable. Attackers are capable of sending fake de-authentication or disassociation frames to terminate the session of active users; thereby leading to denial of service, stolen passwords, or leakage of sensitive information amongst many other cybercrimes. The detection of such attacks is crucial in today's critical applications. Many security mechanisms have been proposed to effectively detect these issues, however, they have been found to suffer limitations which have resulted in several potential areas of research. This thesis aims to address the detection of resource exhaustion and masquerading DoS attacks problems, and to construct several schemes that are capable of distinguishing between benign and fake management frames through the identification of normal behavior of the wireless stations before sending any authentication and de-authentication frames. Thus, this thesis proposed three schemes for the detection of resource exhaustion and masquerading DoS attacks. The first scheme was a resource exhaustion DoS attacks detection scheme, while the second was a de- authentication and disassociation detection scheme. The third scheme was to improve the detection rate of the de-authentication and disassociation detection scheme using feature derived from an unsupervised method for an increased detection rate. The effectiveness of the performance of the proposed schemes was measured in terms of detection accuracy under sophisticated attack scenarios. Similarly, the efficiency of the proposed schemes was measured in terms of preserving the resources of the access point such as memory consumptions and processing time. The validation and analysis were done through experimentation, and the results showed that the schemes have the ability to protect wireless infrastructure networks against denial of service attacks

Contributions to IEEE 802.11-based long range communications

The most essential part of the Internet of Things (IoT) infrastructure is the wireless communication system that acts as a bridge for the delivery of data and control messages between the connected things and the Internet. Since the conception of the IoT, a large number of promising applications and technologies have been developed, which will change different aspects in our daily life. However, the existing wireless technologies lack the ability to support a huge amount of data exchange from many battery-driven devices, spread over a wide area. In order to support the IoT paradigm, IEEE 802.11ah is an Internet of Things enabling technology, where the efficient management of thousands of devices is a key function. This is one of the most promising and appealing standards, which aims to bridge the gap between traditional mobile networks and the demands of the IoT. To this aim, IEEE 802.11ah provides the Restricted Access Window (RAW) mechanism, which reduces contention by enabling transmissions for small groups of stations. Optimal grouping of RAW stations requires an evaluation of many possible configurations. In this thesis, we first discuss the main PHY and MAC layer amendments proposed for IEEE 802.11ah. Furthermore, we investigate the operability of IEEE 802.11ah as a backhaul link to connect devices over possibly long distances. Additionally, we compare the aforementioned standard with previous notable IEEE 802.11 amendments (i.e. IEEE 802.11n and IEEE 802.11ac) in terms of throughput (with and without frame aggregation) by utilizing the most robust modulation schemes. The results show an improved performance of IEEE 802.11ah (in terms of power received at long range while experiencing different packet error rates) as compared to previous IEEE 802.11 standards. Additionally, we expose the capabilities of future IEEE 802.11ah in supporting different IoT applications. In addition, we provide a brief overview of the technology contenders that are competing to cover the IoT communications framework. Numerical results are presented showing how the future IEEE 802.11ah specification offers the features required by IoT communications, thus putting forward IEEE 802.11ah as a technology to cater the needs of the Internet of Things paradigm. Finally, we propose an analytical model (named e-model) that provides an evaluation of the RAW onfiguration performance, allowing a fast adaptation of RAW grouping policies, in accordance to varying channel conditions. We base the e-model in known saturation models, which we adapted to include the IEEE 802.11ah’s PHY and MAC layer modifications and to support different bit rate and packet sizes. As a proof of concept, we use the proposed model to compare the performance of different grouping strategies,showing that the e-model is a useful analysis tool in RAW-enabled scenarios. We validate the model with existing IEEE 802.11ah implementation for ns-3.La clave del concepto Internet de las cosas (IoT) es que utiliza un sistema de comunicación inalámbrica, el cual actúa como puente para la entrega de datos y mensajes de control entre las "cosas" conectadas y el Internet. Desde la concepción del IoT, se han desarrollado gran cantidad de aplicaciones y tecnologías prometedoras que cambiarán distintos aspectos de nuestra vida diaria.Sin embargo, las tecnologías de redes computacionales inalámbricas existentes carecen de la capacidad de soportar las características del IoT, como las grandes cantidades de envío y recepción de datos desde múltiples dispositivos distribuidos en un área amplia, donde los dispositivos IoT funcionan con baterías. Para respaldar el paradigma del IoT, IEEE 802.11ah, la cual es una tecnología habilitadora del Internet de las cosas, para el cual la gestión eficiente de miles de dispositivos es una función clave. IEEE 802.11ah es uno de los estándares más prometedores y atractivos, desde su concepción orientada para IoT, su objetivo principal es cerrar la brecha entre las redes móviles tradicionales y la demandada por el IoT. Con este objetivo en mente, IEEE 802.11ah incluye entre sus características especificas el mecanismo de ventana de acceso restringido (RAW, por sus siglas en ingles), el cual define un nuevo período de acceso al canal libre de contención, reduciendo la misma al permitir transmisiones para pequeños grupos de estaciones. Nótese que para obtener una agrupación óptima de estaciones RAW, se requiere una evaluación de las distintas configuraciones posibles. En esta tesis, primero discutimos las principales mejoras de las capas PHY y MAC propuestas para IEEE 802.11ah. Además, investigamos la operatividad de IEEE 802.11ah como enlace de backhaul para conectar dispositivos a distancias largas. También, comparamos el estándar antes mencionado con las notables especificaciones IEEE 802.11 anteriores (es decir, IEEE 802.11n y IEEE 802.11ac), en términos de rendimiento (incluyendo y excluyendo la agregación de tramas de datos) y utilizando los esquemas de modulación más robustos. Los resultados muestran mejores resultados en cuanto al rendimiento de IEEE 802.11ah (en términos de potencia recibida a largo alcance, mientras se experimentan diferentes tasas de error de paquetes de datos) en comparación con los estándares IEEE 802.11 anteriores.Además, exponemos las capacidades de IEEE 802.11ah para admitir diferentes aplicaciones de IoT. A su vez, proporcionamos una descripción general de los competidores tecnológicos, los cuales contienden para cubrir el marco de comunicaciones IoT. También se presentan resultados numéricos que muestran cómo la especificación IEEE 802.11ah ofrece las características requeridas por las comunicaciones IoT, presentando así a IEEE 802.11ah como una tecnología que puede satisfacer las necesidades del paradigma de Internet de las cosas.Finalmente, proponemos un modelo analítico (denominado e-model) que proporciona una evaluación del rendimiento utilizando la característica RAW con múltiples configuraciones, el cual permite una rápida adaptación de las políticas de agrupación RAW, de acuerdo con las diferentes condiciones del canal de comunicación. Basamos el e-model en modelos de saturación conocidos, que adaptamos para incluir las modificaciones de la capa MAC y PHY de IEEE 802.11ah y para poder admitir diferentes velocidades de transmisión de datos y tamaños de paquetes. Como prueba de concepto, utilizamos el modelo propuesto para comparar el desempeño de diferentes estrategias de agrupación, mostrando que el e-model es una herramienta de análisis útil en escenarios habilitados para RAW. Cabe mencionar que también validamos el modelo con la implementación IEEE 802.11ah existente para ns-3

Experimental characterization of TCP performance on 802.11n 40 MHz-width channels

RESUMEN: Dentro del Grupo de Ingeniería Telemática (GIT) se han venido realizando numerosos trabajos en el campo de la caracterización del rendimiento de los estándares IEEE 802.11 para redes de área local inalámbrica (WLAN). Hasta la fecha se disponía de un conocimiento profundo de cómo era dicho comportamiento para las primeras especificaciones a/b/g del estándar; sin embargo, la norma 802.11n, aprobada en 2009 y de uso mayoritario actualmente, introduce importantes mejoras, tanto en la capa física como en la capa MAC, por lo que se ha hecho necesario ampliar dicha caracterización. Una de estas mejoras consiste en la técnica denominada “Channel Bonding”, que básicamente es la unión de dos canales de 20 MHz en uno de 40 MHz. Para establecer las diferencias que presenta un canal de 40 MHz frente a un canal de 20 MHz, se han realizado una serie de medidas para caracterizar el rendimiento de una red Wi-Fi utilizando tráfico TCP. Las distintas medidas vendrán condicionadas por el algoritmo de control de congestión de TCP utilizado (New Reno o Cubic), la distancia entre cliente (emisor) y servidor (receptor) dentro de una misma red Wi-Fi, y la caracterización del rendimiento de la red dependiendo de si hay o no tráfico de otras fuentes dentro de la misma red Wi-Fi. Este trabajo es una continuación del TFG “Caracterización experimental del rendimiento del estándar 802.11n en un entorno doméstico” realizado también por el alumno Rodrigo Gañán de Andrés.ABSTRACT: The Telematics Engineering Group (GIT) has been doing a lot of work in the field of performance characterization of IEEE 802.11 standards for wireless local area networks (WLAN). However, the 802.11n standard, approved in 2009 and currently in widespread use, introduces significant improvements in both the physical layer and the MAC layer, making it necessary to extend this characterization. One of these improvements consists of the technique called "Channel Bonding", which is basically the union of two 20 MHz channels into one 40 MHz channel. To establish the differences between a 40 MHz channel and a 20 MHz channel, a series of measurements have been carried out to characterize the performance of a Wi-Fi network using TCP traffic. The different measurements will be conditioned by the TCP congestion control algorithm used (New Reno or Cubic), the distance between client (sender) and server (receiver) within the same Wi-Fi network, and the characterization of the performance of the network depending on whether or not there is traffic from other sources within the same Wi-Fi network. This work is a continuation of the TFG "Experimental characterization of 802.11n performance in home networks" also carried out by the student Rodrigo Gañán de Andrés.Máster en Ingeniería de Telecomunicació

SNR-based evaluation of coexistence in wireless system of hospital

Abstract. The wireless system (IEEE Std. 802.11) of North Karelian Central Hospital (NKCH) has been studied in the newly opened J2 building of the hospital. The measurements have been carried out using Ekahau Sidekick spectrum analyser and Ekahau Pro software. Signal propagation has been modelled in the control ward of the Emergency department because many coexisting systems are used with critical requirements of data communication over there. The analytical models have been developed to understand the radio-frequency (RF) signal propagation in the entire building. Measurements have also been carried out on the entire first floor, in the Department of the Abdominal Diseases on the ground floor and in the Children’s wards on the third floor. The multi-slope path-loss propagation models with shadowing have been generated based on the Received Signal Strength Indicator (RSSI) measurements for typical hospital environment at the 2.4 GHz and 5 GHz Industrial, Scientific, and Medical (ISM) band. The measurements have been carried out within the two predefined routes. The models have also been compared to the empirically derived path-loss models. The probability of signal outage has been calculated for both measured routes. The aggregate interference has been measured within the routes that cover the area where remarkable signal variations and the high level of interference has been indicated based on the heatmaps of Ekahau. The use of Ekahau Sidekick and Ekahau Pro software in the coexistence study has been described. The noise floor has been determined based on the averaged values of the six measurement campaigns. The local changes in signal strength of the desired signal and aggregated power of interference have been studied. The Signal-to-Interference Ratio (SIR) models have been generated within the measured routes. The rapid decreases of Signal-to-Noise Ratio (SNR) have been indicated on all measured floors of building J2. They have been studied and their effect on the network performance has been evaluated. The evaluation has been done by comparing the measured values of RSSI, SNR and SIR to the requirements of the respective Modulation and Coding Scheme (MCS). The link margins have been calculated based on the chosen bit error probability and the given SNR requirement of the respective MCS. The comparison between the measured RSSI readings and the required threshold of the respective MCS has been done using the defined shadowing as a link margin. It has been shown that the measured difference between the signal strength of the 2.4 GHz and 5 GHz bands has been caused by the reduced transmit power at the 2.4 GHz band. Based on the SIR measurements, it has been shown that the access points of the neighbouring building have contributed locally to the measured aggregate interference in the Control ward. However, the primary reason for the decrease of SIR at the 2.4 GHz band has been the decrease of desired signal power that has been contributed by the above mentioned reduced transmit power. The strong SNR drops have been indicated on every measured floor before the roaming has occurred.Sairaalan langattoman järjestelmän arviointi signaali-kohina-suhteen avulla. Tiivistelmä. Tässä diplomityössä on tutkittu Pohjois-Karjalan keskussairaalan (PKKS) langatonta verkkoa (IEEE Std. 802.11) äskettäin avatussa sairaalan laajennusosassa (J2-rakennus). Mittaukset on toteutettu käyttäen Ekahau Sidekick spektrianalysaattoria ja Ekahau Pro -ohjelmaa. Päivystyksen valvontaosasto on valittu tutkimuskohteeksi, koska siellä käytetään paljon eri teknologioihin perustuvia järjestelmiä, joiden välinen tiedonsiirto on luonteeltaan kriittistä. Luotujen mallien avulla rakennuksen langatonta toimintaympäristöä tutkitaan RF-järjestelmän (Radio-Frequency) näkökulmasta myös muissa mittausten kohteina olleissa tiloissa. Mittauksia on tehty myös valvontaosaston ulkopuolella 1. kerroksessa sekä 3. kerroksen lastenosastoilla ja Vatsakeskuksen tiloissa pohjakerroksessa. RSSI-mittausten perusteella on luotu radiotiehäviöihin perustuvat etenemismallit molemmilla käytössä olevilla ISM-taajuuskaistoilla (Industrial, Scientific and Medical bands). Varjostuminen ja etenemishäviökertoimen muutokset on otettu huomioon etenemismalleissa. Mittaukset on suoritettu ennalta määritellyillä reiteillä. Luotuja malleja on verrattu myös tutkimuskirjallisuudessa esitettyihin, empiirisesti johdettuihin etenemishäviömalleihin. Signaalikatkoksen todennäköisyys on laskettu molemmille reiteille 2.4 GHz:n taajuuskaistalla. Vastaanotetun häiriötehon summa on mitattu koko mallinnettavan tilan alueelle ulottuvien mittausreittien pohjalta. Mittausreitit on määritelty Ekahau Pron tuottamien kuuluvuus- ja häiriökarttojen avulla ottaen huomioon havaitut signaalitason vaihtelut. Ekahau Sidekick -spektrianalysaattorin ja Ekahau Pro -ohjelman käyttöä on kuvattu tämän tutkimuksen kontekstissa. Kohinataso on määritelty kaikissa kuudessa mittauskampanjassa mitattujen kohina-tehoarvojen keskiarvona. Paikallisten hyötysignaalinvoimakkuus- ja häiriötehovaihteluiden vaikutusta verkon suorituskykyyn on tutkittu ja molemmat mittausreitit kattavat SIR-mallit (Signal-to-Interference Ratio) on luotu. Kaikissa tutkituissa kerroksissa havaittuja äkillisiä signaali-kohinasuhteen vaihteluita on tutkittu ja niiden vaikutusta järjestelmän suorituskykyyn on arvioitu. Mitattujen hyöty- ja häiriösignaalivaihteluiden arviointi on toteutettu vertaamalla mittaamalla saatuja SNR- (Signal-to-Noise ratio), SIR- ja RSSI-arvoja (Received Signal Strength Indicator) eri tiedonsiirtonopeuksia käyttävien MCS-indeksien vaatimiin signaalinvoimakkuus- ja signaali-kohina-suhteen arvoihin. Kynnysarvoille on laskettu linkkimarginaalit käyttäen mitoitusvaatimuksena valittua bittivirhetodennäköisyyden arvoa. Mitattuja RSSI-arvoja on verrattu käyttäen linkkimarginaalina etenemismallinnuksessa määritettyjä varjostumisvaikutuksen arvoja. 2.4 ja 5 GHz:n taajuusalueiden välillä mitatun signaalinvoimakkuuseron on tutkimuksessa saatujen tulosten perusteella osoitettu olevan seurausta alennetusta lähetystehosta 2.4 GHz:n kaistalla. SIR-mittausten perusteella on todettu viereisen rakennuksen tukiasemien kasvattaneen vastaanotettua häiriötehosummaa valvontaosastolla paikallisesti. Ensisijainen syy mitattuihin SIR-arvojen vaihteluihin ovat kuitenkin alhainen signaalinvoimakkuus 2.4 GHz:n kaistalla, mikä osittain johtuu edellä kuvatusta alennetusta lähetystehosta. Voimakkaita SNR-vaihteluita on mitattu kaikissa kerroksissa ennen kuin päätelaite kytkeytyy uuteen tukiasemaan

Evaluation of IEEE 802.11 coexistence in WLAN deployments

This is a pre-print of an article published in Wireless Networks. The final authenticated version is available online at: https://doi.org/10.1007/s11276-017-1540-z.Wi-Fi has become a successful technology since the publication of its first WLAN standard due to continuous advances and updates while remaining always backwards compatible. Backwards compatibility among subsequent standards is an important feature in order to take advantage of previous equipment when publishing a new amendment. At present, IEEE 802.11b support is still mandatory to obtain the Wi-Fi certification. However, there are several harmful effects of allowing old legacy IEEE 802.11b transmissions in modern WLAN deployments. Lower throughput per device is obtained at slow rates, but also the effect known as performance anomaly, which nearly leads to starvation of fast stations, has to be taken into account. Finally, backwards compatibility mechanisms pose an important penalty in throughput performance for newer specifications. This paper presents a thorough analysis of the current state of IEEE 802.11, comparing coverage range and throughput performance among subsequent amendments, and focusing on the drawbacks and benefits of including protection mechanisms.Peer Reviewe