PHY/MAC Enhancements and QoS Mechanisms for Very High Throughput WLANs: A Survey

Charfi, Emna; Fourati, Lamia Chaari; Kamoun, Lotfı

doi:10.1109/surv.2013.013013.00084

Cited by 111 publications

(64 citation statements)

References 60 publications

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“…The RTS/CTS algorithm was significantly improved for use in networks operating under the specifications of 802.11n and ac, but the basic principle when sending an RTS frame -the principle of competitive access to the environment remained [1][2][3][4].…”

Section: телекомунікації та захист інформаціїmentioning

confidence: 99%

Estimation of probabilistic processes in wireless networks of 802.11 standard

Lazebnyi

Yin

2017

Mìkrosist. elektron. akust.

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Abstract-The article analyzes mechanisms of collision in a wireless 802.11 network with competitive access to a radio channel. The calculated relationships for determining the probabilities of collisions in the network as a whole in the presence of N active stations with a saturated load, and also for one station when implementing the binary exponential mechanism of increasing the competitive window are presented. The graphs, which illustrate the proposed equations, are given in this article too. An equation is also proposed for determining the probability of successful transmission of a data frame depending on the number of active stations and the initial value of the competitive window. The equations are obtained using the concept of a virtual competitive window.It was shown that in the case, where the number of active stations is one third of the contention window, the probability of collisions is about 0.25. This means that in the network with such number of active stations, each station will experience the collision at every fourth attempt to transmit a frame of data in average. The next attempt to transmit frame of data will be carried out by using the larger contention window. Collisions will cause the increase of transmitting time duration and its irregularity.It was analyzed the efficacy of application of binary exponential law for the change of the contention window for active stations, caught in a conflict when trying to access the channel.The equation for estimate the changes in the probability of collision and the number of competing stations in the access cycle was obtained by taken into account that it will take place when a quasi-stationary mode of operation of wireless networks is established.It was shown that the most effectively this mechanism is triggered in the early stages of repeated access to radio channel. Those stations that carry out the 5-th and 6-th attempts to access channel have a little impact on the probability of collisions on the network. Such result may be explained because every station after successful transmit the data frame will begin a new attempt from the initial meaning of contention window. So, if the initial number of active stations in the wireless network approximately equal to the value of contention window, in steady state of saturated network the effective number of active stations will be twice less due to application of binary exponential law for the change of the competitive window. If the initial number of active stations will be only 30% from the value of contention window, the effective number of active stations will be less twice too.It was gave the estimation of the overall probability of collisions in a saturated 802.11 network with competitive access to the radio channel. The threat of collisions increases quickly in comparison with the increase of number of active stations in the network From the analysis of the received equations and graphs it follows that for the normal operation of the wireless network, it is necessary that the number of active stat...

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Section: телекомунікації та захист інформаціїmentioning

confidence: 99%

Estimation of probabilistic processes in wireless networks of 802.11 standard

Lazebnyi

Yin

2017

Mìkrosist. elektron. akust.

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“…Estos resultados sirven como medida inicial, antes de adquirir más dispositivos (lo que aumentaría el coste) con los que realizar medidas en paralelo y estudiar los fenómenos de competición de acceso al medio qué estos experimentarán. Sin embargo, no podemos olvidar que se están realizando avances mejorando las tecnologías de acceso WiFi, aumentando el ancho de banda disponible utilizando bandas y protocolos de acceso al medio diferentes [18], y se publican estudios sobre su impacto sobre los protocolos de transporte [19].…”

Section: Descripción Del Entorno Experimentalunclassified

Evaluación de equipamiento de bajo coste para realizar medidas de red en entornos domésticos

Sierra

Muelas

Vergara

et al. 2017

Proceedings XIII Jornadas De Ingenieria Telematica - JITEL2017

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Resumen-En la actualidad, la proliferación de dispositivos móviles y accesos a Internet utilizando tecnologías inalámbricas en los entornos domésticos obliga a cambiar las metodologías para la realización de medidas de red. Para qué estas representen fidedignamente las condiciones ofrecidas a los usuarios, las prestaciones del equipamiento de medida y el número de dispositivos empleados deben adaptarse a las condiciones reales de un despliegue. Para facilitar y abaratar el desarrollo de medidas en estas condiciones, este trabajo presenta una evaluación de las capacidades de varias plataformas de propósito general y bajo coste. Nuestros resultados muestran que, aunque aparecen limitaciones relacionadas con cómo son conectadas a la red y los protocolos empleados, son aptas para medir una gran variedad de situaciones.Palabras Clave-Medidas de red, indicadores de calidad, calidad de servicio, WiFi, COTS I. INTRODUCCIÓNA lo largo de losúltimos años, el auge de las tecnologías WiFi para acceder a Internet ha transformado el uso que los usuarios finales hacen de los sistemas de telecomunicaciones. Por ello, ha aumentado el interés por estudiar la variabilidad de las prestaciones de este tipo de enlaces, ya que en muchos entornos se utilizan puntos de acceso WiFi como mecanismo para proveer conectividad a los usuarios.Las características particulares de este tipo de medio de transmisión y sus interacciones con los protocolos de comunicaciones de Internet ocasionan la aparición de problemas de rendimiento que limitan la Calidad de Servicio (Quality of Service, QoS) y Experiencia (Quality of Experience, QoE) de dichos usuarios finales. Por otro lado, el usuario común realiza medidas con los dispositivos que tiene a su alcance, habitualmente un portátil o un dispositivo tipo Raspberry Pi u ODROID, que suelen tener pocos recursos y hardware de gama media o baja.Teniendo en cuenta la importancia capital que tienen estos factores para los Proveedores de Servicios de Internet (Internet Service Providers, ISPs), para las Instituciones Públicas y para los usuarios finales, resulta indispensable el desarrollo de sistemas que permitan medir con suficiente precisión este tipo de conexiones, manteniendo el coste controlado.En esta dirección, se han impulsado diversas iniciativas, como el Proyecto Bismark [1], el Atlas de RIPE o SamKnows [2], que persiguen el objetivo de caracterizar el comportamiento de las conexiones a Internet desde los accesos domésticos. Estos experimentos han utilizado una estrategia de emplazamiento de pequeñas sondas hardware basadas en arquitecturas de bajo coste (routers domésti-cos con OpenWRT, o dispositivos como Raspberry Pi u ODROID) para realizar medidas activas y pasivas de red.Además, el dimensionado de un acceso inalámbrico que garantice un cierto nivel de QoS a un número determinado de usuarios no es fácilmente extrapolable a partir de medidas con un número reducido de dispositivos. Las características de los protocolos de acceso al medio ocasionan que al aumentar el número de usuarios las prestaci...

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“…Wireless transmission systems, like some versions of the Wi-Fi (Wireless Fidelity) [2], employ OFDM because of its robustness against frequency-selective channels. DVB-T (Digital Video Broadcasting-Terrestrial) [3] and ISDB-T (Integrated Service Digital Broadcasting-Terrestrial) [4] also use OFDM for providing high data throughput and flexible configurations for digital television broadcasting.…”

Section: Introductionmentioning

confidence: 99%

PAPR Reduction and Performance Improvement in OFDM Systems using WHT-based Schemes

Aquino¹,

Mendes²

2017

JCIS

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Abstract-Orthogonal frequency division multiplexing (OFDM) is a robust and reliable multicarrier modulation scheme that has proven to be adequate for broadband communications. It is widely used in broadcasting and broadband wireless and wireline systems. However, in scenarios where the communication devices are power-limited, such as mobile and satellite communications, OFDM has not been massively used or even not used at all. For instance, OFDM is used only in downlink of 4G networks, while the uplink uses single carrier frequency division multiplexing. One of the main culprits of this is the high peak to average power ratio (PAPR) of the OFDM signal. Reducing the PAPR of the OFDM signals is important for a large variety of application. Several PAPR reduction techniques for OFDM have been proposed recently. The aim of this paper is to present a tutorial about a set of algorithms based on Walsh-Hadamard transform (WHT) for reducing the PAPR of the OFDM symbols. We also propose a new technique, named selective mapping based on WHT without extended information (SLM-WHT-WEI), which does not convey the explicit information to the receiver. We will show that the approaches based on WHT can also improve the OFDM symbol error rate performance over frequency-selective channels. Different schemes based on the properties of the WHT are presented and compared, assuming linear and non-linear channels. The PAPR reduction performance analysis shows that the PAPR can be effectively reduced while good performance in terms of symbol error rate can be achieved even in severely constrained channel conditions.

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PHY/MAC Enhancements and QoS Mechanisms for Very High Throughput WLANs: A Survey

Cited by 111 publications

References 60 publications

Estimation of probabilistic processes in wireless networks of 802.11 standard

Estimation of probabilistic processes in wireless networks of 802.11 standard

Evaluación de equipamiento de bajo coste para realizar medidas de red en entornos domésticos

PAPR Reduction and Performance Improvement in OFDM Systems using WHT-based Schemes

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