Evaluación de la capacidad de redes 802.11e transportando VoIP

Estudio de la capacidad VoIP en redes WLAN IEEE 802.11 con simulación de resultados mediante software Scilab. En este trabajo se desarrollan y modelan las conclusiones obtenidas en el artículo 'Capacity Evaluation of VoIP in IEEE 802.11e WLAN Environment', obteniendo capacidad y rendimiento de cada uno de los códecs más utilizados en VoIP (G.711, G.729 y G.723.1).Estudi de la capacitat VoIP en xarxes WLAN IEEE 802.11 amb simulació de resultats mitjançant software Scilab. En aquest treball es desenvolupen i modelen les conclusions obtingudes en l'article 'Capacity Evaluation of VoIP in IEEE 802.11e WLAN Environment', obtenint capacitat i rendiment de cada un dels còdecs més utilitzats en VoIP (G.711, G.729 i G .723.1)

A Multiband CPW-Fed Slot Antenna with Fractal Stub and Parasitic Line

This paper presents a multiband CPW-fed slot antenna with fractal stub and parasitic line. The conventional wideband slot antenna with fractal stub is modified by inserting the parasitic line surrounding the fractal stub that affects the attribution to be a multiband operation suitable for some applications in wireless communication systems. The parasitic line surrounding the fractal stub can generate a dual-notched frequency that can be controlled by varying the parameters of the parasitic structure. The lengths of slit and stub on both sides of the parasitic line can control the lower and higher notched frequencies, respectively. Additionally, the prototype of the proposed antenna can operate and cover the applications of DCS 1800, WiMAX IEEE 802.16, WLAN IEEE 802.11a/b/g, and IMT advance system

A transmit power control proposal for IEEE 802.11 cellular networks

Actually, the idea of designing an outdoor cellular network based on WLAN IEEE 802.11 results very attractive, due to the several advantages that this technology presents. It offers the equipment at a lower cost, operates in unlicensed spectrum and allows higher data rates.If we realize a comparison of the system performance between a cellular environment and an isolated single cell scenario we observe that the first situation exhibits a considerable decrease, due to co-channel interference, that rises with the growth of the transmission data rate employed. In this paper, we propose a power control mechanism, as a method to reduce the interference influence on network performance, and to homogenize the behavior of the different stations in the system. We present its performance under different load conditions and compare this behavior with the original case, without the employment of any power control mechanism.Peer Reviewe

Seguridad en WLAN 802.11: evaluación de las contramedidas para combatir el ataque de falsificación

El objetivo de este trabajo es evaluar la influencia que producen las contramedidas que se emplean para combatir el ataque de falsificación en WLAN IEEE 802.11 sobre el throughput, la justicia y el consumo de las baterías. Se comparan los protocolos de autenticación EAP-TLS, EAP-PEAP, EAP-TTLS y EAP-LEAP en redes IEEE 802.11, mediante IEEE 802.1X-EAP. Se utiliza un simulador de escenarios inalámbricos IEEE 802.11 cuyos resultados se contrastan con un modelo analítico

Performance enhancement of outdoor IEEE 802.11 cellular networks

Most studies about the performance of IEEE 802.11 are limited to a single cell environment. Nevertheless, the idea of designing an outdoor cellular network based on WLAN IEEE 802.11 results very attractive, due to the several advantages that this technology presents: the low cost of the equipment, its operation in unlicensed spectrum and its higher data rates. If we compare the system performance in a cellular environment with its behavior in a single cell environment, we observe that its performance decreases considerably with the growth of the transmission data rate employed and due to co-channel interference. In this paper, we propose some enhancement mechanisms, in order to reduce the interference influence on network performance. Moreover, we study the viability of using sectorised antennas at the access points. We present its performance under different load conditions and compare this behavior with the results obtained in an isolated single cell environment, which has no interference.Peer Reviewe

Multi-channel Utilization Algorithms for IEEE 802.15.4 based Wireless Network: A Survey

In the pass years, IEEE 802.15.4 based Wireless Sensor Networks (WSNs) have received great attention and have been employed in many areas such as inventory checking, local monitoring and alarming etc. One of the key issues affecting WSN's system performance is interference caused by devices operating with the same or different standards on the overlapping frequency within the 2.4 GHz ISM band. This paper addresses the coexistence problem, which is the key motivation for the necessity of flexible channel usage. A review of existing approaches being proposed to date supporting multi-channel utilization in IEEE 802.15.4 based WSNs is categorized and discussed. The paper also presents major functionalities needed in implementing multi-channel utilization