Improving the Performance of Wireless LANs

This book quantifies the key factors of WLAN performance and describes methods for improvement. It provides theoretical background and empirical results for the optimum planning and deployment of indoor WLAN systems, explaining the fundamentals while supplying guidelines for design, modeling, and performance evaluation. It discusses environmental effects on WLAN systems, protocol redesign for routing and MAC, and traffic distribution; examines emerging and future network technologies; and includes radio propagation and site measurements, simulations for various network design scenarios, numerous illustrations, practical examples, and learning aids

Cooperative performance bounds of Wireless Local Area Networks

In a Wireless Local Area Network (WLAN), capacity gain and delay reduction play a crucial role in system performance. In this paper, we focus on performance improvements when WLANs exploit the concept of cooperation among nodes. We propose a geometrical model to determine the potential location area of relay nodes. The analytical results are validated by simulation. Performance bounds and average of capacity gain and delay ratio are studied for different IEEE 802.11 standards

Performance modelling of fairness in IEEE 802.11 wireless LAN protocols

PhD ThesisWireless communication has become a key technology in the modern world, allowing network services to be delivered in almost any environment, without the need for potentially expensive and invasive fixed cable solutions. However, the level of performance experienced by wireless devices varies tremendously on location and time. Understanding the factors which can cause variability of service is therefore of clear practical and theoretical interest. In this thesis we explore the performance of the IEEE 802.11 family of wireless protocols, which have become the de facto standard for Wireless Local Area Networks (WLANs). The specific performance issue which is investigated is the unfairness which can arise due to the spatial position of nodes in the network. In this work we characterise unfairness in terms of the difference in performance (e.g. throughput) experienced by different pairs of communicating nodes within a network. Models are presented using the Markovian process algebra PEPA which depict different scenarios with three of the main protocols, IEEE 802.11b, IEEE 802.11g and IEEE 802.11n. The analysis shows that performance is affected by the presence of other nodes (including in the well-known hidden node case), by the speed of data and the size of the frames being transmitted. The collection of models and analysis in this thesis collectively provides not only an insight into fairness in IEEE 802.11 networks, but it also represents a significant use case in modelling network protocols using PEPA. PEPA and other stochastic process algebra are extremely powerful tools for efficiently specifying models which might be very complex to study using conventional simulation approaches. Furthermore the tool support for PEPA facilitates the rapid solution of models to derive key metrics which enable the modeller to gain an understanding of the network behaviour across a wide range of operating conditions. From the results we can see that short frames promote a greater fairness due to the more frequent spaces between frames allowing other senders to transmit. An interesting consequence of these findings is the observation that varying frame length can play a role in addressing topological unfairness, which leads to the analysis of a novel model of IEEE 802.11g with variable frame lengths. While varying frame lengths might not always be practically possible, as frames need to be long enough for collisions to be detected, IEEE 802.11n supports a number of mechanisms for frame aggregation, where successive frames may be sent in series with little or no delay between them. We therefore present a novel model of IEEE 802.11n with frame aggregation to explore how this approach affects fairness and, potentially, can be used to address unfairness by allowing affected nodes to transmit longer frame bursts.Kurdistan Region Government of Iraq (KRG) sponso

Development and Flight Testing of a Wireless Avionics Network Based on the IEEE 802.11 Protocols

This report describes the development and flight testing of the IEEE 802.11 protocol-based Wireless Flight Management System (WFMS) using low cost Commercial-Off-The-Shelf (COTS) equipment and software. The unlicensed spectrum allocation in the 2.4 GHz and 5 GHz bands by the FCC has encouraged the industry to develop new standards for short-range communication that are commercially viable. This has resulted in new short-range communication technologies like Bluetooth and the Wireless Local Area Network (WLAN). The new modulation techniques developed for wireless communication support wired equivalent data rates. The commercial success of these technologies and their wide market adaptation has resulted in reduced costs for the devices that support these technologies. Applications of wireless technology in aerospace engineering are vast, including development, testing, manufacturing, prognostics health management, ground support equipment and active control. The high data rates offered by technologies like WLAN (IEEE 802.11 a/b/g) are sufficient to implement critical and essential data applications of avionics systems. A wireless avionics network based on IEEE 802.11a/b/g protocols will reduce the complexity and cost of installation and maintenance of the avionics system when compared to the existing wired system. The proposed WFMS imitates the flight management system of any commercial aircraft in terms of functionality. It utilizes a radio frequency for the transmission of the sensor data to the Cockpit Display Unit (CDU) and the Flight Management Computer (FMC). WFMS consists of a FMC, data acquisition node, sensor node and a user interface node. The FMC and the data acquisition nodes are built using PC/104 standard modules. The sensor node consists of an Attitude and Heading Reference System (AHRS) and a GPS integrated with a serial device server. The user interface node is installed with moving map software which receives data from the AHRS and GPS to display flight information including topographic maps, attitude, heading, velocity, et cetera. This thesis demonstrates the performance evaluation of the WFMS both on the ground and in flight, and its advantages over a wired system. This thesis focuses on the evaluation of IEEE 802.11a/b/g protocols for avionics application. Efforts taken to calibrate the available bandwidth of the WLAN network at different operating conditions and varying ranges using different network analysis tools are explained briefly. Considerable research on issues like electromagnetic interference and network security critical to the development of a wireless network for avionics has also been done. This report covers different aspects of the implementation of wireless technology for aircraft systems. This work is a successful starting point for the new fly-by-wireless concept with extensions to active wireless flight control

Performance evaluation of VoIP technology in an extended service set, in concordance with IEEE 802.11g

O desempenho é avaliado experimentalmente com base nas métricas associadas à Qualidade de Serviço [QoS] e à Qualidade de Experiência do Usuário [QoE] no serviço de voz sobre IP [VoIP] para os codecs G.711 e G.729, em um conjunto de serviço estendido com tecnologia Wi-Fi, de acordo com o padrão IEEE 802.11g, implementado através de sistemas embarcados. As métricas de QoS são obtidas através da técnica intrusiva de injeção de tráfego, além disso, a QoE é avaliada por meio da análise MOSc (Mean Opinion Score conversational). Os melhores resultados foram obtidos pelo codec G.729, que atingiu até 25 fluxos simultâneos com valores ótimos de atraso, jitter e perda de pacotes de acordo com a recomendação ITU-T para VoIP. No entanto, o G.711 apresentou melhor throughput. Por outro lado, a avaliação da QoE indica uma ligeira superioridade do G.729 na avaliação MOSc. Finalmente, conclui-se que a perda de pacotes e o atraso são as métricas mais influentes na degradação do serviço VoIP.En este artículo se evalúa experimentalmente el desempeño en función de las métricas asociadas a Calidad de Servicio [QoS] y Calidad de Experiencia de Usuario [QoE] en el servicio de voz sobre IP [VoIP] para los códecs G.711 y G.729, sobre un set de servicio extendido con tecnología Wi-Fi, en concordancia con el estándar IEEE 802.11g, implementado mediante sistemas embebidos. Las métricas de QoS se obtienen mediante la técnica intrusiva de inyección de tráfico, adicionalmente se evalúa la QoE por medio del análisis MOSc [Mean Opinion Score conversational). Los mejores resultados fueron obtenidos por el códec G.729, que alcanzó hasta 25 flujos concurrentes con valores óptimos de retardo, jitter y pérdida de paquetes según la recomendación de la ITU-T para VoIP. Sin embargo, G.711 presentó un mejor throughput. Por otro lado, la evaluación de QoE señala una ligera superioridad de G.729 en la valoración MOSc. Finalmente, se concluye que la pérdida de paquetes y el retardo son las métricas más influyentes en la degradación del servicio de VoIP.In this paper, we evaluate the performance in function of the metrics associated to Quality of Service [QoS] and Quality of user Experience [QoE] in an experimental way in the VoIP service for G.711 and G.729 códecs. This was performed over an extended service set based on Wi-Fi technology in concordance with IEEE 802.11g standard using embedded systems. QoS related metrics are obtained by using the intrusive traffic injection technique. In addition, we assessed the QoE using the MOSc [Mean Opinion Score conversational] analysis. The best results were obtained for G.729, reaching up to 25 simultaneous injections with optimal delay, jitter and packet loss values according to the ITU-T recommendation for VoIP. However, the G.711 codec presented a better throughput. On the other hand, QoE evaluation indicates a slight superiority of G.729 in the MOSc appreciation. Finally, we conclude that packet loss and delay are the most influential metrics in VoIP service degradation

Wireless Handheld Solution for the Gaming Industry

of the essential elements of success in the gaming industry is the requirement of providing exceptional customer service. Technology plays a significant role in bringing state of the art solutions that enhance the overall customer experience. Currently a guest must go through multiple steps and a variety of departments to simply resolve issues with their player accounts (loyalty programs), update customer profiles, book hotel and restaurant reservations, sign up for promotions, etc. In order to effectively take care of these customers in both a timely and efficient manner, a wireless handheld device is needed that employees can carry with them to resolve and address these concerns. This project is aimed at identifying the proper wireless infrastructure for the gaming environment and also the wireless handheld device, such as an Ultra Mobile PC (UMPC) to effectively and efficiently take care of customers