Fairness and transmission opportunity limit in IEEE 802.11e enhanced distributed channel access

Tämä diplomityö tutkii lähetysaikarajan vaikutusta verkon reiluuteen IEEE802.11e tehostettuun ja hajautettuun kommunikaatiokanavaan pääsyyn. IEEE802.11e tuo palvelunlaatuominaisuuksia IEEE802.11 langattomiin verkkoihin. Asemat, jotka käyttävät IEEE802.11e-ominaisuuksia jakavat liikenteen neljään kategoriaan. Kategorioiden välinen erottelu saavutetaan neljällä parametrilla, jotka kontrolloivat kanavaan pääsyä. Tämä työ tutkii yhtä näistä parametreistä, lähetysaikarajaa, joka kontrolloi lähetyksen kestoa. IEEE802.11e antaa referenssiarvoja parametreille, mutta näillä arvoilla verkon kuormituksen lisääntyessä, alemman prioriteetin liikenne kärsii nopeasti. Hyvin pian kuormituksen lisääntyessä alemman prioriteetin liikenne ei pääse verkosta läpi lainkaan. Tällöin myös verkon reiluus on matala. Reiluuden parantamiseksi, häiritsemättä korkean prioriteetin liikennettä, tämä työ tutkii ison lähetysaikarajan käyttöä. Ensimmäisessä simulaatiosarjassa alemman prioriteetin lähetysaikaraja on ääretön. Tämä tarkoitta sitä, että alemman prioriteetin jono voi lähettää kaikki pakettinsa kun se pääsee lähettämään. Tulokset osoittavat, että ääretön lähetysaikaraja parantaa reiluutta kun kanava on kuormittumassa. Tulokset osoittavat myös, että ääretön lähetysaikaraja ei merkittävästi heikennä korkean prioriteetin liikennettä. Toinen simulaatiosarja keskittyy sellaiseen verkon kuormitustilaan, missä äärettömän lähetysaikarajan vaikutus on suurin. Näissä simulaatioissa lähetysaikarajan arvo on staattinen. Simulaatiosta toiseen lähetysaikarajan arvo muutetaan toiseen arvoon väliltä nolla-suurin sallittu arvo. Tulokset näistä simulaatioista ovat hyvin samanlaiset kuin ensimmäisen simulaatiosarjan tulokset.This thesis investigates the effect of transmission opportunity limit on fairness in IEEE802.11e enhanced distributed channel access. IEEE802.11e brings quality of service features into IEEE802.11 wireless local area networks. In stations operating with IEEE802.11e, traffic is divided into categories. Differentiation between these categories is achieved by using four parameters to control the channel access. This thesis investigates one of these parameters, the transmission opportunity limit, which controls the channel access duration. With the reference parameter values given in IEEE802.11e, as the network congestion level increases, low priority traffic suffers quickly to a point where none of it gets transmitted. This makes the network overall fairness poor. To improve fairness while not disturbing high priority traffic, this thesis investigates the use of large transmission opportunity limit values. In the first set of simulations, the low priority traffic transmission opportunity limit values are set to infinite. This means that the low priority queue can send all its packets when it gains access to the channel. The results show that infinite transmission opportunity limit improves fairness when channel is getting congested. Also infinite transmission opportunity limit does not notably weaken high priority traffic performance. Second set of simulations focuses on the network congestion level where the effect of the infinite transmission opportunity limit is the largest. In these simulations the transmission opportunity limit is set to static value ranging from zero to a maximum allowed value. The results from these simulations are similar to the results of the first simulation set

Available Bandwidth Estimation for Adaptive Video Streaming in Mobile Ad Hoc

[EN] We propose in this paper an algorithm for available bandwidth estimation in mobile ad hoc networks and its integration into a conventional routing protocol like AODV for improving the rate-adaptive video streaming. We have introduced in our approach a local estimation of the available bandwidth as well as a prediction of the consumed bandwidth. This information allows video application to adjust its transmission rate avoiding network congestion. We conducted a performance evaluation of our solution through simulation experiments using two network scenarios. In the simulation study, transmission of video streams encoded with the H.264/MPEG-4 advanced video coding standard was evaluated. The results reveal performance improvements in terms of packet loss, delay and PSNR.Castellanos, W.; Guerri Cebollada, JC.; Arce Vila, P. (2019). Available Bandwidth Estimation for Adaptive Video Streaming in Mobile Ad Hoc. International Journal of Wireless Information Networks. 26(3):218-229. https://doi.org/10.1007/s10776-019-00431-0S21822926

OPTIMISING APPLICATION PERFORMANCE WITH QOS SUPPORT IN AD HOC NETWORKS

The popularity of wireless communication has increased substantially over the last decade, due to mobility support, flexibility and ease of deployment. Among next generation of mobile communication technologies, Ad Hoc networking plays an important role, since it can stand alone as private network, become a part of public network, either for general use or as part of disaster management scenarios. The performance of multihop Ad Hoc networks is heavily affected by interference, mobility, limited shared bandwidth, battery life, error rate of wireless media, and the presence of hidden and exposed terminals. The scheduler and the Medium Access Control (MAC) play a vital role in providing Quality of Service (QoS) and policing delay, end-to-end throughput, jitter, and fairness for user application services. This project aims to optimise the usage of the available limited resources in terms of battery life and bandwidth, in order to reduce packet delivery time and interference, enhance fairness, as well as increase the end-to-end throughput, and increase the overall network performance. The end-to-end throughput of an Ad Hoc network decays rapidly as the hop count between the source and destination pair increases and additional flows injected along the path of an existing flow affects the flows arriving from further away; in order to address this problem, the thesis proposes a Hop Based Dynamic Fair Scheduler that prioritises flows subject to the hop count of frames, leading to a 10% increase in fairness when compared to a IEEE 802.11b with single queue. Another mechanism to improve network performance in high congestion scenarios is network-aware queuing that reduces loss and improve the end-to-end throughput of the communicating nodes, using a medium access control method, named Dynamic Queue Utilisation Based Medium Access Control (DQUB-MAC). This MAC provides higher access probability to the nodes with congested queue, so that data generated at a high rate can be forwarded more effectively. Finally, the DQUB-MAC is modified to take account of hop count and a new MAC called Queue Utilisation with Hop Based Enhanced Arbitrary Inter Frame Spacing (QU-EAIFS) is also designed in this thesis. Validation tests in a long chain topology demonstrate that DQUB-MAC and QU-EAIFS increase the performance of the network during saturation by 35% and 40% respectively compared to IEEE 802.11b. High transmission power leads to greater interference and represents a significant challenge for Ad Hoc networks, particularly in the context of shared bandwidth and limited battery life. The thesis proposes two power control mechanisms that also employ a random backoff value directly proportional to the number of the active contending neighbours. The first mechanism, named Location Based Transmission using a Neighbour Aware with Optimised EIFS for Ad Hoc Networks (LBT-NA with Optimised EIFS MAC), controls the transmission power by exchanging location information between the communicating nodes in order to provide better fairness through a dynamic EIFS based on the overheard packet length. In a random topology, with randomly placed source and destination nodes, the performance gain of the proposed MAC over IEEE 802.11b ranges from approximately 3% to above 90% and the fairness index improved significantly. Further, the transmission power is directly proportional to the distance of communication. So, the performance is high and the durability of the nodes increases compared to a fixed transmission power MAC such as IEEE 802.11b when communicating distance is shorter. However, the mechanism requires positional information, therefore, given that location is typically unavailable, a more feasible power control cross layered system called Dynamic Neighbour Aware – Power controlled MAC (Dynamic NA -PMAC)is designed to adjust the transmission power by estimating the communicating distance based on the estimated overheard signal strength. In summary, the thesis proposes a number of mechanisms that improve the fairness amongst the competing flows, increase the end-to-end throughput, decrease the delay, reduce the transmission power in Ad Hoc environments and substantially increase the overall performance of the network

Analysis and design of efficient techniques for video transmission in IEEE 802.11 wireless ad hoc networks

[EN] Wireless mobile ad ho networks, also known as MANETs, are omposed by independent mobile stations that ommuni ate without requiring any sort of infrastru ture for support. These networks are hara terized by variable bandwidth values and frequent path breaks, whi h are due to hannel noise, interferen e between stations and mobility. Su h fa tors require significant adaptation apabilites at different levels of the proto ol suites employed, enabling stations to qui kly respond to fast- hanging network onditions. Resear h on the most adequate proto- ols for the physi al, MAC and routing layers is still on-going, though some basi onsensus has already been rea hed and several testbeds have been setup around the world. To deploy real-time multimedia servi es, namely voi e and video, on top of su h an unreliable network environment is a very hallenging task. In this thesis we propose to a hieve that goal starting from urrently available Wi-Fi te hnology, and gradually finding the most adequate enhan ements to ea h proto ol layer of interest; we then ombine these enhan ements until we a hieve a omplete QoS framework for ad ho networks. By using urrently available te hnology we assure that the proposal of this thesis has an inherent high-level of appli ability on real life environments. Sin e our working field fo uses on video transmission over wireless ad ho networks, we will show how it is possible to support several QoS- onstrained video streams in MANET environments hara terized by moderate to high mobility levels, and by a significant amount of best efort traffic[ES] Las redes inalámbricas ad hoc, también conocidas como redes MANET, están compuestas por un conjunto de estaciones móviles independientes capaces de omunicarse entre sí sin necesidad de ningún tipo de infraestructura común de comunicaciones. Estas redes se caracterizan por tener un ancho de banda variable y pérdidas frecuentes de ruta que se pueden atribuir al ruido del anal inalámbrico, a la interferencia entre las estaciones móviles o bien a la movilidad de las estaciones. Dichos factores requieren una gran capacidad de adaptación en las diferentes capas de la arquitectura de protocolos, permitiendo a una estación responder rápidamente a posibles cambios bruscos en las condiciones de la red. A pesar de que aún se están realizando trabajos de investigación en bus a de los protocolos más adecuados para las capas físicas, a eso al medio (MAC) y encaminamiento, ha sido posible llegar a un nivel básico de consenso, lo cual ha permitido el despliegue de plataformas y entornos aplicados que utilizan tecnología de red MANET. Ofrecer servicios multimedia, como voz y vídeo, en redes con tan poca habilidad es un desafío importante. En esta tesis nos proponemos alcanzar este objetivo partiendo de la tecnología Wi-Fi actualmente disponible, encontrando de forma paulatina las mejoras más importantes en las diferentes capas de la arquitectura de red, para llegar, finalmente, a una solución integrada capaz de ofrecer calidad de servicio (QoS) en las redes MANET. Al utilizar la tecnología que disponemos actualmente nos aseguramos que las propuestas de esta tesis tengan un alto grado de aplicabilidad en entornos reales. Ya que la línea de trabajo de la tesis está aplicada a la transmisión de vídeo en redes MANET, demostraremos que es posible ofrecer calidad de servicio a varios flujos de vídeo en una red MANET caracterizada por altos grados de movilidad en sus nodos y un nivel significativo de tráfico o de tipo best effortTavares De Araujo Cesariny Calafate, CM. (2006). Analysis and design of efficient techniques for video transmission in IEEE 802.11 wireless ad hoc networks [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/135282TESI

Advanced Wireless LAN

The past two decades have witnessed starling advances in wireless LAN technologies that were stimulated by its increasing popularity in the home due to ease of installation, and in commercial complexes offering wireless access to their customers. This book presents some of the latest development status of wireless LAN, covering the topics on physical layer, MAC layer, QoS and systems. It provides an opportunity for both practitioners and researchers to explore the problems that arise in the rapidly developed technologies in wireless LAN