96 research outputs found
Adaptive Traffic Prioritization Algorithm Over Ad Hoc Network Using IEEE 802.11e
This thesis proposes an adaptive traffic prioritization algorithm over ad hoc network using IEEE 802.11e standard that defines a set of Quality of Service enhancements for wireless LAN applications through modifications to the Media Access Control (MAC) layer. The IEEE 802.11e standard aims to provide enhancements that allow traffic with specific requirements to be treated differently from normal traffic. Enhanced Distributed Channel Access (EDCA) is a fundamental and mandatory contention-based channel access method of IEEE 802.11e which delivers traffic based on
differentiated Access Category (ACs). Each AC has its own queue and set of EDCA parameter values. Although IEEE 802.11e has been widely implemented in commercial hardware, the EDCA parameters are normally preset with some default values recommended by the standard. By default, the values of EDCA parameters are not open for changes. This has limited the performance as from literature review, a proper EDCA parameter manipulation will improve the network throughput performance. However, most existing research works on IEEE 802.11e EDCA parameter optimization are done either analytically or in simulated environments and hence are unable to provide its effectiveness in realistic scenarios. This is largely due to the several hurdles associated with real-life implementations which prohibit them to do so, such as hardware limitations, software restrictions, coding bugs in the wireless cards driver and so on.These challengess form part of the motivations behind this work. This thesis first investigates the impacts of EDCA parameters on the network performance and link conditions using open source software and commercially available hardware in ad hoc mode. An adaptive prioritization scheme (APS) is then proposed. The results obtained show that the proposed APS algorithm can improve the single-AC throughput performance up to 10.82% when compared to static EDCA. In dual-AC scenario, APS can improve the throughput performance up to 9.93% as
compared to static EDCA, while another scheme in existing literature, R-AIFSN shows inconsistency in throughput performance. It is also found that the improvement is more
significant in terms of the queue occupancy
A quality of service architecture for WLAN-wired networks to enhance multimedia support
Includes abstract.Includes bibliographical references (leaves 77-84).The use of WLAN for the provision of IP multimedia services faces a number of challenges which include quality of service (QoS). Because WLAN users access multimedia services usually over a wired backbone, attention must be paid to QoS over the integrated WLAN-wired network. This research focuses on the provision of QoS to WLAN users accessing multimedia services over a wired backbone. In this thesis, the IEEE 802.11-2007 enhanced data channel access (EDCA) mechanism is used to provide prioritized QoS on the WLAN media access control (MAC) layer, while weighted round robin (WRR) queue scheduling is used to provide prioritized QoS at the IP layer. The inter-working of the EDCA scheme in the WLAN and the WRR scheduling scheme in the wired network provides end-to-end QoS on a WLAN-wired IP network. A mapping module is introduced to enable the inter-working of the EDCA and WRR mechanisms
Applying fair intelligent congestion control in a hybrid QoS architecture for wireless environment
This simple and scalable Differentiated Services (DiffServ) QoS control model is acceptable for the core of the network. However, more explicit and stringent admission and reservation based QoS mechanisms are required in the wireless access segment of the network, where available resources are severely limited and the degree of traffic aggregation is not significant, thus rendering the DiffServ principles less effective. In this paper we present a suitable hybrid QoS architecture framework to address the problem. At the wireless access end, the local QoS mechanism is designed in the context of IEEE 802.11 WLAN with 802.11e QoS extensions. At the edge and over the DiffServ domain, the Fair Intelligent Congestion Control (FICC) algorithm is applied to provide fairness among traffic aggregates and control congestion at the bottleneck interface between the wireless link and the network core.<br /
Towards End-to-End QoS in Ad Hoc Networks
http://citi.insa-lyon.fr/wons2006/index.htmlIn this paper, we address the problem of supporting adaptive QoS resource management in mobile ad hoc networks, by proposing an efficient model for providing proportional endto- end QoS between classes. The effectiveness of our proposed solution in meeting desired QoS differentiation at a specific node and from end-to-end are assessed by simulation using a queueing network model implemented in QNAP. The experiments results show that the proposed solution provides consistent proportional differentiation for any service class and validates our claim even under bursty traffic and fading channel conditions
QoS support in satellite and wireless networks : study under the network simulator (NS-2)
Aquest projecte es basa en l'estudi de l'oferiment de qualitat de servei en xarxes wireless i satel·litals. Per això l'estudi de les tècniques de cross-layer i del IEEE 802.11e ha sigut el punt clau per al desenvolupament teòric d'aquest estudi. Usant el simulador de xarxes network simulator, a la part de simulacions es plantegen tres situacions: l'estudi de la xarxa satel·lital, l'estudi del mètode d'accés HCCA i la interconnexió de la xarxa satel·lital amb la wireless. Encara que aquest últim punt, incomplet en aquest projecte, ha de ser la continuació per a futures investigacions.Este proyecto se basa en el estudio del ofrecimiento de calidad de servicio en redes wireless y satelitales. Por eso el estudio de las técnicas de cross-layer y del IEEE 802.11eha sido el punto clave para el desarrollo teórico de este estudio. Usando el simulador de redes network simulator, en la parte de simulaciones se plantean tres situaciones: el estudio de la red satelital, el estudio del método de acceso HCCA y la interconexión de la red satelital con la wireless. Aunque este último punto, incompleto en este proyecto, tiene que ser la continuación para futuras investigaciones.This project is based on the study of offering quality of service in satellite and wireless networks. For that reason the study of the techniques of cross-layer and the IEEE 802.11e has been the key point for the theoretical development of this study. Using the software network simulator, in the part of simulations three situations consider: the study of the satellite network, the study of the access method HCCA and the interconnection of the satellite network with the wireless. Although this last point, incomplete in this work, must be the continuation for future investigations
A New Buffer and Energy Based Scheduling Scheme for Supporting QoS in MANETs
Today, the original IEEE 802.11 standard has several problems in providing Quality of Service in MANETs. A single FIFO queue is used in best effort manner and it does not support QoS. The upcoming IEEE 802.11e was drafted to overcome these drawbacks. In this paper we describe a new multiple queuing system with an adaptive scheduling taking into account the states of buffers and energy consumption in a mobile ad hoc network. The proposed scheduling scheme uses dynamic weights for each queue. We study the performance of this scheme and compare it with the original IEEE 802.11b and the upcoming IEEE 802.11e. We show through simulations that the proposed buffer and energy based scheduling scheme improves overall end-to-end throughput, and gives better results than the original 802.11b and the Enhanced Distributed Coordination Function (EDCF), in terms of delay and total received and lost packets, as well as support service differentiation over multi-hop ad hoc networks
Final report on the evaluation of RRM/CRRM algorithms
Deliverable public del projecte EVERESTThis deliverable provides a definition and a complete evaluation of the RRM/CRRM algorithms selected in D11 and D15, and evolved and refined on an iterative process. The evaluation will be carried out by means of simulations using the simulators provided at D07, and D14.Preprin
A differentiated Services Architecture for Quality of Service Provisioning in Wireless Local Area Networks
Currently the issue of Quality of Service (QoS) is a major problem in IP networks due to the growth in multimedia traffic (e.g. voice and video applications) and therefore many mechanisms like IntServ, DiffServ, etc. have been proposed. Since the IEEE 802.11b (or Wi-Fi) standard was approved in 1999, it has gained in popularity to become the leading Wireless Local Area Network (WLAN) technology with millions of such networks deployed worldwide. Wireless networks have a limited capacity (11 Mbits/s in the case of Wi-Fi networks) owing to the limited amount of frequency spectrum available. At any given time there may be a large number of users contending for access which results in the bandwidth available to each user being severely limited. Moreover, the system does not differentiate between traffic types which means that all traffic, regardless of its importance or priority, experiences the same QoS. An important network application requiring QoS guarantees is the provision of time-bounded services, such as voice over IP and video streaming, where the combination of packet delay, jitter and packet loss will impact on the perceived QoS. Consequently this has led to a large amount of research work focussing mainly on QoS enhancement schemes for the 802.11 MAC mechanism. The Task Group E of the IEEE 802.11 working group has been developing an extension to the Wi-Fi standard that proposes to make changes to the MAC mechanism to support applications with QoS requirements. The 802.11e QoS standard is currently undergoing final revisions before approval expected sometime in 2004. As 802.11e WLAN equipment is not yet available, performance reports can only be based on simulation. The objective of this thesis was to develop a computer simulator that implements the upcoming IEEE 802.11e standard and to use this simulator to evaluate the QoS performance enhancement potential of 802.11e. This thesis discusses the QoS facilities, analyses the MAC protocol enhancements and compares them with the original 802.11 standard. The issue of QoS provisioning is primarily concerned with providing predictable performance guarantees with regard to throughput, packet delay, jitter and packet loss. The simulated results indicate that the proposed QoS enhancements to the MAC will considerably improve QoS performance in 802.11b WLANs. However, in order for the proposed 802.11e QoS mechanism to be effective the 802.11e parameters will need to be continually adjusted in order to ensure QoS guarantees are fulfilled for all traffic loads
- …