A Scheduling Algorithm for Providing QoS Guarantees in 802.11e WLANs

In this paper we propose a scheduling algorithm for supporting Quality of Service (QoS) in an IEEE 802.11e network using the HCF Controlled Channel Access (HCCA) function. This is derived from Constant Bandwidth Server with Resource Constraints and adapted to wireless medium. It consists of a procedure to actually schedule transmission opportunities to HCCA flows with Quality of Service guarantees, in particular in the case of multimedia applications which present variable bit rate traffic

A Framework for Enhanced QoS Support in IEEE 802.11e Networks

IEEE 802.11 based WLANs have became popular, but they can only provide best effort services and so they are poorly suitable for multimedia applications. Recently IEEE 802.11e standard has been proposed to support quality of service. The new standard introduces a so-called Hybrid Coordination Function containing two medium access mechanisms: contention-based channel access and controlled channel access. In this paper we propose a novel framework to better support QoS guarantees for multimedia applications. It comprises QoS Manager, Admission Control, Enhanced Scheduler, Predictor and Feedback System. The scheduler adopted supports real-time applications, variable packet sizes and variable bit rate traffic streams. We show that this framework is suitable to be used by applications requesting Application Level Contracts which will be translated in Resource Level Contracts to the scheduler subsystem. The QoS manager component is able to dynamically manage available resources under different load conditions

W-CBS: A Scheduling Algorithm for Supporting QoS in IEEE 802.11e

This paper presents a new scheduling algorithm, the Wireless Constant Bandwidth Server (W-CBS) for the Access Points of an IEEE 802.11e wireless networks to support traffic streams with Quality of Service guarantees, in particular in the case of multimedia applications which present variable bit rate traffic. The performance of W-CBS is compared to that of the reference scheduler defined in 802.11e standard using the ns2 simulator. The results show that the W-CBS outperforms the reference scheduler with VBR traffic, in terms of resource utilization and maximum admitted flows

A Greedy Reclaiming Scheduler for IEEE 802.11e HCCA Real-Time Networks

The IEEE 802.11e standard introduces Quality of Service (QoS) support for wireless local area networks and suggests how to design a tailored HCF Controlled Channel Access (HCCA) scheduler. However the reference scheduling algorithm is suitable to assure service guarantees only for Constant Bit Rate traffic streams, whereas shows its limits for Variable Bit Rate traffic. Despite the numerous alternative schedulers proposed to improve the QoS support for multimedia applications, in the case of VBR traffic satisfactory real-time performance has not been yet achieved. This paper presents a new scheduling algorithm, Unused Time Shifting Scheduler (UTSS). It integrates a mechanism for bandwidth reclaiming into a HCCA real-time scheduler. UTSS assigns the unused portion of each transmission opportunity to the next scheduled traffic stream. Thanks to such feature, traffic variability is absorbed, reducing the waste of resources. The analytical evaluation, corroborated by the simulation results, shows that UTSS is suitable to reduce the delay experienced by VBR traffic streams and to increase the maximum burstiness sustainable by the network

Dynamic TXOP HCCA reclaiming scheduler with transmission time estimation for IEEE 802.11e real-time networks

IEEE 802.11e HCCA reference scheduler guarantees Quality of Service only for Constant Bit Rate traffic streams, whereas its as- signment of scheduling parameters (transmission time TXOP and polling period) is too rigid to serve Variable Bit Rate (VBR) traffic. This paper presents a new scheduling algorithm, Dynamic TXOP HCCA (DTH). Its scheduling scheme, integrated with the central- ized scheduler, uses both a statistical estimation of needed trans- mission duration and a bandwidth reclaiming mechanism with the aim of improving the resource management and providing an in- stantaneous dynamic Transmission Opportunity (TXOP), tailored to multimedia applications with variable bit rate. Performance evaluation through simulation, confirmed by the scheduling analysis, shows that DTH is suitable to reduce the transmission queues length. This positively impacts on the delay and on packets drop rate experienced by VBR traffic streams

Ordonnancement des flux avioniques AFDX sur un support 802.11e HCCA

Session Réseaux de capteursInternational audienceNos activités de recherches visent à mettre en place un réseau hybride IEEE802.11e/AFDX (Avionics Full DupleX switched Ethernet) pour des applications de maintenance au sol des avions. Notre objectif est de véhiculer un trafic de type AFDX sur un support de communication sans fil IEEE 802.11e et de ce fait garantir les exigences des trafics AFDX en terme de QoS (Quality of Service). Ces exigences de l'AFDX sont liées : à une garantie de bande passante, à une latence de bout à bout et une gigue bornée. Dans ce papier, nous présentons un ordonnanceur HCCA appelé AWS (AFDX Wireless Scheduler) qui a pour objectif d'ordonnancer les diffé- rents flux AFDX, tout en garantissant leurs exigences. AWS améliore les performances de l'ordonnanceur de référence (RS, Reference Scheduler) en se basant sur : la classification des VLs, la définition de plusieurs états de chaque VL, un ordonnancement individuel des VLs, la définition d'une politique de gestion de la retrans- mission des trames perdues et le contrôle de la gigue. Nous proposons aussi deux méthodes (OAWS, Optimized AWS et AWS-RB, AWS with Release Bandwidth) pour une meilleure gestion de la bande passante libre dans chaque TXOP

Dynamic decision making for candidate access point selection

Abstract. In this paper, we solve the problem of candidate access point selection in 802.11 networks, when there is more than one access point available to a station. We use the QBSS (quality of service enabled basic service set) Load Element of the new WLAN standard 802.11e as prior information and deploy a decision making algorithm based on reinforcement learning. We show that using reinforcement learning, wireless devices can reach more efficient decisions compared to static methods of decision making which opens the way to a more autonomic communication environment. We also present how the reinforcement learning algorithm reacts to changing situations enabling self adaptation

Quality of service provision in mobile multimedia - a survey

The prevalence of multimedia applications has drastically increased the amount of multimedia data. With the drop of the hardware cost, more and more mobile devices with higher capacities are now used. The widely deployed wireless LAN and broadband wireless networks provide the ubiquitous network access for multimedia applications. Provision of Quality of Service (QoS) is challenging in mobile ad hoc networks because of the dynamic characteristics of mobile networks and the limited resources of the mobile devices. The wireless network is not reliable due to node mobility, multi-access channel and multi-hop communication. In this paper, we provide a survey of QoS provision in mobile multimedia, addressing the technologies at different network layers and cross-layer design. This paper focuses on the QoS techniques over IEEE 802.11e networks. We also provide some thoughts about the challenges and directions for future research