Dynamic prioritization of multimedia flows for improving QoS and throughput in IEEE 802.11 e WLANs (original) (raw)
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Providing throughput guarantees in 802.11 e WLAN through a dynamic priority assignment mechanism
Wireless Personal Communications, 2005
Supporting real-time and interactive traffic in addition to traditional data traffic with a best-effort nature represents a constantly rising need in any kind of telecommunications environment. The IEEE 802.11 based WLAN (Wireless Local Area Network) environment does not represent an exception. This is why at different protocol layers, and primarily at the MAC layer, many efforts are being put by both the research community and the standardization bodies to design effective mechanisms for user QoS (Quality of Service) differentiation. Although early results are coming into sight, such as, for example, the IEEE 802.11e standard release, still a thorough research activity is required. Aim of the present paper is to contribute to the cited research issue by proposing an improvement to the "static" traffic prioritisation mechanism foreseen by the IEEE 802.11e MAC (Medium Access Control) protocol. This latter shows a twofold drawback. First, there is no certainty that QoS requirements relevant to a given application are always fulfilled by the "statically" associated priority. Second, resource requests of the applications are not adapted to the (usually highly) variable traffic conditions of a distributed WLAN environment. The algorithm we propose is specifically tailored to "dynamically" assign 802.11e MAC priorities, depending on both application QoS requirements and observed network congestion conditions. It is carefully designed, implemented into a system simulation tool, and its highly effective behaviour assessed under variable traffic and system conditions.
Evaluation of QoS Support for Multimedia Traffics in IEEE 802.11e
2006 International Conference on Software in Telecommunications and Computer Networks, 2006
The efficient delivery of multimedia over wireless LANs is strongly dependent on the requirements imposed by different traffics contending the channel resources. Mechanisms for supporting QoS are needed, especially when voice and video applications come into play with stringent constraints in terms of delay and throughput. In this paper we evaluate, through simulations, the benefits derived from the adoption of the IEEE 802.11e standard in delivering multimedia over WLANs. The adoption of fine-tuned parameters regulating the EDCA MAC scheme permits to achieve high performance in terms of goodput and delay, allowing multimedia traffics to fully satisfy their QoS requirements. Realistic assumptions have been made in our simulations, by taking into account the shadowing effects, typical of closed environments, and by adopting suitable parameters to simulate 802.11e channels as exactly as possible.
Dynamic priority re-allocation scheme for quality of service in IEEE 802.11e wireless networks
Wireless Networks, 2010
In IEEE 802.11e Enhanced Distributed Coordinator Function (EDCF) (In the recently approved IEEE 802.11e standard, EDCF is renamed to enhanced distributed channel access (EDCA). Throughout this paper, we use EDCF for consistency with early work in the literature.), per-flow service differentiation is achieved by maintaining separate queues for different traffic categories (TCs). However, due to its static Quality of Service (QoS) parameter setting, EDCF does not perform adequately under high traffic load (Romdhani et al., Proceedings of IEEE wireless communications and networking conference, 2003). We present an extended performance model of EDCF and analyze conditions for network getting overloaded. With this extended model, we show that the overall throughput of a network can be improved by changing the distribution of the number of active stations (an active station is one that has a pending packet to be sent) over a set of TCs. Hence, we propose to dynamically re-allocate flow priorities evenly in order to maintain high system performance while providing QoS guarantee for individual real-time flows. Our scheme has several interesting features: (1) performance of EDCF is improved; (2) low priority flows are not starved under high traffic load; (3) misuse of priority (misuse of priority means that a flow requests much higher priority than necessary) can be easily handled. Simulations are conducted for both infrastructure-based and Ad hoc models. Results show that dynamic priority re-allocation does not decrease throughput of real-time flows under low to medium loads, while considerable improvement over EDCF is obtained even under high loads, making it easy to support multimedia applications.
ArXiv, 2021
This paper presents an analytical model for the average frame transmission delay and the jitter for the different Access Categories (ACs) of the IEEE 802.11e Enhanced Distributed Channel Access (EDCA) mechanism. Following are the salient features of our model. As defined by the standard we consider (1) the virtual collisions among different ACs inside each EDCA station in addition to external collisions. (2) the effect of priority parameters, such as minimum and maximum values of Contention Window (CW) sizes, Arbitration Inter Frame Space (AIFS). (3) the role of Transmission Opportunity (TXOP) of different ACs. (4) the finite number of retrials a packet experiences before being dropped. Our model and analytical results provide an in depth understanding of the EDCA mechanism and the effect of Quality of Service (QoS) parameters in performance of IEEE 802.11e protocol.
Prioritized support of different traffic classes in IEEE 802.11e wireless LANs
Computer Communications, 2006
IEEE 802.11e is an amendment to the popular 802.11 standard that defines quality of service mechanisms to support sensitive applications, such as voice and video. An important component of these mechanisms is the traffic scheduler, an entity that decides on the channel allocation among different stations. This paper proposes a scheduling algorithm for IEEE 802.11e, referred to as P-ARROW (Prioritized and Adaptive Resource Reservation over Wireless), that effectively handles multimedia traffic by utilizing the formal specification of each traffic stream. Using a single ''priority factor'' parameter, the scheduling can vary between strict prioritization and purely deadline-driven allocation. Performance evaluation results extracted from an advanced simulation model, show that P-ARROW is very efficient in supporting the desired level of service differentiation and prioritization among different traffic classes.
Wireless Networks, 2007
With the increased popularity of wireless broadband networks and the growing demand for multimedia applications, such as streaming video and teleconferencing, there is a need to support diverse multimedia services over the wireless medium. In order to efficiently address these diverse needs, efforts have been pursued to provide Quality of Service (QoS) mechanisms for medium access, resulting in a standard called IEEE 802.11e. One of the enhancements proposed in IEEE 802.11e is a polling-based access mechanism, which is targeted for real-time multimedia flows. In this polling-based scheme, scheduling and time allocation are based on flow reservations. Hence, the effectiveness of the mechanism is heavily dependent on the accuracy of the flow requirements in the reservation. Flow requirements, however, can vary over time and an allocation based on fixed reservations cannot address this variability. This limitation, which is present in the reference scheduler of IEEE 802.11e, leads to degraded multimedia quality for flows with variable requirements, even when channel resources are available. In order to address the above limitation, we present an adaptation framework that dynamically adjusts the pollingbased access mechanism and associates flows to different modes of access (polling-based/contention-based), according to the current needs of the application, as opposed to solely relying on the reservation parameters. We demon
2006
With fast deployment of wireless local area networks (WLANs), the ability of WLAN to support real time services with stringent quality of service (QoS) requirements has come into fore. In this paper, we evaluate the capability of QoS support in Enhanced Distributed Channel Access (EDCA) mechanism of the IEEE 802.11e standard, which is the medium access control (MAC) enhancements for QoS support in 802.11.EDCA mechanism allow prioritized medium access for applications with high QoS requirements by assigning different priorities to its four access categories. Its performance is evaluated under real time audio and video traffic through simulations using Network Simulator-2(NS 2), parameters like mean delay, throughput are calculated and graphs has been plotted. Simulation results show that EDCA mechanism provides satisfactory service differentiation among its four access categories. With EDCA mechanism, network capacity is effectively increased to better support real-time audio and video transmissions Index Terms-Quality of service, wireless local area networks, enhanced distributed channel access, access categories, 802.11
International Journal of Communication Systems, 2020
Hybrid coordination function controlled channel access (HCCA) is a medium to enhance quality of service (QoS) via the IEEE 802.11e standard. The main limitation of HCAA is that it is only efficient for constant bit rate (CBR) applications. This is due to the nature of its scheduler that allocates transmission opportunities (TXOPs) based on traffic stream (TS) specifications (TSPECs) that are determined during the traffic setup time. Variable bit rate (VBR) traffics used in HCCA have nondeterministic profile, making it not optimally and efficiently supported by HCCA. The result of this inefficiency is a deterioration of the transmission performance of multimedia data as well as a drop in the number of served QoS video traffics. We propose a novel approach to deal with this issue, which is the feedback-based admission control unit (FACU). FACU works by optimizing the usage of extra bandwidth to ensure optimal transmission performance of multimedia data. FACU achieves this by exploiting piggybacked information concerning sequential video frames in order to accurately assign the TXOP. The proposed approach is evaluated by utilizing various video sequences. It is demonstrated that FACU maximizes the overall number of video streams and optimizes the overall usage of the network without having any adverse effects on the QoS constraints determined.
B-EDCA: A New IEEE 802.11e-Based QoS Protocol for Multimedia Wireless Communications
Lecture Notes in Computer Science, 2006
The IEEE 802.11e draft standard is a proposal defining the mechanisms for wireless LANs aiming to provide QoS support to time-sensitive applications. However, recent studies have shown that the IEEE 802.11e (EDCA) performs poorly when the medium is highly loaded due to the high collision rate. Even though several proposals have been proposed to address this problem, they require important changes to the current standard specifications making difficult their actual implementation. In this paper, we propose a simple QoS-aware mechanism and fully compatible with the various operation modes of the EDCA standard as well as the legacy IEEE 802.11 (DCF) scheme. Our design has been based on an in-depth analysis of the several operation modes of both standards. This should ensure full compatibility of operation: an important feature since the transition from the IEEE 802.11 to the IEEE 802.11e will take some time making more likely the existence of hybrid scenarios where both standards will have to coexist. Our simulation results show that our new scheme outperforms the EDCA and other QoS-aware schemes recently reported in the literature.
Dynamic contention window for quality of service in IEEE 802.11 networks
National Conference on …, 2004
There is limited QoS support for multimedia applications in Wireless LANS (WLANs). In this paper the authors present a novel mechanism to allow prioritized medium access for applications with QoS requirements. The performance of the proposed mechanism is evaluated through simulations and the results are compared with EDCF scheme.