Quality Of Service Access Point Research Articles

Performance Analysis of Resource Sharing During Downlink Multi-User Transmissions in CSMA/ECA Full Duplex WLANs

Abstract Full Duplex (FD) wireless communications is considered to be the next big step for future Wireless Local Area Networks (WLANs). Old (IEEE 802.11ac) and new (IEEE 802.11ax) WLAN features are expected to co-exist with FD operation. Some of these features include Downlink Multi-User (DL MU) transmissions at the physical layer while at the Medium Access Control (MAC) layer techniques such as the Transmission Opportunity (TXOP) sharing mechanism facilitates these multiuser transmissions. The traditional Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol is inadequate to support full duplex communications efficiently. A very promising adaptation of CSMA/CA and a powerful candidate as the basic channel access method for future WLANs is the Carrier Sense Multiple Access with Enhanced Collision Avoidance (CSMA/ECA). In this paper, we provide an analytical model to assess the performance of resource sharing techniques in full duplex WLANs operating with the CSMA/ECA protocol. Our analysis is based on Markov chains to obtain an estimate of the achievable throughput of the Quality of Service Access Point (QAP) during DL MU transmissions.

Achieving VoIP Guarantee in Wireless Local Area Networks

Recently, voice over Internet Protocol (VoIP) has gained much attention in wireless local area networks (WLANs). Although IEEE 802.11e enhanced distributed channel access (EDCA) has been standardized to provide voice traffic with quality of service (QoS) support, the voice quality could still be severely degraded by the traffic transmitted from low-priority stations (LP-STAs). Like 802.11b, the 802.11e EDCA also has the performance anomaly problem. Therefore, the voice quality of the high-rate stations (HR-STAs) could be severely degraded by the traffic transmitted from low-rate stations (LR-STAs). In fact, the LP-STAs and LR-STAs can be present simultaneously in practical WLAN environments. In this paper, we consider the effects of LP-STAs and/or LR-STAs on voice traffic and propose an extended EDCA scheme called voice differentiation-EDCA (VD-EDCA) to protect voice traffic from LP-STAs and/or LR-STAs. With VD-EDCA, the voice AC in a HR-STA has an absolute priority over LP-STAs and LR-STAs when they are notified that the wireless delay of a voice frame at the QoS access point (QAP) is larger than or equal to the predefined maximal delay threshold. We evaluate the performance of the proposed VD-EDCA scheme through extensive simulations. The simulation results show that, with appropriate maximal delay threshold settings, the proposed scheme well protects all of the VoIP calls transmitted by HR-STAs from LP-STAs and/or LR-STAs

Towards voice/video application support in 802.11e WLANs: A model-based admission control algorithm

Supporting emergent voice/video applications in all wireless technologies is a requirement in the Next Generation Network (NGN) where Wireless Local Area Networks (WLANs) is a main component. For this type of applications, QoS needs to be fully maintained in order to assure user satisfaction. Actually, QoS control in 802.11e WLANs to support real time voice/video services remains an open problem. All the solutions that only aim to enhance the performance of the Enhanced Distributed Channel Access (EDCA) mechanism cannot resolve the performance degradation problem once the channel becomes saturated. Hence, an efficient admission control scheme in EDCA is the key to guarantee the QoS required by voice/video services in WLANs. In this paper, we propose a model-based admission control algorithm that is located within the QoS Access Point (QAP). An accurate analytical model is used to predict the QoS metrics that can be achieved once a new flow is introduced in the WLAN. Based on this prediction and on the QoS constraints of already admitted (active) flows as well as of the new flow, the QAP takes the appropriate decision for the new flow. The proposed admission control scheme is fully compatible with the legacy 802.11e EDCA MAC protocol. It is validated numerically and through simulations using several realistic usage scenarios.

New adaptive frame aggregation call admission control (AFA‐CAC) for high throughput WLANs

AbstractThe major enhancements introduced by the very high throughput wireless local area network, cannot provide quality of service (QoS) satisfaction for real time and multimedia applications. The recent standard IEEE 802.11n introduced new Medium Access Control (MAC) mechanisms based on aggregation scheme to enhance throughput. Besides that, functional modules for QoS provisioning such as call admission control and bandwidth management should be implemented in the access point. Hence, an efficient call admission control (CAC) algorithm is required for 802.11n network to satisfy QoS requirements of strict multimedia services. In this paper, we propose a new model‐based call admission control algorithm, called adaptation of frame aggregation AFA‐CAC to be implemented within the QoS access point in IEEE 802.11n standard in a way to provide QoS satisfaction to real time services. We first propose an accurate analytical model to estimate the achieved QoS metrics of a new flow entering in the network. Then, we detailed the AFA‐CAC algorithm that supports IEEE 802.11n aggregation schemes aggregated MAC service data unit and aggregated MAC protocol data unit and consider the IEEE 802.11e enhanced distributed channel access. AFA‐CAC is based on both predicting the QoS constraints of the already active flows and the new flow, and adjusting the number of aggregated subframes of each flow. Conducted simulations illustrate the performance of our proposed AFA‐CAC in terms of satisfying QoS throughput and end‐to‐end delay requirements of voice and video traffics. Copyright © 2013 John Wiley & Sons, Ltd.

Data rate estimation algorithm for IEEE 802.11e HCCA scheduler

PurposeAs the real‐time applications used in today's wireless network grow, some schemes are required to provide better quality of services. From the evaluation of referenced scheduling scheme provided in IEEE 802.11e standard document, we know that it does not perform well on traffic which is not strictly constant‐bit‐rate (CBR). Therefore, it is necessary to design a more flexible scheme to dynamically adjust the estimation of transmission opportunity allocated to QoS‐enhanced stations with different characteristics of applications. This paper aims to present a data rate estimation algorithm for the scheduler of the IEEE 802.11e hybrid coordination function controlled channel access.Design/methodology/approachThe performance of the algorithm is evaluated through Network Simulator ‐2.FindingsWith the proposed algorithm, the QoS access point can provide guaranteed parameters such as delay and throughput for both the real‐time variable‐bit‐rate and CBR traffics.Originality/valveThe paper presents a data rate estimation algorithm for IEEE 802‐11e HCCA scheduler.

An efficient cross layer scheduler for multimedia traffic in wireless local area networks with IEEE 802.11e HCCA

This paper proposes a scheduling algorithm, namely Wireless Timed Token Protocol (WTTP), for the Hybrid Coordination Function (HCF) Controlled Channel Access (HCCA) in IEEE 802.11e. WTTP provides traffic streams with a minimum reserved rate, as required by the standard, and it accounts for two types of traffic streams simultaneously, depending on the corresponding application: constant bit rate, which are served according to their rate, and variable bit rate traffic streams. The latter are guaranteed a minimum rate, but they are also allowed to exploit unused bandwidth, which preserves small access delays in case of bursty arrivals. Additionally, WTTP shares the capacity which is not reserved for QoS traffic streams transmissions among traffic flows with no specific QoS requirements. We also propose a strategy for the QoS Access Point to infer the idle/busy status of the uplink transmission buffers, based on cross layer information made available at the MAC by the application layer, which allows channel capacity to be saved. WTTP exhibits O(1) per packet computational complexity. We evaluate the performance of WTTP via simulation under different traffic conditions, and we investigate its resilience to variations of different system parameters.