Providing Dynamic TXOP for QoS Support of Video Transmission in IEEE 802.11e WLANs

The IEEE 802.11e standard introduced by IEEE 802.11 Task Group E (TGe) enhances the Quality of Service (QoS) by means of HCF Controlled Channel Access (HCCA). The scheduler of HCCA allocates Transmission Opportunities (TXOPs) to QoS-enabled Station (QSTA) based on their TS Specifications (TSPECs) negotiated at the traffic setup time so that it is only efficient for Constant Bit Rate (CBR) applications. However, Variable Bit Rate (VBR) traffics are not efficiently supported as they exhibit nondeterministic profile during the time. In this paper, we present a dynamic TXOP assignment Scheduling Algorithm for supporting the video traffics transmission over IEEE 802.11e wireless networks. This algorithm uses a piggybacked information about the size of the subsequent video frames of the uplink traffic to assist the Hybrid Coordinator accurately assign the TXOP according to the fast changes in the VBR profile. The proposed scheduling algorithm has been evaluated using simulation with different variability level video streams. The simulation results show that the proposed algorithm reduces the delay experienced by VBR traffic streams comparable to HCCA scheduler due to the accurate assignment of the TXOP which preserve the channel time for transmission.Comment: arXiv admin note: substantial text overlap with arXiv:1602.0369

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

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

Providing Enhanced Framework to support QoS in Open Wireless Architecture

This paper presents a novel approach to support Quality of Service for Open Wireless Architectures (OWA), building a suitable framework over the top of the heterogeneous wireless MACs. It lets to enhance the existing QoS support provided by standard MAC protocols and it uses the contract model to guarantee QoS, taking into account the applications requests. It negotiates dynamically Application Level Contracts which will be translated seamlessly in Resource Level Contracts for the underlying network services. It receives the feedback by underlying network services to adjust the scheduling algorithms and policies to provide hard and soft guarantees. The framework comprises QoS Manager, Admission Control, Enhanced Scheduler, Predictor and Feedback System. The QoS manager component is able to dynamically manage available resources under different load conditions. A IEEE 802.11e Wireless LAN is simulated to show the benefits of this approach

Improving the QoS support in HCCA-EDCA mixed IEEE 802.11e networks

The multimedia applications require the network to provide a trustworthy service suitable to meet their Quality of Service and real-time requirements, managing efficiently the available resources. In this paper we present a performing solution for the multimedia support over IEEE 802.11e networks that aims to combine both its Medium Access Control functions, Enhanced Distributed Channel Access (EDCA) and Hybrid Coordination Function (HCF) Controlled Channel Access (HCCA), in order to reduce the experienced delay. The proposed scheduler, local to the node, cooperates with the centralized HCCA scheduler, integrating the offered service using the EDCA available resources. The simulations show that the overall scheduler improves the performance with respect to the HCCA schedulers in terms of scheduling efficiency and delay, allowing to guarantee the expected service level

Modeling and performance analysis of an alternative to IEEE 802.11e Hybrid Control Function

Modern wireless networks are offering a wide range of applications that require the efficient integration of multimedia and traditional data traffic along with QoS provision. The IEEE 802.11e workgroup has standardized a new QoS enhanced access scheme for wireless LANs, namely Hybrid Control Function (HCF). HCF consists of the Enhanced Distributed Channel Access (EDCA) and the Hybrid Control Channel Access (HCCA) protocols which manage to ensure QoS support. However, they exhibit specific weaknesses that limit network performance. This work analyzes an alternative protocol, called Priority Oriented Adaptive Polling (POAP). POAP is an integrated channel access mechanism, is collision free, it employs priorities to differentiate traffic in a proportional way, it provides fairness, and generally supports QoS for all types of multimedia applications, while efficiently serving background data traffic. POAP is compared to HCF in order to examine the wireless network performance when serving integrated traffic