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FHCF: A simple and efficient scheduling scheme for IEEE 802.11e wireless networks
The IEEE 802.11e medium access control (MAC) layer protocol is an emerging standard to support quality of service (QoS) in 802.11 wireless networks. Some recent works show that the 802.11e hybrid coordination function (HCF) can improve signi¯cantly the QoS support in 802.11 networks. A simple HCF referenced scheduler has been proposed in the 802.11e which takes into account the QoS requirements of °ows and allocates time to stations on the basis of the mean sending rate. As we show in this paper, this HCF referenced scheduling algorithm is only e±cient and works well for °ows with strict constant bit rate (CBR) characteristics. However, a lot of real-time applications, such as videoconferencing, have some variations in their packet sizes, sending rates or even have variable bit rate (VBR) characteristics. In this paper we propose FHCF, a simple and e±cient scheduling algorithm for 802.11e that aims to be fair for both CBR and VBR °ows. FHCF uses queue length estimations to tune its time allocation to mobile stations. We present analytical model evaluations and a set of simulations results, and provide performance comparisons with the 802.11e HCF referenced scheduler. Our performance study indicates that FHCF provides good fairness while supporting bandwidth and delay requirements for a large range of network loads
Study on QoS support in 802.11e-based multi-hop vehicular wireless ad hoc networks
Multimedia communications over vehicular ad hoc networks (VANET) will play an important role in the future intelligent transport system (ITS). QoS support for VANET therefore becomes an essential problem. In this paper, we first study the QoS performance in multi-hop VANET by using the standard IEEE 802.11e EDCA MAC and our proposed triple-constraint QoS routing protocol, Delay-Reliability-Hop (DeReHQ). In particular, we evaluate the DeReHQ protocol together with EDCA in highway and urban areas. Simulation results show that end-to-end delay performance can sometimes be achieved when both 802.11e EDCA and DeReHQ extended AODV are used. However, further studies on cross-layer optimization for QoS support in multi-hop environment are required
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
Integrated Support for Handoff Management and Context-Awareness in Heterogeneous Wireless Networks
The overwhelming success of mobile devices and wireless
communications is stressing the need for the development of
mobility-aware services. Device mobility requires services
adapting their behavior to sudden context changes and being
aware of handoffs, which introduce unpredictable delays and
intermittent discontinuities. Heterogeneity of wireless
technologies (Wi-Fi, Bluetooth, 3G) complicates the situation,
since a different treatment of context-awareness and handoffs is
required for each solution. This paper presents a middleware
architecture designed to ease mobility-aware service
development. The architecture hides technology-specific
mechanisms and offers a set of facilities for context awareness
and handoff management. The architecture prototype works with
Bluetooth and Wi-Fi, which today represent two of the most
widespread wireless technologies. In addition, the paper discusses
motivations and design details in the challenging context of
mobile multimedia streaming applications
Quality of service differentiation for multimedia delivery in wireless LANs
Delivering multimedia content to heterogeneous devices over a variable networking environment while maintaining high quality levels involves many technical challenges. The research reported in this thesis presents a solution for Quality of Service (QoS)-based service differentiation when delivering multimedia content over the wireless LANs. This thesis has three major contributions outlined below:
1. A Model-based Bandwidth Estimation algorithm (MBE), which estimates the available bandwidth based on novel TCP and UDP throughput models over IEEE 802.11 WLANs. MBE has been modelled, implemented, and tested through simulations and real life testing. In comparison with other bandwidth estimation techniques, MBE shows better performance in terms of error rate, overhead, and loss.
2. An intelligent Prioritized Adaptive Scheme (iPAS), which provides QoS service differentiation for multimedia delivery in wireless networks. iPAS assigns dynamic priorities to various streams and determines their bandwidth share by employing a probabilistic approach-which makes use of stereotypes. The total bandwidth to be allocated is estimated using MBE. The priority level of individual stream is variable and dependent on stream-related characteristics and delivery QoS parameters. iPAS can be deployed seamlessly over the original IEEE 802.11 protocols and can be included in the IEEE 802.21 framework in order to optimize the control signal communication. iPAS has been modelled, implemented, and evaluated via simulations. The results demonstrate that iPAS achieves better performance than the equal channel access mechanism over IEEE 802.11 DCF and a service differentiation scheme on top of IEEE 802.11e EDCA, in terms of fairness, throughput, delay, loss, and estimated PSNR. Additionally, both objective and subjective video quality assessment have been performed using a prototype system.
3. A QoS-based Downlink/Uplink Fairness Scheme, which uses the stereotypes-based structure to balance the QoS parameters (i.e. throughput, delay, and loss) between downlink and uplink VoIP traffic. The proposed scheme has been modelled and tested through simulations. The results show that, in comparison with other downlink/uplink fairness-oriented solutions, the proposed scheme performs better in terms of VoIP capacity and fairness level between downlink and uplink traffic
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