The Experts below are selected from a list of 5403 Experts worldwide ranked by ideXlab platform

Ru-chuan Wang - One of the best experts on this subject based on the ideXlab platform.

  • Self-adaptive implicit Contention Window adjustment mechanism for QoS optimization in wireless sensor networks
    Journal of Network and Computer Applications, 2018
    Co-Authors: Yuan Rao, Deng Cheng, Yan Qiao, Gang Zhao, Xing Shao, Ru-chuan Wang
    Abstract:

    Abstract Synchronous Contention-based medium access control (MAC) protocols play a vital role in the delay guarantee essentially required by many recent delay-sensitive applications. Great efforts have been made to improve the end-to-end delay by means of optimizing the medium access performance. However, their effectiveness is still constrained by the contradiction between reducing the collision probability and idle listening duration. Instead of traditional tradeoff strategies, developing a way to further alleviate the contradiction is definitely beneficial for further improving the medium access performance. To this end, a self-adaptive implicit Contention Window adjustment mechanism for SMAC (Sensor MAC) is proposed based on the investigation of the medium competition behavior impacting the medium access delay and delay jitter, from the perspective of any given contending node. We mathematically derive the expected medium access delay for revealing the strengths and weaknesses of typical dynamic Contention Window mechanisms. Moreover, it is discovered that their delay-oriented optimizing Window only offers fairly limited improvement in the medium access performance since the uniformly random slot-selection mechanism results in high delay jitter and the contradiction between reducing the collision probability and idle listening duration. In order to overcome this drawback, furthermore, an optimization model of the node Contention priority distribution is proposed to alleviate the aforementioned contradiction by means of optimizing slot-selection mechanism. Finally, a self-adaptive implicit Contention Window adjustment (SICA) mechanism is designed integrating delay-oriented optimizing Contention Window, Contention priority optimization model with the estimation method of contenders' number. Through simulations in OMNeT++, the results demonstrate that the proposed SMAC-SICA outperforms its peers in terms of delay guarantee, energy efficiency and throughput.

  • Setting strategy of delay-optimization-oriented SMAC Contention Window size
    PloS one, 2017
    Co-Authors: Yuan Rao, Deng Cheng, Yan Qiao, Jun Zhu, Ru-chuan Wang
    Abstract:

    Some frame components, such as SYNC (frame synchronization) and RTS/CTS (Ready to Send/Clear to Send), are not taken into consideration when the traditional setting strategies conduct the optimization of SMAC (Sensor MAC) Contention Window size. This paper proposes mathematical models that allow the analysis of data packets forwarding delay within one SMAC virtual cluster. Simulation results in OMNeT++ show good agreements with the proposed mathematical models, validating the models’ correctness. The curve analyses of the models confirm the existence of delay-optimization-oriented Contention Window size that is closely related to the number of simultaneously contending nodes. Afterwards, it is shown that SYNC, RTS/CTS and EIFS (Extended InterFrame Space) have impacts on the optimal Contention Window size and expected delivery delay to various degrees, as well as throughput and energy efficiency. One ideal setting strategy of delay-optimization-oriented SMAC Contention Window size requires the combination of the network scale, SYNC, RTS/CTS and EIFS. Additionally, it is demonstrated that the proposed setting strategy makes contributions to the improvement in the existing SMAC extensions when they are integrated with each other, in terms of the end-to-end delay, throughput and energy consumption.

Dharma P Agrawal - One of the best experts on this subject based on the ideXlab platform.

  • effects of Contention Window and packet size on the energy efficiency of wireless local area network
    Wireless Communications and Networking Conference, 2005
    Co-Authors: Xiaodong Wang, Jun Yin, Dharma P Agrawal
    Abstract:

    The paper introduces an analytical model to investigate the energy efficiency of the IEEE 802.11 distributed coordinated function (DCF). Many factors, such as the number of contending nodes, packet size, Contention Window, packet transmission collision probability and channel condition, that affect the energy efficiency of 802.11 DCF have been considered. We determine the packet transmission probability by a method simpler than the existing Markov chain model. The paper identifies the tradeoff in choosing packet size to optimize the energy efficiency of DCF in error-prone environments. The effects of Contention Window and packet size on the energy efficiency are obtained for both DCF basic mode and DCF with four-way handshaking. It is shown that under error-prone environments, optimal packet size can improve more on the energy efficiency than optimal Contention Window. Combining both optimal Contention Window and optimal packet size can achieve the maximum optimization. To validate our analytical results, we have done extensive simulations, and they seem to match very well with the presented analytical results.

  • WCNC - Effects of Contention Window and packet size on the energy efficiency of wireless local area network
    IEEE Wireless Communications and Networking Conference 2005, 1
    Co-Authors: Xiaodong Wang, Jun Yin, Dharma P Agrawal
    Abstract:

    The paper introduces an analytical model to investigate the energy efficiency of the IEEE 802.11 distributed coordinated function (DCF). Many factors, such as the number of contending nodes, packet size, Contention Window, packet transmission collision probability and channel condition, that affect the energy efficiency of 802.11 DCF have been considered. We determine the packet transmission probability by a method simpler than the existing Markov chain model. The paper identifies the tradeoff in choosing packet size to optimize the energy efficiency of DCF in error-prone environments. The effects of Contention Window and packet size on the energy efficiency are obtained for both DCF basic mode and DCF with four-way handshaking. It is shown that under error-prone environments, optimal packet size can improve more on the energy efficiency than optimal Contention Window. Combining both optimal Contention Window and optimal packet size can achieve the maximum optimization. To validate our analytical results, we have done extensive simulations, and they seem to match very well with the presented analytical results.

Ali Balador - One of the best experts on this subject based on the ideXlab platform.

  • congestion control for vehicular environments by adjusting ieee 802 11 Contention Window size
    International Conference on Algorithms and Architectures for Parallel Processing, 2013
    Co-Authors: Ali Balador, Carlos T Calafate, Juancarlos Cano, Pietro Manzoni
    Abstract:

    Medium access control protocols should manage the highly dynamic nature of Vehicular Ad Hoc Networks (VANETs) and the variety of application requirements. Therefore, achieving a well-designed MAC protocol in VANETs is a challenging issue. The Contention Window is a critical element for handling medium access collisions in IEEE 802.11, and it highly affects the communications performance. This paper proposes a new Contention Window control scheme, called DBM-ACW, for VANET environments. Analysis and simulation results using OMNeT++ in urban scenarios show that DBM-ACW provides better overall performance compared with previous proposals, even with high network densities.

  • ICA3PP (2) - Congestion Control for Vehicular Environments by Adjusting IEEE 802.11 Contention Window Size
    Algorithms and Architectures for Parallel Processing, 2013
    Co-Authors: Ali Balador, Carlos T Calafate, Juancarlos Cano, Pietro Manzoni
    Abstract:

    Medium access control protocols should manage the highly dynamic nature of Vehicular Ad Hoc Networks (VANETs) and the variety of application requirements. Therefore, achieving a well-designed MAC protocol in VANETs is a challenging issue. The Contention Window is a critical element for handling medium access collisions in IEEE 802.11, and it highly affects the communications performance. This paper proposes a new Contention Window control scheme, called DBM-ACW, for VANET environments. Analysis and simulation results using OMNeT++ in urban scenarios show that DBM-ACW provides better overall performance compared with previous proposals, even with high network densities.

  • Wireless Days - Reducing channel Contention in vehicular environments through an adaptive Contention Window solution
    2013 IFIP Wireless Days (WD), 2013
    Co-Authors: Ali Balador, Carlos T Calafate, Juancarlos Cano, Pietro Manzoni
    Abstract:

    Intelligent Transportation Systems (ITS) are attracting growing attention both in industry and academia due to the advances in wireless communication technologies, and a significant demand for a wide variety of applications targeting this kind of environments are expected. In order to make it usable in real vehicular environments, achieving a well-designed Medium Access Control (MAC) protocol is a challenging issue due to the dynamic nature of Vehicular Ad Hoc Networks (VANETs), scalability issues, and the variety of application requirements. Different standardization organizations have selected IEEE 802.11 as the first choice for VANET environments considering its availability, maturity, and cost. The Contention Window is a critical parameter for handling medium access collisions by the IEEE 802.11 MAC protocol, and it highly affects the communications performance. The impact of adjusting the Contention Window has been studied in Mobile Ad-Hoc Networks (MANETs), but the vehicular communications community has not yet addressed this issue thoroughly. This paper proposes a new Contention Window control scheme, called DBM-ACW, for VANET environments. Analysis and simulation results using OMNeT++ in a highway scenario show that DBM-ACW provides better overall performance compared with previous proposals, even with high network densities.

  • A Novel Contention Window Control Scheme for IEEE 802.11 WLANs
    IETE Technical Review, 2012
    Co-Authors: Ali Balador, Ali Movaghar, Sam Jabbehdari, Dimitris Kanellopoulos
    Abstract:

    AbstractIn the IEEE 802.11 standard, network nodes experiencing collisions on the shared medium need a mechanism that can prevent collisions and improve the throughput. Furthermore, a backoff mechanism is used that uniformly selects a random period of time from the Contention Window (cw) that is dynamically controlled by the Binary Exponential Backoff (BEB) algorithm. Prior research has proved that the BEB scheme suffers from a fairness problem and low throughput, especially under high traffic load. In this paper, we present a new backoff control mechanism that is used with the IEEE 802.11 distributed coordination function (DCF). In particular, we propose a dynamic, deterministic Contention Window control (DDCWC) scheme, in which the backoff range is divided into several small backoff sub-ranges. In the proposed scheme, several network levels are introduced, based on an introduced channel state vector that keeps network history. After successful transmissions and collisions, network nodes change their cw ...

  • An Adaptive Contention Window Control for Improving DCF Throughput and Fairness
    2010
    Co-Authors: Ali Balador, Mahtab Ghasemivand, Ali Movaghar
    Abstract:

    The IEEE 802.11 provides a MAC layer protocol for controlling competition among nodes to access the channel in wireless local area network. Recent works show that this standard has not suitable performances in mobile ad-hoc networks and especially in error prone channels. Many researchers proposed many algorithms to improve this standard like HBCWC (History Based Contention Window Control) scheme has significant performances but also has fairness problem. In this paper, we present a novel Contentionbased protocol to improve fairness and throughput together. We use an array to keep history of network collision and based on array information, we optimize the Contention Window. The main point is that we get higher priorities to nodes had unsuccessful transmissions unlike most of researches. This helps us to solve fairness problem. Simulation results show that compared to the IEEE 802.11 DCF and HBCWC scheme, our algorithm has better performances in term of throughput, fairness, and network overhead load.

Tetsuya Takine - One of the best experts on this subject based on the ideXlab platform.

  • Dynamic Contention Window Control Scheme in IEEE 802.11e EDCA-Based Wireless LANs
    IEICE Transactions on Communications, 2010
    Co-Authors: B. A. Hirantha Sithira Abeysekera, Takahiro Matsuda, Tetsuya Takine
    Abstract:

    In the IEEE 802.11 MAC protocol, access points (APs) are given the same priority as wireless terminals in terms of acquiring the wireless link, even though they aggregate several downlink flows. This feature leads to a serious throughput degradation of downlink flows, compared with uplink flows. In this paper, we propose a dynamic Contention Window control scheme for the IEEE 802.11e EDCA-based wireless LANs, in order to achieve fairness between uplink and downlink TCP flows while guaranteeing QoS requirements for real-time traffic. The proposed scheme first determines the minimum Contention Window size in the best-effort access category at APs, based on the number of TCP flows. It then determines the minimum and maximum Contention Window sizes in higher priority access categories, such as voice and video, so as to guarantee QoS requirements for these real-time traffic. Note that the proposed scheme does not require any modification to the MAC protocol at wireless terminals. Through simulation experiments, we show the effectiveness of the proposed scheme.

  • VTC Spring - Dynamic Contention Window Control Scheme in IEEE 802.11e Wireless LANs
    VTC Spring 2009 - IEEE 69th Vehicular Technology Conference, 2009
    Co-Authors: B. A. Hirantha Sithira Abeysekera, Takahiro Matsuda, Tetsuya Takine
    Abstract:

    In the IEEE 802.11 MAC protocol, access points (APs) are given the same authority as wireless terminals (WTs) in terms of acquiring the wireless link, even though they aggregate several downlink flows. This feature leads to a serious throughput degradation of downlink flows, compared with uplink flows. In this paper, we propose a dynamic Contention Window control scheme for the IEEE 802.11e EDCA-based WLANs, in order to achieve fairness between uplink and downlink TCP flows while guaranteeing QoS requirements for real-time traffic. The proposed scheme first determines the minimum Contention Window size in the best-effort access category at APs, based on the number of TCP flows. It then determines the minimum and maximum Contention Window sizes in higher priority access categories, such as voice and video, so as to guarantee QoS requirements for these real-time traffic.

Yuan Rao - One of the best experts on this subject based on the ideXlab platform.

  • Self-adaptive implicit Contention Window adjustment mechanism for QoS optimization in wireless sensor networks
    Journal of Network and Computer Applications, 2018
    Co-Authors: Yuan Rao, Deng Cheng, Yan Qiao, Gang Zhao, Xing Shao, Ru-chuan Wang
    Abstract:

    Abstract Synchronous Contention-based medium access control (MAC) protocols play a vital role in the delay guarantee essentially required by many recent delay-sensitive applications. Great efforts have been made to improve the end-to-end delay by means of optimizing the medium access performance. However, their effectiveness is still constrained by the contradiction between reducing the collision probability and idle listening duration. Instead of traditional tradeoff strategies, developing a way to further alleviate the contradiction is definitely beneficial for further improving the medium access performance. To this end, a self-adaptive implicit Contention Window adjustment mechanism for SMAC (Sensor MAC) is proposed based on the investigation of the medium competition behavior impacting the medium access delay and delay jitter, from the perspective of any given contending node. We mathematically derive the expected medium access delay for revealing the strengths and weaknesses of typical dynamic Contention Window mechanisms. Moreover, it is discovered that their delay-oriented optimizing Window only offers fairly limited improvement in the medium access performance since the uniformly random slot-selection mechanism results in high delay jitter and the contradiction between reducing the collision probability and idle listening duration. In order to overcome this drawback, furthermore, an optimization model of the node Contention priority distribution is proposed to alleviate the aforementioned contradiction by means of optimizing slot-selection mechanism. Finally, a self-adaptive implicit Contention Window adjustment (SICA) mechanism is designed integrating delay-oriented optimizing Contention Window, Contention priority optimization model with the estimation method of contenders' number. Through simulations in OMNeT++, the results demonstrate that the proposed SMAC-SICA outperforms its peers in terms of delay guarantee, energy efficiency and throughput.

  • Setting strategy of delay-optimization-oriented SMAC Contention Window size
    PloS one, 2017
    Co-Authors: Yuan Rao, Deng Cheng, Yan Qiao, Jun Zhu, Ru-chuan Wang
    Abstract:

    Some frame components, such as SYNC (frame synchronization) and RTS/CTS (Ready to Send/Clear to Send), are not taken into consideration when the traditional setting strategies conduct the optimization of SMAC (Sensor MAC) Contention Window size. This paper proposes mathematical models that allow the analysis of data packets forwarding delay within one SMAC virtual cluster. Simulation results in OMNeT++ show good agreements with the proposed mathematical models, validating the models’ correctness. The curve analyses of the models confirm the existence of delay-optimization-oriented Contention Window size that is closely related to the number of simultaneously contending nodes. Afterwards, it is shown that SYNC, RTS/CTS and EIFS (Extended InterFrame Space) have impacts on the optimal Contention Window size and expected delivery delay to various degrees, as well as throughput and energy efficiency. One ideal setting strategy of delay-optimization-oriented SMAC Contention Window size requires the combination of the network scale, SYNC, RTS/CTS and EIFS. Additionally, it is demonstrated that the proposed setting strategy makes contributions to the improvement in the existing SMAC extensions when they are integrated with each other, in terms of the end-to-end delay, throughput and energy consumption.