A novel contention window backoff algorithm for IEEE 802.11 wireless networks

Syed, Ikram; Kim, Bosung; Roh, Byeong‐hee; Oh, Ilhyuk

doi:10.1109/icis.2015.7166572

Cited by 9 publications

(4 citation statements)

References 11 publications

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“…In [41], the use of exponential increase-exponential decrease algorithm is proposed as a substitute for standard BEB algorithm. Adaptation of the CW size based on estimated number of active stations is presented in [42]. In [14] authors propose polynomial CW increase after collision, and in [43] resetting of CW to initial size CW 0 is proposed to be restricted depending on number of experienced retransmission failures.…”

Section: 11 Distributed Coordination Function (Dcf)mentioning

confidence: 99%

Design and Modeling of Self‐Adapting MAC (SaMAC) Protocol with Inconstant Contention Loss Probabilities

Kristić

Ožegović

Kedzo

2018

Wireless Communications and Mobile Computing

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Networks based on IEEE 802.11 standard are one of the main options for deployment in industrial environment. Degradation of throughput in congested networks and short-term unfairness are well-known drawbacks of 802.11 DCF and similar MAC protocols. Those shortcomings represent significant limitation in forecasted growth of wireless usage. This is especially important in industrial wireless networks (IWN) where the scalability of wireless MAC is one of the main requirements. In this paper, a novel self-adapting MAC protocol (SaMAC) is defined and mathematically modeled. SaMAC employs constrained countdown freezing enhanced with shifted window mechanism. As a result, the protocol outperforms 802.11 DCF standard as well as shifted contention window (SCW) and constrained countdown freezing (CPCF) protocols in achieved throughput, fairness, and jitter, while keeping simple implementation. Despite protocol’s simple design, it is shown that its mathematical model is extremely complex. For proposed protocol, the assumption of constant contention loss probability, which is normally used for modeling of MAC schemes, does not hold. In the presented multidimensional Markov chain model, a unique iterative method for determining contention loss probability is developed as well as a method for throughput calculation based on such a chain. Accuracy of the presented model is verified in several network scenarios. Considering the performance of the proposed protocol, authors believe that it could be of benefit to deploy it in heavily loaded wireless networks with timing constraints, such as IWNs.

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Section: 11 Distributed Coordination Function (Dcf)mentioning

confidence: 99%

Design and Modeling of Self‐Adapting MAC (SaMAC) Protocol with Inconstant Contention Loss Probabilities

Kristić

Ožegović

Kedzo

2018

Wireless Communications and Mobile Computing

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“…However, the more nodes that try to send a frame, the more collisions can occur. This causes longer backoff times and decreases WLAN throughput [8]. Moreover, the current DCF is designed such that all nodes are equally likely to be able to transmit their frame.…”

Section: Figure 1: Media Access Control By Csma/camentioning

confidence: 99%

A Contention Window Control Method Using Priority Control Based on the Number of Freezes of Wireless LAN

Hanzawa

2018

IJNC

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Because of the widespread adoption of mobile devices, many applications now provide support for wireless LAN (WLAN). This makes it an important issue to provide good WLAN quality of service (QoS). For this purpose, Dhurandher et al. improved the distributed coordination function (DCF). Although the highest-priority throughput increased using this method, throughput for other priorities decreased significantly. The authors proposed a minimum contention window control method based on the collision history for two (high and low) priorities, to improve Dhurandher's method. That method can keep the same average throughput for high-priority traffic as Dhurandher's method yields, but decreases the average total throughput of not only the low-priority traffic but also the high-priority traffic when congestion occurs. To overcome this problem, the method introduced in this paper improves the contention window control method by using a priority control based on the number of freezes, which is defined as a count of the times that a mobile node lets its backoff timer be frozen by the other nodes. The number of freezes is introduced as a more suitable indication of congestion, and to control the contention window for the low priority. Finally, network simulations executed on two scenarios using continuous flows or on-off flows for the low-priority and demonstrated that the proposed method retains the average total throughput of both priority frames as well as reducing the number of freezes of both priorities and the packet delay and jitter for high-priority frames, compared with the controls in Dhurandher's method and the previous method. However, the fairness-index for low-priority flows showed a little unfair in the proposed method.

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“…However, the more nodes that try to send a frame, the more often collisions tend to occur. This causes longer backoff times and decreases throughput in WLAN [9]. Moreover, the current DCF is designed such that all nodes are equally likely to be able to transmit their frame.…”

Section: Distributed Coordination Function (Dcf)mentioning

confidence: 99%

A Minimum Contention Window Control Method for Lowest Priority Based on Collision History of Wireless LAN

Hanzawa

2017

IJNC

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Because of the widespread adoption of mobile devices, many applications have provided support for wireless LAN (WLAN). Under these circumstances, one of the important issues is to provide good quality of service (QoS) in WLAN. For this purpose, Dhurandher et al. improved the distributed coordination function (DCF). In this method, the contention window (CW) is divided into multiple ranges. Each range is independent of all other ranges and is assigned to a different priority. Although the highest-priority throughput increased using this method, throughput for the other priorities decreased significantly. To overcome this problem, this paper proposes a minimum contention window control method for two (high and low) priorities. In the method, all nodes are assumed to use real-time applications or data transmission. The former real-time frames are high priority and are sent by UDP. The latter data frames are low priority and are sent by TCP. The purpose of the proposed method is not only to provide good QoS for the highest priority but also to prevent deterioration in the QoS for other priorities in WLAN. For this purpose, the proposed method keeps the CW for the high priority at a low value and controls the CW for the low priority based on the collision history. Finally, the network simulations demonstrated that the proposed method reduces the decrease in the average total throughput of the low priority frames as well as reducing the packet drop rate of both priorities, compared with those for the DCF and Dhurandher's method. From a simulation scenario where there are only low priority flows in wider bandwidths, all methods give almost same average total throughput and packet drop rate, but the results also suggest that the CW range in the proposed method should be reduced to improve the average total throughput, when no congestion occurs.

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A novel contention window backoff algorithm for IEEE 802.11 wireless networks

Cited by 9 publications

References 11 publications

Design and Modeling of Self‐Adapting MAC (SaMAC) Protocol with Inconstant Contention Loss Probabilities

Design and Modeling of Self‐Adapting MAC (SaMAC) Protocol with Inconstant Contention Loss Probabilities

A Contention Window Control Method Using Priority Control Based on the Number of Freezes of Wireless LAN

A Minimum Contention Window Control Method for Lowest Priority Based on Collision History of Wireless LAN

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