A control theoretic approach to achieve proportional fairness in 802.11e EDCA WLANs

This paper considers proportional fairness amongst ACs in an EDCA WLAN for provision of distinct QoS requirements and priority parameters. A detailed theoretical analysis is provided to derive the optimal station attempt probability which leads to a proportional fair allocation of station throughputs. The desirable fairness can be achieved using a centralised adaptive control approach. This approach is based on multivariable statespace control theory and uses the Linear Quadratic Integral (LQI) controller to periodically update CWmin till the optimal fair point of operation. Performance evaluation demonstrates that the control approach has high accuracy performance and fast convergence speed for general network scenarios. To our knowledge this might be the first time that a closed-loop control system is designed for EDCA WLANs to achieve proportional fairness

Adaptive delayed channel access for IEEE 802.11n WLANs

Abstract— In this paper we investigate potential benefits that an adaptive delayed channel access algorithm can attain for the next-generation wireless LANs, the IEEE 802.11n. We show that the performance of frame aggregation introduced by the 802.11n adheres due to the priority mechanism of the legacy 802.11e EDCA scheduler, resulting in a poor overall performance. Because high priority flows have low channel utilization, the low priority flows throughputs can be amerced further. By introducing an additional delay at the MAC layer, before the channel access scheduling, it will retain aggregate sizes at higher numbers and consequently a better channel utilization. Also, in order to support both UDP and TCP transport layer protocols, the algorithm’s operational conditions are kept adaptive. The simulation results demonstrate that our proposed adaptive delayed channel access outperforms significantly the current 802.11n specification and non-adaptive delayed channel access

Adaptive Transmission Opportunity Scheme Based on Delay Bound and Network Load in IEEE 802.11e Wireless LANs

The IEEE 802.11e EDCA (Enhanced Distributed Channel Access) is able to provide QoS (Quality of Service) by adjusting the transmission opportunities (TXOPs), which control the period to access the medium. The EDCA has a fairness problem among competing stations, which support multimedia applications with different delay bounds. In this paper, we propose a simple and effective scheme for alleviating the fairness problem. The proposed scheme dynamically allocates the TXOP value based on the delay bounds of the data packets in a queue and the traffic load of network. Performance of the proposed scheme is investigated by simulation. Our results show that compared to conventional scheme, the proposed scheme significantly improves network performance, and achieves a high degree of fairness among stations with different multimedia applications

THE INFLUENCE OF MAC BUFFER ON THE CONTENTION-BASED ACCESS SCHEME WITH BURSTING OPTION FOR IEEE 802.11E WIRELESS NETWORKS

Wireless LANs are increasingly being used for inelastic applications. Currently, there is little support for quality of service in the IEEE 802.11 MAC protocol, and IEEE task group E has defined the 802.11e MAC extension. Enhanced distributed channel access (EDCA) is a contention-based scheme of the 802.11e standard. To allow a station to transmit more than one frame from a single contention, an optional feature known as controlled frame-bursting (CFB) is introduced in the standard. In this paper, we initially performed an average analysis to determine a suitable burst duration limit. Then, a detailed evaluation and comparison of the EDCA protocol with the CFB option is carried out through simulation to quantify its performance gain. The impact of the MAC transmit buffer size is also incorporated. Accordingly, we have proposed a suitable approach to guide the configuration of the burst duration limit. It is demonstrated that an optimized CFB configuration allows the MAC protocol to achieve 30% more capacity than the basic EDCA scheme