E Enhanced Distributed Coordination Function Research Articles

HE-MAC: Harvest-Then-Transmit Based Modified EDCF MAC Protocol for Wireless Powered Sensor Networks

Energy transfer (ET) and energy harvesting (EH) through radio frequency (RF) signals are a promising technology that can reduce the dependency on batteries in wireless sensor networks. However, there is a tradeoff between the RF-based ET and data communication when they operate in the same frequency band. Therefore, a proper medium access control (MAC) protocol is needed in wireless powered sensor networks (WPSNs). However, a utilization degradation problem occurs when the distributed coordination function (DCF) MAC protocol of the IEEE 802.11 is applied to WPSNs. In order to overcome this problem, this paper extends the IEEE 802.11e enhanced DCF (EDCF) into a harvest-then-transmit-based modified EDCF MAC (HE-MAC) protocol. In addition, the HE-MAC’s Markov chain model and steady-state probabilities are derived and used in the performance analysis. Next, based on the steady-state conditions, optimization is conducted to maximize the EH rate, which satisfies the frame generation rate and transfers additional energy to achieve a self-sustained energy consumption profile. Finally, the simulation performance of EH protocols HE-MAC, RF-MAC, and DOS are compared, where the results show that HE-MAC provides in a superior performance for the range of interest.

Priority Station Based Queuing Approach to Improve Quality of Service in IEEE 802.11e EDCF

Objectives: To enhance the performance of EDCF for the higher priority traffic under heavy load condition by providing higher throughput to provide desired QoS. To achieve this, we propose a method called Priority Station Based Queuing (PSBQ). An enhancement called as The IEEE 802.11e Enhanced Distributed Coordination Function (EDCF) has been developed to fulfill the growing need for the Quality of Service (QoS) in IEEE 802.11. Methods/Statistical Analysis: In EDCF standard the prioritization applies to the stations based on First in First Out approach (FIFO). Here, the size of the contention window size is reset according to the static equation after successful transmission for each traffic class, resulting in the degradation of the performance. So, we proposed our PSBQ which is the modified version of the already existing mechanism known as PRED, which applies the priority to the stations based on Random Early Detection (RED) instead of FIFO in EDCF Mechanism. Finding: In our approach to enhance the throughput of high priority traffic class, a priority is obtained by to the station based on Adaptive Random Early Detection (ARED), which is an Active Queuing mechanism and tuning was perform. On the parameter of the PSBQ, according to the network conditions and lastly the revision of the contention window adjustment is applied dynamically. Application/Improvements: Simulations was performed using the OpnetSimulator to evaluate its performance and found the results to be better in achieving prioritized, good service differentiation regarding throughput for higher priority traffic class under heavy load conditions to provide a desirable QoS.

Performance Analysis of Priority Schemes for IEEE 802.11e Wireless Local Area Networks Using Multiple Flows Distributed Weighted Fair Queuing Algorithm

In this paper, a novel and simple search algorithm called distributed weighted fair queuing (DWFQ) algorithm is proposed for the quality-of-service (QoS) in IEEE 802.11e wireless local area networks (WLANs). We first propose that the IEEE 802.11e enhanced distributed coordination function (EDCF) is an efficient algorithm to support the QoS in WLANs, although it can provide more bandwidth to packets with higher priority. However, when the system under heavy traffic load situation, IEEE 802.11e EDCF can't guarantee the fair allocation of excess bandwidth of each access categories (ACs), i.e., under heavy traffic load, EDCF guarantees the QoS of packets with higher priority by reducing the QoS of packets with lower priority. This paper discuses an EDCF scheme, in order to distribute bandwidth fairly among different ACs under heavy traffic load situation in WLAN, we propose multiple flows DWFQ algorithm. This algorithm not only supports the concept of differentiating ACs with different priorities but also guarantees the fair allocation of each ACs according to their relative weights. Furthermore, in this propose a mechanism to resolve the overload situation problem and doubling contention window (CW) method to reduce the collision probability. The simulations performed show that multiple flows DWFQ with doubling CW method which can perform an attractive performance even under heavy traffic load.

Cross-Layer Enhancement to Support TCP-Based Traffics in WLANs

Widespread deployment of wireless local area networks and a gradual increase in streaming applications have brought about a demand for improved quality of service (QoS) in wireless networks. However, increasing user datagram protocol based high priority multimedia traffic and the class differentiation introduced in QoS protocols, has resulted into transmission control protocol (TCP) starvation and increased spurious timeouts. While today's Internet traffic is still dominated by TCP based applications, the negative effects of IEEE 802.11e enhanced distributed coordination function (EDCF) scheme on TCP performance in the presence of high priority traffic have not been extensively explored. In this paper, the performance of TCP in 802.11e WLAN competing with high priority traffic is examined. The prioritised adaptive enhanced scheme (PAD_EDCF) is proposed. The proposed scheme gives priority to TCP control packets in order to improve the low traffic transmission flow and acquires additional capability of adjusting the MAC parameters based on the traffic load condition. Simulation results demonstrate that the proposed scheme significantly improves TCP performances in terms of traffic efficiency, throughput and reduces delay.

PABM-EDCF: parameter adaptive bi-directional mapping mechanism for video transmission over WSNs

To support and keep high quality of video transmission over wireless sensor networks, this paper proposes a parameter adaptive bi-directional cross-layer mapping algorithm on the basis of the operation mechanism of IEEE 802.11e Enhanced Distributed Coordination Function (EDCF) supporting video service differentiation, named PABM-EDCF. Instead of classifying video data to a specific access category in 802.11e network, our proposed adaptive cross-layer scheme makes use of the hierarchy characteristic of video stream, dynamically maps video data to the appropriate access categories according to both the significance of the different video frames and the network traffic load. The significance passes from the application layer to the media access layer through a cross-layer architecture. In order to prevent the network congestion and keep the high transmission quality, the proposed algorithm adopts bi-directional floating mapping algorithm and congestion awareness mechanism based on the queue length and frame types. The mapping parameters are updated according to the network condition in time. Our simulation results indicate: the proposed method (a) improves the video transmission quality; (b) optimizes the management and utilization of queue resources; and (c) yields superior performance (under different loads) over 802.11e, static mapping and adaptive mapping schemes.

Performance evaluation for IEEE 802.11e enhanced distributed coordination function

AbstractThe IEEE 802.11e working group aims to enhance the current 802.11 medium access control (MAC) to support integrated data and voice (or video) communications. Till now, a draft of the IEEE 802.11e enhanced distributed coordination function (EDCF) has been proposed. In the literature, there is very limited analysis about EDCF since it is a new protocol, and most related work are only confined to simulation or saturation state. In this paper, we evaluate the performance of EDCF by dividing the traffic into two groups, namely real‐time packets and non‐real‐time packets, and use an analytical model to quantify the performance of both IFS priority and contention window (CW) priority in the EDCF. In our analysis, we assume that the traffic arrival is a Poisson process. We provide a queue model for EDCF. Since there are multiple stations contending for one channel in the system, the queue model for EDCF cannot be a regular M/G/1 model. We redefine the service time and the waiting time so that we can still use M/G/1 model in the analysis. To validate the accuracy of our analytical results, we have done extensive simulations and we observed that EDCF does provide service differentiation between different traffic categories. But due to the inherent contention characteristic of carrier sense multiple access with collision avoidance (CSMA/CA) MAC protocol, the delay cannot be guaranteed, even for the highest priority traffic. A lot more work needs to be done for the MAC protocol to effectively support service differentiation in the future. Copyright © 2004 John Wiley & Sons, Ltd.