Performance Evaluation And Enhancement Of EDCA Protocol To Improve The Voice Capacity In Wireless Network

Enhanced Distributed Channel Access (EDCA) protocol is used to support quality of service (QoS). However, using the default parameter values for EDCA protocol leads to increasing the collisions in the wireless network and decreasing the capacity. This is due to the default EDCA protocol gives the access point and wireless stations the same priority to access the medium, in spite of the access point has high load traffic compared with normal wireless stations. Therefore, in this research work a new algorithm was proposed to enhance the capacity of the EDCA protocol and increase the number of the active voice users. The idea of the algorithm was based on creating different contention window ranges between access point and wireless workstations, and changing the technique of increasing the contention window value when the collision happened. Through the proposed algorithm, the Minimum Contention Window (CWmin) and Arbitration Inter Frame Space (AIFS) parameters were adapted based on the percentage of the collision in the network. By applying the proposed algorithm, the throughput of EDCA protocol was increased by 42.9% and it can support 14 voice users rather than 11 in the default EDCA protocol. The QoS requirements were achieved when the network contained 14 voice users. The end to end delay became 86.44 ms and the packet loss percentage was 0.06 %. In addition to that the uplink and downlink voice throughputs covered the data rate requirements. Moreover, a new mathematical model was designed based on the Markov chain mechanism in order to evaluate the performance of the EDCA protocol under saturation and non saturation conditions, which aimed to separate between the uplink and downlink throughputs with different data types. The separation between uplink and downlink throughputs is based on separating the model equations between the access point and the stations. This separation contributes in determining the effect of access point on the network performance as well as it allows in evaluating the algorithms that based on the differentiation between the access point and stations. The OPNET simulator and the mathematical model were used to evaluate the performance for the proposed algorithm. Therefore, by applying the proposed algorithm, the collisions in network will be decreased and leading to the enhancement of the network capacity. It is believed that this study is useful to cover more voice users in the public wireless network that deployed in bus stations, restaurants, parks, airports and etc

A Comprehensive Study of the Enhanced Distributed Control Access (EDCA) Function

This technical report presents a comprehensive study of the Enhanced Distributed Control Access (EDCA) function defined in IEEE 802.11e. All the three factors are considered. They are: contention window size (CW), arbitration inter-frame space (AIFS), and transmission opportunity limit (TXOP). We first propose a discrete Markov chain model to describe the channel activities governed by EDCA. Then we evaluate the individual as well as joint effects of each factor on the throughput and QoS performance. We obtain several insightful observations showing that judiciously using the EDCA service differentiation mechanism is important to achieve maximum bandwidth utilization and user-specified QoS performance. Guided by our theoretical study, we devise a general QoS framework that provides QoS in an optimal way. The means of realizing the framework in a specific network is yet to be studied

Adaptive MAC Protocols Using Memory for Networks with Critical Traffic

We consider wireless communication networks where network users are subject to critical events such as emergencies and crises. If a critical event occurs to a user, the user needs to send critical traffic as early as possible. However, most existing medium access control (MAC) protocols are not adequate to meet the urgent need for data transmission by users with critical traffic. In this paper, we devise a class of distributed MAC protocols that achieve coordination using the finite-length memory of users containing their own observations and traffic types. We formulate a protocol design problem and find optimal protocols that solve the problem. We show that the proposed protocols enable a user with critical traffic to transmit its critical traffic without interruption from other users after a short delay while allowing users to share the channel efficiently when there is no critical traffic. Moreover, the proposed protocols require short memory and can be implemented without explicit message passing.Comment: 24 pages, 7 figures, 1 tabl

Throughput Analysis Model for IEEE 802.11e EDCA with Multiple Access Categories

IEEE 802.11e standard has been specified to support differentiated quality of service (QoS), one of the critical issues on the conventional IEEE 802.11 wireless local area networks (WLANs). Enhanced Distributed Channel Access (EDCA) is the fundamental and mandatory contention-based channel access method of IEEE 802.11e, and delivers traffic based on differentiated Access Categories (ACs). A general three dimensional Markov chain model of IEEE 802.11e EDCA for performance analysis is proposed in this paper. The analytical model considers multiple stations with an arbitrary number of different ACs. It also differentiates the contention window (CW) sizes and the arbitration interframe spaces (AIFSs), and considers virtual collision mechanism. Based on the model, the saturation throughput of EDCA is derived, and the accuracy of the proposed model is validated via simulations