Analytical Modeling of IEEE 802.11e Enhanced Distributed Channel Access under a Non-Saturation Condition

Prakash Prakash

doi:10.3844/jcssp.2011.554.560

Abstract

Problem statement: The IEEE 802.11e EDCA protocol with different access Categories (ACs) supporting for Quality-of-Service (QoS). Due to internal or external packet collision, the Contention Window (CW) of the station increases the channel idle time under high Bit Error Rate (BER). Approach: In this study, we propose an analytical model for performance evaluation of IEEE 802.11e EDCA scheme under non-saturation condition and error prone channel. The new markov chain model have decrease the channel idle time in IEEE 802.11 EDCA and considerably increases the throughput for minimum number of station. Results: We develop an expression for the nonsaturation throughput as a function of the number of stations, packet sizes and BER. Conclusion: We validate the accuracy of our analysis with simulation expression. Using this model, the contention factors can be set appropriately to attain particular Quality-of-Service (QoS) requirements.

Highlights

In recent years, the IEEE 802.11 Wireless Local Different levels of services are provided to each access Categories (ACs)
The IEEE 802.11e Medium Access Control (MAC) layer is to enhancing the quality of services in WLAN which provides a contention-based channel access function and a centrally controlled channel access function called the Hybrid Coordination Function (HCF)
We present numerical results that show the impact of transmission errors on the system capacity

Summary

INTRODUCTION

Access Categories (AC) services for each station. In recent years, the IEEE 802.11 Wireless Local Different levels of services are provided to each AC. The IEEE 802.11e MAC layer is to enhancing the quality of services in WLAN which provides a contention-based channel access function and a centrally controlled channel access function called the Hybrid Coordination Function (HCF). Bianchi proposed a Markov chain based model to evaluate saturation throughput, the mobile stations always have something to transmit (i.e., the saturation condition), assuming a finite number of stations and ideal channel conditions (no errors).While in (Shyang et al, 2005) the authors extended the Bianchi model in order to consider unsaturated traffic conditions by adding another state (idle) to represent the node with empty queue, not present in the original Bianchi’s model, in which the station buffer is empty, after a successful completion of a packet transmission. In case of transmission error due to fading or packet collision from other stations experiences external collision, the contention window size is doubled for every transmission Based on this previous work of Xiao’s model (2005), Senthilkumar and Krishnan (2010), we developed a Markov chain model for the EDCA analysis.

MATERIALS AND METHODS

RESULTS AND DISCUSSION

CONCLUSION