Performance Evaluation of Flows with Diverse Traffic and Transmission Rates in IEEE 802.11 WLAN

Yiru Wu,Jiandong Li,Yinghong Ma,Hongyan Li

doi:10.4236/cn.2013.53b2114

Abstract

IEEE 802.11 WLAN cannot guarantee the QoS of applications, thus admission control has been proposed as an essen-tial solution to enhance the QoS. Packet delay and throughput are commonly employed as assessment criterions to determine whether a new connection can be admitted into the WLAN. Considering the real network condition, the analytical model is presented in this paper, which is aimed to evaluate the packet delay and throughput performance of IEEE 802.11 WLAN in nonsaturated conditions, taking into account diverse transmission rates and diverse traffic flows (i.e. flows with different packet sizes and arrival rates) simultaneously. This model is based on Markov chain and the theoretical predictions are verified by simulation in OPNET 14.5. We also analyze the influences of transmission rate diversity and traffic flow diversity on throughput performance. It is observed that, the presence of even one station with lower transmission rate can cause a considerable degradation in throughput performance of all the stations when they have the same packet size and arrival rate. Higher system throughput can be achieved if lower transmission rate stations transmit packets with smaller size or arrival rate.

Highlights

In recent years, the IEEE 802.11 based wireless LANs (WLANs) have gained great popularity due to high bandwidth, low cost and simple deployment
Considering the real network condition, the analytical model is presented in this paper, which is aimed to evaluate the packet delay and throughput performance of IEEE 802.11 WLAN in nonsaturated conditions, taking into account diverse transmission rates and diverse traffic flows simultaneously
We analyze the influences of transmission rate diversity and traffic flow diversity on throughput performance and draw the conclusion that, the system throughput can be increased if lower transmission rate stations transmit packets with smaller size or arrival rate

Summary

Introduction

The IEEE 802.11 based wireless LANs (WLANs) have gained great popularity due to high bandwidth, low cost and simple deployment. In [9,10], the probability of a station having at least one packet ready for transmission is expressed as a function of traffic load, which takes into account the packet arrival rate diversity. In order to accurately predicting delay or throughput, we consider the traffic flow diversity (i.e. packet size diversity and arrival rate diversity) and the transmission rate diversity simultaneously, and derive the formulas for delay and throughput in non-saturated cases. We present a discrete Markov chain model to calculate the probability τ of a station transmitting in an arbitrary time slot in nonsaturated conditions. We analyze the influences of transmission rate diversity and traffic flow diversity on throughput performance and draw the conclusion that, the system throughput can be increased if lower transmission rate stations transmit packets with smaller size or arrival rate

Analytical Model

Per-Station Markov Model

Average Packet Delay

Model Verification

Conclusion