Performance Analysis And Optimization For Power Management Schemes In IEEE 802.11 Based Wireless Local Area Networks

IEEE 802.11 based Wireless Local Area Networks (WLANs), which use license-free frequency bands for communication, are widely used due to its supporting users'mobility, deployment flexibility, scalability, and low maintenance cost. Many mobile devices supporting the IEEE 802.11 standard are powered by batteries. Due to limited energy of battery, conserving energy has been the hot spot in the researches on WLANs.The basic power management funcation of IEEE 802.11 based WLAN allows Stations (STAs) in idle to operate in the doze mode for energy efficiency. However, the basic power management strategy is unable to meet the complex application and various requirements of Quality of Service (QoS), which motivates many scholars to research on the improvement of power management. In 2010, a paper published in the journal IEEE Transactions on Wireless Communications proposed a Timer-based Power Management (TPM) for infrastructure WLANs, in which two timers, i.e., idle timer and doze timer, are added to control idle and doze times of a STA.This dissertation proposes a novel modeling and analysis method for the TPM, which is able to distinguish the incoming data stream from the access point (AP) to the STA and the outgoing data stream of STAs and the arrivals of the two streams are modeled by Poisson point processes. In this model, the operations of the STA are classified as three basic states, i.e., free, active and doze states. Then, the active state and the doze state are divided into multiple sub-states for the detailed analysis of the queues of the sending and the receiving data buffer. Under the condition that data processing time meets exponential distribution, the probability that STA is in idle, active, doze, or sub-state are all derived. Moreover, the average power consumption, the numbers of frames buffered at AP/STA when the STA is in doze state are obtained. In addition, Numerical analysis and optimization are presented to demonstrate the impacts of the idle timer, the sleep timer and packet arrival rate on the performance of the TPM. The results of this study can be applied in evaluating the performance of the TPM.