We consider a single station (STA) in the Power Save Mode (PSM) of an IEEE 802.11 infrastructure WLAN. This STA is assumed to be carrying uplink and downlink traffic via the access point (AP). We assume that the transmission queues of the AP and the STA are saturated, i.e., the AP and the STA always have at least one packet to send. For this scenario, it is observed that uplink and downlink throughputs achieved are different. The reason behind the difference is the long term attempt rates of the STA and the AP due to the PSM protocol. In this paper we first obtain the the long term attempt rates of the STA and the AP and using these, we obtain the saturation throughputs of the AP and the STA. We provide a validation of analytical results using the NS-2 simulator.
@cite_5 , Lei and Nilsson @cite_12 , Baek and Choi @cite_7 and @cite_11 evaluated the energy performance of PSM, but none of them attempt to obtain the saturation attempt rates of the STA and the AP. Apart from this, in all the above papers, authors consider the PSM protocol implementation which is not practical. They consider the following sequence of frame exchanges: First the PSM STA sends the PS-POLL frame through contention, after SIFS AP sends the data packet and after SIFS again the STA sends the MAC ACK. So the AP does not contend to send data. In the presence of traffic from the AP to other STAs, when the AP receives the PS-POLL frame, some packets might be already present in the NIC queue of the AP, and these packets need to be sent first. So the above sequence of frame exchange cannot work under the scenario just described. We consider a different implementation of PSM protocol which is explained in the next section.
@cite_5 @cite_7 @cite_12 @cite_11
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For the battery-powered wireless stations, power saving is one of the significant issues in IEEE 802.11 wireless local area network (WLAN). Recently, Lei and Nilsson investigated the power save mode in IEEE 802.11 infrastructure mode by an M G 1 queue with bulk service. They obtained the average packet delay and lower and upper bounds of the average Percentage of Time a station stays in the Doze state (PTD). In this paper, the further investigation of power save mode is done; simple derivation of the average and the variance of packet delay and the exact value of PTD are obtained. Numerical results show that our analytic results for PTD match quite well with simulation results. Using our performance analysis, we can find the maximal listen interval which minimizes the power consumption of a station while satisfying the required quality of service (QoS) on the average and the variance of packet delay. Energy efficiency is an important issue in wireless networks. We investigate the power management scheme in the IEEE 802.11 based infrastructure WLANs (wireless local area network) in order to find the optimal parameters that can achieve good energy efficiency without degrading other performances. With power management, an AP (Access Point) might temporarily buffer packets whose destination stations are in the Doze state. We focus our study on the behavior of the buffered packets and their impacts on the performance metrics. We model the power management scheme as an M G 1 queue with bulk service and obtain the analytical results for the energy efficiency and the response time performance metrics, which are controlled by the listen interval. Our simulation results are in good agreement with the analysis. Based on the analytical model and simulation, we propose to select the largest listen interval with the satisfaction of the response time requirement. In this paper, we focus on the Markov model of IEEE 802.11 distributed coordination function with power saving mode. The throughput evaluation is based on the model, with the comparison with the simulation result for validation. Furthermore, we notice that after each beacon transmission, there're more stations in contention than usual. Excessive contention results in high collision probability and low throughput. To solve this problem, we propose a downlink access scheme which can be used in both the basic access scheme and the access scheme with RTS CTS. This novel scheme enables AP to constrain the number of stations in contention to be an optimal value. Simulation results prove the performance improvement declared. The proposed scheme can be extended for multi-rate or multi-service WLANs.