Design of Power Saving Protocols for IEEE 802.11 WLANs and IEEE 802.16e WMANs

• Main Authors: Shih-Chang Huang, 黃世昌
• Other Authors: Rong-Hong Jan
• Format: Others
• Language: en_US
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/53789232959357167746

博士 === 國立交通大學 === 資訊科學與工程研究所 === 96 === Recently, wireless networks have widely developed. Many different wireless technologies have been proposed for different network aspects. Among all of the wireless technologies, the IEEE 802.11 WLANs and the IEEE 802.16 WMAN directly influence the internet access of end users. The former provides easy and low cost solution for people to build their own local area networks and the latter provides a wireless internet access solution to substitute the last-mile internet accessing in the wired networks. Because most of the mobile devices in the wireless networks are powered by battery, saving power to extend the operation time is a critical issue. Therefore, we design several power saving protocols for the infrastructure and ad hoc mode of IEEE 802.11 WLANs and for the IEEE 802.16e WMANs. For the infrastructure mode of IEEE 802.11 WLANs, a novel method is presented to schedule the listening duration of sleeping stations and to balance the amount of wakeup stations in each beacon interval. This method saves stations’ power by reducing the probability of collision. We also control the amount of wakeup stations which can send the PS-Poll frames to get back their buffered data to avoid contention. Three different mechanisms, single wakeup stations, the smallest association ID, and the smallest queue length, are proposed for to control the access order of wakeup stations. Our simulation results show that the proposed methods are effective in the power-saving. For the ad hoc mode of IEEE 802.11 WLANs, a novel self-configuring power-saving protocol, called as SCPS, is proposed. Stations choose their listening intervals as the infrastructure mode. Besides, all stations in the PS mode can adjust their wakeup schedules whenever a station enters or exits the PS mode. The adjustment can balance the amount of wakeup stations in each beacon interval so that both the contention for transmission medium and the collisions in transmission can be ameliorated, which results in more efficient energy usage. Simulation results show that SCPS successfully balances the amount of wakeup stations in each beacon interval, increases the sleep ratio, and reduces the collision probability. For the IEEE 802.16e broadband wireless networks, we proposed several energy efficient scheduling approaches. Instead of considering a single Mobile Subscriber Station (MSS) as most of the current researchers do, multiple MSSs are considered in our work. We consider constant bit rate traffic with QoS delay constraint. The proposed approaches address both energy efficiency and bandwidth utilization. Two classes of scheduling approaches are proposed, the periodical autonomic sleeping cycle (PASC) and the periodical uniform sleeping cycle (PUSC) approaches. In the PASC, the QoS information of all MSSs needs not to know beforehand. Each MSS uses its own sleeping cycle for power saving. While the possible QoS requirement of the MSSs can be known beforehand, the efficiency of the scheduling can be improved further. Thus, the PUSC approaches let all MSSs use the same length of sleeping cycle for their wakeup schedule. BS simply schedules the MSSs’ wakeup time. Simulation results show that both PUSC and PASC can have higher power efficiency. Besides, the PUSC approaches are superior to the PASC approach on the bandwidth utilization under the application of VoIP.