| Wireless networks have enjoyed the exponential development, and wireless communication has become an essential part of modern life. Many new wireless applications demand higher speed and consume more energy. However, wireless devices are always powered by batteries, which have limited life time and constrain the use of wireless devices and the growth of wireless networks. Energy efficiency becomes an important issue in wireless networks. We study the energy efficiency in the IEEE 802.11 based WLAN (Wireless Local Area Network) and the third generation cellular system UMTS (Universal Mobile Telecommunication System), in which the basic mechanism is to put a mobile device into a low power consumption state when it is idle and wake it up periodically to transmit/receive traffic.; In WLANs, the study is focused on the MAC (Media Access Control) sublayer. Two queueing models for the power management mechanisms in an infrastructure network are proposed: the M/G/1 queue with bulk service and the D/G/1 queue. Based on the analytical and simulation results, suggestions are given about how to optimally configure the power management parameters. We also propose the enhanced power management schemes for both infrastructure and independent networks, which outperform the original schemes based on our analysis and simulation.; In UMTS, the impacts of Discontinuous Reception (DRX) mechanism and inactivity timer are studied. The simulation of the performance of power saving mechanism is carried out by inputting several typical traffic models specified by 3GPP (third generation partnership project). From the results that different traffic models demand different optimal parameters, we propose to adaptively configure the DRX cycle and inactivity timer parameters based on real-time measurements. |
