現在無線感測網路發展已漸趨成熟，開發應用的環境也有 從室內走向室外的趨勢，所以許多通信的規格也朝省電，輕薄， 短小去發展，尤其是省電部份。因為延長無線感測網路裝置工 作生命,這對於長時間處在電源吃緊的戶外無線感測網路裝置 而言，將無疑有如雪中送炭般可貴。例如本文所欲應用之實例， 在山區中預防土石流需自給自足(電源自生)的戶外無線感測網 路裝置而言,因為裝置身處山中,電源的獲得非常不易，所以電 源的節省以延長無線裝置的工作生命這將是十分重要的。因 此，本篇論文主要是提出一些網路工作的機制,在滿足戶外無線 感測網路裝置，最低工作臨界所需時間與能量消耗間做一個評 量。以達到戶外無線感測網路裝置能在固定的電池能量下，去 延長工作時間且網域工作穩定不易中斷，進而能實現無線感測 網路裝置自給自足的理想。 Since the personal wireless network development is getting more maturely, also the application developing environment has been trend from indoor to outdoor. It is easy to see that many standard of communication develop toward to power saving and tiny size characteristic. Especially in powers saving, it is more important for the wireless sensor network devices which has no other power supply expect inside battery. As the example in this article, it is difficult to obtain the power supply for the outdoor wireless sensor network devices which used for detecting landslide; usually equipment in mountainous, and have to provide power by itself. Therefore, it is an important goal to achieve the power saving and extending the working time for the wireless sensor network devices. The propose of this paper is to evaluate between time threshold with lowest power consumption of wireless sensor network devices, and has accomplished to extend working time for the outdoor wireless network devices with limited power, also, maintaining the stability of the network, further to realize the wireless sensor network devices can provides power supply by itself.