無線感測網路是一群許多的由電池供電的感測器組成，而無線感測網路已經被應用於許多地方，利軍事監測、醫療照顧或是環境監測等等應用。在無線感測網路中，週期性醒睡是一個經常被用來減少電量消耗的以及延長網路壽命技巧，然而此技術並不足以應付各種不同的網路環境或是為了節省電量而造成額外的延遲。會如此的原因是使用者很難去制定一個最好的責務週期，而造成難以制定的原因是由於感測事件並不是規律性或週期性的發生，因此無法事先知道何時感測事件會發生，如此造成責務週期難以制定。另外，如果感測網路有對終端延遲做限制的話，則如何制定一個既可盡量省電但又不違反延遲限制的責務週期將會變得更加困難。基於上述理由，本篇論文提出了CBA-EX MAC，一個基於經濟學與統計學來達成動態調整並有效節能的MAC協定。CBA-EX MAC可以十分有效的節省電量並且同時保證網路延遲，而達成此效果的核心概念是CBA-EX MAC可以同時動態調整每一個感測節點的醒睡行程以及責務週期。在CBA-EX MAC中，每一個感測節點會同時參考網路資料量以及延遲限制來各自決定出一個既可有效省電但又同時維持延遲限制的醒睡行程。此外，CBA-EX MAC也同時讓每一個感測節點可以動態調整各自的責務週期來更進一步的節省電量消耗。最後，我們的模擬結果顯現出CBA-EX MAC可以比其他現有的動態調整或是固定責務週期的MAC協定節省更多的電量消耗並且同時維持住各種的延遲限制。

A wireless sensor network consisting of a large number of battery-powered nodes have been witnessed a variety of applications, ranging from military surveillance to health care to environmental monitoring. In a wireless sensor network, the technique of periodic sleep and wake up is usually utilized to save energy and prolong lifetime. However, existing relevant work is not suitable for all kinds of network environments and usually sacrifices latency for energy savings. The reason is that it is hard to decide a perfect duty cycle for nodes to follow since the sensing events or the traffic is not happening regularly and thus is unknown beforehand. In cases when applications have constraint on the end-to-end delay of the data packets, it is even harder to decide a perfect duty cycle for nodes to preserve as much energy as possible, while maintaining the delay constraint. To this end, we propose CBA-EX MAC, an adaptive energy-efficient MAC protocol based on economics and statistics. CBA-MAC achieves significant energy savings while maintaining delay constraint. The key is to change the schedule and duty cycle of nodes dynamically. In CBA-EX MAC, each node takes both network traffic and delay constraint into consideration to get a suitable schedule for nodes to preserve as much energy while maintaining the delay constraint. In addition, each node in CBA-MAC can change its duty cycle to reduce more energy consumption dynamically. The results of our simulation confirm that CBA-MAC can reduce more energy consumption comparing to other existing adaptive or fixed duty cycle MAC protocols, while maintaining different kinds of delay constraint.

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