無線感測網路(wireless sensor network)是由大量的感測節點所組成的。由於感測節點通常是由電池提供電力，也因此在能量的消耗上便顯得格外重要。為此許多活動/睡眠工作週期(active/sleep duty cycle)的機制被提出來以用來降低能量的消耗。雖然低工作週期(low duty cycle)的機制可以降低能量的消耗，但是它卻會增加封包的傳遞延遲。DMAC是一個專為樹狀資料聚合設計的一個MAC協定，它具有低延遲以及低能量消耗的特性。然而在DMAC中所建立的資料聚合樹(data gathering tree)是固定且長久不變的。一個固定的資料聚合樹無法適應無線感測網路中的環境變動，它必須時常重建以適應目前的環境。例如，干擾是會改變環境的其中一種因素，因為它會影響無線感測網路中的節點連結度。在這篇論文中，我們提出了Robust-DMAC(RDMAC)。它可以依照環境的變化而動態地建立資料聚合樹。由於RDMAC把資料聚合樹的建立和醒來時程(wakeup schedule)的分配分開來，所以它可以不用重新調整節點的時程就可以建立一個新的資料聚合樹。在傳輸方面，由於RDMA採用了和DMAC一樣的交錯醒來時程(staggered wakeup schedule)，我們可以將DMAC所提出的傳輸機制(duty cycle adaptation，data prediction，More-To-Send packet)直接引用而只需要小幅的修改。最後，在受干擾的變動環境中所得到的模擬結果中，RDMAC在能量有效消耗的表現上和DMAC相當接近。而在封包到達率(packet arrival ratio)，網路吞吐量(network throughput)，封包傳遞延遲(packet delivery latency)，RDMAC表現比DMAC要來得好。

Wireless sensor networks are composed of a large number of sensor nodes. Since sensor nodes are generally battery-operated, energy consumption is very important. Therefore, active/sleep duty cycle schemes are proposed to reduce energy consumption. Although low duty cycle schemes can reduce energy consumption, it will increase packet delivery latency. DMAC using the staggered wakeup schedule can achieve both low latency and low energy consumption with the low duty cycle scheme. However, the data gathering tree built by DMAC is fixed permanently. A fixed data gathering tree can't adapt to the variability in the environment of wireless sensor networks, and it needs to be reconstructed frequently to suit the current environment. For example, the interference is a factor that will change the environment because it changes node connectivity of wireless sensor networks. In this paper, we propose a Robust-DMAC (RDMAC) which can dynamically construct the data gathering tree according to the changing environment. Because RDMAC separates the formation of the data gathering tree from the arrangement of the wakeup schedules, it can easily construct a new data gathering tree without adjusting nodes' schedules. As for the transmission aspect, since RDMAC adopts the staggered wakeup schedule suggested in DMAC, we can apply these transmission mechanisms (duty cycle adaptation, data prediction, More-To-Send packet) proposed by DMAC with few modifications. From simulation results in variable environments affected by interference, it is shown that RDMAC performs closely with DMAC in effective energy consumption and has remarkable improvement in packet arrival ratio, network throughput, and packet delivery latency over DMAC.

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