無線感測器網路應用設計，是在一個廣大的區域大量的地散佈感測器以達到監測環境的效果。感測器通常是由電池供電而難以改換電池並配置受限的運算處理器。在這樣的劇本之下，無線感測器網路和傳統的區域網路以及無線網路是非常不同的。
在考量設計無線感測器網路的協定時，能源節約和封包傳遞品質是二個非常重要的考量。為了達到這二個要求，已經有非常多的論文提出各種方法來協調感測器之間的睡眠時間以維護必需的網路拓樸。GAF利用地理位置資訊來定義每個感測器之間的等價性進而關掉多餘的感測器無線電。
在本篇論文，我們提出一個群組化GAF演算法。我們主要對著名的GAF做了下面二個修改。首先，我們將GAF裡的方形虛擬網格改成六角形並評估修改之後的效能。之後我們提出一個群輪替方法，它將整個網路分成四個群，每個群輪流起來為並喚醒維持網路連通性必需的點。在理論上用我們的方法能夠將網路中醒著的點數降至GAF的51.96%。而在我們的實驗結果中，我們喚醒的點數是GAF的50.69%。只額外造成了1.16%的封包傳遞延遲時間。由於邊界網格不完全的問題，我們獲得了比理論值還好的實驗值。

Wireless sensor networks can be thought as wireless ad hoc networks with limited energy supply and restricted computation ability. However, unlike traditional local area networks or wireless networks, sensor networks should take these constraints into consideration.
Energy limitation and routing fidelity are two of the most concerns in developing protocols and algorithms for wireless sensor networks. To achieve these two goals, many researches focus on how sensor nodes coordinate with each other to turn off their radio intermittently, thus reduce their energy consumption. For example, Geographical Adaptive Fidelity (GAF) [1] conserves energy by using geographic location information to identify the equivalence between nodes then turn off redundant nodes.
In this thesis, a grouping GAF method is proposed. It replaces GAF virtual grid with hexagonal cell first, and periodically rotates the active nodes between several groups (partition of nodes). Theoretically the proposed method wakes up only 51.96% of nodes that GAF does without losing the property of network connectivity. The simulation results show that with our algorithm, we awake only 50.69% of the nodes compared to GAF with additional 1.16% packet delivery delay.

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