隨著無線區域網路(WLANs)的快速發展及Access Point (AP) 佈建密度的增加，加上頻道(Channel)資源短缺問題，造成雜訊(Interference)干擾問題導致使用者的服務品質下降。對於學校及公司單位，AP可能是以一種集中型(Centralized)方式來架設，但是一般場所架設之AP則是使用分散式(Distributed)方式來建置，這種未經過事先的規劃，將會對於無線訊號的傳輸造成嚴重訊號干擾問題。本研究分成兩個部分，第一個部份為探討在Distributed coordination function (DCF) 架構底下，提出基於分散式頻道選取的方法，藉由給予使用者不同的權重値，再根據系統使用者的Signal Interference Noise Ratio(SINR)來動態調整頻道;此外，AP配合功率控制(Power Control)，能夠在不影響總體效能的前提下而達到節能的效果。由模擬實驗結果顯示，經由整合調整頻道及功率控制，我們所提出的方法與其他文獻方法有效能上改善，至少節省2.7%的傳輸功率，在AP佈建密集的環境下，減少頻道間干擾且達到功率節省的效果。
在支援多速率(multi-rate)傳輸的802.11網路環境底下，當使用者都聚集在特定地方時，導致AP間流量的不平均，所以在第二個部份將探討在Point coordination function (PCF)架構底下，提出一個利用中央控制器(Controller)週期性調整最大負載的AP藉此來平衡系統中每個AP的負載量。我們所設計負載平衡之機制，由模擬實驗的結果顯示，與先前文獻相比能有效改善效能。

Wireless local area networks (WLANs) have spread so rapidly and developed dramatically in areas such as homes, public hotspot, airports, and offices etc. With the dense deployment of access points (APs) and lacking of the sufficient frequency resources, the signal interference problem has become more serious, resulting the throughput degradation of the users. For schools and offices, APs may be constructed in centralized way, but for public hotspot or homes, APs are setting up in distributed way. Such placement without any concerted planning will bring the severe signal interference problem.
We propose a distributed dynamic channel assignment (DCA) algorithm which works on a distributed coordination function (DCF)-based architecture for improving network throughput and decreasing the computation complexity by maximizing the sum of weighted signal to interference plus noise ratio(SINR). Besides, we combine the power control and channel assignment. Our algorithm improves the ratio of power saving by at least 2.7% in high density environment.
Today’s WLANs use 802.11 standards that support multi-rate and the people gather in certain places which will bring the load imbalance problem. Our centralized mechanism which works on a point coordination function (PCF)-based architecture and uses a controller to periodically adjust the AP that carry heavier traffic load. Simulation results show the effectiveness of the proposed mechanism and compare the performance with the other method.

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