近年來，無線網絡的佈署越來越廣泛且普及在人類的生活中，提高網路性能在學術界和工業界中是個重要且熱門的研究議題。調整傳輸信號功率就是提高網路性能的有效方法之一。無線網路的總吞吐量和使用者與無線存取點之間的傳輸速率有關。如今，自動調速和自適性調變是無線存取點用來提高性能及吞吐量的兩項重要方法及技術，而這兩種技術在調整機制上都會受到傳輸功率的影響。由於近年來軟體定義網路(Software Defined Network)越來越受歡迎，以集中式的方法管理無線網絡資源變成實用的方法。軟體定義網路架構提供了一個中央控制器來調整整個網路資源讓管理者能利用更多有效率的集中式演算法提升網路性能。在這篇論文中，我們首先研究了功率調整的問題，自動調速和自適性調變技術。最後，我們提供一個集中式的功率調整演算法來提高整個網絡的總吞吐量。

Recently, wireless network become much common and widely deployed in human life, improving the performance of total network is an important and popular research in both academy and industry. Power control is one efficient way to improve network performance. The total throughput of clients is related to the bit-rate between the AP and its clients. Nowadays, for a wireless access point, auto rate adaptation and adaptive modulation are two importance techniques to enhance transmission throughput, which were greatly influenced by transmission power. Since software-defined networking has gained popular in recent years, manage wireless network resource in centralized method become a practical and popular way. SDN provides a centralized controller to manage whole wireless network resource that manager can apply more efficient centralized algorithms to improve network performance. In this paper, we first studied the power control problem, auto rate adaptation and adaptive modulation techniques. Finally, we provide a centralized power adjustment algorithm for improving the total throughput of network.

1 Introduction........1
2 Related Works........4
3 Network Model........7
4 Power Adjustment........9
4.1 The Problem........9
4.2 Algorithm.......12
5 Performance Evaluations........15
5.1 Simulation Settings........15
5.2 Simulation Result........17
6 Conclusion and Future Works........20

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