對於邊界使用者於支援波束成形之無線區域網路換手之研究

Abstract

IEEE 802.11ac 是一個針對無線區域網路(WLAN)的通訊標準，此標準透過5GHz頻帶進行通訊。此標準能提供最少1Gbps頻寬進行多站式無線區域網路通訊，隨著人們對於網路頻寬需求的提高，他提出了有效的解決方式，並持續地制定當中。在802.11ac中，波束成形技術被納入此標準之中，波束成形利用擺放在空間中的多支天線，調整其相位以及振幅，以便在部分空間中的訊號能夠獲得相位相同、振幅相加、訊號變強的效果；而部分空間產生相位相反、振幅相減、訊號變弱。因為波束成形是有方向性的，所以我們希望夠通過換手演算法盡量地讓不同的AP之間的天線波束不互相干擾，進而達到比較好的換手效果。我們在MATLAB模擬軟體中模擬了光訊號在實體層的能量損耗，以及在不同環境中邊界使用者換手的結果，透過模擬器也可以顯示出我們的演算法能夠提升整體系統效能7%-23%的吞吐量。

IEEE 802.11ac is a wireless networking standard in the 802.11 family, developed in IEEE Standards Association process, providing high-throughput wireless local area networks(WLAN) on the 5 GHz band. The specification has multi-station throughput of at least 1 gigabit per second. 802.11ac add a new technology called beamforming. Beamforming is a signal processing technique used in sensor arrays for directional signal transmission or reception. To change the directionality of the array when transmitting, a beamformer controls the phase and relative amplitude of the signal at each transmitter, in order to create a pattern of constructive and destructive interference in the wave front. In order to decreasing the interference of different AP. We use directional-beam to avoid the interference, and getting better performance of the handoff procedure. In the simulation, we use MATLAB to simulate the signal transmit in the space. Furthermore, the simulator can change the shape, for instance, more wall in the space. According the result of simulation, our algorithm can improve throughput about 7%-23%.