於MIMO-OFDM之智慧型成波束天線之研究

Abstract

為了能夠有效的利用頻寬，使用智慧型天線(smart antenna)與數位訊號成波束技術(digital beamforming)可以提升多輸入多輸出 (MIMO) 的傳輸系統效能，其目地為提高訊號品質與消除其他訊號之干擾。 在這篇論文我們提出一個方法搜尋訊號的入射角來源，此演算法利用接收端的訊號去分析傳送端訊號之強度，藉由訊號強度去調整指向型天線之方向。另一方面，我們偵測進入接收端訊號的延遲，利用此延遲調整訊號，使訊號達到最佳強度，即可增加訊號的容量與訊號品質。 在IEEE 802.11n的系統平台而且符合TGN所規範的通道模型中模擬。模擬結果指出此演算法與最佳調整的效能相比，找出訊號強度對效能之影響。使用訊號偵測器去偵測訊號調整，可以提升整體系統效能。以上皆應用在多輸入多輸出的傳輸系統上模擬。

Smart antenna and digital beamforming in MIMO-OFDM system are an efficient way to improve the performance. Two of them are cancelling the interference signal and emphasize the interested signal. They can be used the antenna array to received signals and control the direction of the maximum gain via different phase adjustment. In this paper, we proposed a method to estimate the arrival of angle in smart antenna system. The method detects correlation of transmitted signal by search the maximal quality form transmitted-end. Moreover, according to this method, we can find an arrival angle on received-end and adjust the antenna angle to steering them. It can improve the interested signal quality. In digital beamforming system, if the signal arrival on received-end is skew, it will cause the signal performance terribly. We proposed a method to detect the channel environment to adjust the signal on received end. The received signal is computed a weighting vector to improve the SINR (Signal Interference Noise Ratio), increase capacity and enhance the signal quality. Through simulation in IEEE 802.11n platform with TGn channel D, It will show that the proposed algorithm with smart antenna performs a little degradation than with the prefect smart antenna system. And in digital beamforming system, using this detector to detect the channel impulse response and via phase adjustment will improve some performance then channel arrival skew. All of these simulations are in MIMO-OFDM 4×4 platform.