利用非視線訊號改善無線網路於二維空間之定位

Abstract

大多數的現有的定位方法都是依據視線訊號(Line of sight, LOS)定位。但在都市裡，常因基地台與接收機中間的障礙物而產生非視線訊號(Non-line of sight, NLOS)，這會讓定位精度下降，甚至無法定位。接收機所收到的究竟是視線訊號亦或是非視線訊號，已有一些研究提出適當方法以為判定之依據。在沒有任何視線訊號之情況下的定位方法，相關的研究則尚不普遍。而本論文之目的就在於借由非視線訊號的抵達角度(Angle of arrival, AOA)與抵達時間(Time of arrival, TOA)，在平行反射面及一次反射假定下，推導出新的定位演算法。 本論文所提出之非視線訊號定位方法，乃藉由平行反射面所對應的AOA與TOA量測值之線段定位。因為此線段必通過目標物，可推測目標物的所在即是兩條線段的交點。又因每條線段至少需要兩組AOA與TOA量測值始可得知，因此本論文所提出的非視線定位方法最少需要四組AOA與TOA量測值方可定位。此外，本論文亦透過幾何分析來探討非視線定位方法之誤差。最後則以模擬結果驗證此非視線定位方法與誤差分析的合理性。

Nowadays, most of localization methods are suitable for line-of-sight (LOS) condition. However, when LOS signal is obstructed in urban or internal environment, considerable localization error is generated due to non-line-of-sight (NLOS) signals in the channel. There are some proper techniques to distinguish NLOS channel from LOS channel in the past while there are a few approaches to localization without LOS signals. In this thesis, we present a mobile localization technique in non-line-of-sight (NLOS) scenarios by using angle-of-arrival(AOA) and time-of-arrival(TOA) measurements from base stations. In addition, we assume that two reflectors of single-bounced NLOS signals are parallel. Our localization technique is based on two parallel reflectors and single-bounce NLOS signals. Two parallel reflectors provide one line where the target is. When there are more parallel reflectors, more lines that target is located on can be constructed, and the target position is determined by the crossing point of those lines. In other words, at least four AOA/TOA measurements of single-bounce NLOS signals which construct two lines are used to find target position in NLOS situation. The localization errors caused by the geometric distributions of base stations and reflectors are analyzed. In our simulations, our geometric analysis is confirmed. Also, more AOA/TOA measurements of two parallel reflectors are used, the performance of localization is more accuracy.