基於接收多頻訊號之強度的穩健三點定位法

Abstract

在定位系統中，常利用的一種方法是藉由多個已知位置的節點(稱之為參考點)測得目標點的距離後，再利用參考點位置和其所測得距離去做定位。而在測量距離這方面，如果是藉由訊號強度來推算，我們就稱之為使用訊號強度資訊的定位系統。利用訊號在被送出後，其強度會隨著傳送距離的增加而衰減的特性，我們可以用衰減模型計算所接收到的訊號強度的傳輸距離。一般而言，訊號在被送出並且被接收後，其強度在此傳輸路徑上是按照一個路徑衰減指數成指數衰減，因此如果可以獲得路徑上的路徑衰減指數，我們就可以做出精確的距離測量。 但另一方面，即使在同一空間中，卻因為存在著許多變數而導致各個不同的路徑都擁有自己的路徑衰減指數，所以此篇論文我們提出先利用兩個不同頻率的訊號測得參考點到目標上的路徑衰減指數後，再利用此數值做此路徑的距離推導，最後再藉由三點定位法做出目標的定位。而透過二個模擬實驗，可以得知此改善的定位系統可以獲得好的定位精確度。

Positioning technique is widely used in many applications such as Global Positioning System (GPS). There are many studies concentrated on this issue. Received-Signal-Strength-based (RSS-based) positioning method is one kind of the positioning mechanisms. It uses the received-signal-strength (RSS) information to estimate the distances from reference nodes to the target, and then uses these distance information and the positions of those reference nodes to perform the positioning task. Therefore, the estimation of the distance between the reference node and the target is the key point which affects the positioning accuracy. In this thesis, we proposed a robust trilateration method to estimate Path Loss Exponent (PLE) which stands for the signal attenuate rate for each reference node to target path by using two different frequency signals and the trilateration method. Then we used every PLE to calculate the corresponding distance and performed the trilateration positioning task using these distances. We also ran two simulations to evaluate our proposed method. The simulation results show that our robust trilateration positioning method is really more precise than positioning methods with fixed PLE for every path.