隨著無線通訊技術的快速發展，如何實現行動台(mobile station, MS)之位置估測是不可或缺的。憑藉精準的定位，無線定位技術可被應用於不同層面，如E911急難救助、安全服務以及智慧型運輸系統。行動台的定位精準度密切依賴訊號的傳播環境，事實上非視線傳播(non-line-of-sight, NLOS)的存在將導致信號量測的誤差。因此減少非視線傳播效應造成之誤差為無線定位系統之首要任務。
非視線傳播影響了無線通訊定位精準度，為了提升定位精準度，幾何權重精度因子被應用於無線定位系統中並挑選基地台。權重幾何精度因子是一個準則用於判斷定位的基地台幾何架構，隨著不同的基地台定位，依照基地台的位置會造成不同的幾何架構並造成不同的定位精準度，根據權重幾何精度因子所挑選出的基地台，定位出來的精準度遠比於隨機挑選的基地台還要精準。因此，權重幾何精度因子確實能降低非視線傳播的影響。
隨著更多的基地台做挑選，權重幾何經度因子越小，也代表著有較佳的幾何架構，但是由於基地台及行動台的可接收能力問題，能接收到的基地台的數目有限。因此，我們假定在蜂巢式通訊系統中僅挑選四個基地台來定位。雖然權重幾何精度因子確實能降低非視線問題，但權重幾何精度因子的計算過複雜且耗時，因此許多近似的方法被提出，為了降低計算複雜度，此篇利用基因演算法來近似權重幾何精度因子，所提出的近似方法確實能有效的避免計算複雜度且保有相似的結果挑選出正確的基地台組合。

Since the rapid development of the wireless communication technology, the ability of how to estimate the location of mobile station (MS) is indispensable. By the accurately positioning, the location technology can be applied to various applications, like the E911 emergency assistance, security services, and intelligent transportation systems. The accuracy of MS location estimation depends on signal propagation environment closely. In practical, non-line-of-sight (NLOS) is existence everywhere and it leads to the error of signal measurement. Therefore, the main task is to cut down the error generated from NLOS in wireless positioning system.

NLOS always influences the accuracy of the wireless position. To enhance the accuracy of position, Weight Geometric dilution of precision (WGDOP) is applied to select the base station s (BSs) to position in wireless communication system. WGDOP is a criterion for choosing the appropriate geometric configuration of the measurement units. Different stations can constitute different combinations and cause different position accuracy. According to the selected BSs with WGDOP, the position accuracy is always better than the selected BSs randomly. As a result, WGDOP can reduce the position error causing by NLOS.

As the more BSs selected, the WGDOP is smaller and the better geometric configuration we have. Because the Hearability problem, the number of BSs are limited. As a result, the research assumes that only four BSs are selected to position in cellular communication system. Although the WGDOP can enhance the position accuracy, the calculation of WGDOP is complicated and cause a lots of time. Hence, many methods of approximating WGDOP are proposed. To reduce the complexity of calculation, Gene algorithm (GA) is utilized to approximate the calculation of WGDOP. The proposed method can avoid the calculation of matrix inversion in WGDOP and only cause a little bias.

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