虛線(dotted line)現象是當一台設備透過網路量測上另一台設備的時脈偏移時，其中一種特殊的時間偏移量的分布圖形。當產生虛線現象時，根據傳統方法需要延長量測的時間才可以收集足夠的時間偏移量來取得較精準的時脈偏移。然而，一個不含離群值與封包遺失的完整虛線圖形因其展示穩定的斜率變化，卻可以使用簡單線性回歸求得高精度的時脈偏移。本研究提出利用虛線特性如虛線長度的規律變化以及每條虛線的固定斜率等來重新建構完整虛線的方法，並開發了對應的演算法。我們透過實驗在2500秒內蒐集5000個偏移量，並使用線性回歸來計算重新建構後的虛線，其結果可以將誤差值由1.79ppm大幅度降低至0.69ppm。

The dotted-line phenomenon is a kind of special pattern in the scatter diagram of offsets when one device measures the clock skew of another device over network. Dotted lines, when happened, lengthen the period of time to collect enough offsets for precise skew measurement. However, a set of complete dotted lines enables highly accurate clock skew measurement by simple linear regression. In this research, an original method is developed to reconstruct and any collected dotted-line set utilizing the characteristics of dotted lines, which includes that the lengths of the dotted lines change in regular pattern and that the slope of each dotted line be of the same value. By eliminating outliers and by complementing package loss, the set of complete dotted lines shows stable slope that can be easily and precisely derived by simple linear programming method. An experiments of measuring clock skew by 5000 offsets collected in 2500 seconds show that the maximum difference reduces from 1.79ppm to 0.69 ppm when we measure the clock skew by using LRM under the complete shape of dotted line.

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