Although the clock synchronization is of utmost importance in communications, it is quite difficult to achieve in practice. Consequently, the asynchronous effect emerges as a critical problem for all pulse-position modulation (PPM) systems. In this paper, the impact of the sampling-period misalignment is studied and evaluated. A new analytical model is established to govern the misalignment between the slot periods of the transmitted and received signals. The ultimate error rate related to this kind of unfavorable misalignment is also derived theoretically. Besides, we propose a new algorithm, which can adjust the onsets of the slot periods dynamically, to mitigate this misalignment and improve the error performance. To justify our new analysis and algorithm, a visible-light communication system using single-pulse PPM is taken as a practical example. Simulation results demonstrate that the effectiveness of our proposed algorithm is very promising. The frame-error rate of the rectified PPM signal is around 10−5 across all of the misalignment values.

中文翻译：

---

脉冲位置调制系统中异步采样效应的分析与校正

虽然时钟同步在通信中是最重要的，但在实际中实现起来却相当困难。因此，异步效应成为所有脉冲位置调制 (PPM) 系统的关键问题。在本文中，对采样周期错位的影响进行了研究和评估。建立了一个新的分析模型来控制发送和接收信号的时隙周期之间的错位。与这种不利的错位相关的最终错误率也是从理论上推导出来的。此外，我们提出了一种新算法，可以动态调整时隙周期的开始，以减轻这种错位并提高错误性能。为了证明我们新的分析和算法的合理性，以使用单脉冲 PPM 的可见光通信系统为例。仿真结果表明，我们提出的算法的有效性是非常有前途的。在所有未对准值中，经整流的 PPM 信号的帧错误率约为 10-5。