Analysis and Rectification of the Asynchronous Sampling Effect in the Pulse-Position Modulation Systems

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.