In this paper, a novel time-based modulation scheme is proposed in the time-asynchronous channel for diffusion-based molecular communication systems with drift. Based on this modulation scheme, we demonstrate that the sample variance of information molecules' arrival time approximately follows a noncentral chi-squared distribution. According to its conditional probability density function (PDF), the asynchronous receiver designs are deduced based on the maximum likelihood (ML) detection, with or without background noise in the channel environment. Since the proposed schemes can be applied to the case of transmitting multiple information molecules, simulation results reveal that the bit error ratio (BER) performance improves with the increase of the number of released information molecules per bit. Furthermore, when the background noise is not negligible, our proposed asynchronous scheme outperforms the asynchronous modulation techniques based on encoding information on the time between two consecutive release of information molecules.

中文翻译：

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用于分子通信的时间异步通道中的新型基于时间的调制方案。

本文针对具有漂移的基于扩散的分子通信系统，在时间异步信道中提出了一种新颖的基于时间的调制方案。基于此调制方案，我们证明了信息分子到达时间的样本方差近似遵循非中心卡方分布。根据其条件概率密度函数（PDF），基于最大似然（ML）检测推论出异步接收器设计，无论信道环境中有无背景噪声。由于所提出的方案可以应用于传输多个信息分子的情况，因此仿真结果表明，随着每比特释放的信息分子数量的增加，误码率（BER）性能提高。此外，