Molecular Communication via Diffusion (MCvD) is one of the most prominent approaches to interconnect the nano-machines which can do some simple communication functions. In this paper, Pulse Position Modulation (PPM) is studied. We divide the received time step to four separated bins and recognized the distribution model of received molecules in each bin. As a benchmark, we derive Maximum Likelihood (ML) detector for comparison with other methods. Furthermore, we propose a technique called MAX detector in order to design the receiver for simplifying the symbol detection procedure. By changing the values of time step and distance between the transmitter and the receiver, we change the effect of Inter Symbol Interference (ISI). Further, we find the BER (BER) of MAX detector analytically. It is seen that two detection methods for PPM can achieve the same BER for some practical cases, while the MAX detector is simpler than ML detector. Compared to other methods such as type-based and concentration-based modulations, we find that at high rates, i.e., low $T_s$, the pulse position modulation works better and it has better performance in the intense ISI conditions.

通过扩散进行分子通信（MCvD）是互连纳米机器的最著名方法之一，纳米机器可以完成一些简单的通信功能。本文研究了脉冲位置调制（PPM）。我们将接收时间步长划分为四个单独的仓，并识别每个仓中接收分子的分布模型。作为基准，我们推导了最大似然（ML）检测器以与其他方法进行比较。此外，我们提出一种称为MAX检测器的技术，以设计用于简化符号检测过程的接收器。通过更改时间步长和发射机与接收机之间的距离的值，我们可以更改符号间干扰（ISI）的影响。此外，我们可以通过分析找到MAX检测器的BER（BER）。可以看出，在某些实际情况下，两种PPM检测方法可以实现相同的BER，而MAX检测器比ML检测器更简单。与其他方法（例如基于类型的调制和基于浓度的调制）相比，我们发现速率较高，即较低${Ť}_s$，在激烈的ISI条件下，脉冲位置调制效果更好，并且具有更好的性能。