Terahertz band (0.1–10 THz)-based electromagnetic nanocommunications could advance several nanotechnology applications in the biomedical, environmental, and military fields. One of the fundamental challenges with nanocommunications is the need for an appropriate modulation and channel access mechanism. In multi-user nanocommunications, detrimental effects of path loss and interference could pose a significant problem for multiple nano-devices trying to access the channel concurrently. This would result in retransmissions, which is barely affordable at the nano-level due to the minute size and energy constraints of nano-devices. In this paper, time-hopping (TH) combined with $M$-ary pulse position modulation (PPM) is proposed as a modulation and multiple access scheme for multi-user nanocommunications systems. PPM, being the most energy-efficient modulation scheme, with TH would allow nano-devices to communicate simultaneously with greater efficiency. Decoding at the receiver is done after non-coherent detection. The symbol-error rate (SER) in the presence of multi-user interference is evaluated in terms of signal-energy-to-noise ratio and the number of interfering users. Moreover, capacity of the system is also evaluated in terms of bits per symbol for different design parameters. Numerical results show that the SER and capacity of the system can be improved by choosing appropriate TH-PPM parameters for a given network condition. The comparisons of simulation results for TH-PPM with another existing scheme witnesses an improved energy efficiency and reduced computational complexity.

基于太赫兹频带（0.1-10 THz）的电磁纳米通信可以推动生物医学，环境和军事领域中的几种纳米技术应用。纳米通信的基本挑战之一是需要适当的调制和信道访问机制。在多用户纳米通信中，路径损耗和干扰的有害影响可能对试图同时访问该信道的多个纳米设备造成重大问题。这将导致重新传输，由于纳米设备的微小尺寸和能量限制，在纳米级别上几乎无法承受。本文将跳时（TH）与$\mathrm{中号}$一元脉冲位置调制（PPM）被提出作为一种多用户纳米通信系统的调制和多址方案。使用TH的PPM是最节能的调制方案，它将允许纳米设备同时以更高的效率进行通信。在非相干检测之后，在接收机处进行解码。在存在多用户干扰的情况下，根据信号的信噪比和干扰用户的数量来评估符号错误率（SER）。此外，还针对不同的设计参数，根据每个符号的位数来评估系统的容量。数值结果表明，通过为给定的网络条件选择合适的TH-PPM参数，可以提高系统的SER和容量。