This survey paper focuses on modulation aspects of molecular communication, an emerging field focused on building biologically-inspired systems that embed data within chemical signals. The primary challenges in designing these systems are how to encode and modulate information onto chemical signals, and how to design a receiver that can detect and decode the information from the corrupted chemical signal observed at the destination. In this paper, we focus on modulation design for molecular communication via diffusion systems. In these systems, chemical signals are transported using diffusion, possibly assisted by flow, from the transmitter to the receiver. This tutorial presents recent advancements in modulation and demodulation schemes for molecular communication via diffusion. We compare five different modulation types: concentration-based, type-based, timing-based, spatial, and higher-order modulation techniques. The end-to-end system designs for each modulation scheme are presented. In addition, the key metrics used in the literature to evaluate the performance of these techniques are also presented. Finally, we provide a numerical bit error rate comparison of prominent modulation techniques using analytical models. We close the tutorial with a discussion of key open issues and future research directions for design of molecular communication via diffusion systems.

中文翻译：

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分子传播中的扩散调制技术综述

这份调查论文侧重于分子通信的调制方面，这是一个新兴领域，专注于构建将数据嵌入到化学信号中的受生物启发的系统。设计这些系统的主要挑战是如何将信息编码和调制到化学信号上，以及如何设计一个接收器，该接收器可以从在目的地观察到的损坏的化学信号中检测和解码信息。在本文中，我们专注于通过扩散系统进行分子通信的调制设计。在这些系统中，化学信号通过扩散（可能在流动的辅助下）从发射器传输到接收器。本教程介绍了通过扩散进行分子通信的调制和解调方案的最新进展。我们比较了五种不同的调制类型：基于浓度，基于类型、基于时间、空间和高阶调制技术。介绍了每种调制方案的端到端系统设计。此外，还介绍了文献中用于评估这些技术性能的关键指标。最后，我们提供了使用分析模型的主要调制技术的数字误码率比较。我们通过讨论通过扩散系统设计分子通信的关键开放问题和未来研究方向来结束本教程。我们提供了使用分析模型的主要调制技术的数字误码率比较。我们通过讨论通过扩散系统设计分子通信的关键开放问题和未来研究方向来结束本教程。我们提供了使用分析模型的主要调制技术的数字误码率比较。我们通过讨论通过扩散系统设计分子通信的关键开放问题和未来研究方向来结束本教程。