Effect of ISI Mitigation on Modulation Techniques in Molecular Communication via Diffusion

Molecular Communication via Diffusion (MCvD) is an effective and energy efficient method for transmitting information across nanonetworks. In this paper, we focus on a diffusion-based communication system in which the reception process is absorption via receptors. Whenever a molecule hits a receiver it is removed from the environment. This kind of process is called a first passage process and it is more complicated than only using a diffusion process. In 3-D environments, obtaining an analytical solution for hitting time distribution for realistic cases is complicated; hence this paper presents an end-to-end simulator for the MCvD system that sends consecutive symbols. In MCvD, each symbol is modulated and demodulated in a time slot called the symbol duration; however, the long tail distribution of the hitting time is the main challenge that affects symbol detection. The molecules arriving in subsequent slots become an interference source when detection takes place. An end-to-end simulator enables us to analyze the effect of Inter Symbol Interference (ISI) without making any assumptions regarding the ISI. The proposed ISI cancellation technique utilizes decision feedback to compensate for the effect of the previously demodulated symbol. Three different modulation types are considered with the pulse, square, and cosine carrier waves. The results show that the proposed ISI mitigation technique improves the symbol detection performance of amplitude-based modulations more than frequency-based modulations. We also define the peak-to-average messenger molecule metric for quantifying and comparing the constraints on the transmitter and receiver nodes.