Optimal Transmission Sequence Design with ISI Matching in Molecular Communication

Molecular communication (MC) offers a ground-breaking approach to communication inspired by biological signaling. It is particularly suited for environments where traditional electromagnetic methods fail, such as fluid mediums or within the human body. This study focuses on addressing a major challenge in MC systems: inter symbol interference (ISI), which arises due to the random, diffusive propagation of molecules. We propose a novel technique that leverages transmission shaping to mitigate ISI effectively by designing optimal transmission pulse (or sequence) for symbols. Our approach centers on solving a multi-objective optimization problem that aims to maximize the separability of individual symbol's responses within the symbol duration while matching the interference caused by molecular spillover for all symbols. By making the ISI of each symbol similar, the approach reduces the effect of previous symbols and thus does not require any adaptive computations. We introduce a geometric analogy involving two families of ellipses to derive the optimal solution. Analytical insights are supported by numerical simulations to design optimized transmission profiles to enhance the resilience toward ISI. The proposed transmission shaping method is evaluated through symbol error rate (SER). These results mark a significant step forward in developing robust and efficient MC systems, opening doors to advanced applications in bio-inspired and nano-scale communication technologies.