An Energy-Efficient Ternary Modulation With Water for Molecular Communication Systems: From Solvent to Information Carrier

In this paper, a ternary-order modulation is proposed for molecular communication (MC) systems, achieving the balance between both energy efficiency and transmission efficiency. When the hydrogen ions are of interest, acidic and basic are conventional binary states in response to acidic and basic solutions, respectively, where water typically acts as the solvent. Yet, the neutrality of water in terms of the pH scale indicates a third state rather than being either acidic or basic, serving as an energy-efficient information carrier due to its abundance in nature. In light of this, bipolar signaling is enabled in MC, leading to a unique ternary modulation. Except for the energy efficiency resulting from an extra neutral state, its transmission efficiency can be further enhanced compared with the binary counterparts given the fixed symbol interval. Finally, field experiments were exemplified to validate the feasibility of the proposed modulation scheme.