Molecular Communication Channel as a Physical Reservoir Computer

Abstract: Molecular Communication (MC) channels inherently possess significant memory and nonlinear dynamics due to diffusion and receptor kinetics, often posing challenges for reliable data transmission. This work reconceptualizes these intrinsic properties as computational resources by framing a canonical point-to-point MC channel, consisting of ligand diffusion and reversible ligand-receptor binding at a spherical receiver, as a physical reservoir computer (PRC). We utilize the time-varying fraction of bound receptors as the reservoir's internal state, employing time-multiplexing to generate high-dimensional virtual nodes without explicit recurrence. Only a linear readout layer is trained via ridge regression. Through deterministic mean-field modeling and particle-based spatial stochastic simulations, we demonstrate the MC system's capability for complex temporal processing by successfully performing next-step prediction on standard chaotic time-series benchmarks (Mackey-Glass and NARMA10). Performance, quantified by Normalized Root Mean Square Error (NRMSE), exhibits a non-monotonic dependence on key system parameters (receptor kinetic rates, diffusion coefficient, transmitter-receiver distance), revealing optimal operational regimes. These findings validate the potential of using MC channel as effective and low-complexity computational substrate.