A Phase Locked Loop for Molecular Communications and Computations

Molecular communication has been considered an emerging technology for both scientific and engineering interests, due to molecular biology and the need for nano-scale communication and computation systems. Molecular communication systems are widely analogue to electrical communication systems involving emitting molecules, diffused propagation of molecules, and reception of molecules, under stochastic characteristics of relatively slow propagation speed and short transmission range. To facilitate large-scale molecular information systems for the purpose of communication and computation, state-of-the-art explorations are generally assumed perfect alignment of timing among molecular devices and sub-systems. To reach synchronous condition in electronics, phase locked loop (PLL) is known to align timing or phase of waveforms. We extend PLL into molecular PLL (MPLL) consisting of basic elements such as molecular phase detector, molecular loop filter, and molecular voltage controlled oscillator. Due to stochastic nature of molecular diffusion, we further analyze MPLL in terms of the diffusion jitter, displacement, and the (particle or molecular) counting noise. Simulations verify the MPLL concept model, tracking performance, and robustness in operation.