Enzymatic cycle-based receivers for approximate maximum a posteriori demodulation of concentration modulated signals

TL;DR

The paper addresses MAP demodulation for concentration-modulated molecular communications by designing an enzymatic-circuit receiver. It develops a tractable framework that combines a front-end enzymatic cycle with a back-end MAP demodulator, deriving an ODE for the log-posterior ratio and approximating it with enzymatic processes. The authors show how to embed a threshold-hyperbolic TH-cycle, a product-molecule circuit, and an integrator to approximate the log-likelihood ratio, and they validate the approach with stochastic simulations and BER analyses. Key findings indicate that high Michaelis-Menten constants in the front-end can improve sensitivity and BER, and that the enzymatic receiver can closely approximate MAP performance under realistic channel conditions. This work advances molecular communications by enabling reaction-based receivers that implement MAP-like demodulation through enzymatic circuitry, with potential implications for synthetic biology-enabled communication systems and bio-inspired computing.

Abstract

Molecular communication is a bio-inspired communication paradigm where molecules are used as the information carrier. This paper considers a molecular communication network where the transmitter uses concentration modulated signals for communication. Our focus is to design receivers that can demodulate these signals. We want the receivers to use enzymatic cycles as their building blocks and can work approximately as a maximum a posteriori (MAP) demodulator. No receivers with all these features exist in the current molecular communication literature. We consider enzymatic cycles because they are a very common class of chemical reactions that are found in living cells. In addition, a MAP receiver has good statistical performance. In this paper, we study the operating regime of an enzymatic cycle and how the parameters of the enzymatic cycles can be chosen so that the receiver can approximately implement a MAP demodulator. We use simulation to study the performance of this receiver. We show that we can reduce the bit-error ratio of the demodulator if the enzymatic cycle operates in specific parameter regimes.

Figures (15)

• Figure 1: Overview of the communication elements (transmitter, receiver and medium) and the signalling molecules. Light blue filled circles depict signalling molecules. A filled circle with a dark blue ring depicts a signalling molecule within a vesicle. The broken ring in the receiver depicts the release of the signalling molecule from a vesicle.
• Figure 2: A plot of $Q(H_{M0},\gamma_{\rm opt}(H_{M0}))$.
• Figure 3: Location of the transmitter (blue) and receiver (red) voxels.
• Figure 4: Number of X_* molecules for Symbol 0 and 1.
• Figure 5: The exact posteriori mean $J_s(t) = {\rm E}[\{XK\}(t) | s, {\cal X}_*(t)]$ and its approximation is \ref{['eqn:Js:approx']}.