Modulation, ISI, and Detection for Langmuir Adsorption-Based Microfluidic Molecular Communication

TL;DR

This work addresses ISI in Langmuir adsorption-based microfluidic molecular communication by formulating a symbol-rate model driven by an effective surface concentration and finite receptors. It derives a closed-form single-pulse kernel $h_T(t)$ and a recursion for the OOK symbol stream, revealing channel memory and ISI, and provides SP/LP kernel-based approximations to quantify pulse- and memory-driven effects. To handle stochasticity, the authors adopt a finite-receptor binomial counting model, implement pulse-end sampling, and propose a low-complexity midpoint-threshold detector with decision-feedback state tracking. Numerical results validate the analysis and illustrate how design choices such as pulse duration $T$, symbol interval $T_b$, and binding-site count $N_p$ influence ISI and detection performance, offering practical guidance for receiver design in diffusion-to-reaction MC systems.

Abstract

This paper studies microfluidic molecular communication receivers with finite-capacity Langmuir adsorption driven by an effective surface concentration. In the reaction-limited regime, we derive a closed-form single-pulse response kernel and a symbol-rate recursion for on-off keying that explicitly exposes channel memory and inter-symbol interference. We further develop short-pulse and long-pulse approximations, revealing an interference asymmetry in the long-pulse regime due to saturation. To account for stochasticity, we adopt a finite-receptor binomial counting model, employ pulse-end sampling, and propose a low-complexity midpoint-threshold detector that reduces to a fixed threshold when interference is negligible. Numerical results corroborate the proposed characterization and quantify detection performance versus pulse and symbol durations.

Figures (4)

• Figure 1: Schematic illustration of reversible binding of IMs at the receiver surface.
• Figure 2: Single-pulse response kernel $h_T(t)$ in the SP and LP regimes, illustrating the impact of $\tau_{\rm on}$ on the rise phase and $\tau_{\rm off}$ on the post-pulse decay (temporal memory).
• Figure 3: Illustration of OOK modulation and deterministic receiver response for the symbol sequence $[1,0,1,1]$ in the SP ($T=0.1\,\tau_{\rm on}$, $T_b=0.5\,\tau_{\rm on}$) and LP ($T=10\,\tau_{\rm on}$, $T_b=10\,\tau_{\rm on}$) regimes. (a),(c) correspond to SP signaling and compare the analytical response with the SP approximation; (b),(d) correspond to LP signaling and compare the analytical response with the LP approximation. Parameters: $\tau_{\rm on}=10$ min and $\tau_{\rm off}=10$ min.
• Figure 4: BER performance of the DF midpoint-threshold detector. (a) BER versus symbol interval $T_b$ for different pulse durations $T$. (b) BER versus the number of binding sites $N_p$ for different $T$, with $T_b=20~\mathrm{min}$.