A Concentration-Time Hybrid Modulation Scheme for Molecular Communications

TL;DR

This paper introduces a hybrid modulation scheme combining pulse position and concentration modulation for molecular communications, effectively mitigating inter-symbol interference and improving data rates with simplified transceiver design.

Contribution

The paper proposes a novel hybrid modulation scheme for molecular communications, including optimal and reduced complexity detectors, and provides a performance analysis and optimization framework.

Findings

MCPM outperforms standard schemes in low power and high data rate regimes.

The proposed detectors achieve near-optimal performance with reduced complexity.

MCPM offers increased robustness against synchronization errors.

Abstract

Significant inter-symbol interference (ISI) challenges the achievement of reliable, high data-rate molecular communication via diffusion. In this paper, a hybrid modulation based on pulse position and concentration is proposed to mitigate ISI. By exploiting the time dimension, molecular concentration and position modulation (MCPM) increases the achievable data rate over conventional concentration and position-based modulations. In addition, unlike multi-molecule schemes, this hybrid scheme employs a single-molecule type and so simplifies transceiver implementations. In the paper, the optimal sequence detector of the proposed modulation is provided as well as a reduced complexity detector (two-stage, position-concentration detector, TPCD). A tractable cost function based on the TPCD detector is proposed and employed to optimize the design of the hybrid modulation scheme. In addition, the approximate probability of error for the MCPM-TPCD system is derived and is shown to be tight with respect to simulated performance. Numerically, MCPM shows improved performance over standard concentration and pulse position-based schemes in the low transmission power and high bit-rate regime. Furthermore, MCPM offers increased robustness against synchronization errors.