Index Modulation for Molecular Communication via Diffusion Systems

TL;DR

This paper introduces novel index modulation schemes for molecular communication via diffusion, significantly reducing inter-symbol and inter-link interference in nano-scale MIMO systems.

Contribution

It proposes MSSK, QMSSK, and MSM modulation schemes inspired by traditional IM, tailored for molecular MIMO systems to improve interference mitigation and error performance.

Findings

MSSK outperforms existing MIMO approaches in combating ISI and ILI.

QMSSK effectively reduces ISI but less so for ILI.

MSM provides reliable error rates with Gray mapping.

Abstract

Molecular communication via diffusion (MCvD) is a molecular communication method that utilizes the free diffusion of carrier molecules to transfer information at the nano-scale. Due to the random propagation of carrier molecules, inter-symbol interference (ISI) is a major issue in an MCvD system. Alongside ISI, inter-link interference (ILI) is also an issue that increases the total interference for MCvD-based multiple-input-multiple-output (MIMO) approaches. Inspired by the antenna index modulation (IM) concept in traditional communication systems, this paper introduces novel IM-based transmission schemes for MCvD systems. In the paper, molecular space shift keying (MSSK) is proposed as a novel modulation for molecular MIMO systems, and it is found that this method combats ISI and ILI considerably better than existing MIMO approaches. For nano-machines that have access to two different molecules, the direct extension of MSSK, quadrature molecular space shift keying (QMSSK) is also proposed. QMSSK is found to combat ISI considerably well whilst not performing well against ILI-caused errors. In order to combat ILI more effectively, another dual-molecule-based novel modulation scheme called the molecular spatial modulation (MSM) is proposed. Combined with the Gray mapping imposed on the antenna indices, MSM is observed to yield reliable error rates for molecular MIMO systems.