Index Modulation for Molecular Communication via Diffusion Systems

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-multipleoutput (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 nanomachines 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 dualmolecule-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.

An ILI Mitigating Modulation Scheme for Molecular MIMO Communications

“…On the other hand, the introduced ILI enhancement hurts the SMUXbased schemes' error performances as tb is increased after a certain point. This phenomenon is also in agreement with the findings of [11] and implies an interesting possible research direction regarding the optimization of tb for SMUX-based molecular MIMO with an objective of minimizing BER.…”

“…Furthermore, the simplicity of the PPM detector is also an advantage over CSK's threshold-based detector since PPM's decoder does not require the channel impulse response (CIR). The findings of this work also agree with [11] that the ILI associated with SMUX increases for larger symbol durations. Stemming from this phenomenon, this work suggests the existence of a trade-off between ISI and ILI combating and hints to the presence of a bit duration value in which SMUX schemes yield their lowest error probabilities.…”

“…Following the system model considerations of [7], [9] and [11], the system in this paper is considered to be an N x N molecular MIMO system, where N = 4 is chosen for demon strative purposes. In the molecular MIMO system of interest, there is a single transmitter unit and a single receiver unit.…”

Simulation Study and Analysis of Diffusive Molecular Communications With an Apertured Plane

“…where R i,k denotes the number of received molecules during the i th symbol interval that were emitted at the start of the k th symbol interval, and R i,k ∼ B(N T x i−k+1 , h k ). Following the findings of [20], (5) can be approximated as a normal random variable given by…”

“…Molecular communication via diffusion (MCvD) is communication paradigm that enables information transfer by utilizing the diffusive nature of messenger molecules in fluid media-um [1]. In an MCvD system, the information can be typically encoded in the quantity [2], type [3], time of release [4], spatial index of emission [5], and other combinations of these physical properties of the molecular wave.…”