Waterborne chemical plumes are studied as a paradigm for representing a means for molecular communication in a macro-scale system. Results from the theory of fluid turbulence are applied and interpreted in the context of molecular communication to characterize an information cascade, the information dissipation rate and the critical length scale below which information modulated onto the plume can no longer be decoded. The results show that the information dissipation decreases with increasing Reynolds number and that there exists a theoretical potential for encoding smaller information structures at higher Reynolds numbers.
The 6th Generation (6G) of wireless systems are likely to operate in environments and scales that wireless services have not penetrated effectively into. Many of these environments are not suitable for efficient data-bearing wave propagation. Molecular signals have the potential to deliver information by exploiting both new modulation mechanisms via chemical encoding and new multi-scale propagation physics. Whilst the fusion of bio-physical models and communication theory has rapidly advanced the molecular communication field, there is a lack of real-world macro-scale applications. Here, we introduce application areas in: 1) defence and securities-ranging from underwater search and rescue to covert communications; and 2) cyber-physical systems-using molecular signals for health monitoring in underground networked systems. These engineering applications not only demand new wireless communication technologies ranging from DNA encoding to molecular graph signal processing, but also demonstrate the potential for molecular communication to contribute in traditional yet challenging engineering areas. Together, it is increasingly believed that molecular communication can be a new physical layer for 6G, accessing and extracting data from extreme wave-denied environments.
In molecular communication (MC), the motion of information molecules in the medium is usually described by the Brownian motion and governed by the Fick’s laws. However, there are some potential scenarios of MC where the kinetics of information molecules is non-Fickian. In this letter, we investigate one of this kind of MC. The manner of information molecules in the channel is subdiffusion. A three-dimensional MC system with a spherical absorbing receiver is considered. The subdiffusion channel is analyzed. The closed-form expressions of the first hitting probability and its peak time are given. Furthermore, we investigate the performance of MC by timing and amplitude modulation schemes in a subdiffusion channel. The error probability for both modulation schemes is analyzed.
Molecular communication (MC) has attracted people’s attention due to its potential applications at the micro-to nano-scale. In MC, the transmission rate is usually very low due to the slow diffusion of information molecules and therefore multiple-input multiple-output (MIMO) system is introduced. However, severe interference occurs when the same types of information molecules are used at different transmission antennas. Up to now, most literature focuses on MIMO systems with symmetrical topology. In this paper, a molecular MIMO communication system with asymmetrical topology, where the number of transmission antennas is not equal to that of the reception antennas, is investigated. The zero-forcing (ZF) detection approach is proposed and discussed for three cases, i.e., the number of transmission antennas is smaller than, equal to and larger than the number of the reception antennas. Considering the inter-link interference (ILI) and the inter-symbol interference (ISI), the error probability of ZF detection is derived and comparisons are made with existing molecular MIMO detection method. Besides, the adaptive observation time for each reception antenna is derived for better performance. Numerical results show that ZF detection performs better than the existing molecular MIMO detection method when the ILI is large.
Mobile molecular communication (MC) attracts much attention in recent years where mobile nanomachines exchange information using molecules. In this paper, we consider a diffusion-based mobile MC system consisting a pair of diffusive nanomachines. Due to the Brownian motion of nanomachines, the distance between them is a stochastic process. In this paper, its probability density function (PDF) is derived by characterizing nanomachines' motion as Wiener process. Besides, the initial distance between nanomachines is a significant parameter of diffusive mobile MC systems. With the knowledge of initial distance, the expected channel impulse response (CIR) can be obtained and the detection threshold can be set in advance. A novel two-step scheme is proposed to estimate the initial distance by maximum likelihood (ML) estimation. Firstly, the releasing distance is estimated based on observations of the number of received molecules. Secondly, the estimation of the releasing distance is used as an observation to estimate the initial distance by ML estimation. The performance of proposed scheme is evaluated via particle-based simulation of the Brownian motion.
Information embedded in the fluid dynamic properties undergo stochastic behaviour when propagating from transmitter (Tx) to receiver (Rx). This is due to the high di-mensionality and continuous dynamic forces of the environment, which erodes the achievable mutual information. Quantifying the statistical noise distribution and mutual information with respect to the key fluid dynamic parameters is important to molecular communication. Here, we empirically study macro-scale molecular signal propagation using a planar laser induced fluorescence (PLIF) method. We first statistically characterize both the additive and jitter noise distribution. We show that mutual information is maximized under certain transmission strategies and varies with the receiver size. The statistical results can benefit future studies to analyse the impact on communication reliability, and design superior modulation coding schemes.
Molecular signals are fundamental to achieving synchronous func-tionality in both biological and bio-engineering systems. Synchronization on complex molecular signaling networks depend on both local diffusion-advection dynamics and the overall complex network topology. Here, we consider a spatial-temporal dynamic complex network with molecular signaling. Unlike current Kuramoto phase models that only consider scalar coupling between oscillator units, we introduce diffusion-advection lag that represents realistic molecular transportation processes. Our results across different networks and molecular dynamics show that the local connectiv-ity status and dynamics dominate system-wide synchronization behaviour. We go on to create distributed control that can allow different networks to achieve similar overall synchronization profiles. We expect these findings to help the design of IoNT mesh networks and understanding of chrono-biological systems.
Molecular communication offers new possibilities in the micro-and nano-scale application environments. Similar to other communication paradigms, molecular communication also requires clock synchronization between the transmitter and the receiver nanomachine in many time-and control-sensitive applications. This letter presents a novel high-efficiency blind clock synchronization mechanism. Without knowing the channel parameters of the diffusion coefficient and the transmitter-receiver distance, the receiver only requires one symbol to achieve synchronization. The samples are used to estimate the propagation delay by least square method and achieve clock synchronization. Single-input multiple-output (SIMO) diversity design is then proposed to mitigate channel noise and therefore to improve the synchronization accuracy. The simulation results show that the proposed clock synchronization mechanism has a good performance and may help chronopharmaceutical drug delivery applications.