Channel modeling of multilayer diffusion-based molecular nano communication system

Abstract

In nanoscale communication, diffusion-based molecular communication (dbmc) in which information is encoded into molecule patterns by a transmitter nanomachine, has emerged as a promising communication system, particularly for biomedical and healthcare applications. although, numerous studies have been conducted to evaluate and analyze dbmc systems, investigation on dbmc system through a multilayer channel has received less attention. the aims of this research are to mathematically model a closed-form expression of mean molecular concentration over multilayer dbmc channel, to formulate channel characteristics, and to conduct performance evaluation of multilayer dbmc channel. in the mathematical model, the propagation of molecules over an n-layer channel is assumed to follow the brownian motion and subjected to fick’s law of diffusion. the partial differential equation (pde) of the time rate change of molecular concentration is obtained by modeling the n-layer channel as an n-resistor in series and considering the conservation law of molecules. fourier transform and laplace transform were used to obtain the solution for the pde, which represents the mean molecular concentration at a receiver nanomachine. in the formulation, channel characteristics such as impulse response, time delay, attenuation or the maximum peak, delay spread and capacity were analytically obtained from the mean molecular concentration. in this stage, the multilayer channel is considered as a linear and deterministic channel. for the performance evaluation, the air-waterblood plasma medium representing the simplified multilayer diffusion model in the respiratory system was chosen. it was found that both analytical and simulation results of mean molecular concentration using matlab and n3sim were in good agreement. in addition, the findings showed that the higher the average diffusion coefficient resulted in a smaller dispersion of channel impulse response, and shortened the channel delay spread as well as time delay. however, the channel attenuation remains unchanged. in the performance evaluation, an increase of 100% in the transmission distance increased the time delay by 300% but decreased the maximum peak of molecular concentration by 87.5%. a high channel capacity can be achieved with wide transmission bandwidth, short transmission distance, and high average transmitted power. these findings can be used as a guide in the development and fabrication of future artificial nanocommunication and nanonetwork systems involving multilayer transmission medium. implication of this study is that modeling and analyzing of multilayer dbmc channel are important to support biomedical applications as diffusion can occur through a multilayer structure inside the human body.