| In recent years,due to the demand of miniaturization of communication equipment,the development of nano networks(NNs)has been widely concerned.The operation ability of a single nano machine is limited by the size and power.For complex applications,the communication between Nano machines is particularly important.Traditional electromagnetic communication is not suitable for Nanonetworks due to the volume of transceivers and other factors.Molecular communication(MC)technology based on bio inspired technology has become one of the most suitable choices to realize nano network.MC is a new kind of short distance communication technology,which takes biochemical molecules as information carrier.It is a new interdisciplinary subject integrating biomedicine,nanotechnology,computer and communication technology.Compared with the traditional communication,MC has the characteristics of large information capacity,high biocompatibility,low energy consumption,and has a wide range of applications in health monitoring,nanomedicine,environmental protection,industrial manufacturing and military fields.Among the existing MC methods,the molecular communication via diffusion(MCvD)is an efficient and energy-saving information transmission method.The current research methods of MC mainly focus on mathematical modeling research and simulation experiment stage due to the complexity of highly interdisciplinary and expensive experimental equipment.In this paper,molecular communication is studied from two aspects of theory and simulation,and the accuracy of theoretical derivation is verified by simulation experiment results.Channel model and channel characteristics are the basic research content and theoretical development foundation of MC,and also the bridge between basic research and application research in MC.In this paper,the channel characteristics of MCvD are the main research content,and two typical channel models in molecular communication are selected as the research object,and their channel characteristics and applications are studied.The main work and innovation of the paper are as follows.1.This paper introduces the diffusion of molecules and the correlation between them from the macro and micro perspectives in view of the channel transmission mode in MC,and introduces the receiving methods including the molecular concentration,the receiving probability and the difference and connection between the number of receiving molecules.2.In this paper,we study the channel characteristics of MCvD in a completely closed spherical boundary in three-dimensional environment,in which the spherical boundary is divided into a completely reflecting boundary and a completely absorbing boundary,and study the influence of the two boundaries on the free diffusion of molecules in MC.By substituting the boundary conditions to solve the Fick diffusion equation,the analytical expressions of the molecular concentration distribution function of free diffusion in the boundary are derived,and the analytical expressions of the peak concentration time are analyzed.The channel model can be used to monitor the absorption of drugs by human cells or organs.3.In this paper,for the detection of silent absorbing target(SAT),a three-node molecular communication(TNMC)system including SAT is constructed,which includes a point source transmitter(S),a receiver and a SAT.The receiver is the absorbing receiver(AR)and passive receiver(PR),respectively.Firstly,a probability equivalent modeling(PEM)method is proposed to model the channel of TNMC system,and the channel impulse response(CIR)of the receiver is obtained.Besides,the distance between SAT,transmitter and receiver is estimated respectively,and a maximum likelihood estimation method is proposed.In this paper,a relative position estimation algorithm based on maximum likelihood estimation(MLE)and Newton-Raphson method is proposed,and the error of relative position estimation is analyzed by simulation experiment.This provides a reference for the study of multi node MC system. |
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