Performance Analysis And Optimal For Relay In Diffusion-based Molecular Communication Systems

Diffusion molecular communication is a communication method using in-formation molecules as information carriers.However,as information molecules are freely diffused in the fluid medium,the number of information molecules received at the receiver decreases significantly with the increase of the trans-mission distance thus limited the communication range of molecular commu-nication.Inspired by traditional wireless communication relays,the use of transceivers as relays in diffusion molecular communications become a reliable solution to expand the range of communications.The research on relay trans-mission technology of diffusion molecular communication can not only solve the problem of long-distance molecular communication reliability but also play a positive role in the research of constructing nano communication network.This paper mainly studies the relay scheme for long-distance molecular com-munication and analyzes and optimizes its performance.The specific work of the thesis includes:Firstly,in order to alleviate the effect of the fading characteristic of the diffusion channel and improve the communication performance of the system.This paper proposes a scheme of placing a relay between the transmitter and the receiver for decoding and forwarding.Base on this scheme,two informa-tion molecule receiving modes are designed,and then the corresponding relay molecular communication system model is constructed.In addition,future re-search directions based on this system model,such as multi-hop communication and nano-machine routing transmission,are analyzed.Secondly,this paper constructs a decoding and forwarding diffusion molec-ular communication relay model based on the fully absorbed reception mode and derives its communication bit error rate formula based on the three-dimensional fluid environment.In order to improve the performance of relay communica-tion,the receiver decision threshold under this model is optimized.In addi-tion,a simulation framework for simulating the entire communication process of information molecules is proposed for this model,and the influence of re-lay location and molecular number allocation on communication performance is further analyzed.Simulation analyses show that relay-assisted transmission can significantly improve communication performance in the receiving mode of fully absorbing.In addition,aiming at the receiving mode of the receptor-binding informa-tion molecule in nature,this paper constructs decoding and forwarding molec-ular communication relay model based on the reversible receiver.The spatial time-varying distribution in the three-dimensional fluid environment based on this model has been derived in the paper.For analysis,the Skellam distribution is used to approximates the number of information molecules received by the reversible receiver.Further,this paper derived the bit error rate formula under the model and constructed a simulation framework based on reversible receiver.It can be concluded from the simulation results that the communication system based on the reversible receiver can improve the communication performance with respect to the direct transmission.Moreover,the performance can be im-proved by optimizing the relay position and the molecular number allocation scheme.