Research On Channel Capacity Of Single-Hop Diffusive Molecular Communication System

Diffusive molecular communication(DMC)is a nano-scale communication paradigm with broad application prospects.In the DMC system,the transmitter nanomachine releases a certain number of molecules that diffuse freely in the biological environment and follow Brownian motion rules,eventually arrive at the receiver nanomachines randomly.Since DMC is different from the characteristics of traditional communication technologies and is suitable for many specific application environments(such as human body),it is generally accepted in the academia that bio-inspired DMC is one of the most feasible communication technologies for realizing nano-networks.Considering the single-hop static multi-user DMC system,since multiple transmitter nanomachines share the same physical channel,inter-symbol interference and inter-user interference exist simultaneously,which greatly affects the communication capability of the system.In addition,considering the single-hop mobile DMC system,the mobility of the nanomachine and the time-varying of the channel lead to increase the bit error rate of information transmission of the system.Therefore,how to improve the channel capacity of these two single-hop DMC systems is one of the important challenges in molecular communication research.In response to the above problems,the main work of this paper is as follows:1.For single-hop static multi-user DMC system,multiple transmitter nanomachines and one receiver nanomachine are fixed,and the transmission channel is modeled by the running time of the probability density function of one-dimensional molecular Brownian motion.By analyzing the inter-symbol interference of the transmitter nanomachine itself,the inter-user interference generated by other transmitter nanomachines and the external noise of the system,and using the minimum error criterion to derive the optimal decision threshold,thereby obtaining the expression of mutual information of the system.The simulation results show that the optimal channel capacity and the minimum bit error rate are achieved by controlling the distance between the nanomachines,the diffusion coefficient of the information molecules,the number of molecules released per time slot,the length of the time slot,the number of users,and external noise.2.For the single-hop mobile DMC system,the transmitter nanomachine and the receiver nanomachine are moving.Using the Gaussian distribution to model the motion of the nanomachine,analyzing the communication characteristics of the system model,considering the multi-slot inter-symbol interference,and using the weighted sum detector to model the receiver nanomachine.By using the Poisson distribution to approximate the binomial distribution to obtain the total number of molecules received by the receiver nanomachine in the current time slot,thereby mathematical expression of the channel capacity of the system is derived.Finally,experimental simulations show the impact of different parameters to the channel capacity and bit error rate of the system,including the number of molecules released per time slot,the initial distance between the transmitter and receiver nanomachines,the number of samples,the length of the bit interval,and the diffusion coefficient of the nanomachine.