Molecular Communication Modulation And Signal Detection Methods Based On Mobile Nanomachines

With the rapid development of nanotechnology,it has more and more application prospects in the fields of communications,materials science,biomedicine and military.Using nanotechnology,it is possible to design and manufacture nanomachines with special functions at the microscopic scale.Due to the small size of nanomachines,it is difficult for a single nanomachine to achieve complex tasks.Therefore,it is necessary to use a large number of nanomachines to communicate to each other to form a nanoscale communication network,and the work efficiency of nanomachines will be improved.However,traditional electromagnetic communication,optical communication,and acoustic communication are difficult to apply to power-constrained nanomachines.What is exciting is that researchers have discovered molecular communication(MC)methods.Studies have shown that molecular communication is the most likely method of communication between nanomachines.Molecular communication is a communication technology that uses chemical molecules as information carriers.Nanomachines transmit or receive chemical molecules to transmit information.In general,nanomachines are deployed in a fixed location.The transmitter uses molecular communication modulation schemes such as On-Off Keying(OOK)to modulate the signal to be sent into a chemical signal.The receiver detects the concentration of molecules in the environment.However,due to the limited communication distance of fixed nanomachines,researchers consider using mobile nanomachines to expand the communication range and perform more complex tasks such as health monitoring and targeted therapy.However,the mobile nanomachine will change the communication distance,the concentration of molecules detected by the nanomachine will fluctuate greatly,and the communication will also cause a great time delay.These will make it difficult for the modulation and signal detection schemes for fixed nanomachines to be directly applied to mobile molecular communication.At present,the research on the modulation and signal detection schemes of nanomachines with different mobile characteristics in different communication environments is insufficient,and there are still situations where the communication error rate or complexity is high.Therefore,for nanomachines with different environments and different mobile characteristics,this thesis proposes a signal detection scheme for a mobile nanoreceiver with a limited range of movement in a free diffusion environment,and two modulation and signal detection schemes for mobile nanomachines in a diffusive-drift environment.The research works of the thesis consists of the following three parts:(1)In free diffusion channel,under the premise of using the OOK modulation scheme,a molecular concentration signal detection scheme based on concentration difference is proposed.This scheme judges the transmitted signal by comparing the changes in the concentration of molecules sampled by the receiver within a communication interval.Experimental results show that this scheme can effectively reduce the influence of Inter-Symbol Interference(ISI)caused by the accumulation of molecular concentration in the channel in the free diffusion channel.Compared with the existing schemes,this scheme can reduce the bit error rate 4%.(2)In diffusive-drift channel,we propose a new modulation scheme suitable for this scenario and a new signal detection scheme.The fixed transmitter modulates the signal to be transmitted in blocks by using multiple types of molecules.The information molecules diffuse freely from the transmitter to the randomly moving receiver along with the flow of the channel medium.The receiver sets dynamic thresholds for signal detection through threshold prediction.Experimental results show that,compared with the existing schemes,our proposed modulation and signal detection scheme can effectively reduce the signal detection impact of mobile receivers in a drift-diffusion environment.(3)In diffusive-drift channel,considering that a constant-speed mobile nanomachine performs an active task as a transmitter,a reasonable modulation and signal detection scheme has not yet been proposed for this scenario.Therefore,we propose a concentration signal modulation scheme for a constant-speed mobile transmitter.This solution can dynamically adjust the number of molecules released by the mobile transmitter at different positions and ensure that the fixed nanoreceiver can detect signals at the same time interval and the same concentration threshold.The result shows that when the signalto-noise ratio exceeds 10,the bit error rate will below 1%.