| In recent years,researchers have devoted themselves to exploring areas where com-munication theory is combined with biology and medicine,and related molecular com-munication research has become increasingly active.Molecular communication is usually defined as a communication technology based on biological or chemical molecules as a carrier to complete the transmission of information between biological cells or nanoma-chines on a microscopic scale.At present,the main obstacles to molecular communication research include low transmission efficiency and high bit error rate.The multiple-input multiple-output(MIMO)technology in traditional communication can significantly im-prove link performance.Therefore,how to apply MIMO technology to molecular com-munication models has become an urgent research direction in this field.This dissertation takes the diffusion channel-based molecular communication MIMO technology as the research topic,focuses on the molecular communication 2×2 MIMO model modeling analysis,and proposes a related adaptive double threshold decision al-gorithm,and finally studies the molecular communication n×n parallel communication Model modeling,the main research content and contributions are as follows:(1)We use Fick's second law to derive the probability formula of the molecular po-sition in the diffusion channel changing with time,and further obtain the Gaussian distri-bution of the number of molecules reached in the fixed region of the channel.Aiming at the interference characteristics of the MIMO model,we studied the formula derivation of inter-symbol interference(ISI)and inter-link interference(ILI)based on probability the-ory.Moreover,we consider OOK(on-off keying)as the modulation technique to obtain the reception probability distribution of the receiver.Finally,we obtain the single receiver decision threshold according to the likelihood ratio test(LRT),and give the corresponding bit error rate(BER).In addition,we obtained the qualitative influence of model-related parameters on BER through simulation.(2)Based on the established 2×2 MIMO model,we propose a more reliable receiving algorithm,an adaptive dual-threshold receiving decision algorithm.This algorithm mainly addresses the inconsistency of the receiver's decision results in the decision scenario,and proposes a solution with a lower bit error rate:a new decision threshold is obtained by adjusting the original threshold,and a more reliable decision result is obtained after re-decision.Finally,we verified that the decision algorithm has a good effect of reducing BER through simulation,and proved the superiority of the MIMO model compared to the SISO and SIMO models in terms of error performance.(3)We hope that MIMO technology can bring higher communication transmission rates,so we consider the uncorrelated bit sequence sent and received by each transmitter and receiver,which is defined as parallel communication here.We established a 2×2 paral-lel communication model of molecular communication based on diffusion channels,and extended it to an nxn parallel communication model on this basis.Finally,we verified the superiority of the parallel communication model compared to the MIMO communica-tion model in terms of transmission rate through simulation,and analyzed the qualitative influence of the relevant parameters of the n×n parallel communication model on the BER.Research work shows that the two models proposed in this paper can well fit the molecular communication process in the diffusion channel environment.The MIMO com-munication model needs the support of a suitable receiving decision algorithm to show better error performance than the SISO and SIMO models.If the transmission reliability is not considered,the parallel communication model is far superior to the MIMO commu-nication model in terms of transmission rate,so it can be applied to related scenarios;but the MIMO communication model has good error performance and has a wider range of application scenarios. |
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