Synaptic communication is based on a biological Molecular Communication (MC) system which may serve as a blueprint for the design of synthetic MC systems. However, the physical modeling of synaptic MC is complicated by the possible saturation of the molecular receiver caused by the competition of neurotransmitters (NTs) for postsynaptic receptors. Receiver saturation renders the system behavior nonlinear in the number of released NTs and is commonly neglected in existing analytical models. Furthermore, due to the ligands' competition for receptors (and vice versa), the individual binding events at the molecular receiver are in general statistically dependent and the binomial model for the statistics of the received signal does not apply. In this work, we propose a novel deterministic model for receptor saturation in terms of a state-space description based on an eigenfunction expansion of Fick's diffusion equation. The presented solution is numerically stable and computationally efficient. Employing the proposed deterministic model, we show that saturation at the molecular receiver reduces the peak-value of the expected received signal and accelerates the clearance of NTs as compared to the case when receptor occupancy is neglected. We further derive a statistical model for the received signal in terms of the hypergeometric distribution which accounts for the competition of NTs for receptors and the competition of receptors for NTs. The proposed statistical model reveals how the signal statistics are shaped by the number of released NTs, the number of receptors, and the binding kinetics of the receptors, respectively, in the presence of competition. We show that the impact of these parameters on the signal variance depends on the relative numbers of NTs and receptors. The accuracy of the proposed deterministic and statistical models is verified by particle-based computer simulations.
翻译:同步通信基于生物分子通信系统,该系统可作为合成MC系统设计的蓝图,然而,由于神经传输器(NTs)对后合成受体的竞争导致分子接收器可能饱和,合成MC的物理模型因分子接收器可能饱和而变得复杂。接收器饱和使系统的行为在释放的NT数量上非线性,并且在现有分析模型中通常被忽视。此外,由于离子体对受体(和反向)的竞争,分子接收器的单个约束性事件一般在统计上具有相对依赖性,而且所接收信号的统计的二进制模型不适用。在这项工作中,我们提出了一个新的确定性模型,用于感官控制Fick扩散方的扩张。这些模型提出的解决方案是数字稳定且具有计算效率。在使用拟议的确定性模型时,我们显示分子接收的信号接收器的信号的饱和性事件,在接受的Sentrations信号发布后,统计的信号发布时间将逐渐变现。