# A Photolysis-Assist Molecular Communication for Tumor Biosensing
## 4 Numerical and Simulation Results  
The performance of the proposed scheme is verified by simulations in this section. Parameters in our model are given in Table 1.  
First, we evaluated the effect of the photolysis reaction on the ISI. Figure 3 shows the signal amplification decreases rapidly when the photolysis reaction happens because the photolysis reaction accelerates the information molecules degradation, the number of the information molecules observed by the receiver decreases instantly. As shown in Figure 4, when the first symbol is transmitted, the amount of ISI depends on the following symbol. During the symbol \"0\" transmitted, the received signal declines sharply as shown by the green line, which indicates the ISI is mitigated rapidly by the light impulses. Although synchronization molecules with a lower diffusion coefficient can be detected quickly, the delay time is still evaluated. To achieve the large channel capacity and guarantee enough time to receive the information molecules, we set the time intervals between connected symbols \(T_{b}=4*t_{p}\). Figure 5 shows the channel capacity varies with the time duration \(T_{b}\) between two symbols along in the different photolysis rate coefficient \(J\). We can observe that channel capacity results in a better performance with a higher photolysis rate coefficient. As the time duration T increases, channel capacity increases rapidly and reaches the maximum, when the time duration \(T_{b}=3t_{p}\), then decreases gradually. As seen in Figure 5, the standard deviations equals 0.52 and stand error is 0.14. Moreover, as the photolysis reaction is completed rapidly, the changes in channel capacity as a result of increasing the photolysis rate coefficient are not significant. Thereby, it is necessary to demonstrate that this difference is significant using a \(p\)-value. To further explain the difference of channel capacity between J = 10 and J = 20, we calculated the \(p\)-value, \(4\times 10^{-4}\), which indicates that their difference is significant. To obtain the optimal channel capacity, we can set the time duration \(T_{b}=3t_{p}\) \begin{table}
\begin{tabular}{c c c} \hline \hline
**Parameters** & **Symbol** & **Value** \\ \hline Released molecules & Q & 10,000 \\ \hline Information molecules diffusion coefficient (m\({}^{2}\)/s) & D & \(1\times 10^{-9}\) \\ \hline Synchronization molecules diffusion coefficient (m\({}^{2}\)/s) & D & \(4\times 10^{-9}\) \\ \hline Distance (\(\mu\)m) & d & 10 \\ \hline Degradation rate (s\({}^{-1}\)) & J & 20 \\ \hline Symbol interval (s) & Tb & 0.2 \\ \hline Signal-to-noise ratio(dB) & SNR & 2-18 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: System parameters used for simulation. In Figure 6, the BER performances vary with SNR for four methods mitigating ISI are plotted. The red line denotes the proposed method in this paper that adopts photolysis reactions to mitigate redundant molecules with synchronization precision. In contrast, the blue line indicates that the corresponding method adopts photolysis reactions without synchronization. The green line represents the method proposed in [43], which indicates the signal's convexity. The black line indicates the pure diffusion method. We obtain the simulation results in the same parameters. For fairness, we selected the more significant D as the diffusion coefficient of information molecules to compare the different strategies. Above all the methods, we observe that the BER decreases when the SNR increases. Since  
Figure 4: ISI illustrations in two different scenarios, in which the two connected symbols is “\(11\)” and “\(10\)”. The blue line and the red line denote the received signals when the previous symbol “\(1\)” and the current symbol “\(1\)”, while the green line denotes the received signal when the previous symbol “\(1\)” and the current symbol “\(0\)”. The ISI-0 (green shadowed area) denotes the ISI when transmitted symbols are “\(10\)”, and ISI-1 (blue shadowed area) denotes the ISI when transmitted symbols are “\(11\)”.