# Channel Modeling for In-Body Optical Wireless Communications +
## 3 Results
### Pathloss
Furthermore, when taking into consideration the effect of scattering, the complete pathloss took much higher values and the fluctuations of the absorption became almost obsolete, with its impact being visible only in the 400 to 500 nm range. By observing Figure 3b, it became evident that the impact of \(\mu_{a}\) varied greatly with the wavelength, which resulted in fluctuations of the relation between \(\mu_{s}\) and \(\mu_{a}\). For instance, for \(\delta=1\) mm, as \(\lambda\) increased from 400 to 700 nm, the relation between the scattering and absorption coefficient increased from 10x to 400\(x\). In Figure 3c, the pathloss for transmission through breast tissue is presented with regard to the transmission wavelength for various values of tissue thickness. When taking into account only the absorption phenomenon, it was evident that, as the \(\delta\) increased, the pathloss increased as well. On the contrary, the wavelength influenced the pathloss in a non-linear manner. Additionally, a single transmission window was observed for all the plotted values of \(\delta\) for wavelengths higher than 450 nm. Although the optimal transmission wavelength for breast tissue with regard to the absorption was 700 nm, after introducing the scattering coefficient into the analysis, the complete pathloss exhibited an almost linear behavior and the optimal wavelength shifted to 1000 nm. The increased impact of \(\mu_{s}\) varied between 1 and 3 orders of magnitude more than the absorption coefficient's impact. Specifically, for \(\delta=1\) mm and \(\lambda=400\) nm, \(\mu_{s}\) was approximately 33 times higher than \(\mu_{a}\), while for \(\lambda=650\) nm, it was 600 times higher. Finally, Figure 3d depicts the pathloss through bone tissue as a function of the transmission wavelength for various transmission distance values. Yet again, pathloss increases  
Figure 3: Pathloss due to absorption and scattering of various tissues as a function of the transmission wavelength for different values of tissue thickness. Continuous and dashed lines denote the complete pathloss and the pathloss only due to the absorption coefficient. (**a**) Skin tissue. (**b**) Brain tissue. (**c**) Breast tissue. (**d**) Bone tissue. with tissue thickness, while its behavior, with regard to \(\lambda\), depends. The optimal \(\lambda\) for transmission through bone tissue is 700 nm. For the plotted \(\delta\) values, only one transmission window exists for \(\lambda\) higher than 425 nm, while for higher values, two transmission windows can be formed. For example, the first window was between 475 and 525 nm, while the second was in the range of 600-950 nm. However, the complete pathloss appeared to be the most detrimental between the studied tissues, which was expected due to the more compact constitution of the bone tissue. This effect was highlighted by the fact that after adding the scattering phenomenon in our simulations, the complete pathloss increased by almost three orders of magnitude. In more detail, for a specific value of \(\delta\) equal to 5 mm, as the transmission wavelength increased from 400 to 950 nm, the relation between the \(\mu_{s}\) and \(\mu_{a}\) increased from 200\(x\) to 2000\(x\).