# Patient Mobility Support for Indoor Non-Directed Optical Body Area Networks
## 4 Simulation Results  
The validation of the analytical expressions was performed by Matlab simulations and the parameters are described in Table 1. Figure 5 shows the transmitted and received ECG signals in the non-directed optical links with all the reflections considered. The ECG biomedical signals are obtained from PhysioNet database [17]. The received signals from the non-directed links consist of various components arriving from different paths with different path lengths. This phenomenon results in the lengthening of the received signal. \begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Values** \\ \hline Room dimensions (x, y, z) & 5 m \(\times\) 5 m \(\times\) 3 m \\ Number of LEDs & 2 (1 at shoulder, 1 at wrist) \\ Transmitted power per light emitting diode (LED)) & 20 mW \\ Semiange at half power & 50\({}^{\circ}\) \\ Number of PD & 1 \\ Physical area of the receiver PD & 1.0 cm\({}^{2}\) \\ Receiver Field of view ( FOV) & 70\({}^{\circ}\) \\ Responsivity & 1 A/W \\ Reflection coefficient & 0.8 \\ Speed of the patient & 0.5 m/s \\ Distance between the LED (above the floor) and PD (ceiling) & 1.5 m \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Simulation parameters. Based on the analysis of the indoor channel model, we plotted the PDF of the static gain \(H(0)\) values in dB as shown in Figure 6. As expected, it can be seen that the gain reaches its highest value (around \(-3.0036\) and \(-3.0038\) dB) corresponding to LOS paths, whereas the maximum gain reaches at \(-3.0039\) dB from the non-directed configurations. Figure 7 represents the indoor channel path loss characteristics. The path loss is obtained using a curve fitting technique with the second order polynomial function. It is noted that the fitted and experiment values are in good agreement. The received power decreases when the distance between the transmitter and the receiver increases. Figure 5: Transmitted and received electrocardiography (ECG) signal in non-directed optical links. Figure 6: Probability density function (PDF) of optical channel gain. We plotted the BER relative to the transmitted power \(P_{t}\). Figure 8 shows the result. For the third scenario, synchronous transmission was performed with no interference between the two transmitters. The BER performance of Scenario 3 outperforms Scenarios 1 and 2. In addition, we performed further analysis in order to highlight the superiority of the proposed model. Specifically, we considered the following three schemes:  
* Proposed scheme: VLC link, OOK modulation, LED (on body), PD (ceiling), 2 nodes (shoulder and wrist);
* IR-OCDMA scheme [11]: IR link, OCDMA, IR-LED (on body), IR-PD (on body), 5 nodes;
* VLC-OCDMA scheme: VLC link, OCDMA, LED (on body), PD (ceiling), 2 nodes (shoulder and wrist). It should be noted that the VLC-OCDMA scheme was not reported in the literature, but it is newly created for comparison purposes. The performance comparison is depicted in Figure 9. The proposed mobility support scheme is found to be superior in performance to the other two considered schemes as it achieves very low BER even by employing a fewer number of transmitting nodes, i.e., 2. In addition, it can be seen that in the proposed scheme the BER decreases with increasing transmitting power. Meanwhile, the error performance of the VLC-OCDMA is far poorer than the proposed scheme. The IR-OCDMA [11] produces relatively much higher BERs as the transmit power increases, compared with the proposed scheme. Moreover, the irreducible error performance occurs at the transmit power of 100 mW. Figure 8: Performance analysis relative to transmit power. Figure 7: Channel path loss characteristics. Some numerical comparative analysis is presented in Table 2. This comparison highlights the superiority of the proposed scheme in terms of achievable BER and number of nodes employed. In addition, the proposed scheme offers a very convenient and practical mobility support model compared with previous schemes reported in the literature.