### Experimental Testing Procedure  
To validate the feasibility of the proposed concept and plan the future course of this project, the VLC-based smart backpack prototype underwent experimental assessment in controlled laboratory conditions. As depicted in Figure 4, the optical communications component was integrated into the indoor lighting system, forming the basis for the experimental testing environment. These initial tests were structured into two distinct phases, each serving a unique and different purpose. In the first phase, the system's capability to receive data from the indoor lighting component and relay it to the user in the form of audio and haptic information was evaluated. Thus, the first component of these tests was focused on investigating the VLC's ability to provide low BER communication, to support communication in light dimming conditions, to support user mobility or to support connectivity within the area of the VLC transmitter. Therefore, these tests aimed to confirm the proper functionality of the VLC component. The second phase is focused on assessing the system's ability to operate in scenarios where VLC coverage is unavailable or obstructed. In this regard, the backpack was used by two individuals who were blindfolded. Their task was to exit the laboratory, traverse a 23 m corridor, open a door, and reach a point situated behind it to find an object placed on a table. During this process, the user wearing the backpack initially received location guidance from the indoor lighting system through VLC. Upon processing this signal, the user was provided with audio instructions such as \"_Walk 4 meters to reach the door. After passing through the door, turn right and proceed down the 23-m hallway. The destination is 1 meter behind the door, on the left side._\" As the user moved beyond the VLC-covered area, he relied only on the obstacle detection sensors integrated into the backpack. As previously mentioned, these sensors should provide relevant information to the user through haptic feedback, utilizing the four vibration motors strategically positioned within the backpack. Vibration frequencies vary based on the distance to the obstacle, with higher frequencies indicating closer proximity to the obstacle. This experimental setup was conducted with each of the two users repeating the task only five times. Although five experiments could be considered insufficient from a statistical point of view, limited tests have been made in order to prevent the users from accommodating with the trials, a fact that would influence the results. Consequently, one can consider that the results of these tests are relevant for users traveling in unfamiliar locations. For comparative purposes, the same task was also performed by a blindfolded user who did not use the smart backpack. It is important to underscore that individuals with visual impairments often face challenges in maintaining a straight direction, and therefore, the proposed solution seeks to address this specific issue by providing navigational assistance. Apart from these tests, where the smart backpack should guide the user from one point to the other, by relying on either VLC or on obstacle detection sensors, another obstacle detection challenge has been introduced. In order to test the prototype's effectiveness in providing a safe path, obstacles were intermittently introduced along the path to test if the  
Figure 4: Visible light communication testing scenario: The indoor lighting system uses VLC to provide the user with information concerning a certain point of interest. After leaving the area, the user is no longer in VLC coverage and has to rely on the embedded obstacle localization sensors and on the haptic systems to travel the distance until the point of interest. device could assist the users in safely navigating from one location to another. This third test aimed to determine if the prototype is able to prevent users from bumping into persons present in the path, or into certain objects.