## 2 Related Work  
A VLC system mostly utilizes the illumination infrastructure for communication. Even though minor fluctuations in illumination within a room are acceptable for general lighting, uniform illumination must be attained to provide full room coverage, avoid significant variations in \(SNR\), and guarantee a reliable link. Hence, uniform lighting conditions, which refer to evenly distributed lighting across a room, are critical from the communication perspective, since the \(P_{r}\) profile at the PD corresponds to the values of illuminance [14]. Additionally, illuminance uniformity is also essential to ensure smooth coverage over any given area. Therefore, the optimum LED lamp layout can play a crucial role in improving the system performance. The transmitter locations can either be evaluated by using illuminance or \(P_{r}\)[18]. There are a few studies available in the literature which have examined the effects of lamp locations and its number on the uniformity of illuminance, for instance, in [19], an optimized layout was obtained to maximize the average area spectral efficiency for more than one light fixtures using the Genetic algorithm. In [20], the effects of different layouts were analyzed by considering simplified and non-simplified sources. In [15], a layout was presented to minimize the fluctuations in \(SNR\) in the presence of multiple users. In [21], the authors presented an inverse design to determine the optimal arrangement while using a convex optimization algorithm. Nevertheless, most of these studies either used more than five transmitters or utilized complex optimization algorithms to obtain optimum transmitter locations. Besides, these studies only accentuated the impact of LED lamp layouts on the uniformity of illuminance and \(P_{r}\) of a generalized VLC set-up, e.g., high-speed internet. However, an OBAN system has stringent QoS requirements in terms of reliability, where any negligence could result in a lethal event. Hence, OBANs are different from the regular optical-based wireless network infrastructure and must be investigated separately. For instance, when using VLC for patient monitoring, the subject wearing the on-body receiver could have various postures that tend to alter the receiver height. Because \(P_{r}\) is inversely proportional to the square of the distance between the transmitters and receivers, varying heights may affect it accordingly. Additionally, the body also introduces some loss, depending on the on-body receiver location. Consequently, these additional losses must also be taken into account when dealing with patient monitoring. The performance of VLC and/or IR links in OBANs has been under investigation for over a decade now; nevertheless, its feasibility study was first presented by [PERSON] et al in [22]. The authors used diffused IR technology to monitor patients' vital signs and developed a model of the mobile channel in 2D and 3D scenarios for on-off keying (OOK) modulation. Moreover, they demonstrated that optical technology could potentially be used as an alternative to RF in patient monitoring systems. Later, several studies exploited the use of VLC technology for healthcare data transmission. For instance, diffuse VLC links in healthcare scenarios in the presence of ambient light interference were experimentally demonstrated in [8] and they achieved a BER of \(10^{-5}\) for 10 Mbps transmission. In [23], white-light LEDs were used to successfully transmit biomedical data and healthcare information. In [6], the blocking effects were considered to showcase their impact on OBAN communication. While all of these studies focused on a single-user environment, Refs. [9; 24; 25] discussed the use of VLC in multi-user environments. Recently, the authors in [26] characterized the intra-OBAN channels by considering the effects of mobility and shadowing that occurred as a result of body parts and realistic body movements.