## 3 Simulation Results and Discussion  
In this section, simulations are used to compare the performance of the three non-imaging angle-diversity receivers described in the previous section and shown in Figure 3: the conventional angle-diversity receiver (CDR), the sectored angle-diversity receiver (SDR), and the self-orienting receiver (SOR). The comparison is based on calculating the rms delay spread, the path loss, and the SNR when the MRC, SB, and EGC combination techniques are employed. To this end, the simulation algorithm described in the previous section was implemented, the models for the three non-imaging angle-diversity receivers were included, and the IR signal propagation for different configurations of optical links in the room shown in Figure 4 was studied. The simulation tool implemented allows us to study the infrared signal propagation inside any simulation environment or 3D scene. The tool features two fully differentiated parts. The first is charged with defining the 3D scene, which the user can describe by means of any CAD software that is capable of generating or storing the scene in 3 DS format. In our simulations, we have used the Blender graphic design program because it offers multi-platform support in a freeware product that can output a 3 DS file. The second part consists of implementing the propagation model. This refers to the mathematical models that characterize the effect of each of the elements present in the simulation environment (reflecting surfaces, emitters, and receivers), and to the simulation algorithm that, aided by these models, allows the channel response to be computed. The part of the tool that implements the propagation model and into which the 3D scene is input was programmed in C++. A detailed description of the simulation tool developed was presented in [19], where the parallelization of the simulation algorithm was also discussed. The indoor environment shown in Figure 4 was based on the channel models for a \(14\times 14\times 3\) m\({}^{3}\) office, a \(6\times 6\times 3\) m\({}^{3}\) living room, and an \(8\times 8\times 3\) m\({}^{3}\) hospital room, which were proposed by the IEEE802.15.7 VLC work group [28]. The room selected is almost analogous to the living room, but with a rectangular instead of square shape. Furthermore, in order to make the comparison as independent as possible of the characteristics of the emitter and the furniture distribution in the room, no obstacles and a diffuse emitter were assumed. In general, the topology of an infrared-based sensor network can vary from a simple star network to a multihop wireless mesh network. However, regardless of the network topology, the sensor nodes should be able to collect data and route them to the sink node. That is, in a wireless sensor network there is a large number of tiny transmitters collecting data and routing them to a small number of receiver nodes. For this reason, in order to compare the performance of the three angle-diversity receivers used as the input sensor of a receiver sensor node, we have proposed a simulation scenario consisting of an angle-diversity receiver located in the centre of the room and multiple transmittersuniformly distributed along the diagonal from the northwest to the southeast of the room, as shown in Figure 4b. As previously mentioned, the angle-diversity receiver is located in the centre of the room, 1 m above the floor and aimed vertically towards the ceiling. We have assumed that the CDR uses photodetectors with a physical area of \(A_{R}=1\) cm\({}^{2}\), the SOR employs a photodetector with an area of 3.53 mm\({}^{2}\), and the sectored receiver makes use of a hemisphere of radius \(r=1.4\) cm, meaning the largest sector has a physical area of about 1 cm\({}^{2}\). Specifically, the sectors in the first, second and third crown of the sectored receiver have an area of 0.27 cm\({}^{2}\), 0.95 cm\({}^{2}\) and 0.92 cm\({}^{2}\), respectively. Every photodetector in the three angle-diversity receivers has a responsivity of 0.6 A/W.