Channel Estimation and Error Analysis of a Narrow FoV VLC System With Random Receiver Orientation

With the rapid increase in user demands, visible light communication (VLC) has been emerging as a promising technology for next-generation wireless communication networks to supplement the limited radio frequency spectrum. However, the reliability of VLC channels significantly depends on the orientation of the line-of-sight links, as the received signal strength is sensitive to the angular alignment between the transmitter and receiver. This paper studies this aspect by considering a VLC system where the light-emitting diode (LED) transmitter employs a binary modulation to transmit data to a photodetector receiver whose orientation with respect to the transmitter LED varies randomly within a narrow field-of-view (FoV). This random orientation of the receiver is modeled by a uniform distribution between θ1 and θ2 for which the probability density functions for the square of the channel gain are derived for various combinations of θ1 and θ2. Furthermore, employing optimal maximum likelihood receiver structures, series form expressions for the symbol error probabilities (SEPs) are derived for the cases when the VLC system has perfect knowledge of the channel gain and when the system utilizes the least-square technique for channel estimation prior to data transmission. Numerical results are presented to corroborate the analytical framework wherein the correctness of the statistical characterization is verified, and the variations of the SEPs are presented with the system parameters. It is observed that a narrow FoV plays a crucial role in the superior performance of the VLC system in terms of achieving a lower SEP value and mitigating saturation in the SEP by increasing the system’s signal-to-noise ratio.