The impact of location errors on achievable rates in OFDM-based multi-user visible light communication systems

Visible light communication (VLC) is a communication technology in which data is transferred by modulating the visible light intensity. VLC signals degrade significantly due to the absence of the line of sight (LOS) between the transmitter and the receiver. Hence, any errors in determining the location of the users and equivalently the distance between the nodes can result in performance degradation. In this paper, we investigate the impact of location errors on performance of a VLC network exploiting power control. We consider the achievable rate region of two VLC communication pairs as the performance criterion. The system employs optical orthogonal frequency division multiplexing (O-OFDM) with power control. The power control algorithm exploits the receivers locations information to determine the distances between the transmitters and the receivers, which will be used to find the optimal transmission powers. We consider the case of random errors in the location estimation process modeled with a general error probability density function. In calculating the achievable rates of the communication pairs, the optical signal clipping effect is taken into consideration that results from the physical limitations at the transmitters. The numerical results show the effects of the system parameters including the location error variance, the desired illumination power and the relative positions of the receivers relative to the light emitting diodes (LED) transmitters on the achievable rate region.