Cooperative OFDM-based multi-user visible light communication systems with limited information

In this paper, we consider a cooperative visible light communication (VLC) system in which multiple access points (APs) cooperate while transmitting data to a number of associated mobile terminals (MTs). The optimal transmission power control requires information about the exact locations of the MTs and hence a large amount of information needs to be processed at the controller and needs to be transferred from the APs to the controller. In this paper, we consider the system performance in the cases where the controller employs limited available information about the MTs. We consider a system in which the APs employ optical orthogonal frequency division multiplexing (OOFDM) with power control. A centralized controller determines the data electrical power based on the available information about the MTs. We consider three levels of information which are (i) the exact locations of the MTs, (ii) the exact numbers of MTs associated with the APs, and (iii) the average numbers of MTs possibly connected to the APs. Moreover, we consider the cases in which the controller optimizes the transmission powers based on various utility functions including maximizing the summation of the achieved rates of the MTs and maximizing the minimum achieved rate of any of the MTs. The numerical results show the effect of various system parameters on the achieved utility function including the average number of MTs, the APs and MTs locations, and the required illumination powers of the APs.