Influence of MAI in a CDMA VLP system

In this paper, we study a Visible Light Positioning (VLP) system using Code Division Multiple Access (CDMA). In order to facilitate implementation, the LEDs are transmitting data in a non-synchronized way to the receiver requiring no backbone network. The positioning algorithm uses the received optical power calculated from the auto- correlation peak value. Because of the asynchronous system Multiple Access Interference (MAI), random interference with the auto- correlation peak, will occur and cause position errors. Practical results show that a CDMA VLP system can have position errors smaller then 40 cm and not be influenced by synchronization problems due to MAI. The positioning error and synchronization aren´t only determined by the MAI but also the receiver Field Of View (FOV) is an important parameter. Depending on the CDMA code, the LEDs still have 97% of the illumination functionality compared when there is no communication.