A test bench for a VLP system using CDMA as Multiple Access Technology

In this paper, we present a test bench for a Visible Light Positioning (VLP) system using Code Division Multiple Access (CDMA). A VLP system should be easy and low cost to install in existing infrastructures meaning there is no backbone network between the LEDs. CDMA can therefore be used as multiple access technology, with the challenging observation that the LEDs are transmitting data in a non-synchronized way to the receiver. Because the VLP system uses the received optical power for the positioning algorithm, Multiple Access Interference (MAI) can introduce errors. For the evaluation of the influence of MAI a test bench was developed where different CDMA codes are used in a VLP system. From practical measurements it is demonstrated that our approach leads to position errors smaller than 20 cm, making the system suitable for indoor Location Based Services (LBS).