Coupled data transmission and indoor positioning by using transmitting trichromatic white LEDs and a SiC optical MUX/DEMUX mobile receiver

In this paper, we present an indoor positioning system were trichromatic white LEDs are used both for illumination proposes and as transmitters, and an MUX/DEMUX device, based on a-SiC:H technology, is used as the mobile receiver. OOK modulation scheme was used, and it provides a good trade-off between system performance and implementation complexity. The receiver is implemented using a double p-i-n/pin SiC photodetector with light filtering properties. The relationship between the optical inputs (transmitted data) and the associated digital output levels (received data) is established and decoded. Two topologies are used and tested as lighting plans: The square and the triangular. The key differences between both topologies are discussed in the following. The received signal is used in coded multiplexing techniques for supporting communications and navigation concomitantly on the same channel. The position of the device is estimated using the visible multilateration method by measuring the strength of the MUX signal from several non-collinear transmitters. The location and motion information is calculated by position mapping and estimating the location areas. For both topologies, the transmitted data information, indoor position and motion direction of the mobile device are determined. Data analysis showed that by using a pinpin double photodiode based on a a-SiC:H heterostucture as receiver, and RBGLEDs as transmitters it is possible not only to determine the mobile target's position but also to infer the motion direction over time, along with the received information in each position.