LED-tracking and ID-estimation for indoor positioning using visible light communication

We are focusing our research on indoor positioning technology; specifically, a type that uses Visible Light Communication (VLC); modulatable LED lights transmit data at 9600 bps, using 4 Pulse Position Modulation (4PPM), while a fish-eye lens-equipped camera receives the light signal over a 160-degree field-of-view. This type of lighting requires neither additional space nor-power. We assigned a unique ID to each LED, in order to recognize its position. Self-location is calculated from the relationship between the LED positions and coordinates on the image plane. In our previous research, we confirmed that self-location can be determined within 10 cm, using our system. However, we needed to attach dedicated transmitters to each LED used for positioning, especially in large buildings such as hospitals and shopping malls. So, in this paper, we propose LED-tracking and ID-estimation using LEDs with known IDs; doing so will significantly reduce the cost of installing- and running transmitters. Additionally, with the increased use of LEDs for positioning, accuracy naturally improves. We conducted experiments with the camera moving in 2 different environments: a) a small area, with just 4 LEDs; b) the VLC platform with a total of 24 LEDs, to demonstrate that as many as 13 LEDs can be identified. With 2 or more IDs detected beforehand, unidentified LEDs, as well as some that failed to be tracked, could be estimated, while the camera was in motion. Average positioning error in the smaller environment and the VLC platform were 3.78 cm and 6.96 cm, respectively. From this, location can be determined, even when some LEDs are offline.