Month: December 2018

Authors: Robin Amsters, Nobby Stevens

With the rise of solid-state lighting, wireless positioning based on visible light is becoming more appealing. However, current visible light positioning systems require additional hardware at the transmitter end in order to modulate the light intensity. A receiver demultiplexes the combined signal from multiple sources into its components, which are then used by the positioning algorithm. This paper investigates the possibility of using unmodulated visible light for mobile robot positioning. Less hardware is required, consequently, cost and complexity are much lower. Position estimation is achieved by modeling the received signal strength inside a room, which is used as input for an Iterated Extended Kalman filter. We show that the proposed approach can achieve decimeter level accuracy in a simulation environment. Even with imperfect calibration, the total positioning error usually remains below 0.5 m. Positioning errors due to the blocking of the receiver can be mitigated by employing an innovation magnitude bounds test. We also show that by employing multiple receivers, accuracy and robustness can be further improved.

Authors:  Nobby Stevens, Heidi Steendam

In this work, a set of general expressions taking into account the impact of transmitter and receiver tilt invisible light positioning on the channel gain is elaborated. A rigorous approach involving Euler rotations results in a compact expression for the modified channel gain that can be interpreted graphically. The relative modification of this gain is numerically evaluated for a number of representative configurations. A first-order approximation in case of small tilt angles leads to a number of interesting conclusions that can be utilized directly when applying received signal strength visible light positioning.

Authors: Willem Raes, David Plets, Lieven De Strycker, Nobby Stevens

In this work, the experimental evaluation of the distance estimation variance is executed for received signal strength based visible light positioning. It is shown that based on the signal to noise ratio at the matched filter output, an accurate determination of the precision is achieved. In order to suppressed ambient light which contains no information regarding the distance between the LED and the receiver, matched filtering with the dc-balanced part of the transmitted signal is required. As a consequence, the theoretical lower bound for the precision can not be achieved.