A wireless indoor positioning system using white LED lights is proposed. The time difference of arrival technique is employed and the phase differences between the received signals are determined to develop a positioning algorithm which can estimate the receiver location with a mean localisation error as low as 1 mm in a room of dimensions 5 × 5 × 3 m. Through simulations, it is identified that the optimum receiver height where localisation error gets minimised is between 2.5 and 3 m from the ceiling which corresponds well with the typical dimensions of a room.
The performance of time division multiplexing and frequency division multiplexing protocols for light emitting diode light emitting diode (IPS) designs using visible light emitting diode lights is evaluated. The impact of timing synchronisation errors on the localisation accuracy of IPS designs is also determined.Introduction: In this Letter, we consider a visible light emitting diode (LED) based indoor positioning systems (IPS) design comprising multiple LED panels placed on the ceiling and transmitting their location coordinates to a photodiode receiver whose location coordinates are to be determined. The localisation accuracy provided by such a design is largely dependent on ability of receiver to distinguish individual signals coming from different LEDs. To facilitate the receiver, LED transmissions are multiplexed either in time division multiplexing (TDM) [1] or in frequency division multiplexing (FDM). In this Letter, we always refer to an IPS design using the TDM protocol as 'TDM-IPS', and an IPS design using the FDM protocol as 'FDM-IPS', respectively. We design a fingerprinting algorithm and then determine localisation accuracy of a fully synchronised TDM-IPS. We then consider the impact of timing synchronisation errors between any two transmitting LEDs. We propose a relatively simpler FDM-IPS transmitter and receiver. The localisation accuracy provided by our FDM-IPS is greater than that for TDM-IPS when any two LEDs have a timing synchronisation error of 10%.
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