Towards Robust VLC Beacon Identification in Camera Based Localization Systems

Undersampled protocols are widely used in camera communication systems since they can provide flicker-free operation even with ordinary cameras. In this paper a potential problem of undersampled protocols is highlighted: if the transmitter and receiver are not synchronized, the frequency slip between the transmitter and receiver clocks will periodically cause a burst of potential decoding errors. If the frequency slip is small (i.e. good quality clocks are used in both the transmitter and the receiver), the time between bursts of errors is longer but at the same time the length of the bursts are also longer. An error analysis is provided as a function of protocol parameters and various error sources. Based on the results a novel Robust- UPSOOK protocol is proposed which guarantees the correct operation even in the presence of sensor noise, jitter, and clock inaccuracies, without the utilization of any error correcting codes. The properties of the proposed Robust-UPSOOK protocol are demonstrated using real measurements.