High-accuracy scheme based on a look-up table for motion detection in an optical camera communication system

In this paper, a high-accuracy motion detection (MD) scheme based on a look-up table (LUT) is proposed and experimentally demonstrated in an optical camera communication (OCC) system. The LUT consists of predefined motions and strings that represent the predefined motions. The predefined motions include straight lines, polylines, circles, and number shapes. At the transmitter, the data with on-off keying (OOK) format is modulated on an 8×8 light-emitting diode (LED) array. The motion is generated by the user's finger in the free space link. At the receiver, the motion and data are captured by the mobile phone front camera. The captured motion is expressed as a string indicating directions of motion, then it is matched as a predefined motion in LUT by calculating the Levenshtein distance (LD) and modified Jaccard coefficient (MJC). Using the proposed scheme, four types of motions are recognized accurately and data transmission is achieved simultaneously. Also, 1760 motion samples from 4 users are investigated over the free space transmission. The experimental results show that the accuracy of the proposed MD scheme can reach 98% at the distance without the loss of finger centroids. In addition, as the transmitter is not blocked, the bit error rate (BER) is below 1e-6 at the distance of 80cm.