Abstract
Modern handheld mobile devices are equipped with a complementary metal-oxide-semiconductor (CMOS) image sensor. These image sensors are capable of perceiving intensity changes in optically modulated signals, driving the rapid development of optical camera communication (OCC). In this study, direct-current offset orthogonal frequency division multiplexing (DCO-OFDM) was developed for a rolling shutter OCC system in order to improve the data transmission rates of OCC systems. Two DCO-OFDM OCC signal detection algorithms, namely the parabolic column vector selection (P-CVS) algorithm and the decomposition of extremely low frequency component (D-ELFC) algorithm, were proposed, along with a frequency-domain downsampling scheme, to eliminate the influence from both the blooming effect and shot noise. The experimental results, obtained after using a self-built DCO-OFDM OCC testbed with a general commercial smartphone camera, demonstrated that the D-ELFC algorithm outperformed in the bit error rate (BER) in comparison to the P-CVS algorithm and achieved a data transmission rate >22 kbps under the conditions of the BER being below the 20% forward error correction (FEC) limit and the illuminance being higher than 510 lux.
Highlights
Due to significant improvements in the technology used to manufacture light-emitting diodes (LEDs), the lighting cost per unit for LEDs has continued to decrease, prompting the LED to gradually become the mainstream form of indoor lighting
The experimental results, obtained after using a self-built D-ELFC method is (DCO)-orthogonal frequency division multiplexing (OFDM) optical camera communication (OCC) testbed with a general commercial smartphone camera, demonstrated that the decomposition of extremely low frequency component (D-ELFC) algorithm outperformed in the bit error rate (BER) in comparison to the parabolic column vector selection (P-column vector selection (CVS)) algorithm and achieved a data transmission rate >22 kbps under the conditions of the BER being below the 20% forward error correction (FEC) limit and the illuminance being higher than 510 lux
The cameras included in handheld mobile devices have generally been equipped with complementary metal-oxide-semiconductor (CMOS) image sensors, and these sensors have driven the rapid development of optical camera communication (OCC) [3], [4]
Summary
Due to significant improvements in the technology used to manufacture light-emitting diodes (LEDs), the lighting cost per unit for LEDs has continued to decrease, prompting the LED to gradually become the mainstream form of indoor lighting. The use of commercial image sensors built into general mobile devices for DCO-OFDM OCC signal demodulation was investigated in the present study in order to achieve the objective of low-cost and high-speed OCC transmission. In this approach, the image sensor is basically used to receive the DCO-OFDM signal emitted by the LED, but the captured image is interfered with by blooming effect interference (BEI) and shot noise.
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