Nearest neighbor bit assisted decision scheme for ISI mitigation in optical camera communications.

To enable a higher transmission rate in optical camera communication (OCC) systems, severe inter-symbol interference (ISI) occurs owing to the reduction of the number of pixel-row-per-bit (PPB). Therefore, those pixels representing data bit 0 or 1 may have same gray scale values, significantly deteriorating the bit decision when using the conventional thresholding scheme. In this Letter, a simple yet efficient scheme, referred to as nearest neighbor bit assisted decision (NNBAD) scheme, is proposed and experimentally demonstrated for signal decision in OCC systems. NNBAD leverages the nearest neighbor bit to jointly assist bit decision for pixels with severe ISI. Experimental results show that, for OCC systems with on-off keying (OOK) modulation, those pixels with severe ISI cannot be distinguished by the conventional thresholding scheme. Yet, the NNBAD scheme exhibits strong robustness against ISI, remarkably improving the bit error rate (BER) performance. The proposed scheme can achieve a throughput of 8.2 kbps with OOK modulation under an illuminance of 600 lx.