A novel sampling frequency offset mitigation scheme based on rotated K-means clustering for OFDM-VLC system

Sampling frequency offset (SFO) between digital-to-analog converter (DAC) and analog-to-digital converter (ADC) will severely degrade the transmission performance of orthogonal frequency division multiplexing (OFDM) based visible light communication (VLC) system. In this paper, a novel SFO mitigation scheme based on rotated K-means clustering is proposed, which differs from traditional SFO compensation based on phase estimation and feedback. When SFO causes the constellation points to deviate from their original positions, this scheme can adaptively update the clustering centroids to achieve the correct symbol demapping without phase estimation and compensation. Experimental results indicate that after 3.5 m free-space transmission, the SFO tolerance of quadrature phase shift keying (QPSK) and 16-ary quadrature amplitude modulation (16-QAM) can reach ±130 and ±65 ppm with a bit error rate (BER) less than the hard-decision forward error correction (HD-FEC) threshold of 3.8e−3, respectively.