Digital DSM-Enabled DAC-Free Gigabit FBMC-VLC System With FWHT-Based Interleaved Block Precoding

Digital-to-analog converters (DACs) are widely used in bandwidth-limited visible-light communication (VLC) systems for high spectral-efficiency multi-carrier signal generation. To reduce the implementation complexity of the transmitter, a digital 1-bit low-pass delta-sigma modulation (DSM)-enabled DAC-free filter-bank multi-carrier (FBMC) signal generation scheme is proposed and experimentally investigated in a red light-emitting diode-based VLC system. In this scheme, one field programmable gate array gigabit transceiver in combination with a low-pass filter is employed to realize the 609 MHz baseband FBMC signal generation. Besides, a low-complexity fast Walsh-Hadamard transform (FWHT)-based interleaved block precoding (IBP) technique is also proposed to reduce peak-to-average power ratio and achieve a uniform signal-to-noise ratio profile, and then improve the bit error rate (BER) performance. The experimental results exhibit that the net data rate of 2.38-Gbit/s 16-ary quadrature amplitude modulation-encoded FBMC signal, generated by the proposed scheme, can transmit 2.3-m free space with the BER less than 3.8×10^-3. With the help of the FWHT-IBP technique, about 2-dB improvement in receiver sensitivity is achieved. In addition, the proposed scheme can provide a slight improvement in the BER performance, compared to the conventional DAC-based FBMC-VLC.