RESUMO
Linear and nonlinear impairments severely limit the transmission performance of high-speed visible light communication systems. Neural network-based equalizers have been applied to optical communication systems, which enables significantly improved system performance, such as transmission data rate and distance. In this paper, a memory-controlled deep long short-term memory (LSTM) neural network post-equalizer is proposed to mitigate both linear and nonlinear impairments in pulse amplitude modulation (PAM) based visible light communication (VLC) systems. Both 1.15-Gbps PAM4 and 0.9Gbps PAM8 VLC systems are successfully demonstrated, based on a single red-LED with bit error ratio (BER) below the hard decision forward error correction (HD-FEC) limit of 3.8 x 10-3. Compared with the traditional finite impulse response (FIR) based equalizer, the Q factor performance is improved by 1.2dB and the transmission distance is increased by one-third in the same experimental hardware setups. Compared with traditional nonlinear hybrid Volterra equalizers, the significant complexity and system performance advantages of using a LSTM-based equalizer is demonstrated. To the best of our knowledge, this is the first demonstration of using deep LSTM in VLC systems.
RESUMO
This paper first brings a single receiver multiple-input-multiple-output (SR-MIMO) model to realize the space multiplexing in the visible light communication (VLC) system. The signals from two transmitters are super-imposed in the receiver thus to realize a specially superposed modulation. Depending on the power ratio between two transmitters, various superposed signal structures can be obtained. In order to separate the superposed signal, we design a novel detection algorithm which consists of the successive interference cancellation (SIC) and the look-up table (LUT). Extensive experiments demonstrate that a data rate of 1.5Gbit/s is achieved in the 1.3-m indoor line-of-sight (LOS) scenario with the bit error rates (BERs) are below the forward error correction (FEC) threshold.
RESUMO
In this paper, we have experimentally demonstrated the feasibility of a LMS-Volterra based joint MIMO equalizer in multiband super-Nyquist carrierless amplitude phase modulation visible light communication system. To obtain higher spectrum efficiency, overlapping between different sub-bands is introduced in this experiment. By using joint MIMO equalizer, an aggregate data rate of 1.26 Gb/s is successfully achieved in 1-m indoor free space transmission with the BER below the 7% FEC limit of 3.8 × 10-3. To our best knowledge, this is the first time that our proposed joint MIMO equalizer is used to equalize multiband super-Nyquist data in VLC system.