Yingjun Zhou

Efficient MMSE-SQRD-Based MIMO Decoder for SEFDM-Based 2.4-Gb/s-Spectrum-Compressed WDM VLC System

A spectrally efficient frequency division multiplexing (SEFDM) modulation has been proposed to improve system spectral efficiency, particularly for bandwidth-limited visible-light communication (VLC) systems. It employs non-orthogonal subcarriers to achieve bandwidth savings at the expense of serious intercarrier interference (ICI); thus, complicated detectors are required at the receiver to extract signals from the ICI. In this paper, we carry out an analysis of SEFDM modulation and establish a quasi-multiple-input multiple-output (MIMO) model for SEFDM-based systems. Based on this quasi-MIMO system model, for the first time, we propose to use an MMSE-sorted QR decomposition (MMSE-SQRD)-algorithm-based MIMO decoder to efficiently eliminate the ICI in a high-speed SEFDM-based wavelength-division multiplexing (WDM) VLC system. Using the MMSE-SQRD decoder, the WDM VLC system at an aggregate data rate of 2.4 Gb/s is experimentally demonstrated over a 2-m indoor free-space transmission, and up to 20% of bandwidth savings is achieved compared with that of the orthogonal frequency-division multiplexing (OFDM). The results clearly validate the effectiveness of the proposed MMSE-SQRD detector for SEFDM-based spectrum-compressed VLC system.

Transmission Performance Comparison for 100-Gb/s PAM-4, CAP-16, and DFT-S OFDM With Direct Detection

Metro network, as a medium distance transmission system, poses a special challenge of transmission capacity and cost. In this paper, we present a detailed comparison of applying three advanced modulation formats including pulse amplitude modulation-4 (PAM-4), carrierless amplitude and phase modulation-16 QAM (CAP-16), and discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S OFDM) with low-cost direct detection for 100-Gb/s/λ metro optical transmission systems. These modulation formats are all experimentally demonstrated with similar digital signal processing algorithms. Three kinds of chromatic dispersion (CD) compensation ways named CD precompensation method, single sideband (SSB), and dispersion compensating fiber (DCF) are also compared. Two types of modulators including an IQ modulator and a dual-drive Mach–Zehnder modulator are employed to generate SSB or CD precompensated signals in this experiment and their transmission performance is also evaluated. To the best of our knowledge, this is the first time that the performance of single-wavelength 100-G signal transmission based on direct detection is evaluated over 480 km of standard single mode fiber with PAM-4, CAP-16, and DFT-S OFDM modulation formats.

High speed LED based visible light communication for 5G wireless backhaul

New VLC based wireless backhaul technologies are studied for high data-rate access. In this paper, we summarize the latest progress on VLC systems including pre-/post-equalization hardware, electrical differential receivers, bitloading OFDM, and MRC, which supporting VLC Gigabit capacity over long-range free-space transmission.

2.32 Gbit/s phosphorescent white LED visible light communication aided by two-staged linear software equalizer

We proposed two-staged linear software equalizer to be applied in high speed visible light communication system. Through the experimental demonstration, we implemented 2.32 Gbit/s VLC transmission based on a phosphorescent white LED with 450MHz bandwidth and 1m transmission distance. The other key technologies are adaptive bit and power loading OFDM, differential amplification PINs and maximum ratio combing algorithm. As far as we know, this is the highest data rate implemented based on a phosphorescent white LED in VLC system.

2.08Gbit/s visible light communication utilizing power exponential pre-equalization

This paper introduces applying power exponential software pre-equalization in visible light communication system based on a commercial phosphorescent white LED for high speed transmission. Simulations and experiments are carried out to verify the performance of power exponential pre-equalization. 2.08Gbit/s VLC transmission over 1m free-space distance is implemented through experimental demonstration. As far as we know, this transmission data rate is higher than the data rate record created by applying hardware pre-equalization in a phosphorescent white LED based VLC system.

Experiment of audio visual communication system based on white LED and intelligent mobile terminal

With the innovation of mobile digital terminals and the development of visible light communication system, how to combine mobile terminals and existing visible light communication systems will become an important issue. This paper puts forward one kind of visible light communication system, which is used in the room with the earphone jack as the receiving channel of the mobile terminal. The system takes the commercial white light emitting diodes as the transmitter, and the receiver is composed of a high sensitivity PIN and a mobile phone. This system utilize QPSK-OFDM modulation format, and the relationship among bit error rate, transmission rate and distance is investigated. When the transmission rate is lower than 16 kB/s, bit error rate (BER) in this system are under the error threshold within 1 meter.