Jianyang Shi

8-Gb/s RGBY LED-Based WDM VLC System Employing High-Order CAP Modulation and Hybrid Post Equalizer

In this paper, for the first time, we propose the use of a hybrid post equalizer in a high-order carrierless-amplitude-and-phase-modulation-based visible light communication (VLC) system. The hybrid equalizer consists of a linear equalizer, a Volterra-series-based nonlinear equalizer, and a decision-directed least mean squares equalizer to simultaneously mitigate the linear and nonlinear distortions of the VLC system. A commercially available red-blue-green-yellow light-emitting diode (RBGY LED) is utilized for four-wavelength multiplexing. By the hybrid equalizer, an aggregate data rate of 8 Gb/s is experimentally achieved over a 1-m indoor free-space transmission with the bit error rate (BER) below the 7% forward error correction (FEC) limit of 3.8 × 10-3. To the best of our knowledge, this is the highest data rate ever reported in high-speed VLC systems.

4.5-Gb/s RGB-LED based WDM visible light communication system employing CAP modulation and RLS based adaptive equalization

Inter-symbol interference (ISI) is one of the key problems that seriously limit transmission data rate in high-speed VLC systems. To eliminate ISI and further improve the system performance, series of equalization schemes have been widely investigated. As an adaptive algorithm commonly used in wireless communication, RLS is also suitable for visible light communication due to its quick convergence and better performance. In this paper, for the first time we experimentally demonstrate a high-speed RGB-LED based WDM VLC system employing carrier-less amplitude and phase (CAP) modulation and recursive least square (RLS) based adaptive equalization. An aggregate data rate of 4.5Gb/s is successfully achieved over 1.5-m indoor free space transmission with the bit error rate (BER) below the 7% forward error correction (FEC) limit of 3.8x10(-3). To the best of our knowledge, this is the highest data rate ever achieved in RGB-LED based VLC systems.

1.6 Gbit/s phosphorescent white LED based VLC transmission using a cascaded pre-equalization circuit and a differential outputs PIN receiver.

We proposed a cascaded amplitude equalizer used for high speed visible light communications (VLC) system. With the cascaded pre-equalization circuit, the -3dB bandwidth of VLC system can be extended from 17MHz to 366MHz using a commercially available phosphorescent white LED, a blue filter and a differential outputs PIN receiver. The data rate is 1.60Gbit/s exploiting 16QAM-OFDM with 400MHz modulation bandwidth over 1m free-space transmission under pre-forward error correction (pre-FEC) limit of 3.8 × 10(-3). To our knowledge, this is the highest data rate ever achieved by using a commercially available phosphorescent white LED in VLC system.

Network Architecture of a High-Speed Visible Light Communication Local Area Network

A novel ultrahigh-speed LED visible light communication (VLC) local area network to provide beyond 10-Gb/s optical wireless access based on star topology architecture is proposed and experimentally demonstrated for massive users. Fiber link is used as the backbone of the bidirectional VLC network. The hybrid access protocol is utilized: 1) frequency division multiplexing for downlink and uplink fiber transmission and 2) time division multiplexing for bidirectional VLC transmission. A full-duplex VLC network for eight VLC access points (VAPs) has been successfully demonstrated with the total throughput of 8 Gb/s. Each VAP is offered 500-Mb/s downstream and 500-Mb/s upstream. The measured bit error rates of downlink and uplink for all the VAPs are under 7% FEC limit of 3.8 × 10-3 over 25-km standard single mode fiber and 65-cm free space, clearly validating the promising potential of the proposed VLC network architecture for future 40- and 100-Gb/s wireless access.

Enhanced Performance of a High-Speed WDM CAP64 VLC System Employing Volterra Series-Based Nonlinear Equalizer

The light-emitting diode nonlinearity in visible light communication (VLC) systems is considered to be a major problem that deteriorates system performance. In this paper, we experimentally demonstrate a high-speed WDM CAP64 VLC system employing a Volterra series-based nonlinear equalizer to mitigate the nonlinear effect. A modified cascaded multimodulus algorithm (M-CMMA) is utilized to calculate the error function and update the weights of the nonlinear equalizer without using training symbols. An aggregate data rate of 4.5 Gb/s is successfully achieved over 2-m indoor free-space transmission with a bit error rate (BER) below the 7% forward error correction limit of 3.8 × 10-3. With the Volterra nonlinear equalizer, the Q factor of the VLC system is 1. 6 dB better than that without using the nonlinear equalizer, and the transmission distance is also increased by about 110 cm at the BER of 3.8 × 10-3. To the best of our knowledge, this is the first time that the Volterra nonlinear equalizer is utilized for high-speed carrierless amplitude and phase (CAP) modulation-based VLC systems.

2.0-Gb/s Visible Light Link Based on Adaptive Bit Allocation OFDM of a Single Phosphorescent White LED

In this paper, we present a high-speed visible light communication (VLC) system based on a single commercially available phosphorescent white light-emitting diode (LED). In this system, a preequalization circuit is used to extend the modulation bandwidth, and a differential output receiver is utilized to reduce the system noise. With adaptive bit and power allocation and orthogonal frequency-division multiplexing (OFDM), we experimentally demonstrated a 2.0-Gb/s visible light link over 1.5-m free-space transmission, and the BER is under a preforward error correction limit of 3.8×10-3. To the best of our knowledge, this is the highest white-light VLC data rate using a single phosphorescent white LED.

A Gb/s VLC Transmission Using Hardware Preequalization Circuit

In this letter, we proposed a constant-resistance symmetrical bridged-T amplitude equalizer for high-speed visible light communication (VLC) system. Using the hardware equalizer, we successfully demonstrated a gigabit per second VLC transmission over 80-cm free space based on a RGB LED. The measured bit error rates (BERs) for the signals in 64-quadratic-amplitude modulation (64QAM) single carrier modulation at 1.05-Gb/s, 64QAM-orthogonal frequency division multiplexing (OFDM) at 1.05 Gb/s, and bit and power loading OFDM modulation at 1.42 Gb/s, are under 7% pre-forward error correction (pre-FEC) limit of 3.8 × 10-3, clearly validating the feasibility of the proposed equalizer. Compared with the system without using the equalizer, the BER performance of the VLC systems can be improved at least by 1 order of magnitude. Moreover, the equalizer can be easily integrated into amplifier or LED because of its compact size and easy installation for just using passive component. To the best of our knowledge, it is the highest data rate with longest transmission distance using preequalization circuit.

Interleaved single-carrier frequency-division multiplexing for optical interconnects

In this paper, we propose a real-valued interleaved single-carrier frequency-division multiplexing (I-SC-FDM) scheme for intensity-modulation and direct-detection optical interconnects. By simplifying the encoding structure, the computational complexity can be reduced from Nlog2N complex multiplications to N complex multiplications. At the complementary cumulative distribution function of 10-2, a reduction of 10 dB and 7.5 dB for the peak-to-average power ratio (PAPR) of the I-SC-FDM is achieved than that of orthogonal frequency-division multiplexing modulated with QPSK and 16QAM, respectively, when the subcarrier number is set to 4096. We experimentally demonstrate the I-SC-FDM scheme for optical interconnects with data rates of 12 Gbit/s, 24 Gbit/s and 128 Gbit/s transmitted over 22.5-km, 22.5-km and 2.4-km standard single mode fiber, respectively. The I-SC-FDM scheme shows great potential for cost-sensitive and power-sensitive optical interconnects owing to its low computational complexity and low PAPR.

Reversed Three-Dimensional Visible Light Indoor Positioning Utilizing Annular Receivers with Multi-Photodiodes.

Exploiting the increasingly wide use of light emitting diodes (LEDs) lighting, in this paper we propose a reversed indoor positioning system (IPS) based on LED visible light communication (VLC) in order to improve indoor positioning accuracy. Unlike other VLC positioning systems, we employ two annular receivers with multi-photodiodes installed on the ceiling to locate the persons who carry LEDs. The basic idea is using multi-photodiodes to calculate the angle while using the received signal strength (RSS) method to calculate the distance. The experiment results show that the effective positioning range of the proposed system is 1.8 m when the distance between two receivers is 1.2 m. Moreover, a positioning error less than 0.2 m can be achieved under the condition that the radius of the PIN circle is between 0.16 m and 0.2 m, and the distance of the transmitter-receiver plane is less than 1.8 m, which will be effective in practice.

Long-range high-speed visible light communication system over 100-m outdoor transmission utilizing receiver diversity technology

Abstract. Visible light communication (VLC) has no doubt become a promising candidate for future wireless communications due to the increasing trends in the usage of light-emitting diodes (LEDs). In addition to indoor high-speed wireless access and positioning applications, VLC usage in outdoor scenarios, such as vehicle networks and intelligent transportation systems, are also attracting significant interest. However, the complex outdoor environment and ambient noise are the key challenges for long-range high-speed VLC outdoor applications. To improve system performance and transmission distance, we propose to use receiver diversity technology in an outdoor VLC system. Maximal ratio combining–based receiver diversity technology is utilized in two receivers to achieve the maximal signal-to-noise ratio. A 400-Mb/s VLC transmission using a phosphor-based white LED and a 1-Gb/s wavelength division multiplexing VLC transmission using a red–green–blue LED are both successfully achieved over a 100-m outdoor distance with the bit error rate below the 7% forward error correction limit of 3.8×10−3. To the best of our knowledge, this is the highest data rate at 100-m outdoor VLC transmission ever achieved. The experimental results clearly prove the benefit and feasibility of receiver diversity technology for long-range high-speed outdoor VLC systems.