MIMO Visible Light Communication Systems Research Articles

Superposed probabilistically shaped QAM constellation design based on nonlinear coding for MIMO visible light communication systems

Superposed probabilistically shaped QAM constellation design based on nonlinear coding for MIMO visible light communication systems

Simplified Neural Network With Physics-Informed Module in MIMO Visible Light Communication Systems

Simplified Neural Network With Physics-Informed Module in MIMO Visible Light Communication Systems

An Energy Efficient Based Enhanced Optical OFDM for SISO and MIMO Visible Light Communication System in Indoor Environment

An Energy Efficient Based Enhanced Optical OFDM for SISO and MIMO Visible Light Communication System in Indoor Environment

Low spatial complexity adaptive artificial neural network post-equalization algorithms in MIMO visible light communication systems.

In this paper, we experimentally propose a feasible and low spatial complexity adaptive artificial neural network (AANN) post-equalization algorithm in MIMO visible light communication (VLC) systems. By introducing the power ratio and the MIMO least mean square (MIMO-LMS) post-equalization algorithm into the structure design process of the artificial neural network (ANN) post-equalization algorithm, we reduced the spatial complexity of the post-ANN equalization algorithm to less than 10%. At the same time, the bit error rate (BER) performance of AANNs did not decrease. Finally, we achieved a data rate of 2.1Gbps in the AANN equalized 16QAM superposition coding modulation (SCM) and carrier-less amplitude-phase (CAP) single-receiver MIMO (SR-MIMO) VLC system.

Enhanced Optical OFDM: A novel approach for SISO and MIMO Visible Light Communication system in indoor environment

Enhanced Optical OFDM: A novel approach for SISO and MIMO Visible Light Communication system in indoor environment

Physical Layer Security for Multi-User MIMO Visible Light Communication Systems With Generalized Space Shift Keying

We consider the physical layer security (PLS) of multi-user (MU) multiple-input-multiple-output visible light communication (VLC) systems with an eavesdropper (Eve) and propose a novel spatial constellation design technique based on generalized space shift keying (MU-GSSK-SCD). The received signals of the legitimate users are optimized jointly, such that their bit error ratios (BERs) are minimized and Eve's BER is significantly degraded. The emission power of randomly selected light-emitting diodes is adjusted, by exploiting users' channel state information at the transmitter. Our strategy ensures that legitimate users receive confidential messages fully in an undistorted fashion, while any meaningful leakage to Eve is strongly prohibited, without any artificial noise addition. Every user can decode only its information, hence inter-user security is also guaranteed. The PLS improvements are presented in terms of both BERs and achievable secrecy rates in practical VLC scenarios. For various user configurations, it is shown that MU-GSSK-SCD increases the BER at Eve to the 0.5 level, while providing minimized BERs to the legitimate users. The achievable secrecy rate region is derived for MU-GSSK-SCD and it is shown that full secrecy can be achieved at 0 dB signal-to-noise ratio (SNR) level with a user separation as small as 90 cm.

IMPACT OF TRANSCEIVER PARAMETERS ON THE ACHIEVABLE DATA RATE IN MIMO VISIBLE LIGHT COMMUNICATION SYSTEM

IMPACT OF TRANSCEIVER PARAMETERS ON THE ACHIEVABLE DATA RATE IN MIMO VISIBLE LIGHT COMMUNICATION SYSTEM

Indoor MIMO VLC systems using optical orthogonal frequency division multiple access

This paper proposes an indoor multiuser visible light communication (VLC) system using multiple lamps with orthogonal frequency division multiple access (OFDMA) techniques. For the users located in different places, the diversities of their channels help to optimally allocate the subcarriers to the users for high-speed transmissions. Considering the peak radiation power limited light sources, the modulation index on each subcarrier is jointly optimized with the subcarriers assignment scheme. This paper proposes a genetic algorithm and a two-stage searching method to solve this joint optimization problem. Considering the computational complexity, a distributed optimization scheme together with the resource block methods are applied. From simulation results, the distributed optimization method significantly reduces the computational complexity and only sacrifices about a 30% data rate. This paper takes the illumination requirements into account. By changing the additive DC bias, the average optical power is adjusted; then, the throughput performances over different illumination levels are discussed. Due to the channel feedback error, the channel uncertainty is modeled and considered in this paper. Based on the simulation results, knowing the channel uncertainty can provide around 6 times higher bit rate than not knowing the uncertainty when the normalized variance of channel uncertainty is −3 dB.

Enhanced performance of MIMO multi-branch hybrid neural network in single receiver MIMO visible light communication system.

For the single receiver multiple-input-multiple-output (SR-MIMO) visible light communication (VLC) system, the superposing of two transmitters will introduce severe distortion in the time-domain and frequency-domain. In this paper, we first proposed a MIMO multi-branch hybrid neural network (MIMO-MBNN) as the post-equalizer in the SR-MIMO pulse amplitude magnitude eight levels (PAM8) VLC system. Compared with the traditional single-input-single-output least mean square equalizer with Volterra series (SISO-LMS) and SISO deep neural network (SISO-DNN), MIMO-MBNN can achieve at most 3.35 dB Q factor improvement. Furthermore, the operation range of MIMO-MBNN is at least 2.33 times of SISO-DNN and SISO-LMS among the measured signal peak to peak voltage. At last, 2.1 Gbps data rate is achieved by MIMO-MBNN below the 7% hard-decision forward error correction (HD-FEC) threshold. As far as we know, this is the highest data rate in the SR-MIMO VLC system.

Dynamic Physical-Layer Secured Link in a Mobile MIMO VLC System

This paper proposes a novel approach to provide a privately secured multiple-input and multiple-output visible light communication (VLC) in the mobility conditions. In the proposed system, a private secured VLC link is adaptively allocated to a mobile user all the time thanks to the movement tracking assistance by a camera-based detection system. The generation of the dynamic location-based scrambling matrix will be introduced providing a secured communication zone within a full normal coverage illumination area. An extensive range of numerical evaluation and practical experiments is carried out to demonstrate and evaluate the proposed system performance in different environment configurations including the mobility, camera resolutions, link range, and environment light intensity. We demonstrate that the proposed system is fully capable of securely steering the information with respect to a receiver location with a high level of reliability.

Analysis of channel correlation and channel capacity for indoor MIMO visible light communication systems.

In indoor multi-input-multi-output (MIMO) visible light communication (VLC) systems, spatial multiplexing (SMP) is employed to improve spectral efficiency. However, the performance of SMP in an indoor VLC system depends on a low channel correlation. In this paper, a receiver model with angular diversity detectors is considered. The objective is to reduce the channel correlation and hence the system performance in terms of bit error rate (BER) and channel capacity compared to vertically oriented detectors under no-line-of-sight (NLOS) channel conditions. For a vertical detector setup, the results show that the channel correlation cannot be further reduced by varying the transmitter separation, transmitter semi-angle, or field of view of the receiver in NLOS conditions due to the design of receiver separation being very small in small mobile devices. In comparison to vertical detector setups, by varying the detector axis of each photodetector (PD) detector axis in angular diversity detector setups, the channel matrix rank is improved under LOS conditions, and the channel correlation is effectively reduced under NLOS conditions without requiring any implementation complexity at the receiver. Therefore, it is found that the angular diversity detector setup can substantially improve the BER performance of SMP, since it makes each PD more spatially separated to improve channel conditions. Notably, we deduce the channel capacity expression to approximate the capacity of the indoor highly correlated MIMO channel and verify the theoretical analysis by numerical simulations. The results show that the angular diversity detector setup provides capacity improvement when compared with the vertical detector setup. Even though it diminishes the received power when the elevation angle exceeds the optimal elevation angle, it outweighs this degradation by providing reduced channel correlation.

An efficient MIMO–OFDM VLC system of combining space time block coding with orthogonal circulant matrix transform precoding

An efficient precoding scheme combining space-time block code (STBC) and orthogonal circulant matrix transform (OCT) is proposed to improve the performance of multiple input–multiple output-orthogonal frequency division multiplexing (MIMO–OFDM) based visible light communication (VLC) systems in this work. An experimental 2×2 MIMO–OFDM VLC system is designed and setup to evaluate the performance of the proposed STBC–OCT precoding scheme, which bit error rate (BER) performance is investigated experimentally for different sample rates, amplitudes and quadrature amplitude modulation (QAM) order. It is shown that the system using proposed STBC–OCT precoding has more excellent BER performance compared with the system using other precoding methods, and 157.5 Mbit/s transmission rate can be realized for the MIMO VLC system with 0.5 m distance. This is because that the proposed scheme can effectively alleviate the bandwidth limitation issue of the VLC system and offers the optimal reliability.

Robust Signal Recovery for MIMO VLC System With Incomplete Channel

Visible light communication (VLC) based on light emitting diodes (LEDs) has attracted much attention because of its high data rate and energy efficiency. However, the shadowing that blocks the line-of-sight (LoS) link is one of challenges in the indoor VLC system, which may lead to severe performance degradation. Instead of investigating the statistical properties of shadowing, we model the link blockage as missing elements which results in incomplete channel. With the incomplete channel, we strive to recover the transmitted signal by $\ell _{0}$ -norm minimization of the transmitted signal while eliminating the effect of missing elements on system performance. It is further approximated as $\ell _{2}$ - $\ell _{1}$ minimization with optimum solution iteratively achieved via alternating direction method of multipliers (ADMM) algorithm. Simulation results indicate that the effectiveness of the proposed algorithm on robust signal recovery.

Filter-Bank Modulation Based Signal Design and Transmission Techniques for Intensity Modulated MIMO Visible Light Communication Systems

Current research in wireless communication undoubtedly points towards the tremendous advantages of using visible light as a spectrum for significantly boosting the capacities and capabilities of communication systems. The intensity of light can be rapidly modulated to obtain a communication scheme which can transport much larger volumes of data at higher rates and lesser latency compared to current radio frequency methods. In this paper, we have developed two novel filter bank based multicarrier techniques for communication using visible light. We propose a new signal design that employs pulse shaping with square root raised cosine filtering and frequency translation to generate orthogonal multicarrier signals. Based on this, we propose a filter bank modulation technique for multiple-input–multiple-output visible light communication. Further, we develop another filter bank modulation method using spatial indexing which further improves the data rate and spectral efficiency. The advantages of the proposed methods are thoroughly investigated through exhaustive simulation studies. The methods are found to yield very good bit error rate performance and high data rates.

Performance enhancement based on machine learning scheme for space multiplexing 2[formula omitted]2 MIMO VLC system employing joint IQ independent component analysis

With the increasing demand for Visible Light Communication (VLC) bandwidth, the space-multiplexing technique has been widely utilized to enhance the capability of the VLC system. In this paper, we proposed a novel MIMO detection scheme to decompose the superposed signals in a 2×2 multiple-input-multiple-output (MIMO) VLC system. With the help of the proposed machine learning scheme, two received optical signals can be separated into two independent parallel signals. By simulation, the unmixing matrix can be quickly converged by iterations. Extensive experiments demonstrate an average BER of 6.191×10−4 is achieved at a bitrate of 750 Mbps over a 1.3-m line of sight (LOS) in the 2×2 MIMO scenario. Finally, to evaluate the performance of the algorithm, the Q factor yielded a gain of about 2.5 dB compared with the traditional Alamouti Space–Time Block Coding (STBC) scheme.

Robust Beamforming-Aided Signal Recovery for MIMO VLC System With Incomplete Channel

Visible light communication (VLC) based on light emitting diodes (LEDs) has attracted much attention because of its high data rate and energy efficiency. However, the shadowing caused by any mobile obstacles could block the light-of-sight (LoS) link which may have a dramatical effect on the indoor VLC channel state information (CSI). Instead of investigating the shadowing channel characteristics, we model the link blockages as the incomplete channel matrix with sparse missing elements and reconstruct the transmitted signal by the l 0 -minimization with additional constraint on shadowing loss. However, the indoor VLC channel is highly correlated especially in cases with small emitter separation. To further improve the accuracy performance, we design the transmit beamforming to reduce the total coherence. Simulation results illustrate the effectiveness of the proposed signal recovery algorithm with incomplete channel and further significant enhancement via the proposed beamforming design.

Transceiver Design for MIMO VLC Systems With Integer-Forcing Receivers

In this paper, we investigate the transceiver design for multiple-input multiple-output visible light communication (VLC) systems that employ the integer-forcing (IF) lattice decoding technique. To facilitate the joint design of the transmitter precoder, the integer matrix and the receiver equalizer, we first give a necessary and sufficient condition for the integer matrix to be invertible over 1-D lattice. Based on this condition, we then propose a new method for choosing the integer matrix which achieves better performance than the existing lattice reduction method. Moreover, taking into account two typical constraints in VLC, we optimize transmit and receive matrices using the conditional gradient method or the projected gradient method. Finally, the integer matrix and the transmit and receive matrices are jointly optimized in an iterative manner. Simulation results are provided to demonstrate the performance improvement achieved by the proposed framework.

A Novel Mirror-Aided Non-Imaging Receiver for Indoor $2\times 2$ MIMO-Visible Light Communication Systems

Indoor visible light communication (VLC) systems are now possible because of advances in light emitting diode and laser diode technologies. These lighting technologies provide the foundation for multiple-input multiple-output (MIMO) data transmission through visible light. However, the channel matrix can be strongly correlated in indoor MIMO-VLC systems, preventing parallel data streams from being decoded. Here, in $2\times 2$ MIMO-VLC systems, we describe a mirror diversity receiver (MDR) design that reduces the channel correlation by both blocking the reception of light from one specific direction and improving the channel gain from light from another direction by utilizing a double-sided mirror deployed between the receiver’s photodetectors. We report on the channel capacity of the MDR system and the optimal height of its mirrors in terms of maximum channel capacity. We also derived analytic results on the effect of rotation on MDR’s performance. Based on numerical and experimental results, we show that the double-sided mirror has both constructive and destructive effects on the channel matrix. Our design can be used with previously described non-imaging systems to improve the performance of indoor VLC systems.

A joint precoding scheme for indoor downlink multi-user MIMO VLC systems

In this study, we aim to improve the system performance and reduce the implementation complexity of precoding scheme for visible light communication (VLC) systems. By incorporating the power-method algorithm and the block diagonalization (BD) algorithm, we propose a joint precoding scheme for indoor downlink multi-user multi-input-multi-output (MU-MIMO) VLC systems. In this scheme, we apply the BD algorithm to eliminate the co-channel interference (CCI) among users firstly. Secondly, the power-method algorithm is used to search the precoding weight for each user based on the optimal criterion of signal to interference plus noise ratio (SINR) maximization. Finally, the optical power restrictions of VLC systems are taken into account to constrain the precoding weight matrix. Comprehensive computer simulations in two scenarios indicate that the proposed scheme always has better bit error rate (BER) performance and lower computation complexity than that of the traditional scheme.

A multiple-input-multiple-output visible light communication system based on VCSELs and spatial light modulators

A multiple-input-multiple-output (MIMO) visible light communication (VLC) system employing vertical cavity surface emitting laser (VCSEL) and spatial light modulators (SLMs) with 16-quadrature amplitude modulation (QAM)-orthogonal frequency-division multiplexing (OFDM) modulating signal is proposed and experimentally demonstrated. The transmission capacity of system is significantly increased by space-division demultiplexing scheme. With the assistance of low noise amplifier (LNA) and data comparator, good bit error rate (BER) performance, clear constellation map, and clear eye diagram are achieved for each optical channel. Such a MIMO VLC system would be attractive for providing services including data and telecommunication services. Our proposed system is suitably applicable to the lightwave communication system in wireless transmission.