MIMO-VLC System Research Articles

Enhanced transmitter designs for indoor MIMO-VLC systems

Enhanced transmitter designs for indoor MIMO-VLC systems

Enhancing MIMO-VLC system performance using reflective phase change materials

Abstract In this paper, the impact of phase change materials (PCM) as reflecting surfaces on the bit error rate (BER) performance of multiple-input multiple-output (MIMO) visible light communication (VLC) systems has been investigated. The optical properties of PCM, including absorption and reflection characteristics have been analyzed to optimize the design and functionality of PCM-based VLC systems. The current study investigates the BER performance of 4 × 4 and 8 × 8 MIMO-VLC systems using non-line of sight (NLoS) signal under varying refractive index, temperature, and incidence angle conditions. Additionally, different types of PCM has been assessed, such as organic compounds, salt hydrates, and paraffin wax, to determine their suitability for implementation in MIMO-VLC systems.

Capacity, Convergence, and Complexity Improvements for LDPC-Coded MIMO-VLC Systems With Generalized Spatial Modulation

Capacity, Convergence, and Complexity Improvements for LDPC-Coded MIMO-VLC Systems With Generalized Spatial Modulation

Design of protograph LDPC-coded MIMO-VLC systems with generalized spatial modulation

Design of protograph LDPC-coded MIMO-VLC systems with generalized spatial modulation

Multiuser downlink communication for MIMO-VLC system using spatial modulation and optical orthogonal codes

In this paper, a novel multiuser spatial modulation (SM) scheme is proposed and applied in downlink multiple input-multiple output (MIMO) visible light communication (VLC) system. In the transmitter side, each user's temporal symbol is first modulated onto user specific optical orthogonal code (OOC), then being emitted by the specific LED that is activated by its spatial symbol. At the front end of each user terminal (UT), array of photodetectors (PDs) convert optical into electrical signal, then chip-level detection scheme is employed to eliminate multiuser interference (MUI). Two computationally attractive detection algorithms are then proposed: Maximum likelihood (ML) algorithm premises on jointly estimating both temporal and spatial symbols. While the two-stages algorithm first identifies the index of the activated LED followed by a M-ary PAM demodulator to extract the desired user's spatial and temporal symbols sequentially. Extensive Monte Carlo simulations are undertaken to evaluate system performance in terms of the overall symbol error rate (SER). It is demonstrated that the chip-level detection scheme can effectively alleviate MUI and both ML and the two-stages detection algorithms work reliably in various scenarios. Hence, it is promising to apply the proposed scheme in multiuser MIMO-VLC system.

Error performance of an L-PPM modulated ADR-based MIMO-VLC system with and without channel estimation error.

In recent years, visible light communication (VLC) has emerged as a potential technique for beyond 5G communication networks. In this study, an angular diversity receiver (ADR) is used to propose a multiple-input multiple-output (MIMO) VLC system employing L-pulse position modulation (L-PPM). Repetition coding (RC) is used at the transmitter, while receiver diversity techniques such as maximum-ratio combining (MRC), selection best combining (SBC), and equal gain combining (EGC) are used at the receiver to improve performance. This study presents the exact probability of error expressions for the proposed system with and without channel estimation error (CEE). The analysis shows that the probability of error of the proposed system increases as the estimation error increases. Further, the study shows that the increase in signal-to-noise ratio is not enough to counter the impact of CEE, especially when the estimation error is large. The distribution of error probability of the proposed system using EGC, SBC, and MRC throughout the area of the room is presented. The simulation findings are compared to the analytical results.

Compressed Sensing Channel Estimation for MIMO-VLC Systems Based on DFT-SAMP Algorithm

Compressed Sensing Channel Estimation for MIMO-VLC Systems Based on DFT-SAMP Algorithm

Performance Analysis of MIMO Techniques for a Pyramid Receiver in an Indoor MIMO-VLC System

In an indoor multiple-input multiple-output (MIMO) visible light communication (VLC) system, line of sight (LoS) channel links are present between a light-emitting diode (LED) based transmitter and a photodetector (PD) based receiver. The PDs in the receiver are closely packed resulting in a high channel correlation. To overcome channel correlation and improve the performance of the MIMO-VLC system, angle diversity receivers (ADRs) are commonly employed. The channel matrix entries depend on the normal vectors of the PDs, which in turn depend on the elevation angle (EA) of the PDs. Thus, by having normal vectors pointing in different directions, the channel correlation can be considerably reduced. This paper considers a special type of ADR called pyramid receiver (PR) and employs a 4x4 MIMO-VLC system. In this paper, different MIMO algorithms such as repetition coding (RC) and spatial multiplexing (SMP) are considered to exhibit and compare the bit-error-rate (BER) performance of the fixed and variable EA MIMO-VLC systems. The results show that an SMP-employed MIMO-VLC system outperforms the RC-employed MIMO-VLC system. SMP results in an spatial multiplexing gain that varies linearly with the number of LEDs whereas RC does not yield any spatial multiplexing gain. To attain the same spectral efficiency i.e. 4 bit/s/Hz, a larger signal constellation size is required for RC employed MIMO-VLC system to achieve the same BER as of an SMP employed MIMO-VLC system. Similarly, the BER performance of variable EA MIMO-VLC systems is better as compared to fixed EA MIMO-VLC systems.

High-Speed Adaptive MIMO-VLC System With Neural Network

Rooms are typically lit with multiple luminaires, which open the possibility of creating Multiple-Input Multiple-Output (MIMO) Visible Light Communications (VLC) systems. At its most complex, the luminaires in the system might transmit different data at different power levels to a terminal containing multiple receivers, allowing a substantial increase in data rates. However, crosstalk between the transmitted channels, dependent on the location and orientation of the receiver, may cause the best strategy to be to group transmitters together and transmit the same data stream. In this paper, we report a transmitter coordination algorithm determining how to use the transmitters optimally as the receiver location varies. The data rate using this approach is on average 41 per cent higher than the conventional spatial multiplexing approach. Neural networks are then employed in the coordination algorithm. It increases the speed of operation by a factor of four compared to the initial coordination algorithm while achieving the same level of performance. The neural network also gives good performance for room geometries and receiver orientations outside the scope of the training data. Finally, the neural network is benchmarked against a water-filling algorithm approach with maximum system capacity. The neural network shows a factor of three speed-up in computing time with only a 12 per cent reduction in the average data rate. These results show the potential of the approach to achieve a near-maximal data rate with a straightforward and efficient channel selection technique.

Wavelet transform based non-hermitian symmetry OFDM technique for indoor MIMO-VLC system with an imaging receiver

Wavelet transform based non-hermitian symmetry OFDM technique for indoor MIMO-VLC system with an imaging receiver

Unipolar Precoder Designs for Generalized Spatial Modulation MIMO-VLC Systems

Unipolar Precoder Designs for Generalized Spatial Modulation MIMO-VLC Systems

Construction method of space-time code in MIMO-VLC system

In the recent years, the design of any order of space-time block code did not appear in the previous. In this paper, we investigate the criterion that how to design the space-time block code in Multiple input multiple output(MIMO) visible light communication(VLC) system. Based on the second order space-time block code, we give the design criterion of space-time block code of arbitrary order. Then we discuss the space-time block difference between traditional MIMO system and optical system. It is found that the space-time block codes of visible light system can be modified by the traditional space-time block codes and it can also realize independent decoding at the receiving end. In addition, in the receiver, how to realize fast calculation of the estimated value of the transmitted signal and a unified independent decoding scheme is presented.

Performance enhancement for a non-orthogonal multiple access system using 4 × 4 multiple-input multiple-output visible-light communication

A multi-user visible-light communication (VLC) system based on 4 × 4 multiple-input multiple-output (MIMO) was investigated. The system consists of four light-emitting diodes (as a transmitter) and four photodetectors (as a receiver). The proposed system was simulated for two, three, and four users. The objective of this study is to optimize the system power consumption and to utilize the sum rate on the system coverage area. By expanding the system from a 2 × 2 MIMO-VLC to a 4 × 4 MIMO-VLC, the results demonstrate that the total sum rate of the system can be improved. The findings reveal that the 4 × 4 MIMO-VLC achieves a maximum sum-rate enhancement of 143% compared with the 2 × 2 MIMO-VLC. The results also show that the efficiency of 4 × 4 MIMO-VLC system with non-orthogonal multiple access (NOMA) and gain ratio power allocation (GRPA) was increased by around 181% compared to 2 × 2 MIMO-NOMA-based VLC with GRPA in combination. For the 4 × 4 MIMO-NOMA-VLC device with GRPA, the sum bit rate for two, three, and four users was increased by 40%, 33%, and 24%, respectively. Through this study, it can be concluded that GRPA scheme plays an important role in utilizing MIMO-VLC system sum rate of the MIMO-VLC system.

Constant Weight Space-Time Codes for Dimmable MIMO-VLC Systems

Visible light communication(VLC), which combines communication and illumination, is regarded as a potential wireless communication. For illumination requirements of VLC systems, dimming control is a significant function. Many schemes have been proposed for multi-input multi-output (MIMO) VLC systems or dimmable VLC systems, but few schemes combine the two. The dimming control scheme that has been proposed for MIMO-VLC systems in the reference still has a probability for improvement in spectral efficiency and error performance. This paper proposes a dimming control scheme that utilizes the constant weight space-time codes (CWSTC) to improve spectral efficiency and error performance for MIMO-VLC systems. Simultaneously, we also present the codeword structure and a low implementation complexity detection algorithm for the scheme. Finally, performance analysis and simulation results provide comparisons between the proposed scheme and other existing dimming control schemes.

16×16 태양광 패널 MIMO 가시광통신 시스템에서 음영효과에 의한 오류를 복구하는 방법에 관한 연구

16×16 태양광 패널 MIMO 가시광통신 시스템에서 음영효과에 의한 오류를 복구하는 방법에 관한 연구

BER performance analysis of OFDM‐based integrated PLC and MIMO‐VLC system

In the present paper, the bit error rate (BER) performance of hybrid power line communication (PLC) and multiple-input multiple-output (MIMO) visible light communication (VLC) system (HPMV) has been investigated using line-of-sight (LOS) and LOS plus first reflection (L-R1) signals for room size of 5 m × 5 m × 3 m (configuration A) and 7.5 m × 7.5 m × 3.5 m (configuration B). In the work, Rayleigh fading and Barry channel models have been considered for PLC and VLC channels respectively. The BER has been analysed by varying separations between LEDs as 0.2 m, 0.6m and 1m for both configurations. The results show that the BER for LOS and L-R1 signals decreases upto optimal separation of 0.6 m for configuration A. However, the result indicates that the required optimal separation for configuration B is more than configuration A. The channel frequency response of MIMO-VLC and HPMV system has been inspected and it supports the results of BER simulation. It has been found that, with increase in spatial separation between LEDs, the deep notches and attenuation in the frequency response of MIMO-VLC system decrease. The overall investigation shows that even though OFDM is resilient to frequency selective fading, an optimum separation between LEDs must be chosen according to the room size for the HPMV system.

User-Centric MIMO Techniques for Indoor Visible Light Communication Systems

Multiple-input multiple-output (MIMO) is a promising technology to efficiently improve the achievable rate of white light-emitting diodes (LEDs) enabled visible light communication (VLC) systems. Nevertheless, for conventional MIMO techniques such as spatial diversity (SD) and spatial multiplexing (SMP), the working mode of each LED transmitter is independent of users’ spatial positions. In this article, we propose and investigate three user-centric MIMO techniques, including SD/SMP switching, adaptive SMP (aSMP), and SD-aided aSMP (SD-aSMP), for achievable rate improvement of indoor MIMO-VLC systems, by exploiting users’ spatial positions as a new degree of diversity. The analytical and simulation results show that the achievable rate of a 4 × 4 MIMO-VLC system in a typical indoor environment can be significantly improved by applying the user-centric MIMO techniques compared with the conventional ones. More specifically, SD/SMP switching can enjoy both high diversity gain of SD and high multiplexing gain of SMP at different signal-to-noise ratio (SNR) regions, while aSMP mitigates the adverse effect of noise amplification in conventional SMP and SD-aSMP can benefit from additional diversity gain. Furthermore, we also show that the proposed user-centric MIMO techniques outperform conventional MIMO techniques under the condition of only slightly increased computational complexity with limited feedback information.

A Novel Non-DC Biased Intensity Modulated Indoor MIMO-VLC System Using Walsh Precoder

In this paper, we propose an indoor visible light communication (VLC) system which makes use of Walsh precoding and multiple light-emitting diodes (LEDs) at the transmitter for multiplexing the data. The proposed VLC system is based on intensity modulation and uses the notion of spatial modulation for communicating the positive and negative values of the synthesized transmit signal using signal processing technique at the transmitter. We also illustrate the flexibility, ability, and easiness of the system to configure well in a multiuser environment. We have also developed a near-maximum likelihood (ML) detection technique for efficiently decoding the data bits at the receiver. The proposed near-ML reduces the search space involved in ML technique by using the initial ZF solution. The results of the simulation studies illustrate that the proposed technique offers a higher data rate and good bit error rate (BER) performance in indoor VLC environments.

A Block Bi-Diagonalization-Based Pre-Coding for Indoor Multiple-Input-Multiple-Output-Visible Light Communication System

Visible Light Communication (VLC) is a promising field in optical wireless communications, which uses the illumination infrastructure for data transmission. The important features of VLC are electromagnetic interference-free, license-free, etc. Additionally, Multiple-Input-Multiple-Output (MIMO) techniques are enabled in the VLC for enhancing the limited modulation bandwidth by its spectral efficiency. The data transmission through the MIMO-VLC system is corrupted by different interferences, namely thermal noise, shot noise and phase noise, which are caused by the traditional fluorescent light. In this paper, an effective precoding technique, namely Block Bi-Diagonalization (BBD), is enabled to mitigate the interference occurring in the indoor MIMO-VLC communications. Besides, a Quadrature Amplitude Modulation (QAM) is used to modulate the signal before transmission. Here, the indoor MIMO-VLC system is developed to analyze the communication performance under noise constraints. The performance of the proposed system is analyzed in terms of Bit Error Rate (BER) and throughput. Furthermore, the performances are compared with three different existing methods such as OAP, FBM and NRZ-OOK-LOS. The BER value of the proposed system of scenario 1 is 0.0501 at 10 dB, which is less than that of the FBM technique.

Quantitative analysis of the stacked autoencoder method in MIMO-ACO-OFDM VLC systems

In this paper, a stacked autoencoder network is utilised to realise the signal constellation and transceivers adapted to the dimmable indoor visible light communication system in order to acquire lower symbol error probability. Its decoder parts function as denoising and the equaliser for the proposed multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) visible light communication system which can compensate the non-linear transfer function and the crosstalk between multiple LED data streams. The bit error rate performance as well as the influence of LED spatial intervals on root mean square delay spread, impulse response and bit rate have been analysed considering multipath reflections of the indoor MIMO-VLC system. The numerical results show that the a stacked autoencoder technique performs better in bit error rate reduction compared with state-of-art the zero forcing and minimum mean squared error algorithm. The experiment also shows, when the semi-angle at half power of LEDs and the field of view of Photodetectors become small, better performance can be achieved at the centre of the room, which can be explained by strong beam converge and the decreased multipath interference. Moreover, enlarging the separation between LEDs leads to improved bit error rate performance and reduced channel correlation of channel matrix, which need to be optimally chosen in practice.