Subcarrier Multiplexing for Parallel Data Transmission in Indoor Visible Light Communication Systems (original) (raw)
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Parallel Data Transmission in Indoor Visible Light Communication Systems
IEEE Access, 2018
This paper presents an indoor visible light communication (VLC) system in conjunction with an imaging receiver with parallel data transmission (spatial multiplexing) to reduce the effects of the inter-symbol interference (ISI). To distinguish between light units (transmitters) and to match the light units used to convey the data with the pixels of the imaging receiver, we propose the use of subcarrier multiplexing (SCM) tones. Each light unit transmission is multiplexed with a unique tone. At the receiver, a SCM tone decision system is utilized to measure the power level of each SCM tone and consequently associate each pixel with a light unit. In addition, the level of co-channel interference (CCI) between light units is estimated using the SCM tones. Our proposed system is examined in two indoor environments taking into account reflective components (first and second order reflections). The results show that this system has the potential to achieve an aggregate data rate of 8 Gb/s with a bit error rate of 10 −6 for each light unit, using simple on-off-keying (OOK). INDEX TERMS Parallel data transmission, imaging receiver, inter-symbol-interference, co-channelinterference, subcarrier multiplexing tones, on-off-keying.
Multi-user visible light communication systems with precoded SM and SPPM
2015 IEEE/CIC International Conference on Communications in China (ICCC), 2015
Visible light communications (VLC), a short-range optical wireless communication scheme using light-emitting diodes (LEDs) as transmitters, has been proposed to support multiple users, predominantly in indoor environments. This paper explores using orthogonal frequency division multiple access (OFDMA) for VLC due to its high spectrum utilization efficiency and potentially high transmission data rate. The proposed optical OFDMA uses adjacent subcarriers as a set to support each user. Doing so allows some users to sample at a lower sampling rate and employ a smaller fast Fourier transform (FFT) to lower the computational complexity and hardware cost. A multi-cell structure is naturally obtained in VLC since more than one LED lamp is usually installed in an indoor environment. In this paper, users located in different cells can reuse the same subcarrier sets, potentially causing multiple access interference. Analysis and simulation results are used to predict the subcarrier-set reuse probability over the entire indoor space. When the OFDM modulation index is optimized considering the peak-power-limit of the LEDs, the average transmission data rate is twice that of using OFDM that does not reuse the spectral resources, for the scenarios tested.
IEEE Access
Owing to its several advantages over other wireless schemes, visible light communication (VLC) shall be at the forefront of optical wireless communication technology. However, due to multipath reflections and spatial distribution of light-emitting diode (LED) transmitters, there is an inherent delay spread in the VLC channels. We perform a comprehensive quantitative study on the effect of several practical factors like LED semi-angle, wall reflectivity, number of reflections, number of LED panels, room size, and user locations on the channel delay parameters, namely RMS delay spread and coherence bandwidth of the channel. We present the detailed derivation of the multipath VLC channel model and incorporate the effect of inter-symbol interference in bit error rate (BER) performance of the multipath VLC system. We analyze the average BER of the system under different practical scenarios and determine the penalty in signal to noise ratio entailed by a change in the system parameters mentioned above. We conclude that it is sufficient to model up to three reflections in the VLC channel to emulate the effect of multipath propagation on the channel characterization and BER analysis of the system. The results and analyses presented herein provide critical insights into the effect of multipath reflections in indoor VLC links, particularly the BER performance and channel delay characteristics. We also provide some key recommendations for the design of practical VLC systems by outlining the data rates that can be served under different system configurations. INDEX TERMS Multipath channel, delay spread, coherence bandwidth, inter-symbol interference, bit error rate, visible light communication. I. INTRODUCTION Visible light communication (VLC) is an upcoming optical wireless communication technology that integrates communication and illumination by utilizing the illumination infrastructure of white light-emitting diodes (LEDs) for data communication [1]-[4]. Due to rapid advancements in the field of solid-state lighting devices [5] and a simultaneous boom in Internet traffic over the last few decades, the research on VLC has garnered much interest in the area of wireless communication systems. VLC opens up the untapped visible range (∼400-700 THz) of the electromagnetic spectrum that is unlicensed and free. Thus, VLC promises to support The associate editor coordinating the review of this manuscript and approving it for publication was Wenchi Cheng .
Multi-Branch Transmitter for Indoor Visible Light Communication Systems
2020 22nd International Conference on Transparent Optical Networks (ICTON), 2020
One of the main aims of indoor visible light communication (VLC) systems is to deliver a high data rate services in a single user scenario and in multiuser scenarios. A key obstacle is the ability of the indoor VLC channel to support high data rates in the scenarios of interest. Here, we assess the potential of a multi-branch transmitter (MBT) and its use to achieve higher data rates in single user and multiuser indoor VLC systems. For the single user VLC system, the performance of the MBT is examined with a wide field of view (W-FOV) receiver and an angle diversity receiver (ADR) while for the multiuser VLC system we evaluate the performance of the MBT with a non-imaging angle diversity receiver (NI-ADR). In addition, for the multiuser VLC system, we propose subcarrier multiplexing (SCM) tones to allocate an optimum transmitter to each user. Furthermore, wavelength division multiplexing (WDM) is examined to support higher data rates for each user while using on-offkeying (OOK) modulation. The effect of diffuse reflections, mobility and lighting constraints are taken into account. In addition, the effect of co-channel interference (CCI) is considered in the multiuser VLC system. Index Terms-Multi-branch transmitter, wide-field of view receiver, angle diversity receiver, non-imaging angle diversity receiver, subcarrier multiplexing tones, wavelength division multiplexing, co-channel interference.
The aim of this paper is to determine the viability of Indoor Optical Wireless Communication System. This paper introduces Visible Light Communication along with its merits, demerits and applications. Then the main characteristics of VLC system are described, around which the project is designed. Multiple Input-Multiple Output (MIMO) technique is used in the project in order to enhance the data rate of transmission. Instead of using a system of only one LED and one APD, which transmits only one bit at a time, a system of 4 LEDs and 4 APDs is introduced, which increases the data rates by 300% from the previous case. We observe the signal, noise, SNR, BER etc. across the room dimension. Finally, in the last chapter we summarize our results on the basis of MATLAB simulations and propose some modifications to this model that can be implemented in future.
Diversity-Multiplexing Tradeoff for Indoor Visible Light Communication
In the past few years, visible light communication (VLC) has been a surge of interest in the research community. Different studies on VLC based communication systems were part of the research in the recent few years. However, there is no study on the development of the diversity-multiplexing tradeoff (DMT) metric to compare and design new multiple-input multiple-output (MIMO) VLC schemes. This paper introduces the concept of DMT for indoor VLC-based communication systems that utilize intensity modulation and direct detection technique for which channel coefficients are real and positive. DMT is characterized as a vital performance metric for comparing different MIMO techniques. For simplifying the presentation, we start with a single-input single-output VLC system and broaden this analysis to MIMO-VLC systems to have better useful insights. Index Terms-Diversity-multiplexing tradeoff (DMT), multipleinput multiple-output (MIMO), single-input single-output (SISO), visible light communication (VLC).
Channel characterization for indoor visible light communications
2014 3rd International Workshop in Optical Wireless Communications (IWOW), 2014
Through the numerical simulation of the channel impulse response, we investigate the limitation on the data rate due to multipath reflections for an indoor visible light communication system. Three different metrics of channel are studied for medium-sized and large rooms, namely the root-meansquare delay spread, 3-dB bandwidth, and signal-to-interference ratio. To focus on the channel effect, we assume no bandwidth constraint on the LEDs and consider simple intensity modulation techniques excluding discrete multitone modulation. We show the interest of the proposed signal-to-interference ratio metric in determining the necessity of channel equalization at the receiver.
AN OVERVIEW OF VISIBLE LIGHT COMMUNICATION SYSTEMS
Visible Light Communication (VLC) has gained great interest in the last decade due to the rapid developments in Light Emitting Diodes (LEDs) fabrication. Efficiency, durability and long life span of LEDs make them a promising residential lighting equipment as well as an alternative cheap and fast data transfer equipment. Appliance of visual light in data communication by means of LEDs has been densely searched in academia. In this paper, we explore the fundamentals and challenges of indoor VLC systems. Basics of optical transmission such as transmitter, receiver, and links are investigated. Moreover, characteristics of channel models in indoor VLC systems are identified and theoretical details about channel modelling are presented in detail.