8 research outputs found
Design of a CSK-CDMA Based Indoor Visible Light Communication Transceiver using Raspberry Pi and LabVIEW
Visible Light Communication (VLC) has drastically drawn the attention of both academia and industry as it can offer simultaneous lighting and data communication in an indoor environment. Additionally, VLC also tender a viable means to assuage the radio spectrum crunch. However, the data rate of the VLC system is choked because of the limited modulation bandwidth of Light Emitting Diode (LED), baseband modules, and intersymbol interference (ISI). In this article, an indoor VLC based software-defined radio (SDR) is designed and implemented that make use of Color Shift Keying (CSK) modulation, Code Division Multiple Access (CDMA) technique, and Raspberry Pi (RPi) to enabled the ISI free high data rate communication. The SDR is designed in LabVIEW software interfaced with the MATLAB and tested for text transmission. Numerous experiments were conducted on SDR at different alignments of transmitter and receiver. Our findings through experimentation showed that the SDR delivers an improved data rate of 2.645Mbps. Over and above, MATLAB based simulation packages are also conceived that validate the effectiveness of the proposed CSK-CDMA based VLC system. The bit-error-rate (BER) results of the proposed system are compared with the traditional CSK-OOK based VLC system. The results are quite impressive and show remarkable coding gain
ASK-based spatial multiplexing RGB scheme using symbol-dependent self-interference for detection
We propose a vsible light communication scheme utilizing red, green and blue lightemitting diodes (LEDs) and three color-Tuned photodiodes. Amplitude shift keying modulation is considered, and its effect on light emission in terms of flickering, dimming, and color rendering is discussed. The presence of interference at each photodiode generated by the other two colors is used to improve detection since interference is symbol-dependent. Moreover, the capability of the photodiodes to follow the LEDs speed is considered by analyzing the possibility of equalizing the received signal, and also self-interference mitigation is proposed. The system performance is evaluated both with computer simulations and tests on an Arduino board implementation
Merging color shift keying and complementary pulse position modulation for visible light illumination and communication
The rising need of indoor broadband services without increasing the electromagnetic pollution has led the scientific community to look for smart spectrum usage. From this, it stems the need of emerging paradigm of visible light communications. In the context of the IEEE 802.15.7 Task Group activities, a new modulation format named color shift keying (CSK), based on sending signals spaced in the domain of the wavelength and able to both support the communication and the illumination of indoor environments, has been proposed. In this paper, we propose a transmission/reception scheme based on CSK modulation that also makes use of a modulation format that descends from the pulse position modulation by taking care of illumination level to be granted. The aim of this contribution is twofold: to propose the receiver architecture for that kind of transmission and to evaluate its performance by performing also comparisons with other contributions in the literature. The proposed scheme is robust with respect to optical interference and presents high rate and low bit error rate at the cost of a limited increasing of complexity of the receiver with respect to other approaches
Merging color shift keying and complementary pulse position modulation for visible light illumination and communication
The ever increasing need to be able to take advantage of broadband services without the need to increase the electromagnetic pollution, has led the scientific community, in recent years, to look for alternatives to the use of a radio frequency communication. From this, it stems the need of budding paradigm of visible light communications. In the context of the activities of the IEEE 802.15.7 Task Group, a new modulation format named Color Shift Keying (CSK), based on sending signals spaced in the domain of the wavelength able to both support the communication and the illumination of indoor environments has been tackled. In this paper, a transmission scheme based on the use of the CSK modulation which also makes use of a modulation format that descends from the Pulse Position Modulation (PPM) has been proposed. The aim of this contribution is also proposing the receiver architecture for that kind of transmission and then evaluate its performance in terms of Bit Error Rate (BER) of Transmission Rate by performing also comparisons with the literature. The proposed scheme is robust with respect to optical interference and presents high rate and low BER at the cost of a bit complexity increasing with respect to other approaches. © 2014 AEIT
10  Gbps Mobile Visible Light Communication System Employing Angle Diversity, Imaging Receivers, and Relay Nodes
Over the last decade, visible light communication (VLC) systems have typically operated between 50 Mbps and 3.4 Gbps. In this paper, we propose and evaluate mobile VLC systems that operate at 10 Gbps. The enhancements in channel bandwidth and data rate are achieved by the introduction of laser diodes (LDs), angle diversity receivers (ADR), imaging receivers, relay nodes and delay adaptation techniques. We propose three mobile VLC systems; an ADR relay assisted LD-VLC (ADRR-LD), an imaging relay assisted LD-VLC (IMGR-LD) and select-the-best imaging relay assisted LD-VLC (SBIMGR-LD). The ADR and imaging receiver are proposed for the VLC system to mitigate the intersymbol interference (ISI), maximise the signal to noise ratio (SNR) and reduce the impact of multipath dispersion due to mobility. The combination of IMGR-LD with a delay adaptation technique adds a degree of freedom to the link design, which results in a VLC system that has the ability to provide high data rates under mobility. The proposed IMGR-LD system achieves significant improvements in the SNR over other systems in the worst case scenario in the considered real indoor environment
Spectrum and energy efficient digital modulation techniques for practical visible light communication systems
The growth in mobile data traffic is rapidly increasing in an unsustainable direction
given the radio frequency (RF) spectrum limits. Visible light communication (VLC)
offers a lucrative solution based on an alternative license-free frequency band that is safe
to use and inexpensive to utilize. Improving the spectral and energy efficiency of intensity
modulation and direct detection (IM/DD) systems is still an on-going challenge in
VLC. The energy efficiency of inherently unipolar modulation techniques such as pulse-amplitude
modulation discrete multitone modulation (PAM-DMT) and asymmetrically
clipped optical orthogonal frequency division multiplexing (ACO-OFDM) degrades at
high spectral efficiency. Two novel superposition modulation techniques are proposed
in this thesis based on PAM-DMT and ACO-OFDM. In addition, a practical solution
based on the computationally efficient augmented spectral efficiency discrete multi-tone
(ASE-DMT) is proposed. The system performance of the proposed superposition
modulation techniques offers significant electrical and optical power savings with up
to 8 dB in the electrical signal-to-noise ratio (SNR) when compared with DC-biased
optical orthogonal frequency division multiplexing (DCO-OFDM). The theoretical bit
error ratio (BER) performance bounds for all of the proposed modulation techniques
are in agreement with the Monte-Carlo simulation results. The proposed superposition
modulation techniques are promising candidates for spectrum and energy efficient
IM/DD systems.
Two experimental studies are presented for a VLC system based on DCO-OFDM with
adaptive bit and energy loading. Micrometer-sized Gallium Nitride light emitting
diode (m-LED) and light amplification by stimulated emission of radiation diode (LD)
are used in these studies due to their high modulation bandwidth. Record data rates are
achieved with a BER below the forward error correction (FEC) threshold at 7.91 Gb/s
using the violet m-LED and at 15 Gb/s using the blue LD. These results highlight
the potential of VLC systems in practical high speed communication solutions. An
additional experimental study is demonstrated for the proposed superposition modulation
techniques based on ASE-DMT. The experimentally achieved results confirm the
theoretical and simulation based performance predictions of ASE-DMT. A significant
gain of up to 17.33 dB in SNR is demonstrated at a low direct current (DC) bias.
Finally, the perception that VLC systems cannot work under the presence of sunlight is
addressed in this thesis. A complete framework is presented to evaluate the performance
of VLC systems in the presence of solar irradiance at any given location and time. The
effect of sunlight is investigated in terms of the degradations in SNR, data rate and
BER. A reliable high speed communication system is achieved under the sunlight
effect. An optical bandpass blue filter is shown to compensate for half of the reduced
data rate in the presence of sunlight. This thesis demonstrates data rates above 1 Gb/s
for a practical VLC link under strong solar illuminance measured at 50350 lux in clear
weather conditions