Combining Illumination Dimming Based on Pulse-Width Modulation With Visible-Light Communications Based on Discrete Multitone

Ntogari, Georgia; Kamalakis, Thomas; Walewski, Joachim W.; Sphicopoulos, T.

doi:10.1364/jocn.3.000056

Cited by 108 publications

(63 citation statements)

References 6 publications

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“…The light should be dimmable arbitrarily in VLC systems, without the communications becoming interrupted, which means that the data should be modulated in such a way that any desired level of dimming is supported [14]. Numerous valuable modulation schemes supporting dimming control have been proposed for the LEDs, such as the variable OOK [48], [72], variable PPM [73], pulse width modulation with DMT [74], etc. When the light intensity changes, it should be flickering above the human eyes' fusion frequency, so that the human eye cannot perceive it.…”

Section: Phy Techniques 1) Modulation Schemesmentioning

confidence: 99%

Optimization of Visible-Light Optical Wireless Systems: Network-Centric Versus User-Centric Designs

Zhang

Hanzo

2018

IEEE Commun. Surv. Tutorials

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Abstract-In order to counteract the explosive escalation of wireless tele-traffic, the communication spectrum has been gradually expanded from the conventional radio frequency (RF) band to the optical wireless (OW) domain. By integrating the classic RF band relying on diverse radio techniques and optical bands, the next-generation heterogeneous networks (HetNets) are expected to offer a potential solution for supporting the ever-increasing wireless tele-traffic. Owing to its abundant unlicensed spectral resources, visible light communications (VLC) combined with advanced illumination constitute a competent candidate for complementing the existing RF networks. Although the advantages of VLC are multi-fold, some challenges arise when incorporating VLC into the classic RF HetNet environments, which may require new system architectures. The user-centric (UC) design principle for VLC environments constitutes a novel and competitive design paradigm for the super dense multi-tier cell combinations of HetNets. The UC concept may be expected to become one of the disruptive techniques to be used in the forthcoming fifthgeneration era. This paper provides a comprehensive survey of visible-light-aided OW systems with special emphasis on the design and optimization of VLC networks, where the radically new UC design philosophy is reviewed. Finally, design guidelines are provided for VLC systems.

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Section: Phy Techniques 1) Modulation Schemesmentioning

confidence: 99%

Optimization of Visible-Light Optical Wireless Systems: Network-Centric Versus User-Centric Designs

Zhang

Hanzo

2018

IEEE Commun. Surv. Tutorials

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“…An electrical signal is converted to an opticalintensity signal via LEDs, which is known as intensity modulation (IM), and a noncoherent receiver, such as a photodetector (PD), restores the electrical signal proportionally to the received optical intensity, which is known as direct detection (DD). Considerable research has been conducted on VLC systems, such as implementation techniques [5][6][7][8], channel characteristics [9], multiple-input/multiple-output techniques [10,11], orthogonal frequency-division multiplexing (OFDM) [12][13][14][15][16][17][18][19], and schemes for dimming requirements . Dimming is a unique characteristic of VLC, which makes it different from conventional optical wireless communications (OWCs).…”

Section: Introductionmentioning

confidence: 99%

“…For ON-OFF keying (OOK) modulation, the ratio of the "ON" time to "OFF" time of the signal is adjusted in a transmission data frame to meet the dimming requirements, resulting in the design of a scheme maintaining the Hamming weights associated with the dimming requirement. Pulse-width modulation (PWM) is applied for dimming support [19][20][21], and can also be superposed with OOK and pulse-position modulation (PPM) [22,23]. These schemes are simple, but they either produce marginal rate enhancement or are vulnerable to noise.…”

Section: Introductionmentioning

confidence: 99%

Optimal Signal Amplitude of Orthogonal Frequency-Division Multiplexing Systems in Dimmable Visible Light Communications

Yun

Lee

Ahn

et al. 2014

Journal of the Optical Society of Korea

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Visible light communications (VLC) using the intensity modulation of light-emitting diodes (LEDs) provides a new communication medium to overcome the shortage of radio spectrum, and allows reuse of LED lighting infrastructures. Orthogonal frequency-division multiplexing (OFDM) was introduced to VLC for its merits in mitigating the fading effects resulting from delay spread, and in avoiding low-frequency ambient interference. Noise and clipping are two major factors that degrade the performance of OFDM in VLC. A larger signal easily overcomes noise, but experiences impairment by clipping. Therefore, degradation due to clipping has a trade-off relationship with that due to noise, depending on the signal amplitude of OFDM. In this paper, the optimal signal amplitude in the trade-off is obtained by simulation when the dimming and LED intensity are given. The former indicates a user's requirement for lighting, and the latter represents the channel quality. The required LED intensity-to-noise ratio, as the channel quality that guarantees dimming as well as an adequate bit-error rate (BER), is also discussed.

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“…A fast channel characterization algorithm was presented for VLC channel modeling considering the sophisticated reflections [2] . Moreover, discrete multi-tone modulation [3] and multiple pulse position modulation [4] were recommended for use in VLC systems to address the flicker problem. An effective model was also presented to reduce LED nonlinearity distortion in VLC systems [5] .…”

mentioning

confidence: 99%

“…The PD sensitivity determines the minimal required signal power to guarantee correct reception. The LED lighting has a Lambertian radiation pattern [3] , as shown in Fig. 3.…”

mentioning

confidence: 99%

Efficient user access and lamp selection in LED-based visible light communication network

Huang¹,

Ji²

2012

中国光学快报

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We present a network-level signaling mechanism for user access and service setup in light emitting diode (LED)-based visible light communication (VLC) networks and define the corresponding signaling messages. In this mechanism, lamp selection is an important step for realizing flexible user access and efficient resource allocation. Two basic selection schemes are proposed, and an enhanced bandwidth-based scheme is presented. Simulation results show the different advantages among these schemes.OCIS Recently, due to the large-scale deployment of white light emitting diodes (LEDs) as the next-generation green lighting, LED-based visible light communication (VLC) has attracted much attention. Current studies on VLC primarily focus on system-level technologies, such as dimming control, flicker mitigation, and novel modulation mechanisms, which aim to raise the transmission speed and signal quality. A previous study analyzed the in-door channel characteristics of multipath dispersion [1] and showed that VLC can provide a wider transmission bandwidth than infrared (IR) communications. A fast channel characterization algorithm was presented for VLC channel modeling considering the sophisticated reflections [2] . Moreover, discrete multi-tone modulation [3] and multiple pulse position modulation [4] were recommended for use in VLC systems to address the flicker problem. An effective model was also presented to reduce LED nonlinearity distortion in VLC systems [5] . As a collective achievement for current VLC system research, IEEE standard 802.15.7 presented the definition of the PHY and MAC layer technologies for VLC [6] . Based on the aforementioned system-level studies, the network-level VLC technology was analyzed. An Ethernet-VLC network interface was designed to realize IP broadcast applications [7] , and a rapid link recovery scheme was proposed to guarantee link visibility [8] . However, such network has a basic problem that has not been studied thoroughly. The light wave of a LED is not as diffractive as the radio wave, making the coverage of one single LED lamp limited. Therefore, in a large in-door environment, such as a museum or a supermarket, multiple LED lamps are required to extend the coverage scale. In most of the current VLC experimental or simulation networks [2,7] , all LED lamps transmit the same signal to obtain uniform signal power within the in-door environment. However, in this scenario, the bandwidth of the whole VLC network becomes very limited (similar to that of a single LED lamp). Thus, different lamps should carry different signals to realize broad-band access. This goal is achieved using the lamp-based space division multiplexing (SDM) method, in which one LED lamp acts as an individual channel. In such SDM VLC network, the selection of the proper LED lamp to achieve efficient user access and channel allocation becomes the key problem. Network signaling is required to solve such problem [9] . Hence, in this letter, we propose a network-level signaling mechanism for flexible user access and...

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Combining Illumination Dimming Based on Pulse-Width Modulation With Visible-Light Communications Based on Discrete Multitone

Cited by 108 publications

References 6 publications

Optimization of Visible-Light Optical Wireless Systems: Network-Centric Versus User-Centric Designs

Optimization of Visible-Light Optical Wireless Systems: Network-Centric Versus User-Centric Designs

Optimal Signal Amplitude of Orthogonal Frequency-Division Multiplexing Systems in Dimmable Visible Light Communications

Efficient user access and lamp selection in LED-based visible light communication network

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