Sub-Carrier Loading Strategies for DCO-OFDM LED Communication

Mardanikorani, Shokoufeh; Deng, Xiong; Linnartz, Jean-Paul M. G.

doi:10.1109/tcomm.2019.2953612

Cited by 48 publications

(64 citation statements)

References 34 publications

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“…This can for instance be reached by applying a pre-emphasis circuit at the transmitters, in which higher frequencies are boosted such that the output spectrum of the LED channel is assumed to be flat across the frequency range [0, B], with B the communication bandwidth. The achievable throughput at RXj in time-slot s can be modelled as [17]:…”

Section: A Lifi Channel Modelmentioning

confidence: 99%

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TDMA Scheduling in Spatially Extended LiFi Networks

Beysens

Linnartz

Wageningen

et al. 2020

IEEE Open J. Commun. Soc.

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Optical Wireless Communication (OWC) has attracted significant attention from academia and industry as a promising solution to complement traditional radio frequency communication. In Light-Fidelity (LiFi) networks, to enable soft handover and provide robustness against blockage of the line-of-sight links, LiFi receivers are designed to see multiple LiFi transmitters within their field-of-view. To trade-off spatial multiplexing with harmful interference, a proper user scheduling technique is required. In this work, we first derive practical and exact expressions for determining which simultaneous transmissions will create harmful interference and should be scheduled in multiple time-slots. Afterwards, relying on this expression, we propose our semi-distributed Spatially Extended TDMA algorithm, which is based on a time division contention-free access scheme. In contrast to more complex algorithms in the state-of-the-art, our scheduling protocol can reduce the computation time while also achieving a superior minimal user throughput. For a scenario with 9 transmitters and up to 15 receivers, our protocol is at least a factor 120 faster and can improve the minimal user throughput up to 91%, making it suitable for practical roll-out as a promising solution for very dense LiFi networks.

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Section: A Lifi Channel Modelmentioning

confidence: 99%

“…Every TX is positioned at a height of 2.8 m and has a Lambertian emission pattern with a semi-angle φ 1/2 = 25 • , unless specified otherwise. Inspired by the specifications of the Luxeon Rebel LXMLPB02-0023 LED which has a flat frequency response up to 50 MHz [17], we consider a communication bandwidth B = 50 MHz.…”

Section: A Simulation Setupmentioning

confidence: 99%

TDMA Scheduling in Spatially Extended LiFi Networks

Beysens

Linnartz

Wageningen

et al. 2020

IEEE Open J. Commun. Soc.

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“…There is a persistent debate on whether multi-carrier OFDM outperforms carrier-free modulation, such as Pulse Amplitude Modulation (PAM) over an OWC low-pass channel. In fact, O-OFDM allows one to optimize the distribution of the available modulation power among the sub-carriers and to select the bit load independently on every sub-carrier to maximize the data rate [5]. However, the OFDM composition of multiple frequency components has a high Peak to Average Power Ratio (PAPR) that increases the power consumption.…”

mentioning

confidence: 99%

“…However, the practical limitations of a discrete modulation order and an optimization of the modulation bandwidth for OFDM were not discussed. On a pre-emphasized channel, the use of a fixed number of constellation bits over a fixed (non-optimized) bandwidth causes pronounced, abrupt discontinuities in the throughput, versus changes in the SNR [5]. That is, e.g., if the receiver gradually moves away from the transmitter, there will be a stepwise, nongraceful cut-off in throughput.…”

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Optimization and Comparison of M-PAM and Optical OFDM Modulation for Optical Wireless Communication

Mardanikorani

Deng

Linnartz

2020

IEEE Open J. Commun. Soc.

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Illumination LEDs, but also infrared LEDs have limited bandwidth. To achieve high throughput, one needs to modulate the LED significantly above its 3 dB bandwidth. Orthogonal Frequency Division Multiplexing (OFDM) is a popular modulation technique to cope with the frequency selectivity of the LED channel. In this paper, we challenge whether its large Peak-to-Average-Power Ratio (PAPR) and resulting large DC bias are justified. We compare systems using the same power and derive how PAM and OFDM variants reach their optimum throughput at different bandwidths and differently shaped spectral densities, thus at very different Signal to Noise Ratio (SNR) profiles but nonetheless the same transmit power. When corrected for the path loss and normalized to the noise power in the 3 dB bandwidth of the LED, we call this the Normalized Power Budget (NPB). OFDM can exploit the low-pass LED response using a waterfilling approach. This is attractive if the NPB exceeds 60 dB. OFDM will then have to spread its signal over more than ten times the LED bandwidth and requires a DC bias of more than 4 times the rms modulation depth. Second-order distortion and LED droop may then become a limitation, if not compensated. At lower power (NPB between 30 and 60 dB), DCO-OFDM outperforms PAM, provided that it significantly reduces its bias and only if it uses an appropriate adaptive bit and power loading. Without adaptive bit loading, thus using a frequency-constant modulation order, for instance made feasible by a pre-emphasis, OFDM always shows lower performance than PAM; about 2.5 dB at a NPB around 60 dB. Below 30 dB of NPB, even waterfilling cannot outweigh the need for a larger bias in OFDM, and PAM should be preferred. We argue that a mobile system that has to operate seamlessly in wide coverage and short-range high-throughput regimes, needs to adapt not only its bandwidth and its bit-loading profile, but also its DCO-OFDM modulation depth, and preferably falls back from OFDM to PAM.

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Asymmetric Additive‐Assisted Organic Solar Cells with Much Better Energy Harvesting and Wireless Communication Performance

Lei,

Wang,

Liang

et al. 2023

Advanced Energy Materials

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Organic solar cells (OSCs), exhibiting better sensitivity to different light intensities and higher power conversion efficiencies (PCEs) under indoor illumination, have great potential to be simultaneously used for solar energy harvesting and optical communication. However, the poor intrinsic molecular stacking and phase separation in active layers significantly hinder the charge transport and extraction in OSCs for achieving this aim. Here, an effective heterohalogen‐substitution asymmetric additive strategy is proposed to fine‐tune the non‐covalent interaction with nonfullerene molecules and optimize the morphology of active layer, which greatly boosts both the OSC photovoltaic performance with the PCEs of up to 18.30% and 29.52% under AM 1.5G and indoor light illumination respectively, and the ‒3 dB communication bandwidths of 4.11, 3.14, and 3.04 MHz at red, green, and blue (RGB) wavelengths respectively. Of particular note, combining the wavelength division multiplexing and adaptive bit‐loading technologies, the visible light communication system comprised of the RGB light sources and additive‐treated OSCs delivers more remarkable data throughput of 302.7 Mb s−1 and higher harvesting power of 7.38 mW simultaneously, presenting an excellent self‐powered capability for enhanced endurance. This work demonstrates that high‐performance OSCs with excellent energy harvesting and wireless communication capacity can be perfectly achieved by a heterohalogen‐substitution asymmetric additive strategy.

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Sub-Carrier Loading Strategies for DCO-OFDM LED Communication

Cited by 48 publications

References 34 publications

TDMA Scheduling in Spatially Extended LiFi Networks

TDMA Scheduling in Spatially Extended LiFi Networks

Optimization and Comparison of M-PAM and Optical OFDM Modulation for Optical Wireless Communication

Asymmetric Additive‐Assisted Organic Solar Cells with Much Better Energy Harvesting and Wireless Communication Performance

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