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

Abstract

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.

Efficient Cross-Room Switch Mechanism for Indoor Room-Division-Multiplexing Based Visible Light Communication Network

“…8 presents the results. It shows that TSA is less than 400ms and then the radius of the annular switching area is suggested to be R SA = T SA × V human = 0.4 s × 1.5 m/s = 0.6 m = 60 cm (6) The whole handoff latency T HO is less than 1300 ms, which is acceptable in practical cross-room communication considering the existence of the protection area. In the crossroom switch process, the hardware switching and signaling processing latency is less than the time for the human crossroom movement, so the service interruption time is mainly determined by the common speed of human walking.…”

“…In practical deployment, the RDM is recommended to be employed with other advanced modulation and multiplexing mechanisms [4,6,9].…”

“…Besides the advanced modulation schemes [4][5][6], multiplexing techniques are also basic methods to increase the system speed and network capacity. Many multiplexing mechanisms have been utilized in current wireless communication such as time-division-multiplexing (TDM), code-divisionmultiplexing, and space-division-multiplexing (SDM).…”

An In-depth Survey of Viisiiblle Liight Communiicatiion Modullatiing and Codiing schemes for Diimmiing/Flliicker Avoiidance Technollogiies

“…PWM can also improve the dimming levels over traditional OOK [25][26], where PWM-based dimming control provides a wide range of dimming levels [18,[27][28]. A key advantage is enhancing power consumption [27,29].…”

Bandwidth Allocation Under Multi-Level Service Guarantees of Downlink in the VLC-OFDM System

“…Compared to the radio-based wireless communication, visible light communication (VLC) brings multiple advantages such as greater bandwidth, higher data rate, being harmless to human bodies, ubiquitous data transmission and so on [1][2][3]. Orthogonal frequency division multiplexing (OFDM) which allows for parallel transmission on orthogonal subcarriers with a low-complexity transceiver [4] was introduced into VLC to improve data rate, mitigate the fading effects resulting from delay spread, and avoid low-frequency ambient interference [5]. In VLC-OFDM systems, the amplitude variation of the OFDM signal drives the intensity change of LED light.…”