Using delta-sigma modulators in visible light OFDM systems

Abstract

Abstract-Visible light communications (VLC) are motivated by the radio-frequency (RF) spectrum crunch and fast-growing solid-state lighting technology. VLC relies on white light emitting diodes (LEDs) to provide communication and illumination simultaneously. Simple two-level on-off keying (OOK) and pulseposition modulation (PPM) are supported in IEEE standard due to their compatibility with existing constant current LED drivers, but their low spectral efficiency have limited the achievable data rates of VLC. Orthogonal frequency division multiplexing (OFDM) has been applied to VLC due to its high spectral efficiency and ability to combat inter-symbol-interference (ISI). However, VLC-OFDM inherits the disadvantage of high peakto-average power ratio (PAPR) from RF-OFDM. Besides, the continuous magnitude of OFDM signals requires complicated mixed-signal digital-to-analog converter (DAC) and modification of LED drivers. We propose the use of delta-sigma modulators in visible light OFDM systems to convert continuous magnitude OFDM symbols into LED driver signals. The proposed system has the communication theory advantages of OFDM along with the practical analog and optical advantages of simple two level driver signals. Simulation results are provided to illustrate the proposed system.

Light Fidelity (Li-Fi): Is it Possible to Replace Wi-Fi?

“…A simplified version of the OFDM in the Li-Fi system is shown in Figure 8. One of the OFDM variations is introduced by [11] as indicated in Figure 9. The main idea is to use Delta Segma modulator after the cyclic prefix folowed by digital-to-analog converter (DAC).…”

Image sequence decomposition via sigma-delta cellular neural network having coupled cells

“…A spike-rate coding is also known as a pulse density modulation typified by the sigma-delta modulation (SDM) [16]. Recently, the SDM has been utilized for LED control of on-off keying in visible light communication (VLC) [17,18]. A VLC using LED is a well-known cost-effective, high-speed data communication technology.…”

ESIM‐OFDM‐based transceiver design of a visible light communication system

“…This is mainly due to its low PAPR value and ability to cope with error propagation. Instead of using such an expensive DAC, this paper proposes to make use of sigma-delta modulator (SDM) to first convert real values of output signal of a multicarrier scheme into binary bits [12]. To transmit such signal by an LED directly, LED needs to operate in its linear region [11]; therefore, signals with low PAPR are suitable to directly drive LEDs via IM/DD.…”

“…A complex DAC would be required to produce such signals in the first place to produce real valued output. Such DAC is expensive and complex to build [12]. Instead of using such an expensive DAC, this paper proposes to make use of sigma-delta modulator (SDM) to first convert real values of output signal of a multicarrier scheme into binary bits [12].…”

“…Such DAC is expensive and complex to build [12]. Instead of using such an expensive DAC, this paper proposes to make use of sigma-delta modulator (SDM) to first convert real values of output signal of a multicarrier scheme into binary bits [12]. The overall system is implemented in LABVIEW, which is then loaded into NI cDAQ chip [13] to use it standalone along with other hardware components such as LED driving circuit and photodiode.…”