Abstract
In visible light communications with the optical orthogonal-frequency-division multiplexing (O-OFDM) technique, the high peak-to-average-power-ratio (PAPR) is an important issue due to the limited dynamic range of light emitting diode (LED)-based light sources. To address this problem, we propose a hybrid OFDM-pulse time modulation (PTM) scheme where bipolar O-OFDM samples are converted into the digital PTM formats of pulse width modulation (PWM) and pulse position modulation (PPM) for the intensity modulation of LEDs. We convert the DC biased optical OFDM (DCO-OFDM) and asymmetrically clipped optical OFDM (ACO-OFDM) samples to PTM and show that DCO-OFDM-PTM offers improved bit error rate (BER) performance. For example, for 16-quadrature amplitude modulation (QAM) at the BER of 10−3, the signal-to-noise ratio (SNR) gains are 1.35 dB and 1 dB for DCO-OFDM-PPM and DCO-OFDM-PWM compared to ACO-OFDM-PPM and ACO-OFDM-PWM, respectively. Simulation results show that DCO-OFDM-PPM displays an improved BER performance compared with DCO-OFDM-PWM for both lines of sight (LOS) and diffuse configurations. For instance, for an ideal LOS channel and for 16-QAM at the BER of 10−3, the required SNR values are 4.5 and 10.2 dB for DCO-OFDM-PPM and DCO-OFDM-PWM, respectively.
| Original language | English |
|---|---|
| Pages (from-to) | 65-71 |
| Journal | Optics Communications |
| Volume | 429 |
| Early online date | 6 Aug 2018 |
| DOIs | |
| Publication status | Published - 15 Dec 2018 |
Keywords
- Visible light communications
- Optical wireless communications
- Hybrid OFDM-PPM
- Hybrid OFDM-PWM
- PAPR