Spatial summation in optical orthogonal frequency division multiplexing (O-OFDM) provides opportunity of simultaneously transmitting narrowband visible light communications (VLC) signals using G light emitting diode (LED) groups. However, the number of transmit chains increases as the number of LED groups G increases. The limited dynamic range of these LEDs reinforces the need to reduce peak-to-average-power-ratio (PAPR) of O-OFDM signal in the VLC system. In this paper, we present study of the pilot-assisted (PA) PAPR reduction technique in O-OFDM using multiple LEDs. The PA technique is based on data symbol phase rotation with P iterations of pilot symbol to achieve PAPR reduction. Results show tradeoff between multiple LEDs hardware complexity and the PA technique to achieve desirable PAPR reduction. In comparison with basic O-OFDM with G = 12, simulation results show that PA technique is capable of reducing G by about half to achieve same PAPR of approximately 12 dB using P = 2 at a complementary cumulative distribution function (CCDF) of 10-3. Using the PA technique, further PAPR reduction can be achieved with the combination of increased P and G.
- spatial summation
- VLC system