On the performance degradation of optical wireless OFDM communication systems due to changes in the LED junction temperature

Thermal management is a significant issue in the design of high power light emitting diodes (LEDs). In this letter, the effect of practical changes in the LED junction temperature on the performance of indoor optical wireless (OW) communication system based orthogonal frequency division multiplexing (OFDM) modulation is studied and analyzed. Junction temperature changes occur due to variations in the drive current, ambient temperature and by self-heating due to electrical power dissipation. The changes in junction temperature affect the LED forward voltage, the output luminous flux and the LED dominant wavelength. The effects of these changes on the performance of DC-biased (DCO) and asymmetrically clipped (ACO) OW OFDM systems are studied. While it is shown that the changes in the dominant wavelength are insignificant, it will be shown that significant performance degradation may occur due to small variations of LED forward voltage and luminous flux.