# Effect of Temperature on Channel Compensation in Optical Camera Communication
## 2 Related Work  
This work underlines the importance of considering the effect of temperature on LEDs when compensating the channel in OCC. Temperature effects on those light sources have thoroughly been studied in the literature. A number of studies have found that the efficiency and the spectral features of the LEDs are very sensitive to thermal changes. Furthermore, several approaches have been proposed to perform channel compensation in VLC and OCC systems, but none have dealt with the mentioned temperature effects. Photo-Electro-Thermal (PET) modeling of LED sources has a significant impact on luminaire design and optimization. These three domains are usually tightly coupled, and the design of illumination fixtures must take into account the interactions between them. Commercial LED lamps are customarily manufactured using arrays of LED. Due to the manufacturing process, each device presents slightly different characteristics that could affect the performance (and ultimately the reliability) of the LED system. [PERSON] et al. proposed a 3D PET model for predicting the behavior of lamps built with non-identical LED parts [14]. The model, based on the use of a grid-like partition of the domain of interest combined with coupling equations, presented high accuracy compared to the experimental results. [PERSON] et al. proposed a PET model that included transient analysis for predicting the impact of driving current ripple effects on both the thermal and the photometric outputs of an LED. The authors obtained experimental evidence about the benefits of driving LED devices with rippled inputs (DC current plus a sine-like signal) for improving the lifespan of these devices without affecting the human perception [15]. This type of input enables smaller capacitance filter values, which allow the use of more reliable technologies compared to electrolytic capacitors (such as film capacitors). In addition to these models, [PERSON] et al. included the effects of phosphor temperature in a PET model, showing that a good thermal design considering this aspect is capital to maintain performance in White LED (WLED) devices [16]. Unlike [PERSON] et al., a dynamic PET analysis was carried out by [PERSON], [PERSON], and [PERSON] in [17]. The authors proposed a modification of the steady-state PET equations from [PERSON] et al. [14], including the coupling effect of phosphor-to-LED (and vice versa) in the thermo-electric domain, as well as the electro-optic efficiency reduction on phosphor due to temperature. All these models were focused on the lighting industry and aimed to develop models suitable for manufacturers and designers. Nonetheless, communication metrics have not been included in PET models yet (up to the authors' knowledge). Regarding the emitted spectrum variation due to the p-n junction temperature, [PERSON] et al. carried out an investigation measuring the spectrum of a Surface Mount Device (SMD) LED at ambient and high-temperature conditions that demonstrated a red-shift in the peak wavelength and a decrease in intensity as temperature grew [18]. Some studies related to thermal effects on LED focused on the emitted color variation. [PERSON] et al. performed experimental measurements of color variation in RGB LEDs as a function of temperature, concluding that the blue LED has the highest color point variation [19]. [PERSON] et al. discussed LED applications in railway and traffic light signals proposing a system that compensate intensity and color stability in order to respect limits imposed by the norms [20]. [PERSON] et al. established a relationship between color difference and temperature using a blue transparent flexible mini-LED array [21]. Furthermore, the LED luminous efficiency has been enhanced over the past few years owing to different techniques. [PERSON] et al. investigated the thermal and optical characteristicsof a warm white LED, studying both the effects of thermal interface materials (TIM) and the impact of the driving current on the LED performance.