LAUSR

Abstract In this work, the nonlinear behavior on pulse-amplitude-modulation (PAM) and their impact on the performance of RGB light-emitting-diodes (LED) based visible light communications (VLC) is presented. Particularly, how the limited source bandwidth affects the nonlinearity of fully modulated RGB LEDs is investigated. It is found that when symbol-rate is higher than the channel bandwidth the nonlinearity gradually diminishes. It causes the symbol-rate dependent nonlinearity. When applying PAM in VLC links, a pre-distortion method is often applied to compensate for the nonlinearity. Due to this symbol-rate dependency, however, the conventional pre-distortion method has a limitation on linearizing the non-linear VLC channel, especially in the case of applying various symbol-rates according to the channel condition. Although it can be adaptively compensated by nonlinear equalizers, their complexity is considerably high. In this work, the characteristics of multi-level PAM scheme in a band-limited nonlinear channel is presented. Also, the feasibility of a low complex but efficient pre-distortion method derived from monotonically decreasing characteristics of the frequency dependent nonlinearity is investigated.