ABSTRACT
This chapter addresses channel modeling for visible light communications (VLC) systems mainly focusing on indoor systems. It introduces different sources of impairment in VLC systems arising from beam propagation or transmitter (Tx)/receiver (Rx) devices. The chapter outlines the limitations arising from the aggregate channel while focusing on the problem of intersymbol interference (ISI) and how it affects the link performance particularly in the absence of a line of sight (LOS). It also presents the channel modeling for multiple-input multiple-output (MIMO) VLC systems. The ideal LOS channel impulse response (CIR) is essentially a time delayed and scaled delta functions representing amplitude degradation of the transmitted signal. Multipath propagation of emitted signals leads to time dispersion and ISI, which will limit the transmission rate. Another impairment that can affect the performance of a VLC system is the nonlinearity of the light-emitting diode (LED) transfer function, regarding both voltage–current and current-emitted optical power relationships.
