Contents I. Introduction
Existing Li-Fi systems often deploy some variation of orthogonal frequency-division multiplexing (OFDM) as a modulation format, and it is the base of recent Li-Fi standards [1], [2], [3]. This is mainly due to OFDM’s ability to adapt to a variety of different use cases and to reach high spectral efficiencies, as demonstrated by wired technologies like DSL [4], mobile radio communication standards [5], [6], WiFi networks [7], and digital radio and television broadcasting [8]. However, OFDM also shows some drawbacks: Its waveforms exhibit a high peak-to-average power ratio (PAPR) and require linear analog frontends, both driving energy usage and cost up, especially on the transmitter side. On the other hand, in optical communications, on-off keying (OOK) is often used for its simplicity and the efficient use of transmitter power, despite its low spectral efficiency, since bandwidth is less of a limiting factor than in RF applications. For this reason, it is also still deployed, e.g., in optical Ethernet standards [9]. In optical wireless communications (OWC) research, it is also commonly used as a baseline solution [10], [11].
