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Principles of LED Light Communications by Harald Haas, Svilen Dimitrov

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4

Digital modulation schemes

4.1Introduction

The data transmission in optical wireless communication (OWC) with incoherent light sources is realized through intensity modulation and direct detection (IM/DD). For this purpose, the transmitted signal needs to be real-valued and non-negative. In practice, this is achieved by single-carrier modulation techniques, such as multi-level pulse position modulation (M-PPM) and multi-level pulse amplitude modulation (M-PAM), and through multi-carrier modulation such as multi-level quadrature amplitude modulation (M-QAM) optical orthogonal frequency division multiplexing (O-OFDM). Conventionally, the average optical power is defined as the first moment of the transmitted signal, while the average electrical ...

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