Non-Hermitian symmetry OFDM for indoor space division multiplexing visible light communications

We propose a non-Hermitian symmetry orthogonal frequency division multiplexing (NHS-OFDM) scheme for indoor space division multiplexing based visible light communication (SDM-VLC) systems. NHS-OFDM removes the constraint of Hermitian symmetry and generates light-emitting diode (LED) compatible real-valued signals by parallelly transmitting the real (Re) part and the imaginary (Im) part of a complex-valued OFDM signal via a pair of white LED lamps. Compared with conventional Hermitian symmetry based OFDM (HS-OFDM), NHS-OFDM has lower computational complexity and less power consumption, due to its 50% reduced transceiver complexity. The analytical results show that an indoor two-channel SDM-VLC system using the proposed NHS-OFDM achieves 15.9% reduction in the transmitted optical power and 27.9% improvement in the communication coverage for a target BER of 10-3 than the system using conventional HS-OFDM.

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