Hybrid Frequency and Phase-Shift Keying Modulation for Energy Efficient Optical Wireless Systems

International audienceIn this letter, we introduce direct-current (DC) offset hybrid frequency and phase-shift keying (DC-FPSK) modulation for Internet-of-Things based on optical wireless systems. For DC-FPSK, non-negative phase-modulated frequency waveforms are generated by combining frequency-shift keying (FSK), phase-shift keying (PSK) and a DC offset. We propose optimal maximum likelihood and sub-optimal receivers for DC-FPSK. The performance is appraised in terms of Euclidean distance, bit-error-rate (BER) performance and energy efficiency. We determine that combining 4-PSK with conventional DC-FSK is the optimal approach to enhance the energy and spectral efficiencies

Energy Efficient M -ary Frequency-Shift Keying based Modulation Techniques for Visible Light Communication

International audienceIn this article, we introduce two variants of energy efficient M-ary frequency-shift keying (FSK) for low data rate/low power Internet-of-Things (IoT) applications. Both variants , i.e., M-ary direct current (DC)-FSK and M-ary unipolar (U)-FSK are compatible with intensity-modulation and direct detection (IM-DD) implementation of visible light communication (VLC). The two techniques intrinsically differ in the manner of attaining a non-negative signal for intensity-modulation. M-ary DC-FSK uses a DC-offset, while, M-ary U-FSK sequentially transmits the positive and the sign flipped negative halves of the bipolar M-ary FSK symbols. The spectral efficiencies of M-ary DC-FSK and M-ary U-FSK are augmented by biorthogonal extension of frequency waveforms resulting in 2M-ary biDC-FSK and 2M-ary biU-FSK, respectively. Two optimal maximum likelihood (ML) receiver configurations with different complexities are introduced for M-ary DC-FSK/2M-ary biDC-FSK. Whereas, for M-ary U-FSK/2M-ary biU-FSK, an optimal ML and a sub-optimal receiver are proposed. We appraise the performance of these methods in terms of Euclidean distance, bit error rate (BER) in additive white Gaussain noise and time dispersive channels, energy efficiency with respect to spectral efficiency and computational complexity. Simulations confirm that the proposed techniques are more energy efficient than classical M-ary pulse-amplitude modulation (PAM) in an absolute sense