Research On Baseband Transmission And Position Of Visible Lighting Communication

Visible light communications(VLC)can meet the requirements for communication and illumination simultaneously with unregulated bandwidth,which become increasingly attractive.In VLC,binary signals are generally adopted to transmit information,but with poor spectral efficiency.Due to its high spectrum efficiency,Orthogonal Frequency Division Multiplexing(OFDM)technique is considered for VLC to boost data rates.Based on visible light OFDM systems,various OFDM-VLC technologies for anti-linearity are discussed and studied in depth in this paper,including tone reservation-based visible light OFDM systems and Delta-Sigma modulation-based one-bit visible light OFDM systems.Besides,a new scheme of LED-based indoor positioning system combining with visible light OFDM technique is explored in this paper.Firstly,the basic architectures of visible light communication systems including the system block dia-gram,the communication model of photo-electric devices and noises are summarized in this paper? which provide the basic theories for follow-up chapters.Then,sorts of applications of OFDM technique for visible light communication systems are introduced in outline and visible light DCO-OFDM system is described in detail.For LED-based VLC systems,the source of nonlinear effects and its influences on visible light OFDM systems are discussed briefly.Following,considering the influences of LED nonlinearity on OFDM-VLC signals,a Tone Reservation-based VLC-applicable rate-adaptive OFDM system is proposed in this paper.Elaborately,the proposed adaptive rate OFDM-VLC system is based on IM/DD modulation and characteristic of visible light chan-nels.Mainly DCO-OFDM systems,the scheme of positions of reserved subcarriers is optimized based on lowpass channel of VLC.And the scheme of number of reserved subcarriers is also determined based on system achievable rate.With the proposed tone reservation scheme,it contributes to almost 35 percent peak reduction if enough tones are reserved and 9d B effective power gain when signals are normalized prior to transmission in pratice.Additionally,a one-bit Delta-Sigma modulator is employed to quantize high-rate OFDM-VLC sigals,and theoretical performances and structural optimizations are provided for the one-bit OFDM-VLC system,which are tested and verified by experimental simulations.The principle and model of Delta-Sigma modu-lators are summarized briefly and a Delta-Sigma modulator-based visible light OFDM system is described,where system architecture and mathmatical model could be introduced.Then,high-order modulator-based OFDM-VLC systems are mentioned and their stabilities are analyzed in OFDM-VLC systems.Performances of the system such as in-band signal-to-quantization noise ratio and bit error rate are derived and verified by experimental simulations.In order to improve spectrum efficiency and anti-interference ability,modulator sturctures are optimized and N-tones are introduced in noise shaped filter,which are matched with data sub-carriers in OFDM-VLC signals.Thereforce,the N-tones Delta-Sigma modulator-based OFDM-VLC system is proposed in this paper.Finally,LED-based indoor positioning systems are discussed in this paper,which are the critical appli-cations in VLC systems.LED-based indoor positioning models are given in outline,which include system architecture and positioning algorithms.Besides,various RSS-based visble light positioning algorithms and principles are described,including trilateration,fingerprinting and proximity.Then,CSI-based indoor visible light positioning system will be proposed in this paper,which could capture visible light CSIs employed by OFDM-VLC techniques.Moreover,we compare the proposed system with the RSS-based system,and tested by software simulations.