| Visible light communication has become one of the candidate schemes for 6G indoor coverage communication because of its rich spectrum resources and high transmission rate.In order to obtain high link performance,most transmission schemes of visible light communication systems adopt the improved scheme based on OFDM modulation.Focusing on the visible light communication system based on OFDM modulation(OFDM-VLC),this paper studies the power optimization of subcarriers,adaptive bit loading schemes and PAPR reduction in OFDM-VLC system.The main work of this paper is as follows:Firstly,the DC offset and subcarrier power optimization of AV-DCO-OFDM system are studied.The AV-DCO-OFDM system model is given,the achievable spectral efficiency of the system is deduced,and taking it as the objective function,the optimization problems of subcarrier power and DC offset are established.The algorithms to solve the optimization problems are proposed for flat fading channel and frequency selective fading channel respectively,and the optimal values of DC offset and subcarrier power are obtained.The performances of different DC offset and subcarrier power allocation schemes are simulated and compared.Secondly,the DC offset and subcarrier power optimization of AV-DCO-OFDM system with double-sided clipping are studied.The AV-DCO-OFDM system model with double-sided clipping is given,and the achievable spectral efficiency is derived.Taking it as the objective function,the optimization problems of subcarrier power and DC offset are established.The algorithms to solve the optimization problems are proposed for flat fading channel and frequency selective fading channel respectively.The performances of different DC offset and subcarrier power allocation schemes are simulated and compared.Thirdly,the joint optimization of adaptive bit loading and symbol pairing of OFDM-VLC system with pairwise coding is studied.The influence of pairwise coding on the signal-to-noise ratio of the received signal is deduced and the OFDM-VLC system with pairwise coding is given.Under the constraints of bit error rate and optical power,the adaptive bit loading and symbol pairing algorithm is given.The transmission performance and bit error rate performance of this scheme and the traditional adaptive bit loading scheme are simulated and compared.Fourthly,the PAPR reduction method of OFDM-VLC system based on neural network auto-encoder is studied.The PAPR distribution characteristic of AV-DCO-OFDM system is deduced,the method of reducing the PAPR of OFDM-VLC system based on auto-encoder is given,the auto-encoder is designed in detail,and the PAPR and symbol error rate performance of this scheme and traditional SLM scheme are simulated and compared. |
