| With the natural advantages of supporting high-density and high-speed communication,visible light communication can upgrade the lighting system to ’mobile base station’,which can not only make up for the deficiency of traditional wireless spectrum resources,but also provide a wireless coverage method with extremely high speed and extremely low energy consumption.It is expected to become the key technology of 6G communication system in the future.In order to meet the explosive growth of 6G network data in the future,it is particularly important to realize high quality and large capacity indoor visible light information transmission.Traditional modulation methods,such as switch keying modulation and pulse position modulation,have been unable to meet the needs of indoor visible light communication.It is very necessary to use high-order modulation to further increase spectral efficiency.However,the noise tolerance loss caused by high-order modulation technology needs to be compensated by studying other visible light communication technologies.Thus,aiming at the problems raised,this paper will use geometric shaping technology and ACO-OFDM modulation technology to improve the performance of indoor visible light communication system,increase the transmission capacity of the system and improve the anti-interference performance of the system.The concrete research contents and innovative points of this paper are as follows:First of all,in view of the shortcomings of the traditional square 16QAM constellation structure,two new 16QAM constellation structures of arrow and bottle are designed based on geometric shaping technology.By constructing the indoor visible light channel model considering twice reflection,the indoor visible light ACO-OFDM system under Lambert light source is simulated and analyzed.The simulation results demonstrate that when the bit error rate is 10-5,the arrow constellation structure can bring 1.2 dB bit error rate gain,and the bottle constellation structure can bring 0.8 dB bit error rate gain.When the signal-to-noise ratio is 8dB,the arrow-shaped constellation structure and the bottle-shaped constellation structure can bring 0.02 bits/symbol system capacity gain.Among them,the arrow constellation structure is more suitable for indoor visible light positioning system with low delay accuracy,and the bottle constellation structure is more suitable for indoor visible light communication system with high delay accuracy.Secondly,this paper analyzes the radiation characteristics and channel characteristics of EdiPower,LUXEON and Z-Power three non-Landauer light sources through simulation in view of the large difference between the ideal Lambert light source and the actual light source.The simulation results demonstrate that the three kinds of non-Lambert light sources have more concentrated radiation intensity in the range of small emission angle,40 degree emission angle and large emission angle.Compared with the ideal Lambert light source,the non-line-of-sight link of three kinds of non-Lambert light sources has less influence,and EdiPower and Z-Power non-Lambert light sources are more suitable for indoor visible light system with integrated communication and lighting.Finally,according to the requirements of practical applications,this paper simulates the indoor visible light ACO-OFDM system of non-Langbian light source with arrow constellation structure and bottle constellation structure,respectively.The simulation results show that the LUXEON non-Lambert light source has more advantages in improving system capacity and is more suitable for point-to-point communication.Z-Power non-Lambert light source has more advantages in improving BER performance and is more conducive to indoor high-speed communication;the EdiPower non-Lambert light source is more suitable for indoor lighting system with low communication rate. |
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