一种改进的OFDM水下可见光无线通信系统

在水下直流偏置光无线通信正交频分复用(UOWC-DCO-OFDM)系统中, 为了保证光信号在发射端具有较低峰均比(PAPR)并在水下可进行远距离低误比特率传输，采用了子载波预留、最小二乘算法(TR-LSA)与压扩变换相结合的方法，同时运用优化的神经网络对水下环境进行信道估计，并基于该方法在接收端设计信道均衡器，以应对水下环境对光信号的强衰减。结果表明，UOWC-DCO-OFDM系统的PAPR降低9dB，且在信噪比为10dB时误比特率低于10-3，达到水下无线光通信的误比特率标准。该系统可实现光信号水下远距离、低误比特率传输。

An improved scheme of OFDM underwater visible wireless optical communication system

In the underwater optical wireless communication-direct current bias-optical-orthogonal frequency division multiplexing (UOWC-DCO-OFDM) system, in order to ensure that the optical signal has a low peak-to-average power ratio (PAPR) at the transmitting end and can carry out long-distance low underwater, the method combining the tone reservation-least squares algorithm (TR-LSA) and companding transformation was adopted. At the same time, the optimized neural network was used to estimate the channel of the underwater environment. Based on this method, the channel equalizer was designed at the receiving end to deal with the strong attenuation of the optical signal in the underwater environment. The results show that the PAPR of the UOWC-DCO-OFDM system is reduced by 9dB, and the bit error rate is 10-3 lower when the signal-to-noise ratio is 10dB, which is under the bit error rate standard of wireless optical communication. The system can realize long-distance underwater transmission of optical signals with low bit error rate.