室内可见光通信的脉冲响应及矢量编码算法模型

Impulse response and vector coding modelling for indoor visible light communications

在变电站等室内可见光通信(VLC)系统中,发光二极管(LED)光源通过多径色散从发射端经过光通道传输到接收端。文章基于以白光为主的发光二极管特性,通过MATLAB仿真建模,将室内不同反射面的反射率纳入模型,提出了信道脉冲响应算法。仿真信号传输过程引入了直流偏压矢量编码(DCO-VC)技术,采用M位脉冲幅度调制(M-PAM)作为调制方案,通过调节脉冲幅度调制参数来调整系统数据传输效率和准确率。同时,仿真模型中引入了小区间干扰以验证信号传输在干扰存在情况下的表现。研究表明,调制参数越高,系统数据传输效率越高,对信号功率强度的要求也更高;调制参数较低时,系统传输效率相对较低,但同等信号功率条件下传输准确率更高,小区间干扰存在时仍能有效输出。因此实际应用中当信噪比低于35 dB时,应采用2PAM或4PAM调制方式保证传输准确率;信噪比高于40 dB时可按实际需求采用8PAM及以上调制方式提升传输速率。

In indoor visible light communication(VLC) system, the data carried by light-emitting diode(LED) light is transmitted through the optical channel through multipath dispersion. Different indoor reflective surfaces are incorporated into the model through MATLAB simulation modeling, and the channel impulse response algorithm is proposed. Direct current biased optical vector coding(DCO-VC) technology is introduced in the system. The DCO-VC system uses M-ary pulse amplitude modulation(M-PAM) as modulation scheme, to adjust the system data transmission efficiency and accuracy. Intercell interference is introduced into the simulation model. Studies have shown that the higher the modulation parameter is, the higher the data transmission efficiency of the system is. When the modulation parameters are lower, the transmission efficiency of the system is relatively reduced, but the transmission accuracy is higher and the system can still output effectively in the presence of inter-cell interference. In real application, when the system signal-to-noise(SNR) ratio is lower than 35 dB, 2 PAM or 4 PAM modulation should be applied to ensure the transmission accuracy. When the SNR ratio exceeds 40 dB, use the 8 PAM modulation to increase the transmission rate.