可见光通信极性索引正交频分复用技术研究

为了抑制可见光通信(VLC)正交频分复用(OFDM)系 统发光二极管(LED)非线性限幅失真,提出了一种极性 索引OFDM(PIM-OFDM)调制方式。PIM-OFDM通过两个模块分别传输直流偏置 光OFDM(DCO-OFDM)双极性信号的极性信息和幅度信息。在第1模块中,对双极性信号的正 负极性编码并使用 OOK信号传输。在第2模块中,对双极性信号取绝对值得到幅度信息。在相同条件下,PIM- OFDM系统 性能比非对称限幅OFDM(ACO-OFDM)系统提升了接近 3dB。在光功率约束 条件下,在最 大有效(SNR)原则下得到了直流偏置和输入信号的最优功率分配。 仿真结果表明:光功率约束较小时,有 效SNR随着直流偏置增大而变小；光功率约束较大时,有效SNR随着直流 偏置增大会先增大后减小。 实验结果表明:在相同传输速率的情况下,PIM-OFDM误码率(BE R)性能要比ACO-OFDM提升1个数量级。

Research on polarity index modulation orthogonal frequency division multiplexing technique in visible light communication

In order to restrain the nonlinear clipping distortion caused by the l ight emitting diode (LED) in visible light communication orthogonal frequency division multiplexing (VLC-OFDM) syste m,a modulation named polarity index modulation orthogonal frequency division multiplexing (PIM-OFDM) is proposed in this paper.The polarity and amplitude data of the bipolar direct current optical (DCO)-OFDM si gnal are carried by two blocks in PIM-OFDM system.In the first block,the positive and negative polarities of bipolar sign al are coded and transmitted by on-off keying (OOK) signal.In the second block,amplitude information is achieved by t aking the absolute value of the bipolar signal.The system performance of PIM-OFDM is almost 3dB better than th e asymmetrically clipped optical orthogonal frequency division multiplexing (ACO-OFDM) with the same con dition.With the optical power constraints,the optimal power allocation between DC bias and input signal is obt ained under the principle of maximum effective signal-to-noise ratio (SNR).Simulation results show that the effect ive SNR decreases with the increase of DC bias under the low optical power constraints.However,the effective SNR woul d increase first and then decrease with the increase of DC bias under the high optical power constraints. It is also shown by experiments that the bit error ratio of PIM-OFDM improves an order of magnitude than that o f ACO-OFDM with the same transmission rate.