论文标题
IM/DD自由空间光学回程的自适应编码调制：一种概率塑形方法
Adaptive Coded Modulation for IM/DD Free-Space Optical Backhauling: A Probabilistic Shaping Approach
论文作者
论文摘要
在本文中，我们提出了一种实用的自适应编码调制方案，以基于概率塑造的强度调制/直接检测来处理自由空间光学（FSO）通道的能力。编码器有效地使传输速率适应了信噪比，这是由大气湍流引起的褪色。应答器可以使用低复杂性通道编码器以一组支持的速率来支持任意大量的传输模式。因此，它可以为陆地和卫星通信系统中的FSO进行回程提供解决方案，以实现较高的光谱效率。我们提出了两种算法，以通过单极MARY脉冲振幅调制（M-PAM）信号来确定该方案的容量和容量调整分布。然后，信号星座根据最佳分布概率地形状，并且形状信号是通过有效的二进制前向误差校正方案来编码的。提供了广泛的数值结果和模拟来评估性能。所提出的方案产生的速率接近FSO通道容量最紧的下限。例如，编码的调制器从M-PAM容量在0.2 dB之内运行，并且以每个通道使用3位的传输速率超过1.7 dB的均匀信号传导。
In this paper, we propose a practical adaptive coding modulation scheme to approach the capacity of free-space optical (FSO) channels with intensity modulation/direct detection based on probabilistic shaping. The encoder efficiently adapts the transmission rate to the signal-to-noise ratio, accounting for the fading induced by the atmospheric turbulence. The transponder can support an arbitrarily large number of transmission modes using a low complexity channel encoder with a small set of supported rates. Hence, it can provide a solution for FSO backhauling in terrestrial and satellite communication systems to achieve higher spectral efficiency. We propose two algorithms to determine the capacity and capacity-achieving distribution of the scheme with unipolar M-ary pulse amplitude modulation (M-PAM) signaling. Then, the signal constellation is probabilistically shaped according to the optimal distribution, and the shaped signal is channel encoded by an efficient binary forward error correction scheme. Extensive numerical results and simulations are provided to evaluate the performance. The proposed scheme yields a rate close to the tightest lower bound on the capacity of FSO channels. For instance, the coded modulator operates within 0.2 dB from the M-PAM capacity, and it outperforms uniform signaling with more than 1.7 dB, at a transmission rate of 3 bits per channel use.
