Li Ang, Wang Ping, Pang Weina, Chen Wenwen, Liu Sheng, Guo Lixin
Appl Opt. 2020 Feb 10;59(5):1353-1362. doi: 10.1364/AO.59.001353.
The average bit error rate (ABER) performance of a low-density parity-check (LDPC)-coded multi-hop parallel underwater wireless optical communication (UWOC) system is investigated with the combined effects of absorption, scattering, the misalignment characterized by the beam spread function, and the ocean turbulence-induced fading modeled by log-normal distribution. With the max-min criterion as the best path selection scheme, the cumulative distribution function for identically and independently distributed and non-identically and independently distributed links are derived, respectively. Then, the analytical ABER expressions of binary phase shift keying and multiple phase shift keying subcarrier intensity modulation schemes are deduced with the help of the Gauss-Laguerre quadrature rule, and they are also confirmed by Monte Carlo simulation. In addition, LDPC codes are applied in the simulation to improve the system performance. The results show that the combined degrading effects are mainly limited by the link length, especially under the coastal ocean condition. And the multi-hop parallel transmission demonstrates good ABER performance and can expand the communication range in ocean. Furthermore, LDPC codes can significantly improve the ABER performance of the UWOC system, and the coding gain is strongly affected by channel conditions and the corresponding parameters of LDPC codes. This work is beneficial for the UWOC system design.
研究了低密度奇偶校验（LDPC）编码的多跳并行水下无线光通信（UWOC）系统在吸收、散射、由光束扩展函数表征的失准以及由对数正态分布建模的海洋湍流引起的衰落等综合影响下的平均误码率（ABER）性能。以最大最小准则作为最佳路径选择方案，分别推导了同分布且独立分布链路以及非同分布且独立分布链路的累积分布函数。然后，借助高斯 - 拉盖尔求积法则推导了二进制相移键控和多进制相移键控子载波强度调制方案的解析ABER表达式，并通过蒙特卡罗仿真进行了验证。此外，在仿真中应用LDPC码以提高系统性能。结果表明，综合退化效应主要受链路长度限制，特别是在近岸海洋条件下。并且多跳并行传输展现出良好的ABER性能，能够扩展海洋中的通信范围。此外，LDPC码可以显著提高UWOC系统的ABER性能，编码增益受信道条件和LDPC码相应参数的强烈影响。这项工作对UWOC系统设计有益。
