Study of Joint LDPC and PNC Coding-Decoding for Underwater Relay Optical Communication

LI Yanlong; GU Chengyu; JIANG Pengcheng; WANG Bing

doi:10.13756/j.gtxyj.2026.250311

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Study of Joint LDPC and PNC Coding-Decoding for Underwater Relay Optical Communication

更新时间：2026-04-20

- Study of Joint LDPC and PNC Coding-Decoding for Underwater Relay Optical Communication
- Study on Optical Communications Issue 2, (2026)
- 作者机构：
  
  a.桂林电子科技大学　认知无线电与信息处理教育部重点实验室，广西　桂林　541004
  b.桂林电子科技大学　广西无线宽带通信与信号处理重点实验室，广西　桂林　541004
- 作者简介：
- 基金信息：
- DOI：10.13756/j.gtxyj.2026.250311
  CLC： TN929
- Received：22 September 2025，
  
  Revised：2025-11-24，
  
  Published：10 April 2026
- 稿件说明：
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李燕龙，谷城雨，蒋鹏铖，等. 水下中继光通信中LDPC与PNC联合编译码研究[J]. 光通信研究，2026(2): 250311.

Li Y L, Gu C Y, Jiang P C, et al. Study of Joint LDPC and PNC Coding-Decoding for Underwater Relay Optical Communication[J]. Study on Optical Communications, 2026(2): 250311.
李燕龙，谷城雨，蒋鹏铖，等. 水下中继光通信中LDPC与PNC联合编译码研究[J]. 光通信研究，2026(2): 250311. DOI： 10.13756/j.gtxyj.2026.250311.

Li Y L, Gu C Y, Jiang P C, et al. Study of Joint LDPC and PNC Coding-Decoding for Underwater Relay Optical Communication[J]. Study on Optical Communications, 2026(2): 250311. DOI： 10.13756/j.gtxyj.2026.250311.

摘要

目的

水下无线光通信（UWOC）具有高速率低时延等优势，物理层网络编码（PNC）能有效降低中继光通信系统转发时延，然而水下湍流引起的信道不对称性使得中继叠加信号星座点发生混叠，导致了PNC映射歧义问题。文章研究了UWOC 3用户联合低密度奇偶校验（LDPC）编码的PNC算法，旨在提升系统在不对称信道下的鲁棒性与吞吐量性能。

方法

文章对比分析了不同的LDPC-PNC联合编译码架构，并根据信道直流（DC）增益调节各用户的发射功率，提出了基于功率分配与联合LDPC译码的4时隙PNC（FT-PA-JCNC）算法，以减小中继处各路接收功率的差异，增强基于对数似然比（LLR）的LDPC译码软信息的可靠性。

结果

仿真结果表明，文章所提方法与未编码的PNC相比，在前向纠错（FEC）门限处可带来约4.0 dB的信噪比（SNR）提升。与其他常见联合译码方案进行对比，文章所提算法具有最佳的误码率（BER）性能。在室内测试中，系统平台增加单个中继节点与两用户直连相比，可使端到端传输距离延长82.98%。在水下测试中可在8.62 m距离下实现5 Mbit/s的传输速率。

结论

研究表明，引入功率分配策略能有效减小信道不对称导致的映射模糊问题，优化联合编译码处理架构可有效提升BER性能，为UWOC中继系统的设计与优化提供了新思路。

Abstract

Objective

Underwater Wireless Optical Communication (UWOC) offers high data rates and low latency. In addition

Physical-Layer Network Coding (PNC) can effectively reduce the relay forwarding delay. However

turbulence-induced channel asymmetry causes constellation overlap at the relay

producing PNC mapping ambiguity. This work studies a three-user PNC scheme integrated with Low-Density Parity-Check (LDPC) coding for UWOC

aiming to enhance system robustness and throughput under asymmetric underwater channels.

Methods

LDPC-PNC joint coding-decoding architectures are proposed and analyzed

and transmitter powers are adjusted according to per-user channel Direct Current (DC) gains. A Four-Timeslot Power Allocation-based Joint Channel Decoding and PNC (FT-PA-JCNC) algorithm is proposed to reduce the disparities among the relay’s received signal amplitudes and to improve the reliability of Log Likelihood Ratio (LLR) soft inputs for LDPC decoding.

Results

Simulations show that the proposed scheme provides approximately 4.0 dB Signal-to-Noise Ratio (SNR) gain at the Forward Error Correction (FEC) threshold compared with uncoded PNC. The best Bit-Error-Rate (BER) performance is achieved among the considered joint-decoding schemes. In the indoor experiments

the addition of a single relay node increases the end-to-end distance by 82.98% compared to a direct link between two users. In underwater experiments

the system can achieve communication with 5 Mbit/s at distance of 8.62 m.

Conclusion

The study results indicate that introducing a power-allocation strategy can effectively reduce the mapping ambiguity caused by channel asymmetry. Optimizing the joint coding–decoding architecture can significantly improve the BER performance

thereby offering new perspectives for the design and optimization of underwater relay optical communication systems.

关键词

Keywords

references

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