# Performance Analysis of LDPC-Coded OFDM in Underwater Wireless Optical Communications

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## Abstract

**:**

## 1. Introduction

- (1)
- A modulation channel model is established to bridge the EW turbulence channel and the received signal for the simulation;
- (2)
- The bit error ratio (BER) performance is quantified with respect to the scintillation coefficient, signal-to-noise ratio (SNR), length of LDPC, order, and mode of the subcarriers in OFDM.

## 2. System Block Diagram and Channel Model

#### 2.1. System Block Diagram

#### 2.2. Underwater Optical Channel

#### 2.3. Modulation Channel

## 3. Performance Analysis and Simulation

#### 3.1. Performance Evaluation and Parameter Setting

#### 3.2. Simulation Results

^{−6}even without error correction codes and can achieve reliable communication so long as the SNR is large enough. From the figures, it can be seen that the QAM-OFDM has better performance than the PSK-OFDM. There is an interesting phenomenon where even though the BER performance of the 16QAM-OFDM is slightly better than that of the 16PSK-OFDM, the LDPC-coded 16QAM-OFDM has a BER performance much better than the LDPC-coded 16PSK-OFDM, and this will be interpreted in the subsequent section of discussion.

^{−6}, even without error correction codes, and can achieve reliable communication so long as the SNR is large enough.

^{−6}. However, under this condition, even the LDPC-coded OFDM system of 16PSK or 16QAM subcarriers is still unable to reduce the BER to 10

^{−6}or less, only the LDPC-coded 4PSK-OFDM system can do that.

^{−6}for the OFDM system of subcarriers, 16PSK and 16QAM, and cannot achieve reliable communication. However, the LDPC-coded 16QAM-OFDM system can achieve reliable communication; the BER curve goes down quickly like a waterfall. At SNR = 12, especially, the LDPC-coded 16QAM-OFDM system decreases the BER by four orders of magnitude over the 16QAM-OFDM system.

#### 3.3. Comparison and Analysis

## 4. Discussion

## 5. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## Appendix A

## References

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## Share and Cite

**MDPI and ACS Style**

Guo, J.; Xiao, J.; Chen, J.; Shan, X.; Kong, D.; Wu, Y.; Ai, Y.
Performance Analysis of LDPC-Coded OFDM in Underwater Wireless Optical Communications. *Photonics* **2023**, *10*, 330.
https://doi.org/10.3390/photonics10030330

**AMA Style**

Guo J, Xiao J, Chen J, Shan X, Kong D, Wu Y, Ai Y.
Performance Analysis of LDPC-Coded OFDM in Underwater Wireless Optical Communications. *Photonics*. 2023; 10(3):330.
https://doi.org/10.3390/photonics10030330

**Chicago/Turabian Style**

Guo, Jianzhong, Jinpeng Xiao, Jing Chen, Xin Shan, Dejin Kong, Yan Wu, and Yong Ai.
2023. "Performance Analysis of LDPC-Coded OFDM in Underwater Wireless Optical Communications" *Photonics* 10, no. 3: 330.
https://doi.org/10.3390/photonics10030330