Full-duplex dynamic TDMA scheme and clock synchronization and compensation method for the multi-user UWOC system

Area of Science:

• Underwater Wireless Optical Communication (UWOC)
• Optical Networking
• Wireless Communication Systems

Background:

• Underwater wireless optical communication (UWOC) faces challenges in achieving high throughput and reliable full-duplex communication.
• Existing time division multiple access (TDMA) schemes may not efficiently handle variable communication demands among multiple users.

Purpose of the Study:

• To propose a novel full-duplex dynamic time division multiple access (FDD-TDMA) scheme for multi-user UWOC systems.
• To enhance system throughput and achieve precise clock synchronization in UWOC.
• To demonstrate the effectiveness of the proposed scheme in a practical experimental setup.

Main Methods:

• Implementation of a full-duplex communication scheme using wavelength division duplex (WDD).
• Dynamic time resource allocation to enhance system throughput.
• Development and application of a clock synchronization and compensation method for precise timing.
• Establishment of a two-user UWOC system utilizing on-off keying (OOK) modulation.

Main Results:

• Achieved data rates of 25 Mbps without error codes and 40 Mbps with a bit error rate (BER) below the forward error correction (FEC) limit.
• Demonstrated significant improvement in system throughput compared to conventional TDMA, especially under variable user demands.
• Reduced phase deviations from microseconds to ten nanoseconds using the proposed clock synchronization method.

Conclusions:

• The proposed FDD-TDMA scheme effectively supports full-duplex communication and enhances throughput in multi-user UWOC systems.
• The clock synchronization and compensation method ensures precise timing, crucial for reliable optical communication.
• The experimental validation in a 10m water pool confirms the system's performance and potential for practical applications.