Direct-adaptation based bidirectional turbo equalization for underwater acoustic communications: Algorithm and...

Area of Science:

• Underwater Acoustic Communications
• Signal Processing
• Digital Communications

Background:

• Direct-adaptation based turbo equalizers (DA-TEQ) offer good performance for underwater acoustic communications but suffer from slow convergence and error propagation.
• These limitations hinder the practical application of DA-TEQ in challenging underwater environments.

Purpose of the Study:

• To propose a novel direct-adaptation based bidirectional turbo equalizer (DA-BTEQ) for enhanced underwater acoustic communication systems.
• To improve convergence rates and mitigate error propagation effects inherent in traditional turbo equalizers.

Main Methods:

• Developed a DA-BTEQ by integrating forward and backward DA-TEQ structures to leverage bidirectional diversity gain.
• Derived a general symbol combining scheme using the minimum mean square error criterion, suitable for high-order modulations.
• Validated the DA-BTEQ using undersea trial data from a March 2017 experiment in Jiaozhou Bay.

Main Results:

• The DA-BTEQ effectively combats error propagation, a significant issue in underwater acoustic channels.
• Demonstrated superior symbol detection performance compared to traditional single-direction DA-TEQ systems.
• The proposed equalizer showed significant improvements for both single-input multiple-output (SIMO) and single-input single-output (SISO) systems.

Conclusions:

• The DA-BTEQ offers a robust solution for improving the reliability and efficiency of underwater acoustic communications.
• The bidirectional approach effectively overcomes the limitations of conventional single-direction turbo equalizers.
• This advancement holds promise for more stable and high-performance data transmission in underwater environments.