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Improved Frequency Domain Turbo Equalization with Expectation Propagation Interference Cancellation in Underwater
Bin Jiang1,2, Yue Tang1,3, Yinan Zhao1
1School of Communication Engineering, Hangzhou Dianzi University, Hangzhou 310018, China.
Sensors (Basel, Switzerland)
|September 28, 2023
Summary
This study introduces an improved frequency domain turbo equalization (IFDTE) for underwater acoustic communications, enhancing performance and reducing complexity. The new method achieves better bit error rates and faster convergence, making it ideal for UWAC systems.
Area of Science:
- Signal Processing
- Underwater Acoustics
- Communications Engineering
Background:
- Underwater acoustic communication (UWAC) channels are challenging due to multipath propagation and limited bandwidth.
- Traditional equalization methods often struggle to balance performance and computational complexity in UWACs.
- Efficient channel estimation and interference cancellation are critical for reliable UWAC systems.
Purpose of the Study:
- To propose an improved frequency domain turbo equalization (IFDTE) scheme for UWACs.
- To enhance both the performance (bit error rate) and reduce the computational complexity of UWAC systems.
- To develop advanced iterative channel estimation and feedback mechanisms.
Main Methods:
- Utilizing a selective zero-attracting (SZA) improved proportionate normal least mean square (SZA-IPNLMS) algorithm for sparse UWAC channel estimation.
- Employing a set-membership (SM) SZA differential IPNLMS (SM SZA-DIPNLMS) with variable step size for channel status information (CSI) estimation.
- Integrating expectation propagation (EP) interference cancellation within the IFDTE framework for iterative symbol probability estimation.
- Proposing a bidirectional IFDTE with EP interference cancellation to accelerate convergence.
Main Results:
- The proposed channel estimation achieved 1.9 and 0.5 dB gains over IPNLMS and l0-IPNLMS at a 10-3 BER.
- The IFDTE demonstrated performance gains of 0.5-1 dB compared to traditional methods in SPACE'08 and MACE'04 environments.
- The scheme effectively reduces unnecessary UWAC channel coefficient updates.
- Bidirectional IFDTE with EP interference cancellation accelerated convergence.
Conclusions:
- The proposed IFDTE scheme offers a significant improvement in bit error rate performance for UWACs.
- The method achieves low computational complexity, making it suitable for practical UWAC applications.
- Iterative channel estimation with soft feedback and EP interference cancellation are key to the enhanced performance and efficiency.
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