Xi Junyi, Yan Shefeng, Xu Lijun
Institute of Acoustics, Chinese Academy of Sciences, Beijing, 100190, People's Republic of China.
J Acoust Soc Am. 2018 May;143(5):2715. doi: 10.1121/1.5036730.
The direct-adaptation based turbo equalizer (DA-TEQ) has been widely studied for underwater acoustic communications due to its decent performance and simple implementation. However, there are still some inherent problems that limit its practical application, such as slow convergence rate and error propagation effect. In this paper, a direct-adaptation based bidirectional turbo equalizer (DA-BTEQ) is proposed for underwater acoustic communications. The proposed scheme incorporates a forward DA-TEQ with a backward DA-TEQ to exploit bidirectional diversity gain and combat error propagation, thereby enabling faster convergence rate and better symbol detection performance. A general symbol combining scheme, which is suitable for turbo equalizers with high-order modulations, is derived by using the minimum mean square error criterion. The proposed scheme has been tested by the undersea trial data collected in an experiment conducted at the coast of Jiaozhou Bay in March 2017. The results demonstrate that the DA-BTEQ is effective against error propagation and clearly outperforms the traditional single-direction DA-TEQ for both single-input multiple-output and single-input single-output systems.
基于直接自适应的Turbo均衡器（DA - TEQ）因其性能良好且实现简单，在水声通信中得到了广泛研究。然而，仍存在一些固有问题限制其实际应用，如收敛速度慢和误差传播效应。本文提出了一种用于水声通信的基于直接自适应的双向Turbo均衡器（DA - BTEQ）。该方案将前向DA - TEQ与后向DA - TEQ相结合，以利用双向分集增益并对抗误差传播，从而实现更快的收敛速度和更好的符号检测性能。通过使用最小均方误差准则，推导了一种适用于高阶调制Turbo均衡器的通用符号组合方案。该方案已通过2017年3月在胶州湾海岸进行的一次实验中收集的海底试验数据进行了测试。结果表明，DA - BTEQ对误差传播有效，并且在单输入多输出和单输入单输出系统中均明显优于传统的单向DA - TEQ。
