Self-Interference Channel Characterization in Underwater Acoustic In-Band Full-Duplex Communications Using OFDM
Self-Interference Channel Characterization in Underwater Acoustic In-Band Full-Duplex Communications Using OFDM
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DOI：
10.1109/ieeeconf38699.2020.9389027
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发表时间：
2020-05
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影响因子：
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通讯作者：
Mohammad Towliat;Zheng Guo;L. Cimini;X. Xia;A. Song
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文献类型：
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作者：
Mohammad Towliat;Zheng Guo;L. Cimini;X. Xia;A. Song
由于有限的可用带宽和动态信道，水声通信的数据传输速率受到极大限制。为了解决这一问题，带内全双工（IBFD）有可能在给定带宽下将效率提高一倍。在IBFD方案中，在相同频带中同时执行发送和接收。然而，在UWA-IBFD中，由于来自表面和底部的反射以及水的不均匀性，发射信号的很大一部分返回到IBFD接收器。该信号污染了来自远端的期望信号，并且被称为自干扰（SI）。利用自干扰信道脉冲响应（SCIR）的估计，接收机可以估计并消除SI。更好地理解SCIR的统计特性对于精确的SI消除是必要的。在这篇文章中，我们使用正交频分复用（OFDM）信号来表征在湖水实验中的SCIR。为了验证结果，SCIR估计进行使用估计器在频域和时域。我们表明，在我们的实验中，无论水听器的深度如何，SCIR的直接路径都很强、稳定且易于跟踪;然而，反射路径较弱且快速时变，使得SI抵消具有挑战性。在反射中，从水面的第一次反弹是具有约70 ms的短相干时间的普遍路径。
Due to the limited available bandwidth and dynamic channel, data rates are extremely limited in underwater acoustic (UWA) communications. Addressing this concern, in-band full-duplex (IBFD) has the potential to double the efficiency in a given bandwidth. In an IBFD scheme, transmission and reception are performed simultaneously in the same frequency band. However, in UWA-IBFD, because of reflections from the surface and bottom and the inhomogeneity of the water, a significant part of the transmitted signal returns back to the IBFD receiver. This signal contaminates the desired signal from the remote end and is known as the self-interference (SI). With an estimate of the self-interference channel impulse response (SCIR), a receiver can estimate and eliminate the SI. A better understanding of the statistical characteristics of the SCIR is necessary for an accurate SI cancellation. In this article, we use an orthogonal frequency division multiplexing (OFDM) signal to characterize the SCIR in a lake water experiment. To verify the results, SCIR estimation is performed by using estimators in both the frequency and time domains. We show that, in our experiment, regardless of the depth of hydrophone, the direct path of SCIR is strong, stable and easily tracked; however, the reflection paths are weaker and rapidly time-varying making SI cancellation challenging. Among the reflections, the first bounce from the water surface is the prevalent path with a short coherence time around 70 ms.