Leveraging spatial diversity to mitigate partial band interference in undersea networks through waveform reconstruction

Abstract

Many acoustic channels suffer from interference which is neither narrowband nor impulsive. This relatively long duration partial band interference can be particularly detrimental to system performance. We survey recent work in interference mitigation as background motivation to develop a spatial diversity receiver for use in underwater networks. The network consists of multiple distributed cabled hydrophones that receive data transmitted over a timevarying multipath channel in the presence of partial band interference produced by interfering active sonar signals as well as marine mammal vocalizations. In operational networks, many "dropped" messages are lost due to partial band interference which corrupts different portions of the received signal depending on the relative position of the interferers, information source and receivers due to the slow speed of propagation. Our algorithm has been tested on simulated data and is shown to work on an example from a recent undersea experiment.

Robust Noncooperative Spectrum Sharing Game in Underwater Acoustic Interference Channels

“…In the absence of regulation, the simultaneous anarchical access to the UA channel by several sources can lead to mutual interference that degrades the reliability of communication systems. Several examples of jamming by external sound sources have been reported in the recent literature [6], [7]. As the ongoing and future development of underwater applications is likely to increase the anthropogenic acoustic noise [8], there is an NEed for better coexistence of various sound sources in the UA transmission channel.…”

Interference suppression in congested undersea environments

“…The degradation in the received signal is highly variable, depending on the relative position of the interfering signals, information source and receivers as well as the channel conditions. Successful steps to mitigate interference using a single receiver have been reported in [2], and the potential of using multiple receivers to mitigate interference was demonstrated in [3]. The motivation behind this work is to compare the potential benefits that each mitigation strategy provides.…”

“…The PIC algorithm explicitly canceled the interference without information loss or performance degradation caused by approximations. In [3] we developed a multi-receiver algorithm that relied on the spatial diversity inherent in an acoustic network to facilitate the reconstruction of the transmitted waveform from the clean portions of the received signals. Our algorithm also relied on the known time duration and bandwidth of the interference to perform mitigation.…”

“…While both approaches rely on prior knowledge of the interference band and time duration, the techniques differ in the use of the knowledge. In [2] prior knowledge aids in the estimation of the interference parameters and facilitates coherent cancellation where as in [3] prior knowledge facilitates the detection and excision of portions of the received signal that suffer from interference. For both approaches, knowledge of the interference parameters does not need to be particularly precise and can be determined in situ.…”

A Comparison of a Single Receiver and a Multi-Receiver Techniques to Mitigate Partial Band Interference

“…The PIC algorithm explicitly cancelled the interference without information loss or performance degradation caused by approximations. In [3] we developed a multi-receiver algorithm that relied on the spatial diversity inherent in an acoustic network to facilitate the reconstruction of the transmitted waveform from the clean portions of the received signals. Our algorithm also relied on the known time duration and bandwidth of the interference to perform mitigation.…”