Multiplexing of Circular and Spiral Acoustic Fields with Low Cross-Correlation Signals for Underwater Localization

Abstract

The use of underwater spiral acoustic fields is a promising approach for underwater unmanned vehicle (UUV) localization. This technique relies on the transmission of both circular and spiral acoustic fields, enabling the estimation of the departure bearing angle through their phase difference. However, the accuracy of this estimation is strongly influenced by the characteristics of the underwater acoustic channel and the multiplexing strategy employed. This work introduces a novel multiplexing technique for circular and spiral acoustic fields based on low cross-correlation signals. The proposed method is experimentally validated in a pool using a beacon setup consisting of a static spiral acoustic source and a single mobile hydrophone, whose position is acoustically estimated. Ground-truth localization is obtained from top-view video recordings of the pool. Three multiplexing strategies are evaluated and compared: time-frequency division multiplexing (TFDM), code division multiplexing (CDM), and X-division multiplexing (XDM). In general, experimental results show good agreement between estimated and ground-truth azimuth values. However, azimuth estimation accuracy and dispersion differ significantly: TFDM and XDM exhibit lower accuracy and higher variance compared to CDM approaches, while both CDM variants demonstrate consistent and superior angular performance. Overall, the results indicate that CDM-based multiplexing of circular and spiral fields is a promising candidate to enable simultaneous data transmission and single-receiver localization using a spiral source.