Simple Watermarking for ASW Multistatic Improvement (SWAMI)

The U.S. Navy seeks to improve air ASW multistatic systems by adding watermarks to transmit signals, increasing the number of simultaneously active sources during multiple-input multiple-output (MIMO) operations.  These watermarks, and the accompanying signal processing techniques, are conceived to: eliminate ambiguities when associating direct arrivals and echoes to the sources that caused them, enable acoustic communications to submerged friendly assets, and support authentication of multistatic transmissions.  Signal Systems Corporation is proposing several watermarking approaches specially designed for workhorse air ASW multistatic wide area search waveforms – continuous wave (CW) and hyperbolic frequency modulation (HFM) – that minimizes changes to existing hardware and software.  Increasing the number of simultaneously active sources, along with the ability to reliably assign echoes to the correct sources, will significantly reduce search times, increase the likelihood of multi-post detections on a single MIMO ping, and improve target localization area of uncertainty (AOU).  Watermarked direct transmissions also provide a new acoustic communications capability, allowing updated targeting information from continuing search pings to be relayed to submerged friendly assets during subsequent stages of prosecution.