DETECTION OF UNDERWATER ACOUSTIC SIGNALS CHALLENGE – INTRODUCTION
The detection of underwater signal is a key enabling technique for any active and passive underwater acoustic sensor applications. Technologies such as SONAR imaging, acoustic communication, depth detectors, and signal identification, all use as a backbone detection capability. Underwater acoustic detection is different from the established radio frequency techniques. Due to the fast-changing sea environment, approaches based on noise estimation face mismatches between the assume noise model and its actual distribution. Further, the significant multipath that arrives closely in time produces negative and positive superposition, which makes it hard to identify the first arrival. And the time-varying-frequency-selective characteristics of the acoustic channel makes it challenging to loc onto the received signal. A simple binary detection is needed to distinguish between noise and signal. Since the distance to the emitter is also of interest, we target not only the detection rate and the false alarm rate, but also the time of detection. In the applications considered, either a template of the signal is known, or neither the structure of the detected signal nor its statistics are known (e.g., duration, carrier frequency, bandwidth, etc.).
In this challenge, we focus on learning techniques for detection of both known and unknown signal templates. The challenge will test the participants’ skills in signal detection, time-delay estimation, and noise-robust decoding under realistic marine acoustic conditions. The challenge will proceed with a tutorial (Monday, Nov. 10th at 16:15-17:00) to expose the participants to detection techniques.
The participants will then divide into groups and will be introduced to the operation of acoustic recording hardware. During the conference, the groups will perform the challenge task using a provided boat in three available slots, and will present their results in a summary event on Friday Nov. 14th, 13:45-14:30. Results will be presented during the conclusion event on Friday Nov. 14th, 19:30-20:30.
The challenge will include two tasks:1) Offline detection of signal of known structure, and 2) Offline detection of signal of unknown structure. Both signals will be transmitted within a time window of 30min.In the known signal case, the groups are required to provide the time of detection for all detection events. At least 5 transmissions will be performed from a second boat at varying source levels. In the unknown signal case, a pinger will emit an acoustic tone at an unknown frequency. Each pinger has a unique ID encoded in the specific interval pattern between its consecutive pings. The teams will be required to decode the pinger’s ID by determining the time intervals between the detected acoustic pulses.