The invention is a system comprising a wire cage crustacean trap coupled to a remotely controlled subsystem operative to receive a control-coded acoustic signal and thereupon open an electrically controlled pneumatic valve allowing gas under pressure to be conveyed to a deflated bladder, such that the bladder inflates and brings the system to the surface. Backup systems will cause the valve to open when a preprogrammed time duration has elapsed and/or when a water leak is detected inside the remotely controlled subsystems water-tight container.

The invention is a system comprising a wire cage crustacean trap coupled to a remotely controlled subsystem operative to receive a control-coded acoustic signal and thereupon open an electrically controlled pneumatic valve allowing gas under pressure to be conveyed to a deflated bladder, such that the bladder inflates and brings the system to the surface. Backup systems will cause the valve to open when a preprogrammed time duration has elapsed and/or when a water leak is detected inside the remotely controlled subsystems water-tight container.

The invention relates to a system (2), having: a buoyant buoy (4), and a floating hose (6) which has a plurality of buoyant hose segments (8) which are coupled in series. The buoy (4) has a liquid outlet connection (12) which is connected to the floating hose (6), so that the floating hose (6) is arranged in a geometrical arrangement with respect to the buoy (4). A plurality of node units (18) are fastened in a distributed manner to the floating hose (6) and the buoy (4). Each node unit (18) is designed to establish, by means of an associated radio unit, a respective radio link (22, 24, 26, 28) to each of at least two of the further radio units of the respective node units (18, 42, 44, 46, 48), so that a radio network (30) is created. Each node unit (18) is designed to determine a relative distance (32, 34, 36, 38) from each further node unit (18) on the basis of the respective radio link.

The present disclosure provides a method for optimizing a protograph-based LDPC code over an underwater acoustic (UAW) channel. The traditional protograph-based LDPC code over an UAW channel does not consider performance in an error floor region. The method first determines parameters such as a protograph-based LDPC code length, a basic protograph, a target decoding threshold, a threshold adjustment factor, and an ACE check parameter. The protograph is optimized, and the method constructs a parity check matrix by using a UAW channel-based PEG/ACE hybrid algorithm, performs ACE check on the parity check matrix, and calculates a decoding threshold for the matrix passing the check. If the decoding threshold is within a range of an iterative decoding threshold, the parity check matrix is a final optimized matrix. Otherwise, the method continues to optimize the protograph until a parity check matrix passing the check is obtained.

The present disclosure provides a method for optimizing a protograph-based LDPC code over an underwater acoustic (UAW) channel. The traditional protograph-based LDPC code over an UAW channel does not consider performance in an error floor region. The method first determines parameters such as a protograph-based LDPC code length, a basic protograph, a target decoding threshold, a threshold adjustment factor, and an ACE check parameter. The protograph is optimized, and the method constructs a parity check matrix by using a UAW channel-based PEG/ACE hybrid algorithm, performs ACE check on the parity check matrix, and calculates a decoding threshold for the matrix passing the check. If the decoding threshold is within a range of an iterative decoding threshold, the parity check matrix is a final optimized matrix. Otherwise, the method continues to optimize the protograph until a parity check matrix passing the check is obtained.

Embodiments disclosed herein may be implemented in the form of a method or corresponding apparatus for receiving or transmitting network communications carried at acoustic wavelengths via an acoustic medium. The corresponding method or apparatus may include a gate-level digital hardware module communicatively coupled to a communications module and define therein logic blocks configured to perform respective primitive processing functions, sequences of the logic blocks being capable of processing data units in accordance with any of the multiple communications protocols on a data unit-by-data unit basis without reconfiguring. According to some embodiments, the gate-level digital hardware module may be configured to process a data unit in accordance with a first communications protocol by directing the data unit through a first sequence of logic blocks, and process a subsequent data unit in accordance with a second communications protocol by directing the subsequent data unit through a second of sequence logic blocks.

Embodiments disclosed herein may be implemented in the form of a method or corresponding apparatus for receiving or transmitting network communications carried at acoustic wavelengths via an acoustic medium. The corresponding method or apparatus may include a gate-level digital hardware module communicatively coupled to a communications module and define therein logic blocks configured to perform respective primitive processing functions, sequences of the logic blocks being capable of processing data units in accordance with any of the multiple communications protocols on a data unit-by-data unit basis without reconfiguring. According to some embodiments, the gate-level digital hardware module may be configured to process a data unit in accordance with a first communications protocol by directing the data unit through a first sequence of logic blocks, and process a subsequent data unit in accordance with a second communications protocol by directing the subsequent data unit through a second of sequence logic blocks.

Methods and apparatus for acoustic to optical communications. In one example, a method includes performing active optical measurements of modulation-based surface deformations at a surface of a body of water using an active optical receiver to produce modulation data, the modulation-based surface deformations being representative of a modulation of a modulated acoustic signal originating beneath the surface of the body of water, between instances of performing the active optical measurements of the modulation-based surface deformations, optically measuring surface conditions of the body of water to produce channel information, and based on the modulation data and the channel information, recovering data encoded in the modulation of the modulated acoustic signal.

Methods and apparatus for acoustic to optical communications. In one example, a method includes performing active optical measurements of modulation-based surface deformations at a surface of a body of water using an active optical receiver to produce modulation data, the modulation-based surface deformations being representative of a modulation of a modulated acoustic signal originating beneath the surface of the body of water, between instances of performing the active optical measurements of the modulation-based surface deformations, optically measuring surface conditions of the body of water to produce channel information, and based on the modulation data and the channel information, recovering data encoded in the modulation of the modulated acoustic signal.

A surface wave launcher surrounds and provides structure complimentary to an antenna and converts (transforms) a near field produced by the antenna into a cylindrical surface wave structure with a strong electric or magnetic field component parallel to a launching interface and propagating two-dimensionally from the launcher. The surface wave launcher leverages the interface found along ocean-air or ground-air to increase a field strength transmitted for a given antenna size and power available. The surface wave launcher maintains a relatively small structure compared to wavelength offering mobility to a very low frequency transmitter. Due to localization of the surface wave energy near the interface, communications using the surface wave retain a desirable low probability of detection.