The present application provides an apparatus comprising a radio frequency identification (RFID) sensor comprising: an antenna configured to receive an interrogation signal from a reader and to transmit a response signal to the reader; at least one integrated circuit (IC) connected to the antenna; and at least one sensing element. The apparatus further comprises a channel for directing transmission of signals between the antenna and the reader, wherein the RFID sensor is attached or directly adjacent to a first end of the channel. The sensing element is responsive to a change induced by its environment to switch from a conductive state to a non-conductive state, or from a non-conductive state to a conductive state. The present application further provides a method for monitoring the integrity or the change in environment of a buried structure using the RFID sensor-containing apparatus.

A system for transmitting electrical signals through a terrestrial body, the terrestrial body having an upper surface, may include a transmitter. The transmitter may include a first electrode positioned proximate the upper surface of the terrestrial body and at least one second electrode positioned beneath the upper surface of the terrestrial body and spaced from the first electrode. The system may include a power source operable to supply power to the first electrode and the at least one second electrode. The system may include a receiver assembly spaced away from the transmitter. When power is supplied to the transmitter, the transmitter may be operable to propagate an electric non-linear wave signal through the terrestrial body. The receiver assembly may be operable to detect the electric non-linear wave signal.

A system for transmitting electrical signals through a terrestrial body, the terrestrial body having an upper surface, may include a transmitter. The transmitter may include a first electrode positioned proximate the upper surface of the terrestrial body and at least one second electrode positioned beneath the upper surface of the terrestrial body and spaced from the first electrode. The system may include a power source operable to supply power to the first electrode and the at least one second electrode. The system may include a receiver assembly spaced away from the transmitter. When power is supplied to the transmitter, the transmitter may be operable to propagate an electric non-linear wave signal through the terrestrial body. The receiver assembly may be operable to detect the electric non-linear wave signal.

A method for use in controlling pressure based signal transmission within a fluid in a flowline includes transmitting a pressure based signal through a fluid within a flowline using a flow control device, recognising a condition change associated with the flowline, and then controlling the flow control device in accordance with the condition change. Another method, or an associated method for use in communication within a flowline includes determining or composing an optimised pressure based signal for detection at a remote location and then transmitting the optimised signal using a flow control device.

A method for use in controlling pressure based signal transmission within a fluid in a flowline includes transmitting a pressure based signal through a fluid within a flowline using a flow control device, recognising a condition change associated with the flowline, and then controlling the flow control device in accordance with the condition change. Another method, or an associated method for use in communication within a flowline includes determining or composing an optimised pressure based signal for detection at a remote location and then transmitting the optimised signal using a flow control device.

A first optical communication device is provided with a laser light source 3 for emitting communication light CL and a transmitting optical fiber 11 arranged in water WA and having a light incident end portion 14 on which the communication light CL is incident. The transmitting optical fiber 11 transmits the communication light CL incident on the light incident end portion 14 toward the tip end portion 15. The transmitting optical fiber 11 is provided with a core part 21 configured to transmit the communication light CL from the light incident end portion 14 toward the tip end portion 15 and a clad part 23 covering the core part, the clad part being configured to emit at least a part of the communication light CL that transmits the core part 21 from a side surface of the transmitting optical fiber 11.

A data encoding and decoding method for underwater acoustic networks (UANs) based on an improved online fountain code, including: in a build-up phase, subjecting all original packets to sequential encoding according to their serial numbers to generate and send encoded packets with degree 2; merging k original packets to k/8 connected components with a size of 8; performing random encoding until a largest connected component is successfully decoded; in a completion phase, sending, by a receiver, a feedback packet according to a current decoding graph; according to a feedback packet containing decoding states of all the original packets, sending, by a sender, encoded packets with degree m; and randomly selecting original packets for recursive encoding to generate and send encoded packets with degree 1 or 2; and setting, by the receiver, a threshold to restrict the number of feedback packets.

A data encoding and decoding method for underwater acoustic networks (UANs) based on an improved online fountain code, including: in a build-up phase, subjecting all original packets to sequential encoding according to their serial numbers to generate and send encoded packets with degree 2; merging k original packets to k/8 connected components with a size of 8; performing random encoding until a largest connected component is successfully decoded; in a completion phase, sending, by a receiver, a feedback packet according to a current decoding graph; according to a feedback packet containing decoding states of all the original packets, sending, by a sender, encoded packets with degree m; and randomly selecting original packets for recursive encoding to generate and send encoded packets with degree 1 or 2; and setting, by the receiver, a threshold to restrict the number of feedback packets.

An aquatic environment audio system for communication of wireless audio signals between a smartwatch and headphones worn by a user includes one or more wireless repeaters. Each of the one or more wireless repeaters includes a waterproof housing, an attachment mechanism for attaching the waterproof housing to the user between the smartwatch and the headphones. Each of the one or more wireless repeaters further includes a first antenna for receiving wireless signals from the smartwatch, repeater circuitry coupled with the first antenna for processing the wireless signals received from the smartwatch, and a second antenna coupled with the wireless repeater circuitry for transmitting the processed wireless signals to the headphones. One or more of the first antenna, repeater circuitry, and second antenna are contained in the waterproof housing.

A method, apparatus, system, and computer program product for processing low frequency signals. A communications system comprising a low frequency receiver, a denoiser, and a signal extractor. The low frequency receiver receives low frequency signals in which a communications signal is expected. The denoiser is in communication with the low frequency receiver. The denoiser denoises the low frequency signals received from the low frequency receiver. The denoising results in a generation of denoised signals. The signal extractor in communication with the denoiser. The signal extractor extracts the communications signal from the denoised signal.