Abstract: An acoustic communication and messaging system includes an acoustic transducer adapted for communicating signals via a subsurface acoustic medium, and a controller in communication with the acoustic transducer. The controller can include one or more of a signal programmer adapted for defining a limited set of coded signals; e.g., where each of the coded signals selected for low cross-correlation with other coded signals in the limited set, and a signal encoder adapted for defining a set of messages or commands; e.g., where each message is associated with a selected one of the coded signals in the limited set. The acoustic transducer can be adapted to transmit the coded signals associated with identified messages via the subsurface acoustic medium. An interface can be provided for identifying messages for coding and transmission, and for reporting decoded commands to a user.

Abstract: An acoustic communication and messaging system includes an acoustic transducer adapted for communicating signals via a subsurface acoustic medium, and a controller in communication with the acoustic transducer. The controller can include one or more of a signal programmer adapted for defining a limited set of coded signals; e.g., where each of the coded signals selected for low cross-correlation with other coded signals in the limited set, and a signal encoder adapted for defining a set of messages or commands; e.g., where each message is associated with a selected one of the coded signals in the limited set. The acoustic transducer can be adapted to transmit the coded signals associated with identified messages via the subsurface acoustic medium. An interface can be provided for identifying messages for coding and transmission, and for reporting decoded commands to a user.

Abstract: A two-tier communication system for a seismic streamer. The communication system operates over an unshielded twisted-pair communication line extending the length of the streamer. Repeater units having a repeater function and a device controller function divide the twisted pair into line segments. Coils on each segment couple signals inductively to collocated external devices in a low-speed 2400 baud FSK data link between the devices and an associated device controller. A Gaussian 8-level FSK high-speed 60 kbit/s data link is established along all the segments with the repeaters re-transmitting boosted signals along the entire length of the communication line. The coils are transparent at the high-speed data rate. Time division multiple access (TDMA) or frequency division multiple access (FDMA) is used to accommodate the two links on the single twisted pair.

Abstract: A two-tier communication system for a seismic streamer. The communication system operates over an unshielded twisted-pair communication line extending the length of the streamer. Repeater units having a repeater function and a device controller function divide the twisted pair into line segments. Coils on each segment couple signals inductively to collocated external devices in a low-speed 2400 baud FSK data link between the devices and an associated device controller. A Gaussian 8-level FSK high-speed 60 kbit/s data link is established along all the segments with the repeaters re-transmitting boosted signals along the entire length of the communication line. The coils are transparent at the high-speed data rate. Time division multiple access (TDMA) or frequency division multiple access (FDMA) is used to accommodate the two links on the single twisted pair.

Abstract: Apparatus and methods for improving signal detection and tracking in underwater acoustic devices receiving a set of acoustic pulses propagated in response to repetitive synchronizing events. Each of the set of pulses is correlated with a replica of each pulse in a receiver in the underwater devices during an associated time window. The correlated output of the receiver is compared to an adjustable threshold characteristic in a detector for selection of the actual pulse according to predetermined criteria for each of the set of pulses. An actual time of reception relative to the synchronizing event is assigned to the selected pulse. Previous actual times of reception are used to estimate the expected time of reception of the associated pulse relative to the next synchronizing event. The estimate is used to adjust the associated time window to encompass the expected time of reception.