Abstract: Techniques and systems for robotic aquaculture are described. In one embodiment, for example, a mariculture system may include an aquatic animal containment system operative to hold a population of aquatic animals, the aquatic animal containment system comprising an enclosed hull having a receptacle configured to receive a mechanical core, the mechanical core configured to store at least one sub-system to implement at least one function of mariculture system, and a position management system operative to maintain the enclosed hull at a depth below a surface of a body of water. Other embodiments are described.

Abstract: Techniques and systems for robotic aquaculture are described. In one embodiment, for example, a mariculture system may include an aquatic animal containment system operative to hold a population of aquatic animals, the aquatic animal containment system comprising an enclosed hull having a receptacle configured to receive a mechanical core, the mechanical core configured to store at least one sub-system to implement at least one function of mariculture system, and a position management system operative to maintain the enclosed hull at a depth below a surface of a body of water. Other embodiments are described.

Abstract: Techniques and systems for robotic aquaculture are described. In one embodiment, for example, a mariculture system may include an aquatic animal containment system operative to hold a population of aquatic animals, the aquatic animal containment system comprising an enclosed hull having a receptacle configured to receive a mechanical core, the mechanical core configured to store at least one sub-system to implement at least one function of mariculture system, and a position management system operative to maintain the enclosed hull at a depth below a surface of a body of water. Other embodiments are described.

Abstract: Subject matter disclosed herein relates to random linear network coding schemes for reliable communications for time division duplexing channels. In at least one embodiment, a transmitter node transmits M data packets through a half-duplex link using random linear network coding. The transmitter node transmits coded packets back-to-back through the link before stopping to wait for an acknowledgement (ACK) packet. An optimal number of coded packets Ni to be transmitted in a subsequent transmission may then be determined based, at least in part, on a number of degrees of freedom (DOFs) a receiving node needs to decode the M information packets from received coded packets.

Abstract: A new random linear network coding scheme for reliable communications for time division duplexing channels is proposed. The setup assumes a packet erasure channel and that nodes cannot transmit and receive information simultaneously. The sender transmits coded data packets back-to-back before stopping to wait for the receiver to acknowledge (ACK) the number of degrees of freedom, if any, that are required to decode correctly the information. Provided herein is an analysis of this problem to show that there is an optimal number of coded data packets, in terms of mean completion time, to be sent before stopping to listen. This number depends on the latency, probabilities of packet erasure and ACK erasure, and the number of degrees of freedom that the receiver requires to decode the data. This scheme is optimal in terms of the mean time to complete the transmission of a fixed number of data packets.

Abstract: Subject matter disclosed herein relates to random linear network coding schemes for reliable communications for time division duplexing channels. In at least one embodiment, a transmitter node transmits M data packets through a half-duplex link using random linear network coding. The transmitter node transmits coded packets back-to-back through the link before stopping to wait for an acknowledgement (ACK) packet. An optimal number of coded packets Ni to be transmitted in a subsequent transmission may then be determined based, at least in part, on a number of degrees of freedom (DOFs) a receiving node needs to decode the M information packets from received coded packets.

Abstract: Advantageous OFDM-based underwater acoustic (UWA) apparatus, systems and methods are provided according to the present disclosure. In general, OFDM transmissions over UWA channels encounter frequency-dependent Doppler drifts that destroy the orthogonality among OFDM subcarriers. The disclosed apparatus, systems, and methods use a two-step approach to mitigate frequency-dependent Doppler drifts for zero-padded OFDM transmissions over fast-varying channels: (1) non-uniform Doppler compensation via resampling to convert a “wideband” problem into a “narrowband” problem; and (2) high-resolution uniform compensation on the residual Doppler. The disclosed apparatus, systems and methods are based on block-by-block processing and do not rely on channel dependence across OFDM blocks. Thus, the disclosed apparatus, systems and methods are advantageously applicable for fast-varying UWA channels.

Abstract: Described is a method for compensation of an OFDM signal propagating through Doppler-distorted, time-varying multipath channels. The method is based on low-complexity post-FFT signal processing. Minimum mean square error combining of signals is performed for signals received at spatially-distributed receiver elements using adaptive channel estimation and phase tracking. Doppler shifts are modeled as a consequence of motion-induced time compression and dilation. The Doppler rate is assumed constant over one OFDM block but can vary between OFDM blocks. Thus a non-constant Doppler shift is accommodated by the method. Non-uniform Doppler compensation across subchannels is based on adaptive estimation and prediction of the Doppler rate. A single adaptively estimated parameter is used to track the phases of all the carriers and channel estimates are updated on a block by block basis.

Abstract: A new random linear network coding scheme for reliable communications for time division duplexing channels is proposed. The setup assumes a packet erasure channel and that nodes cannot transmit and receive information simultaneously. The sender transmits coded data packets back-to-back before stopping to wait for the receiver to acknowledge (ACK) the number of degrees of freedom, if any, that are required to decode correctly the information. Provided herein is an analysis of this problem to show that there is an optimal number of coded data packets, in terms of mean completion time, to be sent before stopping to listen. This number depends on the latency, probabilities of packet erasure and ACK erasure, and the number of degrees of freedom that the receiver requires to decode the data. This scheme is optimal in terms of the mean time to complete the transmission of a fixed number of data packets.

Abstract: Advantageous OFDM-based underwater acoustic (UWA) apparatus, systems and methods are provided according to the present disclosure. In general, OFDM transmissions over UWA channels encounter frequency-dependent Doppler drifts that destroy the orthogonality among OFDM subcarriers. The disclosed apparatus, systems, and methods use a two-step approach to mitigate frequency-dependent Doppler drifts for zero-padded OFDM transmissions over fast-varying channels: (1) non-uniform Doppler compensation via resampling to convert a “wideband” problem into a “narrowband” problem; and (2) high-resolution uniform compensation on the residual Doppler. The disclosed apparatus, systems and methods are based on block-by-block processing and do not rely on channel dependence across OFDM blocks. Thus, the disclosed apparatus, systems and methods are advantageously applicable for fast-varying UWA channels.

Abstract: Described is a method for compensation of an OFDM signal propagating through Doppler-distorted, time-varying multipath channels. The method is based on low-complexity post-FFT signal processing. Minimum mean square error combining of signals is performed for signals received at spatially-distributed receiver elements using adaptive channel estimation and phase tracking. Doppler shifts are modeled as a consequence of motion-induced time compression and dilation. The Doppler rate is assumed constant over one OFDM block but can vary between OFDM blocks. Thus a non-constant Doppler shift is accommodated by the method. Non-uniform Doppler compensation across subchannels is based on adaptive estimation and prediction of the Doppler rate. A single adaptively estimated parameter is used to track the phases of all the carriers and channel estimates are updated on a block by block basis.

Abstract: A method and apparatus for multichannel combining and equalization in a multichannel receiver is described. The receiver jointly performs diversity combining, equalization and synchronization. The method and apparatus of the present invention may be used to provide a reduced complexity adaptive multichannel receiver for use in a digital communication system.

Abstract: An underwater acoustic communications system utilizes phase coherent modulation and demodulation in which high data rates are achieved through the use of rapid Doppler removal, a specialized sample timing control technique and decision feedback equalization including feedforward and feedback equalizers. The combined use of these techniques drammatically increases data rates by one and sometimes two orders of magnitude over traditional FSK systems by sucessfully combating fading and multipath problems associated with a rapidly changing underwater acoustic channel that produce intersymbol interference and make timing optimization for the sampling of incomming data impossible.