937 results about "Underwater acoustic communication" patented technology

The systems and methods of the invention provide for improved underwater communication systems. In particular, the systems and methods of the invention provide for improved underwater optical modems including optical transmitters and optical receivers that allow omni-directional transmission and reception of optical signals underwater and having a range of about 100 m and allowing data rates greater than 1 Mbit / s. The systems and methods of the invention also provide for underwater communication networks having a plurality of optical modems communicating with each other.

The invention discloses a penetration probe-based deep sea multi-element comprehensive observation system, which comprises an upper computer and a data recovery cabin, wherein the upper end and the lower end of the data recovery cabin are connected with a probe rod through a hydraulic separation releaser and a launching device respectively; a small-sized pile driver is arranged in the launching device; the launching device is provided with an underwater search light, an underwater camera and an underwater acoustic communication transceiver; the top of the data recovery cabin is provided with a floating body; a central controller is included in the data recovery cabin; the outer side face of the data recovery cabin is provided with an underwater acoustic transducer; and the outer surface of the probe rod is provided with more than 10 annular electrodes and more than 2 pore water pressure sensors which are connected with the central controller. The system has a simple structure, is reliable in work and accurate in control, can carry various sensors and adapt to a deep sea high pressure environment, and can synchronously and automatically observe and record states and changes of sea water and sediments within a 10m depth range close to a sea water-sediment interface with over 2,000m water depth, including the state of sediments of 6-7m below a sea bottom surface, the condition ofsea water of a bottom layer of 3-4m above the sea bottom surface and the dynamic change in position of the sea bottom surface.

The invention relates to a method for recognizing an underwater acoustic communication modulation mode based on a deep learning technique. The method comprises the following steps: constructing a deeplearning convolutional neural network model; presetting a training set sample recognition accuracy rate T and a testing set sample recognition accuracy rate P; acquiring experimental data or simulation data in different modulation modes; carrying out pretreatment by taking N sampling point data as an original data sample; randomly dividing pretreated data samples into a training set and a testingset; training the data by virtue of a training sample set; judging whether the training set sample recognition accuracy rate reaches a preset value, if yes, switching input into a data sample testingset, and testing by virtue of the data sample testing set; otherwise, continuing to train; judging whether the testing set sample recognition accuracy rate reaches a preset value, and if yes, finishing the model; and other wise, acquiring extra data, mixing with the original data, and repeatedly carrying out the method. According to the method, the difficult extraction of signal features caused due to time variation and space variation of an ocean channel is solved.

A method of optical underwater communications comprises applying a Fountain code to a plurality of data blocks. A sequence of optical data packets is transmitted through an underwater communications channel. Each optical data packet comprises one of the plurality of data blocks preceded by a preamble. The sequence of optical data packets transmitted through the underwater communication channel is received to generate a sequence of received data packets. The sequence of received data packets is sampled with the sampling clock to recover the plurality of data blocks.

A subsea production system adapted for wireless communication so that production tree operation can be controlled locally wirelessly from a workover umbilical or remotely controlled vehicle. The production system includes a wellhead assembly and an umbilical termination connected to an umbilical that extends to above the sea surface. Dedicated wireless communication devices can be attached to one or both of the wellhead assembly and the umbilical termination. The wireless communication devices can include a radio frequency modem, a sonar device, an infrared communication device, a light emitting diode, an optical modem, and combinations thereof; the wireless communication can include radio frequency waves, acoustic waves, and electromagnetic waves. A subsea control module can be included for controlling / actuating devices in or associated with the production system. The subsea control module can be adapted for wireless communication.

The invention discloses a method for estimating pulse noise in an OFDM (Orthogonal Frequency Domain Multiplexing) underwater acoustic communication system. At a receiving end, sparse estimation is performed on pulse noise on an OFDM signal in an underwater acoustic channel transmission process according to a frequency domain signal subjected to redundant Doppler frequency shift compensation, and frequency offset compensation is performed on the frequency domain signal subjected to the redundant Doppler frequency shift compensation with void subcarriers. Under the consideration of mutual interference between the pulse noise and a carrier frequency offset in underwater acoustic communication, compensation of the carrier frequency offset is added in an iteration process while the pulse noise is estimated with all subcarriers and a posteriori distribution under a framework of conventional sparse Bayesian learning, and the frequency domain signal subjected to the redundant Doppler frequency shift compensation and a measurement diagonal matrix for estimating the pulse noise are updated continuously in order to lower influences between the two types of interference. Moreover, the pulse noise is estimated by full utilization of all the subcarriers in the method, so that the spectrum efficiency and the performance of the communication system are improved.

An underwater communications system is provided that transmits electromagnetic and / or magnetic signals to a remote receiver. The transmitter includes a data input. A digital data compressor compresses data to be transmitted. A modulator modulates compressed data onto a carrier signal. An electrically insulated, magnetic coupled antenna transmits the compressed, modulated signals. The receiver that has an electrically insulated, magnetic coupled antenna for receiving a compressed, modulated signal. A demodulator is provided for demodulating the signal to reveal compressed data. A de-compressor de-compresses the data. An appropriate human interface is provided to present transmitted data into text / audio / visible form. Similarly, the transmit system comprises appropriate audio / visual / text entry mechanisms.

The invention provides a depth neural network system and a method based on modulation mode identification of underwater acoustic communication. The system comprises: a data preprocessing part for preprocessing data of a plurality of modulation modes transmitted through underwater acoustic communication; A first layer neural network generates a feature extraction set of the first layer according toa plurality of modulation mode data transmitted from the pretreated underwater acoustic communication; The second layer neural network generates the second layer high-level feature set; The third layer neural network generates higher level feature set, the fourth layer neural network classifies and identifies the initial data by the feature set extracted in front; The fifth layer is the neural network layer, which generates the final modulation mode judgment and outputs the identified modulation mode. The depth neural network system and method based on the modulation mode recognition of underwater acoustic communication can simulate the actual use situation, improve the use effect in the actual underwater acoustic communication, more conveniently and efficiently complete the modulation recognition of underwater acoustic communication, and improve the accuracy of recognition and judgment.

An underwater communications system includes an antenna array, a sound transmission source for transmitting communication packets, and a receiver including a processor. The processor is programmed for receiving and detecting a Doppler-sensitive probe signal and training sequence, for estimating a channel impulse response function for correlating the received signal to yield a plurality of processed channel outputs, and for summing the channel outputs to yield a common receiver output. The common receiver output is applied to a Decision Feedback Equalizer (DFE) for adaptive correction of the inter-symbol interference and to retrieve the transmitted communication message.

An apparatus for underwater communications. The apparatus may include a high speed communications cable to provide an underwater hardwired communications link to a surface station and a mobile device operative to transport a first end of the high speed communications cable between a submarine and a coupling point to the surface communication station, wherein the high speed communications cable is operative to reversibly form a hardwired connection between the coupling point and the submarine.

Advantageous online and / or real-time OFDM-based underwater acoustic (UWA) apparatus, systems and methods are provided according to the present disclosure. The apparatus, systems and methods employ a receiver with a bank of parallel branches, with each branch having a self-correlator matched to a different waveform scaling factor. A detection is declared when any of the branches leads to a correlation metric larger than a pre-defined threshold. The branch with the largest metric yields a Doppler scale estimate and a coarse synchronization point. The proposed apparatus, systems and methods use one OFDM preamble, thereby avoiding the need to buffer the whole data packet before data demodulation and enabling online and / or real-time operation. Thus, the disclosed apparatus, systems and methods are advantageously applicable to UWA communications.

The invention discloses an indirect self-adaptive equalization method of a shallow-sea underwater acoustic communication system to eliminate transmission intersymbol interference brought by a shallow-sea underwater acoustic channel with the time-varying and multi-diameter characteristics. The method comprises the following steps: designing a signal frame structure suitable for transmission in the shallow-sea underwater acoustic channel at a sending terminal; utilizing a frame head PN sequence to carry out rapid channel estimation and the initialization of equalizer tap coefficients at a receiving terminal; selecting a corresponding threshold according to the practical transmission environment to realize the decentralization of equalizer taps; and adopting an LMS algorithm with a variable step size to further reduce errors so as to better equalize frame body data. The invention enables an equalizer in the shallow-sea underwater acoustic communication system to have rapid convergence and lower hardware complexity, has good equalization effect on a sending signal after high-level modulation and can be effectively applied to the shallow-sea high-speed digital communication system.

The invention discloses a Doppler factor estimation and compensation method of mobile underwater acoustic communication, related to underwater acoustic communication. The Doppler factor estimation andcompensation method of the mobile underwater acoustic communication comprises the following steps: 1) large scale Doppler estimation and compensation; 2) residual Doppler estimation and compensation;and 3) Doppler phase rotation compensation. In order to accurately and efficiently estimate the Doppler factor in the mobile underwater acoustic communication environment, overcome the more obvious Doppler effect compared with the terrestrial radio channel and eliminate the adverse effects on the underwater acoustic OFDM communication system of the Doppler effect, a Doppler factor estimation andcompensation method of the mobile underwater acoustic communication considering both the accuracy and the computationcomplexity is needed. Because the estimation is carried out in the frequency domainand aims at the characteristics of the underwater acoustic channel, the Doppler factor estimation and compensation method of the mobile underwater acoustic communication, especially the Doppler factor estimation and compensation method applied to the mobile underwater acoustic OFDM system is more suitable for the fast changing mobile underwater acoustic channel based on the traditional Doppler estimation and compensation. The estimation accuracy is high; and meanwhile, the computation complexity is reduced appropriately, therefore, the practicability is excellent.

The invention aims at providing an orthogonal frequency division multiplexing (OFDM) underwater acoustic communication parallel iterative inter-carrier interference (ICI) elimination method. The method includes the steps of building an OFDM underwater acoustic communication system, building an acoustic time varying multipath channel model, measuring Doppler factors in the system, estimating frequency response of a time varying channel, estimating an ICI component and a signal interference noise ratio (SINR), and carrying out parallel iterative minimum mean square error (MMSE) equilibrium to received signals. Through combination of a linear approximation method and the MMSE method, and through iteration to improve performance, the parallel iterative ICI elimination method is inducted into the OFDM underwater acoustic communication system, and the method can effectively resist the ICI generated under the underwater acoustic time varying channel, and the OFDM underwater acoustic communication system is steady in response to the change of channel time varying speed. Therefore, inverse operation of a high order matrix is avoided, complexity of the method is reduced, and arithmetic speed is improved.

An underwater communications system for transmitting electromagnetic and / or magnetic signals to a remote receiver, the system having a data input; a digital data compressor for compressing data that is to be transmitted; a modulator for modulating the compressed data onto a carrier signal and an electrically insulated, magnetic coupled antenna for transmitting the compressed, modulated signals.

The invention discloses an OFDM-MFSK underwater acoustic communication broadband Doppler estimation and compensation method based on sub-carrier energy, and belongs to the field of the underwater communication. The specific content is as follows: a transmitting end inserts a pulse pair signal between a synchronization signal and the data; a receiving end firstly detects the synchronization signal to complete the Doppler initial compensation; the demodulation is performed on each OFDM-MFSK data block in the data in a way of one data block by one data block to estimate the effective sub-carrier position, and the energy sum of all effective sub-carrier is used as the cost function to perform the search according to the given different Doppler factors, thereby acquiring the fine Doppler factor of the current data block to complete the fine compensation of the Doppler; and finally the receiving data is demodulated. By using the method disclosed by the invention, the accurate estimation and compensation of the broadband Doppler in the underwater OFDM-MFSK communication system is effectively realized, and the problem that the traditional Doppler estimation method is bad in stability and low in estimation precision is solved.

The invention discloses a device for recovering an autonomous underwater vehicle by an unmanned ship based on a guide cable. The device for recovering the autonomous underwater vehicle is characterized in that the water surface unmanned ship, a recovery device carried on the water surface unmanned ship, the recovered or arranged autonomous underwater vehicle and a guide recovery control system arranged on the autonomous underwater vehicle are included; an underwater acoustic transducer is arranged at the bottom of the water surface unmanned ship and is used for underwater acoustic communication of the water surface unmanned ship and the autonomous underwater vehicle; a hydraulic telescopic rod connected with the recovery device is arranged in a cabin of the water surface unmanned ship; motion of the recovery device in the vertical direction can be achieved through the hydraulic telescopic rod; and an arc-shaped guide arm and cable fastening pliers are arranged at the top end of the bowof the autonomous underwater vehicle. The device for recovering the autonomous underwater vehicle has the beneficial effects that a USV serves as a water surface platform, and the device and method for autonomously recovering the autonomous underwater vehicle (AUV) through a guide cable are adopted so as to overcome the defects that in the prior technological means, water surface arrangement recovery is greatly influenced by sea wind waves, and people and equipment safety risk exists.

An environmental monitoring system including at least one underwater measurement device and a transmitter for transmitting data from the measurement device to an above water station using a magnetically coupled antenna.

The invention provides a mobile underwater acoustic communication method which includes the following steps: carrying out channel encoding and digital modulation on a data source at a sending end to get serial data, and converting the serial data into a parallel data flow; inserting pilot data into each group of parallel data, and carrying out sub-carrier modulation through inverse fractional Fourier transformation; adding a guard interval to modulated symbols, converting the modulated symbols into serial data, and sending the serial data; carrying out serial-to-parallel conversion and removing the guard interval at a receiving end, and searching for the optimal order through an order scanning search iterative algorithm; carrying out sub-carrier modulation on signals through optimal-orderfractional Fourier transformation, and carrying out channel estimation and equalization in the fractional Fourier domain at the receiving end; and after equalization, removing the pilot data, carryingout parallel-to-serial conversion to get serial data, carrying out digital demodulation and channel decoding, and outputting obtained data from the receiving end. The method has the advantages of simple structure and high calculation speed. The algorithm complexity of the transmitter and the receiver is reduced. The Doppler frequency shift in underwater acoustic mobile communication is reduced. The communication effect is improved.

The invention discloses a method and a device of remote uderwater acoustic communication. The device comprises more than one underwater communication nodes and more than one abovewater communication buoys which are responsible for communication with more than one underwater communication nodes within a set distance range through an underwater acoustic channel; and the communication connection is carried out between the abovewater communication buoys through a land wireless channel. In the method, the multi-frequency band combination is adopted to sent data in parallel, and the remote communication is realized by uniting the communication buoys; in the remote communication, a three-time handshake protocol in the carrier sense multiple access (CSMA) needs not to be used in the communicationbetween the underwater communication nodes and the buoys, while a channel can be directly monitored in a full frequency range; the data are synchronously sent to the abovewater communication buoys inparallel on each subchannel on the monitored idle channel by utilizing a frequency modulation method; and the data is transmitted by the abovewater communication buoys through a radio wave manner. Bythe method and device provided by the invention, one-time successful transmission probability of the two parties of the communication can be improved, and the anti-interference performance of a system is enhanced.

The related full-duplex underwater acoustic communication apparatus comprises: connected in turns, a multiplex-frequency communication module, a DAC, a power amplifier, an emission energy converter, a receiver, an ADC, an adaptive filter module between the DAC and multiplex frequency module, wherein the input of filter receives coding modulated data from the communication module, the reference end receives data from ADC, and its output end sends data to the multiplex frequency module. Compared with prior art, this invention can eliminate greatly the local emission interference, and improves system performance.

The invention discloses an underwater acoustic anti-Doppler multicarrier modulation and demodulation method based on linear frequency modulation. The method comprises the following steps: step one, transmitting terminal multicarrier modulation is performed; step two, Doppler frequency shift factor estimation is performed; and step three, receiving terminal demodulation is performed. The invention also discloses a modulation and demodulation device of the underwater acoustic anti-Doppler multicarrier modulation and demodulation method based on linear frequency modulation. The device comprises a transmitting device and a receiving device which are interconnected. The method has advantages of being high in anti-Doppler capability, wide in applicability, diverse in realization method, low in cost, easy to realize, high in efficiency, etc.

The invention discloses an amphibious communication system based on a relay buoy. The system comprises an underwater vehicle carrying a camera used for collecting underwater information, wherein a collected video signal is modulated to a light source to send an optical signal; an optical communication receiving end module is arranged at the bottom of the buoy and is used for receiving the optical signal carrying the information collected by the underwater vehicle, such as image, video and voice; and a main control unit processes an electric signal output by an optical receiving end and then sends a video signal to a land base station through a wireless way. The land base station transmits a control signal through a reverse link to control operation of the underwater vehicle. According to the system, the buoy is taken as relay to complete amphibious communication, and the underwater data communication adopts the optical signal as a carrier, in comparison with acoustic technique, the underwater communication way adopting an optical technology has the advantages of high bandwidth, good security, low cost, high sensitivity and the like.

The invention discloses a sea-region natural gas hydrate seabed methane monitoring system and a method. A mining well position is taken as a center and pilot production well positions are arranged inan equidistance mode. The mining well position is taken as the center and a first monitoring circle and a second monitoring circle are arranged. The first monitoring circle and the second monitoring circle are provided with multiple groups of seabed subsurface buoys used for monitoring a seabed methane concentration so as to form a seabed methane data matrix. The system and the method have advantages that bottom-supported seabed subsurface buoys are used to make up disadvantages in the prior art; through a underwater control technology, physical and chemical sensors capable of measuring a plurality of parameters are integrated together; long-period in-situ observation is performed on a seabed environment of a seabed boundary of a seabed natural gas hydrate reservoir forming area so that ameasurement error which may be caused by an existing method is avoided; and through a underwater acoustic communication technology, a seabed environment parameter is transmitted to a sea surface monitoring platform, real-time seabed methane leakage monitoring is provided for hydrate mining and an important meaning is possessed.

The invention provides small-sized underwater robot combined navigation system and navigation method. The combined navigation system comprises an embedded navigation processor, a pressure-resistant global position system (GPS), a micro attitude sensor, a speedometer, a depth meter and underwater acoustic communication equipment. When an underwater robot carrier is underwater and after the combined navigation system is electrified, the navigation system autonomously runs, a relay is controlled through an input / output (IO) channel of an analog / digital (AD) board to open the sensor for performing data acquisition so as to acquire an initial navigation position, a magnetic declination is calculated according to a magnetic declination database, and planned navigation position correcting instruction information is received for navigation position calculation so as to acquire longitude and latitude position information of an underwater robot. The system has small volume, light weight and lowcost, is favorable for the miniaturization of an underwater navigation system, and can be applied to small-sized underwater robots for underwater observation and detection, which require small size and light weight.