Abstract: Systems and methods for underwater communication using a MIMO acoustic channel. An acoustic receiver may receive a signal comprising information encoded in at least one transmitted symbol. Using a two-layer iterative process, the at least one transmitted symbol is estimated. The first layer of the two-layer process uses iterative exchanges of soft-decisions between an adaptive turbo equalizer and a MAP decoder. The second layer of the two-layer process uses a data-reuse procedure that adapts an equalizer vector of both a feedforward filter and a serial interference cancellation filter of the adaptive turbo equalizer using a posteriori soft decisions of the at least one transmitted symbol. After a plurality of iterations, a hard decision of the bits encoded on the at least one transmitted symbol is output from the MAP decoder.

Abstract: There is provided a Very Low Frequency (VLF) transmit antenna system, method, and apparatus for creating a magnetic field at low frequencies suitable for communications through the earth or other thick, solid barriers. At least two loop antennas are arranged such that a magnetic field of each one of the at least two loop antennas passes through each remaining one of the at least two loop antennas, thereby closely coupling the at least two loop antennas. A full bridge Pulse Width Modulated transmitter is directly connected to each loop antenna for driving the latter. When a loop of a given loop antenna is broken and its magnetic field collapses, the transmitters connected to the remaining loop antennas increase the current in the remaining loops to maintain a constant magnetic field.

Abstract: A synthetic-frequency RF transmitter is provided for transmitting an electromagnetic signal via an electrically short antenna. The transmitter comprises a reactive energy storage with an effective reactance adapted to form with the antenna a resonance circuit with a resonance frequency and a driver adapted to provide to the resonance circuit an electric transmission signal having an instantaneous frequency that varies in dependence on an information signal. The transmitter is characterized in that the transmitter is adapted to dynamically change the resonance frequency by changing the effective reactance in dependence on the information signal. Thus, the instantaneous pass-band of the resonance circuit may be controlled to substantially always comprise the instantaneous frequency of the electric transmission signal and thus of the electromagnetic signal.

Abstract: A method for operating a communication system including a first device with a working oscillator and a second device with a reference oscillator is provided. The method includes calibrating the working oscillator of the first device connected to an asynchronous serial communications bus. The calibrating includes defining a measurement time, and measuring and selecting a predefined pulse space of a first signal. The predefined pulse space of the first signal is formed by a plurality of predefined discrete pulse spaces, generated by a second device including a reference oscillator, and received by the first device during the measurement time over the asynchronous serial communications bus.

Abstract: A method for receiving signals over a power line network, within the power line network at least one transmitter and at least one receiver communicate via at least two channels, each of the channels having a respective feeding port of the at least one transmitter and a respective receiving port of the at least one receiver, and the receiver having at least two receiving ports. The method determines a channel characteristic of each of the channels, applies a receiving port selection criterion based on the channel characteristic, and selects an excluded receiving port among the at least two receiving ports based on the receiving port selection criterion, the excluded receiving port is not used during further communication.

Abstract: Methods and systems for acoustic multiple-input/multiple-output (MIMO) communication in an underwater environment. The method includes: a) receiving signals at multiple receivers representing transmitted signals from multiple transmitters, b) estimating channel responses between the multiple receivers and the multiple transmitters, c) performing an initial demodulation process on the received signals using the estimated channel responses to remove inter-symbol interference (ISI), and d) performing at least one subsequent demodulation process on the received signals. The subsequent demodulation process: i) removes co-channel interference (CoI) using the estimated channel responses and demodulated signals from an immediately preceding demodulation process to form interference cancelled signals and ii) removes ISI from the interference cancelled signals.

Abstract: A mobile device with 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 portable device may be wearable.

Abstract: A method of reducing noise in a sequence of data by linear and non-linear estimation. The method includes receiving a noisy sequence of data indicative of a sequence of physical events; applying a non-linear technique to the noisy sequence to obtain an approximation of a noise-free sequence of data; subtracting the approximation from the noisy sequence to obtain an estimate of noise in the noisy sequence of data; applying a linear technique to the estimate of noise to obtain a filtered sequence; and adding the filtered sequence to the approximation of the noise-free sequence to obtain a reduced-noise sequence of data indicative of the sequence of physical events.

Abstract: Methods and systems for acoustic multiple-input/multiple-output (MIMO) communication in an underwater environment. The method includes: a) receiving signals at multiple receivers representing transmitted signals from multiple transmitters, b) estimating channel responses between the multiple receivers and the multiple transmitters, c) performing an initial demodulation process on the received signals using the estimated channel responses to remove inter-symbol interference (ISI), and d) performing at least one subsequent demodulation process on the received signals. The subsequent demodulation process: i) removes co-channel interference (CoI) using the estimated channel responses and demodulated signals from an immediately preceding demodulation process to form interference cancelled signals and ii) removes ISI from the interference cancelled signals.

Abstract: A method for receiving signals over a power line network, within the power line network at least one transmitter and at least one receiver communicate via at least two channels, each of the channels having a respective feeding port of the at least one transmitter and a respective receiving port of the at least one receiver, and the receiver having at least two receiving ports. The method determines a channel characteristic of each of the channels, applies a receiving port selection criterion based on the channel characteristic, and selects an excluded receiving port among the at least two receiving ports based on the receiving port selection criterion, the excluded receiving port is not used during further communication.

Abstract: An electronic circuit includes: a differential amplifier circuit into which a digital input signal and a reference signal are fed; a feedback circuit outputting an average of amplitude of the input signal; and a peak holding circuit outputting a signal held based on an output signal of the feedback circuit as the reference signal.

Abstract: A method for transmitting signals over a power line network, wherein within the power line network at least one transmitter and at least one receiver communicate via at least two channels, each channel including a respective feeding port of at least one transmitter and the respective receiving port of the at least one transmitter and transmitter including at least two feeding ports. The method: determines a channel characteristic of each of the channels; applies a feeding port selection criterion based on the channel characteristic; and selects an excluded feeding port among the at least two feeding ports based on the feeding port selection criterion, wherein the excluded feeding port is not used during further communication. A corresponding power line communication modem can implement the method.

Abstract: A portable wireless through-the-earth bi-directional communication system for sending and receiving text data using ultra-low-frequency electric current and the earth as the conductive media. A surface controller which executes application software which controls the communication functions of the system. A surface receiver and surface transmitter are connected to sets of electrodes which provide the electric current, and are in communication with the surface controller. Text data are encoded into data packets, modulated onto ultra-low-frequency electric carrier waves, and transmitted through the earth by the surface electrodes to a subsurface transceiver. The subsurface transceiver demodulates, converts and displays incoming signals into text messages. The subsurface transceiver has a user interface to allow subsurface users to submit text data to the surface receiver.

Abstract: An electric power transmission system for communications includes on/off switches; high-voltage power assemblies; groups of high-voltage devices each being powered by the high-voltage power assembly; a carrier waves communications network comprising a transformer and filter, a filter, and a carrier waves coupling device interconnecting the transformer and filter and the filter, wherein the transformer and filter includes a low-voltage power assembly for communications and the filter includes a high-voltage power assembly for communications; and low and high-voltage devices. Data can be communicated between the low-voltage devices, between the high-voltage devices, or between the low-voltage device and the high-voltage device by transmitting carrier waves over the AC power.

Abstract: The present invention discloses a system for digitally modulated radio communication directly between a submerged underwater station and an airborne station. Each of the underwater station and the airborne station has or is associated with a radio communications antenna. Suitable radio communications antennas include loop antennas, solenoid antennas, stacked multiple loop antennas, planar arrayed loop antennas, a multiple resonant loop antennas. In some embodiments, the communications antennas of the submerged underwater station and the airborne station are each deployed horizontally thereby improving the efficiency of the signal transfer between the submerged underwater station and the airborne station.

Abstract: A wireline telemetry system and method of transmitting data on multiple carrier frequencies. The system and method adjust power level and number of bits-per-carrier to optimally or near-optimally utilize the capacity of the wireline cable. Due to the nature of wireline telemetry the overall power level is restricted only by the output capability of the downhole telemetry cartridge and the input power restrictions of the uphole telemetry unit receiver. The optimal power level is determined during a training sequence and is a function of such factors as cable length, cable material, cable temperature and cable geometry. The uplink and downlink transmission are executed using different modulation techniques.

Abstract: Power savings are achieved for digital data transport over short distances by using the characteristics of resonant LC circuits. Economy of circuit elements is achieved by enabling a single pair of resonant circuits to drive large numbers of digital data lines or nodes in parallel. This maximizes power efficiency and minimizes area and cost. Resistance is minimized by insuring that all switches in the current path are fully “ON” whenever significant current is flowing through them. All other parasitic resistances in the circuits, consisting primarily of parasitic interconnect resistances, are minimized. This enables the data transmission circuits to achieve maximum Q or quality factor, which minimizes power dissipation.

Abstract: A communications system including: a plurality of sub-surface portable transceivers each including: a digital data source, a modulator coupled to the digital data source, a power amplifier coupled to the modulator and a loop antenna inductively coupled to the power amplifier; and a base transceiver including: an electrically insulated ferrite core antenna for receiving magnetic signals, an electric di-pole antenna for receiving ambient noise, a noise canceller coupled to the insulated ferrite core antenna and electric dipole antenna and responsive to the electric-dipole antenna to filter noise from signals received via the insulated ferrite core antenna, a demodulator coupled to the noise canceller and a decoder coupled to the demodulator.

Abstract: A radio receiver is selectively operable in a current mode or a voltage mode according to conditions prevailing within a wireless environment. If the signal levels within the wireless environment are relatively low, the radio receiver is operable in current mode. If the signal levels within the wireless environment are relatively high, the radio receiver is operable in voltage mode. The radio receiver is switchable between current and voltage mode of operation via selectively actuable switches that bringing into effect or remove from effect corresponding resistances.

Abstract: Briefly, one way to minimize time and frequency uncertainties when synchronizing between a transmitter and a receiver is to use a position determining method such as global positioning system (GPS) to determine position and velocity. If position can be determined the delay between the transmitter and receiver can be estimated. Additionally, position information can be used to determine the probability that the signal received will be a reflected signal. If the transmitter and receiver are located in an area with obstructions between them then it is more likely that a signal received will be a reflected signal. If it is determined that it is likely that the signal received will be a reflected signal then the receiver can attempt to acquire the transmitted signal over a wider range of propagation delay possibilities. Additionally, another uncertainty that complicates synchronization is uncertainty regarding frequency.

Abstract: A method of distributing wide band data using a neutral-to-ground circuit within an electrical wiring installation includes modifying a load center with an interface module which interfaces to the neutral-to-ground circuit and configuring the interface module to compensate for varying impedance within the neutral-to-ground circuit to improve data transmission characteristics. Multiple embodiments are included within the method for compensation of varying impedance including channel sounding, spectral waterfilling, and communications using spread spectrum techniques, for example, frequency hopping and direct sequencing techniques.

Abstract: A synchronized communication system for communicating signals into and from a medium is disclosed. The communication system utilizes a transmitter located at a central station external to the medium, which transmits a low frequency synchronization signal into the medium. Transceivers located within the medium receive the low frequency synchronization signal and send information radio signals synchronized with the low frequency synchronization signal to a receiver located at the central station. Zone transceivers are located within the medium to receive and retransmit the synchronization signal at the low frequency within a zone. The zone transceivers also receive information signals from transceivers in the zone and transmit zone information radio signals to the central station containing information corresponding to the information received from the transceivers in the zone.

Abstract: A method and system are provided for communicating in a time-varying medium. A transmitter sends transmissions of the same message data separated in time with respect to one another. A single sensor receives the transmissions. Each received transmission is buffered until all of the transmissions that were sent are received. The buffered transmissions are simultaneously processed via multichannel adaptive equalization only when all of the transmissions that were sent are received.

Abstract: The secure communication keying system has a noise generator whose output a predetermined finite band of noise within, for example, the zero to eleven hundred cycle per second range. The noise generator may be a pseudorandom noise generator that is synchronized with a given clock frequency. The output of the system may have noise-like characteristics, but it is encoded with any type of intelligence desired to be transmitted. The output signals simulate the ambient noise occurring within the communication medium and has the same frequency spectrum regardless of the frequency of the modulating signals supplied thereto.