Abstract: An underwater acoustic communication system includes a transmission device including N transmitters, and a reception device. The reception device includes M (M is an integer of two or more) receivers configured to receive M reception signal sequences corresponding to N transmission signal sequences transmitted from the N transmitters through sound waves, a beam former configured to suppress multipath waves other than direct waves of the M received reception signal sequences and to generate L (L is an integer of two or more) signal sequences from the M reception signal sequences, and a signal estimation unit configured to estimate the N transmission signal sequences based on the L generated signal sequences.

Abstract: A receiving apparatus includes: M receivers configured to receive signals based on sound waves propagating in water; M FIR filters configured to perform waveform operation on the signals received by the receivers; a combiner configured to combine output signals of the M FIR filters; and a filter coefficient calculation portion configured to calculate a tap coefficient of the M FIR filters so as to reduce an error of the output signals combined by the combiner. The M FIR filters have a tap length that is shorter than a delay spread that is a possible range between a time of arrival of a direct wave and a time of arrival of a delayed wave of the sound waves.

Abstract: An aspect of the present invention is a Doppler compensation system including: a sound wave receiving element that receives a sound wave transmitted by a transmitter; a ground-speed-related quantity acquisition unit that acquires a ground-speed-related quantity that is a physical quantity related to a vector representing a ground speed of a receiver including the sound wave receiving element based on an acceleration of the receiver; an extraction unit that extracts a sound wave including an estimation target sound wave that is a sound wave to be estimated from among sound waves received by the receiver; an arrival direction estimation unit that estimates an arrival direction of the estimation target sound wave based on the estimation target sound wave; a reception-direction-speed-related quantity estimation unit that estimates a quantity related to a speed in a reception direction that is a direction in which the estimation target sound wave viewed from the receiver arrives based on the ground-speed-related q

Abstract: A plurality of transmit antennas of a radio transmission device and a plurality of receive antennas of a radio reception device are located under the sea that is a line-of-sight environment, wherein the radio transmission device selects a frequency channel to be used based on an index value per frequency channel indicating orthogonality between the transmit and receive antennas defined based on a distance between the transmit and receive antennas and an angle indicating a direction of arrival of a radio signal, an interval between the plurality of transmit antennas, an interval between the plurality of receive antennas, and a modulation scheme, the distance between the transmit and receive antennas and the angle indicating the direction of arrival of the radio signal estimated by the radio reception device, and a desired bit error rate to be predetermined, selects the modulation scheme for providing a maximum transmission capacity per the selected frequency channel, separates transmission data into a pluralit

Abstract: An OAM multiplexing communication system uses one or more OAM modes and multiplexes signals of one or more sequences for each OAM mode. A transmitting station includes a transmitting antenna using an M-UCA, and an OAM mode generation unit that simultaneously generates one or more OAM modes from each UCA. A receiving station includes a receiving antenna equivalent to the M-UCA, an OAM mode separation unit that separates signals received by each UCA for each OAM mode, and a received signal processing unit that estimates channel information for each OAM mode and performs an equalization process for each OAM mode by using a receiving weight calculated from the channel information. The received signal processing unit is configured to estimate, for each OAM mode, channel information of another OAM mode causing interference and calculate the receiving weight of a subject OAM mode by using the channel information of the subject OAM mode and said another OAM mode.

Abstract: A radio terminal accommodation determination device includes: an average received power calculation unit for calculating an average received power for each mesh constituting an area; an interfering signal power CDF creation unit for creating a cumulative distribution function of all interfering signal powers; an intended signal power PDF creation unit for creating a fourth probability density function indicating a probability density function of an intended signal power; and a communication success rate estimation unit for calculating, for each base station, a communication success rate of the intended terminal based on the cumulative distribution function and the fourth probability density function.

Abstract: A communication device includes: a light output unit for outputting light; a light splitting unit for splitting the light output by the light output unit into a plurality of split beams; and a plurality of spatial optical communication units provided in correspondence to the plurality of split beams, wherein the spatial optical communication units respectively transmit a corresponding split beam which is input from the light splitting unit to a partner communication device across space.

Abstract: A phase difference distribution estimation method includes: receiving an optical signal via a space and detecting a phase of the optical signal; calculating characteristic values related to characteristics of the atmosphere through which the optical signal propagates from the optical signal received in the receiving; estimating a phase difference distribution of an optical signal received after a certain period of time, on the basis of the characteristic values calculated in the calculating; and controlling a phase of an optical signal in the receiving on the basis of the phase difference distribution estimated in the estimating.

Abstract: A communication device includes a channel estimation unit configured to estimate an impulse response based on signals of sound waves received by each of a plurality of hydrophones, a long delay removal unit configured to remove a long-delay impulse response from the impulse response to generate a post-removal impulse response, a weighting factor calculation unit configured to calculate a weighting factor based on the post-removal impulse response, and a synthesizing unit configured to synthesize the signals received by each of the plurality of hydrophones based on the weighting factor.

Abstract: A receiving apparatus includes: M receivers configured to receive signals based on sound waves propagating in water; M FIR filters configured to perform waveform operation on the signals received by the receivers; a combiner configured to combine output signals of the M FIR filters; and a filter coefficient calculation portion configured to calculate a tap coefficient of the M FIR filters so as to reduce an error of the output signals combined by the combiner. The M FIR filters have a tap length that is shorter than a delay spread that is a possible range between a time of arrival of a direct wave and a time of arrival of a delayed wave of the sound waves.

Abstract: Provided is a radio communication system including a radio transmission apparatus including a plurality of transmission antennas and a radio reception apparatus including a plurality of reception antennas.

Abstract: A monitoring system comprises a monitoring agent that keeps information related to a communication status of a low-power terminal that communicates under low power, and a monitoring device that monitors the status of the low-power terminal. The monitoring device includes a requesting unit that requests information related to the communication status of the low-power terminal. The monitoring agent includes a response generation unit that generates a response to the request from the monitoring device on a basis of the information related to the communication status of the low-power terminal, and a transmission unit that transmits the response to the monitoring device.

Abstract: A plurality of transmit antennas of a radio transmission device and a plurality of receive antennas of a radio reception device are located under the sea that is a line-of-sight environment, wherein the radio transmission device selects a frequency channel to be used based on an index value per frequency channel indicating orthogonality between the transmit and receive antennas defined based on a distance between the transmit and receive antennas and an angle indicating a direction of arrival of a radio signal, an interval between the plurality of transmit antennas, an interval between the plurality of receive antennas, and a modulation scheme, the distance between the transmit and receive antennas and the angle indicating the direction of arrival of the radio signal estimated by the radio reception device, and a desired bit error rate to be predetermined, selects the modulation scheme for providing a maximum transmission capacity per the selected frequency channel, separates transmission data into a pluralit

Abstract: A communication quality calculation unit (11) of a base station placement design device (1) calculates communication quality of each terminal in a case where a base station is installed at a base station placement candidate location for a plurality of base station placement candidate locations. An aggregation unit (12) aggregate the number of terminals whose communication quality calculated by the communication quality calculation unit (11) is equal to or greater than a threshold value for each of the plurality of base station placement candidate locations. A base station placement location selection unit (13) selects a base station placement location from among the plurality of base station placement candidate locations, based on the number of terminals aggregated by the aggregation unit (12) for each of the plurality of base station placement candidate locations.

Abstract: A communication device includes a channel estimation unit configured to estimate an impulse response based on signals of sound waves received by each of a plurality of hydrophones, a long delay removal unit configured to remove a long-delay impulse response from the impulse response to generate a post-removal impulse response, a weighting factor calculation unit configured to calculate a weighting factor based on the post-removal impulse response, and a synthesizing unit configured to synthesize the signals received by each of the plurality of hydrophones based on the weighting factor.

Abstract: A transmission device includes a modulation unit that performs chirp-spread modulation on an input information series to generate a modulation signal; a delay unit that provides, to a plurality of modulation signals obtained by duplicating the modulation signal generated by the modulation unit, delays having lengths different from each other, a difference between the delays being an integral multiple of a reciprocal of a bandwidth of the modulation signal; and a plurality of transmission antennas that transmit the plurality of modulation signals, respectively, to which the delays are provided by the delay unit.

Abstract: In an OAM multiplexing communication system in which an M-UCA is provided in each of a transmitting station and a receiving station, signals in a plurality of OAM modes are generated and transmitted from each UCA of the transmitting station, signals in the plurality of OAM modes are received and demultiplexed by each UCA of the transmitting station, and streams of the number of UCAs×the number of OAM modes are subjected to spatial multiplex transmission, in which the transmitting station includes a signal processing unit generating the streams to be transmitted in the plurality of OAM modes from each of the UCAs of the M-UCA, and the receiving station includes a signal processing unit receiving the signals in the plurality of OAM modes demultiplexed by each of the UCAs of the M-UCA, and demultiplexes the received signals for each stream from signals in an identical OAM mode.

Abstract: A station installation designing assistance device that divides a service providing area into a plurality of areas, and performs station installation designing for the plurality of areas in parallel, the station installation designing assistance device including: an area dividing unit that divides an entirety of the service providing area into a plurality of areas that are each composed of a predetermined number of small areas; a small area specifying unit that specifies a small area number that identifies a small area in each of the areas, where the same number is given to the small area in each of the areas; and a station installation location selecting unit that selects, for each of the plurality of areas, a plurality of station installation locations from among station installation location candidates that are present in the small area specified by the small area specifying unit.

Abstract: A station installation designing assistance device that divides a service providing area into a plurality of areas, and performs station installation designing for the plurality of areas in parallel, the station installation designing assistance device including: an area dividing unit that divides an entirety of the service providing area into the plurality of areas; a station installation priority determining unit that determines, for each of the plurality of areas, station installation priorities of station installation location candidates that are present in the area; and a station installation priority adjusting unit that adjusts the station installation priorities determined by the station installation priority determining unit, based on a degree of overlap of cells formed as a result of base stations being installed in station installation location candidates in the areas, respectively.

Abstract: A communication control device that transmits a packet to be transmitted to a terminal to a base station that performs wireless communication with the terminal, includes: a terminal classification unit that classifies, on the basis of a magnitude of radio wave interference from a base station different from a neighboring base station, a plurality of the terminals into a first terminal set and a second terminal set that is relatively larger in the magnitude of radio wave interference than the first terminal set; and a transmission unit that transmits, in a case where packets destinations of which are terminals belonging to the first terminal set are to be transmitted to respective neighboring base stations of the terminals, the packets at the same timing and transmits, in a case where packets destinations of which are terminals belonging to the second terminal set are to be transmitted to respective neighboring base stations of the terminals, the packets at timings different from each other.