Nippon Telegraph and Telephone Corporation

Yosuke Fujino

Hiroyuki Fukumoto

Kazunori Akabane

Kazumitsu Sakamoto

Yohei Katayama

Marina Nakano

Daisei Uchida

Kenji Suzuki

Daisuke Goto

Kiyohiko Itokawa

Yasuyoshi Kojima

Takafumi Fujita

Kento Yoshizawa

Hajime Katsuda

Yusuke Asai

Fumihiro Yamashita

Toshimitsu Tsubaki

Masahiro Umehira

Osamu Kagami

Ryo Miyatake

Shigeru Teruhi

Miharu Oiwa

Yuya Ito

Akabane Kazunori

A wireless communication system includes: a measurement unit that measures a signal level of an analog signal corresponding to a received radio signal; a first output unit that amplifies an amplitude of the analog signal and extracts an analog signal with a desired frequency band from the analog signal with the amplified amplitude; a second output unit that extracts an analog signal with a desired frequency band from the analog signal and amplifies an amplitude of the extracted analog signal; and a switching control unit that inputs the analog signal corresponding to the received radio signal to the first output unit when the signal level of the analog signal other than the desired frequency band is less than a threshold, and inputs the analog signal corresponding to the received radio signal to the second output unit when the signal level of the analog signal other than the desired frequency band is equal to or greater than the threshold.

Wireless communication system, relay apparatus and wireless communication method

A first offset compensator configured to compensate for frequency offsets occurring during communications between a plurality of communication devices and a relay device, wherein when the first offset compensator is provided on the relay device, the first offset compensator gives a statistical frequency offset obtained from a statistic of a plurality of frequency offsets occurring during communications between respective ones of the plurality of communication devices and the relay device to a receiver configured to receive wireless signals transmitted from respective ones of the plurality of communication devices, and when the first offset compensator is provided on each of the plurality of communication devices, the first offset compensator gives a frequency offset occurring during communications between the communication device provided with the first offset compensator and the relay device to a transmitter configured to transmit wireless signals to the relay device.

Wireless communication system, relay device, communication device, and wireless communication method

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 quantity and a result of the estimation from the arrival direction estimation unit; and a Doppler compensation unit that compensates for waveform distortion due to Doppler effect of the estimation target sound wave based on a result of the estimation from the reception-direction-speed-related quantity estimation unit.

Doppler compensation system and doppler compensation method

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.

Receiving apparatus

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.

Station placement designing assistance apparatus, station placement designing assistance method and program

A communication quality calculation unit () of a base station placement design device () 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 () aggregate the number of terminals whose communication quality calculated by the communication quality calculation unit () 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 () 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 () for each of the plurality of base station placement candidate locations.

Station placement designing apparatus, station placement designing method and program

A radio transmission apparatus includes a communication distance measurement unit configured to measure a distance between a plurality of transmission antennas and a plurality of reception antennas, a selection unit configured to select a modulation scheme common to all frequency channels, the modulation scheme satisfying an average value of index values for each of the frequency channels according to a measured distance and satisfying a predetermined desired bit error rate, a transmission signal generation unit configured to separate transmission data, modulate each item of the separated transmission data by the selected common modulation scheme, and output the transmission signals multiplexed by the number of multiplexing indicating the number of the plurality of transmission antennas to be used. A radio reception apparatus includes a demodulation unit configured to demodulate a reception signal by a demodulation scheme corresponding to the modulation scheme to generate reception data.

Technique to maintain formation of a parallel transmission line in spatial multiplex transmission

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.

Communication control apparatus, communication control method and program

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.

A communication method determination apparatus includes a comparison unit and an instruction unit. The comparison unit obtains a bit string of a portion of a physical header for synchronization from a wireless frame that includes the physical header for synchronization in which information for synchronization in a physical layer is set and a physical data portion in which data of a higher-level layer than the physical layer is set, and compares the obtained bit string with a bit string pattern specific to a communication method targeted for determination. The instruction unit performs communication method determination processing for determining whether or not the communication method targeted for determination is used for the wireless frame, based on a result of comparison. If it is determined that the communication method targeted for determination is not used for the wireless frame, the instruction unit changes the communication method targeted for determination, instructs the comparison unit to newly obtain a bit string of a portion that follows the obtained bit string, from the physical header for synchronization, and to compare the newly obtained bit string with a bit string pattern specific to the post-change communication method targeted for determination, and performs the communication method determination processing again.

Communication scheme determination apparatus, communication scheme determination method and program

An arrival rate estimation device includes an average received power calculation unit that calculates an average received power for each mesh that constitutes an area, with respect to each of a plurality of base stations and each of a plurality of antennas included in each of the base stations and an arrival rate estimation unit that calculates a communication arrival rate by substituting the average received power into a cumulative distribution function of an instantaneous received power value, and based on the calculated communication arrival rate, calculates a communication arrival rate while giving consideration to a site diversity effect and an antenna diversity effect, the cumulative distribution function being obtained from a probability density function of an amplitude that instantaneously changes due to Rayleigh fading.

Arrival rate estimation apparatus, arrival rate estimation method and program

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.

Hydroacoustic communication system and receiving apparatus

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 plurality of pieces of transmission data the number of which corresponds to the number of frequency channels, modulates each of the plurality of pieces of transmission data separated in accordance with the selected modulation scheme, and outputs a transmission signal obtained by multiplexing, with a multiplexing order, each of the plurality of pieces of transmission data, the multiplexing order indicating the number of transmit antennas of the plurality of transmit antennas to be used.

Wireless communication system and wireless communication method

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.

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Tokyo, Japan

Yosuke Fujino