Nippon Telegraph and Telephone Corporation

Mizuki Suga

Naoki Kita

Kota Ito

Yushi Shirato

Nobuaki Otsuki

Kazuto Goto

Hideki Toshinaga

A communication system includes a central station device and a base station device. The central station device includes: a plurality of signal processing units, each generating an electrical signal of a wireless signal by performing signal processing corresponding to a wireless system; a conversion unit that generates an optical signal by performing intensity modulation on the electrical signal; and a signal processing control unit that controls the conversion unit to generate an optical signal in which a plurality of the electrical signals are multiplexed. The base station device includes: an electrical signal generation unit that receives the optical signal generated in the central station device via an optical transmission path and converts the received optical signal into a plurality of electrical signals; and a plurality of antenna devices, each wirelessly transmitting the wireless signal according to the electrical signal generated by the electrical signal generation unit.

Communication system, communication method, accommodation station device and base station device

An APand STAsacquire time information from an external device, and synchronize time. The APsets, in a first signal, a transmission start time of the first signal, and transmits the first signal to the STA. The STAstransmit, to the AP, a second signal in which a delay time is set, the delay time being calculated from a difference between the transmission start time acquired from the first signal and a reception start time of the first signal at the own station. The APacquires delay time from the second signal of each STA, decides a timing for permitting transmission by each of the STAsby time division, on the basis of the acquired delay time, and notifies the STAsthereof. The STAseach effect control to start transmission of signals to the APat the timing notified from the AP

Wireless communication system, access point apparatus, wireless station apparatus and wireless communication method

An accommodation station transmission unit modulates light to generate an optical signal based on an RF signal and outputs the generated optical signal, a base station transmission unit obtains the optical signal from an input port, demultiplexes the obtained optical signal for each wavelength, outputs the demultiplexed optical signals from output ports of corresponding wavelengths from among a plurality of output ports allocated to each of the wavelengths of the light, and demodulates the RF signal by converting the optical signals output by the output ports into electrical signals, a plurality of transmission antennas emit the demodulated RF signal, and a reflect array or a transmit array receives the RF signal emitted by each of the transmission antennas and forms a transmission beam in a different direction for each position of the transmission antenna that is a transmission source of the RF signal for each RF signal.

Wireless transmitting system, wireless receiving system, base station apparatus, wireless communication system, wireless transmitting method, and wireless receiving method

An allocation method for allocating individual downlink data signals to positions on a time axis when a base station transmits the individual downlink data signals to a plurality of terminal stations. The allocation method includes provisionally allocating individual downlink data signals of the individual downlink data signals for terminal stations having long propagation delay times to positions of relatively early timings and provisionally allocating individual downlink data signals of the individual downlink data signal for terminal stations having short propagation delay times to positions of relatively late timings, changing the positions such that, when it is estimated that a collision will occur when receiving response signals transmitted from the terminal stations, it is estimated that a collision will not occur, in the provisionally allocating, and fixing, as the positions of the individual downlink data signals on the time axis, the positions changed in the changing of the positions.

Allocation method and signal processing apparatus

An accommodation station transmission unit modulates light based on an RF signal to generate an optical signal and outputs the generated optical signal, a base station transmission unit demultiplexes the output optical signal for each of wavelengths, outputs the demultiplexed optical signals, converts the demultiplexed optical signals into electrical signals to demodulate the RF signal, outputs the demodulated RF signal, and each of first ports of a matrix operation unit including the plurality of first ports and a plurality of second ports and configured to use each of the first ports as a reference port and perform, on signals obtained by the reference ports, a BFN matrix operation of performing phase changes that are different for each of positions of the reference ports and cause each of phases of signals output from the plurality of second ports to have a linear inclination receives the demodulated RF signal and forms transmission beams in different directions for each of wavelengths by a plurality of transmission antennas emitting the RF signal output by each of the second ports of the matrix operation unit.

A derivation method includes: a transmission step of transmitting, to a wireless terminal, a first radio-wave signal according to an optical signal with a first wavelength and a second radio-wave signal according to an optical signal with a second wavelength; a communication start time information acquisition step of acquiring information on a first communication start time and information on a second communication start time; a reception time information acquisition step of acquiring information on a first reception time and information on a second reception time; a transmission time period derivation step of deriving a first round trip time and deriving a second round trip time; and an optical fiber length derivation step of deriving an optical fiber length, based on the first round trip time, the second round trip time, a group velocity or a group delay time of the optical signal with the first wavelength, and a group velocity or a group delay time of the optical signal with the second wavelength.

Derivation method, communication system and accommodation station apparatus

A derivation method is a derivation method performed by a communication system, including: a transmission step of transmitting a first radio-wave signal according to an optical signal with a first wavelength and a second radio-wave signal according to an optical signal with a second wavelength; a communication start time information acquisition step of acquiring information on a first communication start time and information on a second communication start time; a reception time information acquisition step of acquiring information on a first reception time that is a reception time related to the first radio-wave signal, and information on a second reception time that is a reception time related to the second radio-wave signal; and an optical fiber length derivation step of deriving a length of the optical fiber, based on the first communication start time, the first reception time, the second communication start time, the second reception time, a group velocity or a group delay time of the optical signal with the first wavelength, and a group velocity or a group delay time of the optical signal with the second wavelength.

n wavelengths set such that delay differences between optical signals due to wavelength dispersion in an optical fiber between accommodation and base stations are at equal intervals are assigned to n antenna elements of the base station which are at predetermined intervals. The accommodation station adjusts the phases of optical signals of the wavelengths or modulated signals that modulate the optical signals such that the amounts of phase shift of their RF signals are at predetermined intervals. The accommodation station transmits beacon signals multiple times while varying a transmission phase shift interval &#x3b1;and the terminal transmits beacon number information of a beacon signal selected based on received power multiple times. The accommodation station varies a reception phase shift interval &#x3b1;for each piece of beacon number information to determine a reception phase shift interval &#x3b1;which maximizes the received power and determines the transmission phase shift interval &#x3b1;based on the beacon number information received from the terminal.

Wireless communication system, accommodation apparatus and wireless communication method

A master station device is connected to a slave station device that emits a transmission signal received by light via an optical transmission path from a plurality of antenna elements. The master station device includes an optical signal output unit that outputs optical signals of a plurality of wavelengths, a phase adjustment unit that adjusts, for each wavelength, a phase of the transmission signal based on phase rotation that the optical signal is to undergo while being transmitted through the optical transmission path and a phase in one of the antenna elements corresponding to the wavelength of the optical signal, an optical modulation unit that modulates, for each wavelength, the optical signal output by the optical signal output unit with the transmission signal the phase of which is adjusted in accordance with the wavelength of the optical signal, and an optical combining unit that multiplexes the optical modulated signal of each wavelength and outputs the multiplexed signal to the optical transmission path. The slave station device includes an optical demultiplexing unit that demultiplexes the optical modulated signal transmitted through the optical transmission path and an optical/electric conversion unit that outputs the transmission signal obtained by converting the optical modulated signal of each wavelength into an electric signal to one of the plurality of the antenna elements corresponding to the wavelength.

Wireless communication system, parent station apparatus and wireless communication method

A wireless transmitter/receiver generates a first signal which notifies timing of a time slot allocated to each wireless station device, a conversion unit converts the first signal into an optical signal, and each of a plurality of antenna units converts the first signal from the optical signal into an electrical signal and transmits the electrical signal wirelessly. The wireless station device transmits a second signal at the timing reported by the first signal. Each of the plurality of antenna units converts the second signal wirelessly received from each wireless station device into an optical signal, and the conversion unit converts the second signal from the optical signal into an electrical signal. The wireless transmitter/receiver calculates, for each wireless station device, a transmission delay by using a difference between a reception time of the second signal and a reception time of a signal transmitted at the allocated timing by the wireless station device when it is assumed that there is no transmission delay. The wireless transmitter/receiver determines guard time between the time slots allocated to the wireless station devices based on the transmission delays of the wireless station devices.

Optical wireless communication system, wireless transmitting/receiving apparatus and optical wireless communication method

To n antenna elements of the base station, n wavelengths set at predetermined intervals in a range in which chromatic dispersion in an optical fiber between accommodation and base stations can be regarded as constant are assigned. The accommodation station adjusts the phases of optical signals of the wavelengths or modulated signals that modulate the optical signals such that the amounts of phase shift of their RF signals are at predetermined intervals. The accommodation station transmits beacon signals multiple times while varying a transmission phase shift interval &#x3b1;and the terminal transmits beacon number information of a beacon signal selected based on received power multiple times. The accommodation station varies a reception phase shift interval &#x3b1;for each piece of beacon number information to determine a reception phase shift interval &#x3b1;which maximizes the received power and determines the transmission phase shift interval &#x3b1;based on the beacon number information received from the terminal.

Growing community of inventors

Musashino, Japan

Mizuki Suga