Patents by Inventor Tomoaki Ishifuji

Tomoaki Ishifuji has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 6889051
    Abstract: An offset measuring method according to the present invention accurately measures a transmitting time offset of a base station. The offset measuring method for receiving signals from the radio base station and measuring the transmitting time offset of the radio base station includes the steps of calculating estimated values of transmitting time offset based on signals received at a plurality of observation points and selecting a minimum from the estimated offsets to determine the selected minimum value as transmitting time offset of the radio base station.
    Type: Grant
    Filed: January 16, 2002
    Date of Patent: May 3, 2005
    Assignee: Hitachi, Ltd.
    Inventors: Atsushi Ogino, Mikio Kuwahara, Tomoaki Ishifuji, Kenzaburo Fujishima
  • Publication number: 20050078633
    Abstract: The mobile station has a monitor for monitoring the communication qualities of plural wireless interfaces and selecting one of the wireless interfaces to communicate, and a memory for storing the correspondence between the address unique to the selected wireless interface and the network address unique to the mobile station. The mobile station notifies the gateway of the correspondence. The mobile station supplies power to a not operating wireless interface at constant intervals and during a constant time to monitor the communication quality.
    Type: Application
    Filed: August 31, 2004
    Publication date: April 14, 2005
    Inventors: Koji Watanabe, Tomoaki Ishifuji
  • Patent number: 6865394
    Abstract: A positioning method, which is related to a technique to measure a correct position of a terminal by preventing time required for the position measurement, of calculating a position of a receiver according to signals from a plurality of wireless transmitters includes a first step of measuring propagation delay time of the signal from each of the wireless transmitters and calculating a position of the receiver and a standard deviation about measuring distance error, a second step of calculating a positioning error of the receiver a third step of determining, according to the positioning error calculated by the second step, wireless transmitters in directions nearer to a direction in which the positioning error is large, and a fourth step of re-detecting signals from the wireless transmitters determined by the third step and thereby re-calculating the position of the receiver.
    Type: Grant
    Filed: January 18, 2002
    Date of Patent: March 8, 2005
    Assignee: Hitachi, LTD
    Inventors: Atsushi Ogino, Mikio Kuwahara, Tomoaki Ishifuji
  • Publication number: 20040228400
    Abstract: The code system is realized by that a plurality of waveforms A and B each having duty ratios of 50% in which only any one of a rising edge and a falling edge is present are combined with each other, and “1” and “0” are allocated to the combined waveform. In accordance with the present invention, both a clock and data can be transmitted at the same time, and can be readily demodulated without using a complex PLL circuit. As a trial manufacture according to the present invention, the demodulator could be realized which could allow variations contained in an input frequency by more than 1 digit under operating voltage of 2 V. The effectiveness of this patent could be confirmed.
    Type: Application
    Filed: June 4, 2004
    Publication date: November 18, 2004
    Applicant: Hitachi, Ltd.
    Inventors: Satoshi Tanaka, Tomoaki Ishifuji, Kenji Nagai, Katsuhiro Furukawa
  • Patent number: 6765959
    Abstract: The code system is realized by that a plurality of waveforms A and B each having duty ratios of 50% in which only any one of a rising edge and a falling edge is present are combined with each other, and “1” and “0” are allocated to the combined waveform. In accordance with the present invention, both a clock and data can be transmitted at the same time, and can be readily demodulated without using a complex PLL circuit. As a trial manufacture according to the present invention, the demodulator could be realized which could allow variations contained in an input frequency by more than 1 digit under operating voltage of 2 V. The effectiveness of this patent could be confirmed.
    Type: Grant
    Filed: June 4, 1999
    Date of Patent: July 20, 2004
    Assignee: Hitachi, Ltd.
    Inventors: Satoshi Tanaka, Tomoaki Ishifuji, Kenji Nagai, Katsuhiro Furukawa
  • Patent number: 6731905
    Abstract: In a P-MP fixed wireless access system using quasi-millimeter and millimeter wave bands, a relaying path is autonomously set up for subscriber stations without the need for additional provision of a repetition radio circuit using a costly MMIC. A subscriber station in the fixed wireless access system is provided with a repeating function for relaying signals between a different subscriber station and a base station, a buffer memory for temporarily storing signals to be communicated therebetween, and a table for registering information for identifying a relaying path between an own reference wireless station and a lower-level subscriber station for signal repetition. The base station is provided with a table in which, in order to perform signal communication with an arbitrary subscriber registered in the base station, routing information is registered for determining whether or not to set up a relaying path via a different subscriber station registered in the base station.
    Type: Grant
    Filed: March 9, 2001
    Date of Patent: May 4, 2004
    Assignee: Hitachi, Ltd.
    Inventors: Atsushi Ogino, Hideya Suzuki, Tomoaki Ishifuji, Nobukazu Doi
  • Patent number: 6731602
    Abstract: A packet communication system which includes a first communication apparatus for transmitting input time information about input packets before transmitting the packets, and a second communication apparatus for receiving the input time information about the packets and transmitting the packets over a transmission path in an order based on the input time information. The first communication apparatus performs packet transmission in units of frames, each frame being composed of at least one packet. The second communication apparatus transmits the packets over the transmission path in chronological order of the input times of the packets input to the first communication apparatus.
    Type: Grant
    Filed: February 9, 1999
    Date of Patent: May 4, 2004
    Assignee: Hitachi, Ltd.
    Inventors: Koji Watanabe, Tomoaki Ishifuji
  • Publication number: 20040066332
    Abstract: Under a multi-path environment, receive timing for the incoming wave of the minimum propagation delay time cannot be accurately measured using the prior art.
    Type: Application
    Filed: October 8, 2003
    Publication date: April 8, 2004
    Applicant: Hitachi, Ltd.
    Inventors: Katsuhiko Tsunehara, Nobukazu Doi, Mikio Kuwahara, Tomoaki Ishifuji
  • Patent number: 6704547
    Abstract: An apparatus, system and method for measuring timing of a signal transmitted from a wireless base station antenna. The apparatus and system include a wireless base station antenna that transmits a first signal, and a transmission timing measurement apparatus having a first antenna and a second antenna that receives an accurate time value and the first signal, and that outputs an offset of the first signal from the accurate time value. The method includes receiving an accurate time, receiving the reception time transmitted from the wireless base station antenna, receiving the reception time value and the accurate time value, and comparing of the reception time value and the accurate time value.
    Type: Grant
    Filed: February 28, 2001
    Date of Patent: March 9, 2004
    Assignee: Hitachi, Ltd.
    Inventors: Mikio Kuwahara, Tomoaki Ishifuji, Nobukazu Doi
  • Patent number: 6675007
    Abstract: A charging system for use in a network composed of wireless terminals with a repeater function. As each terminal with a repeater function receives a communication session start request from a user terminal, it searches for a destination user terminal; when it finds the destination user terminal, it transfers the signal sent from the requesting user terminal to the destination user terminal without the mediation of base stations. The information about the amount of data thus transferred or communication time for transferring data is sent to the charging system which is under the control of the communications service provider concerned.
    Type: Grant
    Filed: February 4, 2002
    Date of Patent: January 6, 2004
    Assignee: Hitachi, Ltd.
    Inventors: Tsuyoshi Tamaki, Masaaki Shida, Tomoaki Ishifuji, Nobukazu Doi, Kazuko Hamaguchi
  • Patent number: 6671649
    Abstract: A position calculation method that calculates the correct position of a terminal even when errors are not distributed symmetrically for positive and negative values, by calculating the position of a terminal using the delay time of received signals. The method calculates a first range that is a difference between a range from the terminal to each of antenna and a range from the terminal to a base antenna, the range being calculated from a wireless signal delay time; calculates a second range that is a difference between a range from an assumed terminal position for calculation to each antenna and a range from the assumed terminal position for calculation to the base antenna; calculates a likelihood of the position of the terminal, repeats these procedures to obtain a point where the likelihood is maximized, and determines an obtained most likely solution as the position of the terminal.
    Type: Grant
    Filed: March 19, 2003
    Date of Patent: December 30, 2003
    Assignee: Hitachi, Ltd.
    Inventors: Mikio Kuwahara, Tomoaki Ishifuji, Takashi Yano, Kenzaburo Fujishima
  • Publication number: 20030236103
    Abstract: A system and method are provided for wireless communication. In one example, a wireless communication system that enhances total system throughput is provided. The system performs parallel data transmission from a plurality of access points to a plurality of user terminals. On terminals with power control function, their transmit power can be set to minimize interference. The wireless communication system comprises a management server which performs centralized management of time of access-point-to-terminal packet transmission, access points, and user terminals that perform data transmission, according to transmission time control information from the management server. Transmit queues for measuring downlink traffic and receive queues for measuring uplink traffic are provided on the access points or the management server. The system determines uplink and downlink periods from the transmit and receive queue lengths.
    Type: Application
    Filed: June 2, 2003
    Publication date: December 25, 2003
    Applicant: Hitachi, Ltd.
    Inventors: Tsuyoshi Tamaki, Takashi Yano, Takaki Uta, Tomoaki Ishifuji
  • Patent number: 6657579
    Abstract: Under a multi-path environment, receive timing for the incoming wave of the minimum propagation delay time cannot be accurately measured using the prior art. By using the delay profile created by delay profile creating section 102 and the first threshold value 330 received from the first threshold value calculation section 105, the first threshold value timing detection section 103 selects only the earliest receive timing exceeding the first threshold value, from all the timing that the correlation value in the delay profile becomes a maximum. By using the receive timing and the second threshold value 331 received from the second threshold value calculation section 107, reference timing calculation section 106 selects the reference timing required for calculating the receive timing for the incoming wave of the minimum propagation delay time.
    Type: Grant
    Filed: June 11, 2002
    Date of Patent: December 2, 2003
    Assignee: Hitachi, Ltd.
    Inventors: Katsuhiko Tsunehara, Nobukazu Doi, Mikio Kuwahara, Tomoaki Ishifuji
  • Publication number: 20030191604
    Abstract: A position calculation method that calculates the correct position of a terminal even when errors are not distributed symmetrically for positive and negative values, by calculating the position of a terminal using the delay time of received signals. The method calculates a first range that is a difference between a range from the terminal to each of antenna and a range from the terminal to a base antenna, the range being calculated from a wireless signal delay time; calculates a second range that is a difference between a range from an assumed terminal position for calculation to each antenna and a range from the assumed terminal position for calculation to the base antenna; calculates a likelihood of the position of the terminal, repeats these procedures to obtain a point where the likelihood is maximized, and determines an obtained most likely solution as the position of the terminal.
    Type: Application
    Filed: March 19, 2003
    Publication date: October 9, 2003
    Applicant: Hitachi, Ltd.
    Inventors: Mikio Kuwahara, Tomoaki Ishifuji, Takashi Yano, Kenzaburo Fujishima
  • Publication number: 20030189483
    Abstract: A contactless IC card having an antenna, a transmit/receive circuit for recovering data (clock) and electric power from a carrier signal received by the antenna, a logic circuit operated with the electric power supplied thereto from the transmit/receive circuit, and a memory. The transmit/receive circuit has a rectifier circuit for outputting data (clock) and rectifier circuits for electric power in such a manner that the carrier signal is inputted to each of the rectifier circuit for outputting data (clock) and the rectifier circuit for electric power. With this configuration, high frequency matching can be optimized separately for the rectifier circuit for outputting data (clock) and the rectifier circuit for electric power. It is also possible to separately optimize adjustments to a voltage of recovered data (clock) and a recovered supply voltage.
    Type: Application
    Filed: April 1, 2003
    Publication date: October 9, 2003
    Applicant: Hitachi, Ltd.
    Inventors: Takeshi Saitoh, Masaaki Shida, Tomoaki Ishifuji
  • Patent number: 6570490
    Abstract: A contactless IC card having an antenna, a transmit/receive circuit for recovering data (clock) and electric power from a carrier signal received by the antenna, a logic circuit operated with the electric power supplied thereto from the transmit/receive circuit, and a memory. The transmit/receive circuit has a rectifier circuit for outputting data (clock) and rectifier circuits for electric power in such a manner that the carrier signal is inputted to each of the rectifier circuit for outputting data (clock) and the rectifier circuit for electric power. With this configuration, high frequency matching can be optimized separately for the rectifier circuit for outputting data (clock) and the rectifier circuit for electric power. It is also possible to separately optimize adjustments to a voltage of recovered data (clock) and a recovered supply voltage.
    Type: Grant
    Filed: May 15, 1998
    Date of Patent: May 27, 2003
    Assignee: Hitachi, Ltd.
    Inventors: Takeshi Saitoh, Masaaki Shida, Tomoaki Ishifuji
  • Patent number: 6556943
    Abstract: A position calculation method that calculates the correct position of a terminal even when errors are not distributed symmetrically for positive and negative values, by calculating the position of a terminal using the delay time of received signals. The method calculates a first range that is a difference between a range from the terminal to each of antenna and a range from the terminal to a base antenna, the range being calculated from a wireless signal delay time; calculates a second range that is a difference between a range from an assumed terminal position for calculation to each antenna and a range from the assumed terminal position for calculation to the base antenna; calculates a likelihood of the position of the terminal, repeats these procedures to obtain a point where the likelihood is maximized, and determines an obtained most likely solution as the position of the terminal.
    Type: Grant
    Filed: August 1, 2001
    Date of Patent: April 29, 2003
    Assignee: Hitachi, Ltd.
    Inventors: Mikio Kuwahara, Tomoaki Ishifuji, Takashi Yano, Kenzaburo Fujishima
  • Publication number: 20030054795
    Abstract: A charging system for use in a network composed of wireless terminals with a repeater function. As each terminal with a repeater function receives a communication session start request from a user terminal, it searches for a destination user terminal; when it finds the destination user terminal, it transfers the signal sent from the requesting user terminal to the destination user terminal without the mediation of base stations. The information about the amount of data thus transferred or communication time for transferring data is sent to the charging system which is under the control of the communications service provider concerned.
    Type: Application
    Filed: February 4, 2002
    Publication date: March 20, 2003
    Applicant: Hitachi, Ltd.
    Inventors: Tsuyoshi Tamaki, Masaaki Shida, Tomoaki Ishifuji, Nobukazu Doi, Kazuko Hamaguchi
  • Publication number: 20030054796
    Abstract: A charging system for use in a network composed of wireless terminals with a repeater function. As each terminal with a repeater function receives a communication session start request from a user terminal, it searches for a destination user terminal; when it finds the destination user terminal, it transfers the signal sent from the requesting user terminal to the destination user terminal without the mediation of base stations. The information about the amount of data thus transferred or communication time for transferring data is sent to the charging system which is under the control of the communications service provider concerned.
    Type: Application
    Filed: May 30, 2002
    Publication date: March 20, 2003
    Applicant: Hitachi, Ltd.
    Inventors: Tsuyoshi Tamaki, Masaaki Shida, Tomoaki Ishifuji, Nobukazu Doi, Kazuko Hamaguchi
  • Patent number: 6527177
    Abstract: In a conventional method which defines an authentication key for each record, as the number of the records is increased in an access right management for records in a memory of an IC card, the number of the types of authentication keys is also increased to require a larger memory area for storing the authentication keys, thus causing lower memory efficiency. In order to solve such a problem, terminal types (ex. “0H”-“7H”) are defined for interrogators, so that only the number of authentication keys equal to the number of the terminal types are stored. Each record has the number of access permission bits equal to the number of the terminal types, and specifies terminal types, to which an access is permitted, by setting the bits ON or OFF.
    Type: Grant
    Filed: February 24, 2000
    Date of Patent: March 4, 2003
    Assignee: Hitachi, Ltd.
    Inventors: Tomoaki Ishifuji, Masaaki Shida