Patents by Inventor Kei Igarashi

Kei Igarashi 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).

  • Publication number: 20100080162
    Abstract: An object of the present invention is to suppress quality deterioration of a multicast packet due to transmission delay jitter. An access point comprises: a received packet analysis unit which extracts, from a packet transmitted from a wireless communication station, identification information for identifying a wireless communication station, MC reception information to indicate whether the wireless communication station receives a multicast packet or not, and communication operation information to indicate whether the communication operation of the wireless communication station is set to PS mode or not; an STA table management unit which generates an STA table associating the extracted identification information, MC reception information and communication operation information, and stores this STA table in a memory; and a packet transmission timing control unit which controls a transmission timing of the multicast packet based on the STA table stored in the memory.
    Type: Application
    Filed: September 21, 2009
    Publication date: April 1, 2010
    Applicant: NTT DoCoMo, Inc.
    Inventors: Kei Igarashi, Akira Yamada
  • Publication number: 20100054168
    Abstract: When a wireless communication station, which is about to communicate while intermittently receiving a multicast service, transmits, to an access point, a request packet describing information on the multicast service and an intermittent reception request, the access point describes, in a packet, intermittent reception timing information corresponding to the multicast service information described in this request packet, and replies with this packet to the wireless communication station. The wireless communication station reads the intermittent reception timing information from the received packet, and performs transition to the Awake state or the Doze state according to this intermittent reception timing. The access point, on the other hand, transmits the multicast packet to the wireless communication station according to the intermittent reception timing.
    Type: Application
    Filed: August 28, 2009
    Publication date: March 4, 2010
    Applicant: NTT DoCoMo, Inc
    Inventors: Kei IGARASHI, Akira Yamada
  • Publication number: 20100054214
    Abstract: An access point for establishing wireless connection with one or more wireless communication stations which can perform intermittent reception operation, based on a packet transmission system which allocates wireless bands by CSMA/CA, has: unit for describing, in a same packet or in respective packets, buffering information on a downlink packet addressed to a subordinate wireless communication station currently in an intermittent reception state, and transmission prohibition period information indicating a period where transmission from the subordinate wireless communication station is prohibited; unit for transmitting the instruction described packet, in which the description has been made, to the subordinate wireless communication station; unit for making a state of the access point transit to a Doze state immediately after the instruction described packet is transmitted, or when a predetermined number of downlink packets are transmitted; and unit for making a state of the access point transit to an Awake s
    Type: Application
    Filed: August 28, 2009
    Publication date: March 4, 2010
    Applicant: NTT DoCoMo, Inc.
    Inventors: Kei IGARASHI, Akira Yamada
  • Publication number: 20090279524
    Abstract: Embodiments of the present invention include a method and apparatus for reducing control signaling overhead in a hybrid wireless network.
    Type: Application
    Filed: May 12, 2009
    Publication date: November 12, 2009
    Inventors: Yifan Yu, Lei Du, Yong Bai, Lan Chen, Akira Yamada, Kei Igarashi
  • Publication number: 20090257368
    Abstract: A radio terminal includes a radio interface configured to allow radio communication with a radio base station, and a controller configured to control switching between a wake-up state in which the radio interface is turned on and a sleep state in which the radio interface is turned off. The radio terminal acquires a reference wake-up timing scheduled as a wake-up timing for switching from the sleep state to the wake-up state. The controller shifts the wake-up timing from the reference wake-up timing.
    Type: Application
    Filed: April 15, 2009
    Publication date: October 15, 2009
    Applicant: NTT DoCoMo, Inc.
    Inventors: Imad AAD, Luis Loyola, Joerg Widmer, Kei Igarashi, Akira Yamada
  • Publication number: 20090257369
    Abstract: A radio terminal includes: a controller configured to control switching between a wake-up state in which a radio interface is turned on and a sleep-state in which the radio interface if turned off; a battery configured to accumulate electric power to be supplied to the radio interface; a remaining battery amount acquiring unit configured to acquiring a remaining battery amount being a remaining amount of electric power accumulated in the battery. The controller performs switching from the sleep state to the wake-up state, according to a communication order where own radio terminal performs radio communication. The own-terminal communication order is scheduled based on the remaining battery amount.
    Type: Application
    Filed: April 15, 2009
    Publication date: October 15, 2009
    Applicant: NTT DoCoMo, Inc.
    Inventors: Kei Igarashi, Akira Yamada, Luis Loyola, Imad Aad, Joerg Widmer
  • Publication number: 20090040991
    Abstract: An object of the present invention is to realize a distributed autonomous transmission scheduling by using a terminal without the need to observe packets in relation to communication of other wireless terminals in a cell, such as VoIP, in which a plurality of wireless terminals that periodically transmit packets exist, thereby allowing intermittent reception during the packet observation and enabling to control power consumption of the wireless terminal as well as to reduce the load to thereby improve the communication quality. To attain the object, a VoIP terminal 100 recognizes and retains a scheduling table received by a wireless terminal that is connected to a wireless base station and that is not communicating with other wireless terminals, additionally writes terminal information of the terminal in the scheduling table at the start of communication of the terminal, and broadcasts the scheduling table.
    Type: Application
    Filed: August 8, 2008
    Publication date: February 12, 2009
    Applicant: NTT DoCoMo, Inc.
    Inventors: Kei IGARASHI, Akira Yamada
  • Publication number: 20080043688
    Abstract: A wireless communication terminal comprises: a packet receiving unit for receiving a packet from a wireless base station; module for obtaining a transmission rate and a required transmission time from the received packet; module for calculating a time required to perform a packet transmission/reception procedure on the basis of the required transmission time; an analysis unit that functions as module for recognizing the existence of other terminal by decoding a destination MAC address described in the packet when the obtained transmission rate is equal to or lower than a transmission rate used by the wireless communication terminal; and a same-cell terminal list creation unit and band use time period scheduling unit for setting a band use time period that is equal to or greater than the time required to perform the packet transmission/reception procedure, for a time period, within a predetermined period corresponding to a packet generation period, regarding the other terminal and the wireless communication te
    Type: Application
    Filed: August 20, 2007
    Publication date: February 21, 2008
    Applicant: NTT DoCoMo, Inc.
    Inventors: Kei Igarashi, Akira Yamada
  • Publication number: 20070223413
    Abstract: A wireless communication device that transmits packets, on the basis of a packet transmission scheme for allocating wireless bands with virtual carrier sensing, has: monitoring module for monitoring packets communicated between other wireless communication devices and base stations for a local cell and another cell; determination module for determining whether a possibility exists that a local station receives other-cell interference resulting from communication between the wireless communication device in the other cell and the base station, on the basis of the monitoring result; occupancy period detection module for detecting an occupancy period occupied due to communication between the wireless communication device in the other cell and the base station, on the basis of the monitoring results, when determination is made that receiving the other-cell interference is possible; and timing recognition module for recognizing a timing for avoiding the other-cell interference in a predetermined period on the basi
    Type: Application
    Filed: March 19, 2007
    Publication date: September 27, 2007
    Applicant: NTT DoCoMo, Inc.
    Inventors: Kei IGARASHI, Akira YAMADA
  • Publication number: 20070201505
    Abstract: A communication terminal used in a mobile communication system complying with a carrier sense multiple access scheme is disclosed. The communication terminal includes: a receiving unit configured to receive a wireless packet transmitted by another communication terminal or a base station; a determination unit configured to determine periodic transmission timing of the communication terminal based on determination criterion information included in the wireless packet; and a transmission unit configured to periodically transmit wireless packets to the base station based on the transmission timing.
    Type: Application
    Filed: February 27, 2007
    Publication date: August 30, 2007
    Applicant: NTT DoCoMo, Inc.
    Inventors: Akira Yamada, Kei Igarashi, Takatoshi Sugiyama
  • Publication number: 20070183326
    Abstract: A wireless communication device that performs packet transmission in accordance with a packet transmission system that performs wireless bandwidth allocation by virtual carrier sensing has a time-point management section that manages the time-point and outputs current time-point information, and a parameter management section that manages a parameter relating to packet transmission right acquisition priority.
    Type: Application
    Filed: February 5, 2007
    Publication date: August 9, 2007
    Applicant: NTT DoCoMo, Inc.
    Inventors: Kei Igarashi, Akira Yamada, Atsushi Fujiwara, Takatoshi Sugiyama
  • Publication number: 20070086471
    Abstract: A wireless communication apparatus comprises a transmission buffer configured to store packets addressed to one or more communication nodes in the network until a transmission timing; a requesting interval determination unit configured to determine a listen interval for each of the communication nodes based on the amount and/or the priority of packets accumulated in the transmission buffer; and a transmission unit configured to transmit a request frame to each of the communication nodes to request the communication nodes to receive a beacon from the wireless communication apparatus at the determined listen interval.
    Type: Application
    Filed: September 18, 2006
    Publication date: April 19, 2007
    Applicant: NTT DoCoMo, Inc.
    Inventors: Kei Igarashi, Akira Yamada, Atsushi Fujiwara