Abstract: A base station of a radio communication system emits a radio wave having the same frequency by time division toward a plurality of specific areas from a plurality of antenna elements by using a multiple-beam antenna to form a plurality of spot beams, and transmits broadcast information through a plurality of beacon channels. Upon reception of the broadcast information, a terminal that exists in any one of the plurality of specific areas selects an optimum beacon channel, and transmits a communication establishment request and a bandwidth request to the base station through a request channel corresponding to information for identifying the antenna element, which is included in the broadcast information received through the selected optimum beacon channel. Upon reception of the requests, the base station schedules, when a channel is to be allocated, a channel allocation time including downlink and uplink data bandwidths and the like.

Abstract: Within a communication system in which an ARQ control is exercised, in a transmission-side communication apparatus 11, a transmission scheduling unit 113 determines a transmission amount to be transmitted to a reception-side communication apparatus 21; an erasure correction encoding unit 112 performs an erasure correction encoding process on an information packet group that is made up of a plurality of packets to be transmitted so as to generate one or more erasure correction coded packets that fit the transmission amount instructed by the transmission scheduling unit 113 and specifies the one or more erasure correction coded packets as a unit of delivery confirmation; and a modulating unit 115 transmits a transmission data signal that has been generated by performing a predetermined modulation process on each of the erasure correction coded packets.

Abstract: When prohibiting data transmission by a radio communication terminal, such as a radio communication terminal L-STA, a terminal control apparatus generates radio data including information about a data transmission prohibition time interval in an L-SIG which is a header region which each radio communication terminal can recognize in common, and, if a use state checking unit 21 has checked to see that a channel CH_a is being not used, transmits the radio data to the radio communication terminal L-STA and so on in the form of frames which the radio communication terminal L-STA can recognize by using the channel CH_a.

Abstract: A base station for a wireless LAN system has physical layers corresponding to channels, and a MAC layer. The physical layers each transmits and receives a radio signal conforming to an IEEE 802.11 standard using a corresponding channel. When transmitting, the MAC layer divides an entire data frame conforming to the standard from a head of the data frame, in accordance with a transmission rate of each physical layer, and allots the divided data frame to the physical layers so that burst times of the channels are substantially equal. When receiving, the MAC layer combines data frames received via channels through operations opposite to those performed when transmitting.

Abstract: A method aggregates frames to be transmitted over a channel in a wireless network into a single frame. Multiple MSDU frames having identical destination addresses and identical traffic classes, received in the media access control layer from the logical link layer in a transmitting station are aggregated into a single aggregate MPDU frame, which can be transmitted on the channel to a receiving station. In addition, aggregate MSDU frames with different destination addresses and different traffic classes received from the media access control layer can be further aggregated into a single aggregate PPDU frame before transmission.

Abstract: Upon receiving a frame from a transmitting radio device, a propagation attenuation calculator calculates a propagation attenuation amount from information in the received frame and registers a propagation attenuation amount for each transmission rate in a table. When transmitting a frame, a transmission power controller, selects optimum transmission power to the transmission destination radio device from the table and sends the frame at the selected optimum transmission power, and detects whether there is a value smaller than the selected optimum transmission power in the optimum transmission power at a minimum transmission rate of a radio device different from a transmission destination radio device registered in the optimum transmission power table.

Abstract: A radio tag is arranged in each of a plurality of radio tag areas. The radio tag areas can be parking lots. A radio tag reader is configured to perform radio communications with the radio tags. The radio tag reader performs radio communications with each radio tag and based on the radio communication determines whether an object, which can be a vehicle, is present in the radio tag area corresponding to the radio tag.

Abstract: A combination-information creating unit creates combination information for determining a maximum number of combinations or a maximum frame length according to a usable radio band and a modulation method and combination possibility information for indicating that a combination of frames is possible. A frame combining unit combines a plurality of frames received from an outside access line, based on the combination information, the combination possibility information, and predetermined packet information. A frame dividing unit divides a combined frame included in a received radio signal into individual frames.

Abstract: A reception processing unit measures reception states of input reception signals of each of a plurality of channels, generates local channel reception information, and applies a reception processing to the input reception signals to generate decoded signals. A media-access-control unit generates transmission frames for each of the channels using transmission data. A transmission processing unit generates radio signals including each of the transmission frames. A channel-information processing unit generates local feedback information, and inserts the local feedback information generated into at least one of the radio signals that are transmitted by the radio communication apparatus.

Abstract: A reception processing unit measures reception states of input reception signals of each of a plurality of channels, generates local channel reception information, and applies a reception processing to the input reception signals to generate decoded signals. A media-access-control unit generates transmission frames for each of the channels using transmission data. A transmission processing unit generates radio signals including each of the transmission frames. A channel-information processing unit generates local feedback information, and inserts the local feedback information generated into at least one of the radio signals that are transmitted by the radio communication apparatus.

Abstract: A communication method for a CSMA network including a radio terminal and a base station supporting RTS/CTS, includes: the base station transmitting and RTS frame to the radio terminal during a transmission-suspend-period in which the radio terminal suspends transmission to prevent a collision of packets; the radio terminal transmitting an RTR frame to the base station after the transmission-suspend-period has elapsed; and the base station transmitting a date frame to the radio terminal in response to the RTR frame.

Abstract: A base station for a wireless LAN system has physical layers corresponding to channels, and a MAC layer. The physical layers each transmits and receives a radio signal conforming to an IEEE 802.11 standard using a corresponding channel. When transmitting, the MAC layer divides an entire data frame conforming to the standard from a head of the data frame, in accordance with a transmission rate of each physical layer, and allots the divided data frame to the physical layers so that burst times of the channels are substantially equal. When receiving, the MAC layer combines data frames received via channels through operations opposite to those performed when transmitting.

Abstract: A MAC unit divides data to be transmitted into number of applying channels, thereby generating transmission data. An applying-channel notifying unit inserts channel information for identifying an applying channel into a used area of the transmission data. Transmission processing units corresponding to the applying channels generate radio frames from the transmission data into which the channel information is inserted, and transmit the generated radio frames to the radio communication apparatus at the reception side.

Abstract: A method aggregates frames to be transmitted over a channel in a wireless network into a single frame. Multiple MSDU frames having identical destination addresses and identical traffic classes, received in the media access control layer from the logical link layer in a transmitting station are aggregated into a single aggregate MPDU frame, which can be transmitted on the channel to a receiving station. In addition, aggregate MSDU frames with different destination addresses and different traffic classes received from the media access control layer can be further aggregated into a single aggregate PPDU frame before transmission.

Abstract: A reception processing unit measures reception states of input reception signals of each of a plurality of channels, generates local channel reception information, and applies a reception processing to the input reception signals to generate decoded signals. A media-access-control unit generates transmission frames for each of the channels using transmission data. A transmission processing unit generates radio signals including each of the transmission frames. A channel-information processing unit generates local feedback information, and inserts the local feedback information generated into at least one of the radio signals that are transmitted by the radio communication apparatus.

Abstract: An electromagnetic clutch includes a first rotatable member for connection to an external driving source and a second rotatable member for connection to a driven member. An annular magnetic member is connected to the second rotatable member through a plurality of leaf springs. A third rotatable member is connected to the second rotatable member to limit the axial movement of the annular magnetic member. A plurality of connecting and absorbing devices are fixedly disposed between the annular magnetic member and the third rotatable member. These devices absorb vibration and impact forces when the annular magnetic member is attracted to the first rotatable member. A device is provided for preventing the destruction of the connecting and absorbing device due to the impact force and vibration created upon engagement of the electromagnetic clutch.

Abstract: An electromagnetic clutch includes a first rotatable member for connection to an external driving source and a second rotatable member for connection to a driven member. An annular magnetic member is connected to the second rotatable member through a plurality of leaf springs. A third rotatable member is connected to the second rotatable member to limit the axial movement of the annular magnetic member. A plurality of connecting and absorbing devices are fixedly disposed between the annular magnetic member and the third rotatable member. These devices absorb vibration and impact forces when the annular magnetic member is attracted to the first rotatable member. A device is provided for preventing the destruction of the connecting and absorbing device due to the impact force and vibration created upon engagement of the electromagnetic clutch.

Abstract: An electromagnetic clutch includes a first rotatable member for connection to an external driving source and a second rotatable member for connection to a driven member. An annular magnetic member is connected to the second rotatable member through a plurality of leaf springs. A third rotatable member is connected to the second rotatable member to limit the axial movement of the annular magnetic member. A plurality of connecting and absorbing devices are fixedly disposed between the annular magnetic member and the third rotatable member. These devices absorb vibration and impact forces when the annular magnetic member is attracted to the first rotatable member. A device is provided for preventing the destruction of the connecting and absorbing device due to the impact force and vibration created upon engagement of the electromagnetic clutch.