Abstract: An originator selects at least one sub-network from a plurality of sub-networks to establish a scope of a multicast group and multicasts group characteristic information, which includes a specific group identifier to the scope. The sub-networks include nodes to accept a mobile host. The mobile host is related to one of the nodes to be managed by it. Each node receives the group characteristic information when it is in the scope and judges whether or not to transfer the group characteristic information to the mobile host in response to the content of the group characteristic information. The mobile host judges where the group characteristic information is sent from when it receives the group characteristic information. Then the mobile host judges whether or not the originator admits the mobile host to participate in the multicast group on the basis of the group characteristic information.

Abstract: In a channel selection method for a radio communication system constituted by a plurality of radio stations, each radio station transmits a control signal only when required, but need not constantly transmit a control signal.

Abstract: To provide a channel selection method of a wireless communication system which enables a wireless station to select a wireless channel dynamically even when there are but an insufficient number of wireless channels, a channel selection method of selecting a wireless channel from a plurality of wireless channels prepared for the wireless communication system comprises: a channel search step (202) of checking whether any one of the plurality of wireless channels is left unused by other wireless stations of the wireless communication system or not; a sharing channel selection step (207) of selecting a wireless channel to be shared from wireless channels under use of the other wireless stations, said sharing channel selection step being performed when every of the plurality of wireless channels is found (205) to be under use of one of the other wireless stations at the channel search step; and a link establishment step of establishing the wireless link by sharing the wireless channel selected at the sharing chann

Abstract: A communication control system in a packet communication network having a plurality of radio sub-networks, the radio sub-networks being connected to a wired sub-network by learning type bridges, respectively, the system including a radio terminal for communicating with the radio sub-networks, the radio terminal including first means for detecting whether or not the terminal moves from one of the radio sub-networks to other radio sub-networks, and second means for transmitting a dummy packet when movement between the radio sub-networks is detected.

Abstract: A method for allocating a geographical identifier is executed in a network for supporting a plurality of movable hosts being moved among a plurality of sub networks as keeping communications therebetween. When movable hosts 100, 101 moves to a sub network 110, an agent 120 of the sub network 110 allocates the same geographical identifier depending on the sub network 110 to the movable hosts 100 and 101 and stores logical identifiers and link layer addresses of the movable hosts 100 and 101. The packets destined for the movable hosts 100 and 101 are sent to the agent 120. The agent gets to know the link layer address corresponding to the logical identifier of a destination movable host described in a network layer header of the received packet from the registration table, generates the link layer header of the destination movable host, and add the link layer header to the received packet before transferring the received packet.

Abstract: In a mobile communication system comprising base stations (11, 12) covering microcells (16, 17) and a base station (13) covering a macrocell (18), each of the base stations (11, 12) monitors utilization conditions in speech channels to produce a monitored result indicative of the utilization conditions and controls transmission power on the basis of the monitored result. Responsive to a communication request, each base station (11, 12, 13) selects, as a selected speech channel, one of the speech channels and assigns the selected speech channel when the selected speech channel has a power ratio of a desired wave to an interference wave that is not less than a predetermined level.

Abstract: A location information management table 14 stores information on the location of the host both at present and prior to the movement. The host is movable based on the transmission address contained in the frame transmitted therefrom. The frame addressed to the host is transferred to the segment presently connected and to the segment that has been previously connected based on the table 14. Even though the host locates halfway among a plurality of segments, stable communication can be realized. When the host moves away from other segment toward the center of one segment, the frame is transferred to one segment at a time when the timer terminates its counting operation, thus deleting unnecessary traffic.

Abstract: The object of the present invention is to provide an automatic equalizer which can automatically equalize distortion including a precursor component with a small amount of calculation and a small circuit scale.

Abstract: An automatic gain control circuit comprising a variable gain amplifier for controlling a gain of an input signal in accordance with a gain control signal, and outputting the controlled signal, a demodulator for demodulating an output signal from said variable gain amplifier and outputting a baseband signal, an amplitude detecting circuit for detecting an amplitude of the baseband signal to output an amplitude signal, a target amplitude generating circuit for outputting a target amplitude signal, a subtracter for outputting an amplitude error signal based on a difference between the amplitude signal and the target amplitude signal, a sequence control circuit for outputting trigger signals corresponding to not less than a given one-bit interval, and a gain setting circuit for setting a gain with a precision corresponding to a width of (1/N).sup.

Abstract: In a computer network where each mobile host is assigned a subnetwork-independent logical identifier (L-ID), the mobile host acquires a subnetwork-dependent geographical identifier (G-ID) from an agent-existing subnetwork and sends the G-ID to the home subnetwork of the mobile host for location registration if a beacon received therefrom is a first one or different from a previous one or acquires a G-ID from an agentless subnetwork and sends the G-ID to the home subnetwork if no beacons are received. At intervals, a multicast packet is sent from the mobile host, containing the acquired G-ID to the agentless subnetwork. A similar multicast packet is received from a second mobile host and the G-ID contained therein is stored in a database corresponding to the L-ID of the second mobile host. When establishing a session, a data packet is sent from the mobile host to the network along with a G-ID corresponding to a L-ID of the data packet stored in the database.

Abstract: A protocol conversion system for use with a circuit for realizing a protocol in a CSMA/CD system for converting the protocol in the CSMA/CD system into a protocol in a CSMA/CA system. The protocol conversion system includes first counter for performing counting for a first period from a timing of termination of a carrier sense signal indicative of input of a reception signal of a data, a random number generator for generating a random number, a second counter for performing counting for a period corresponding to a value of the random number generated by the random number generator after termination of counting by the first counter, a reset circuit for forcedly stopping the first and second counters at a timing of beginning of the carrier sense signal, and dummy signal generator for generating a pseudo receive data while the second counter is active for counting.

Abstract: In a transmission system having a procedure to exchange control information at least one time between a first terminal and a second terminal to transfer data from the first terminal to the second terminal, a relay station receives control information transmitted from the first terminal and detects existence of the control information from the second terminal during a preset detection time interval from a time of reception of the control information. If the control information has not been detected, the relay station exchanges the control information with said first terminal instead of the second terminal, receives data from the first terminal and transfers the data to the second terminal.

Abstract: In a data communication system having a sending station and multiple receiving stations interconnected by a satellite or a local area network, the sending station transmits a request signal containing an assigned logical link number to the receiving stations. If the assigned logical link is available to each of the receiving stations, each receiving station establishes a logical link to the sending station and transmits an acknowledgement signal to the sending station. During a predetermined period following the transmission of the request signal, the sending station increments a count value in response to receipt of each acknowledgement signal. When the count value exceeds a threshold value, the sending station transmits a broadcast message over the established logical link to the receiving stations.

Abstract: In a point-to-multipoint communication network wherein communication channels are established between a transmitting station and a plurality of receiving stations for transmission of data as a multicast signal, a reception confirming arrangement confirms reception of the multicast signal by the receiving stations to locate failing stations that fail to receive at least portions of the multicast signal. A retransmitting arrangement establishes relevant ones of the communication channels between the transmitting station and the failing stations for transmission of the portions to the failing stations. For reception confirmation, the data may be identified by data identifiers, as by a serial number. Alternatively, each receiving station may send back for comparison at the transmitting station a predetermined portion of datum which may be each of the data or a datum received latest at the receiving station under consideration.