Abstract: Different subnets are allocated to respective wireless LAN terminals. It is assumed that when the setting of IP addresses is completed, a packet is to be sent from wireless LAN terminal 1 to wireless LAN terminal 2. Since the different subnets are allocated to respective wireless LAN terminals 1, 2, wireless LAN terminals 1, 2 are unable to communicate directly with each other. Wireless LAN terminal 1 sends a packet destined for wireless LAN terminal 2 to a default gateway (=access limiter). Since the packet received by the access limiter is destined for wireless LAN terminal 2, the access limiter transfers the packet to wireless LAN terminal 2.

Abstract: A wireless communication system includes an access point and a terminal exchanging a packet with the access point. When receiving the packet, the access point determines whether the received packet includes a Weak Initial Vector (Weak IV). When the packet includes the Weak IV, the access point transmits a disturbance packet that has been encrypted with an encryption key different from a predetermined encryption key.

Abstract: A wireless communication system includes an access point 101 and a terminal 102 exchanging, with the access point 101, a packet encrypted with an encryption key that has been previously set on the basis of a Wired Equivalent Privacy (WEP). When receiving the packet, the access point 101 determines whether the received packet includes a Weak Initial Vector (Weak IV) having a specified bit pattern. When the packet includes the Weak IV, the access point 101 transmits a disturbing signal for preventing the packet from being eavesdropped.

Abstract: Different subnets are allocated to respective wireless LAN terminals. It is assumed that when the setting of IP addresses is completed, a packet is to be sent from wireless LAN terminal 1 to wireless LAN terminal 2. Since the different subnets are allocated to respective wireless LAN terminals 1, 2, wireless LAN terminals 1, 2 are unable to communicate directly with each other. Wireless LAN terminal 1 sends a packet destined for wireless LAN terminal 2 to a default gateway (=access limiter). Since the packet received by the access limiter is destined for wireless LAN terminal 2, the access limiter transfers the packet to wireless LAN terminal 2.

Abstract: The present invention enables voice packet communication in a wireless LAN utilizing inexpensive LAN equipment not supporting QoS, such as preferential control, band control and so forth, and can realize preferential control of voice packet without modifying an existing wireless LAN access point not supporting QoS. In a case where voice packets are admixed in packet communication via the wireless LAN, when a round trip period becomes large, a voice packet preferential control equipment gives preference for voice packet transmission with interrupting data packet transmission to a wireless LAN access point in a valve in order to prevent deterioration of communication quality of the voice packet.

Abstract: A wireless LAN system, includes an access point; and a plurality of terminals. The plurality of terminals are wirelessly connected to the access point. The access point has a server. The server treats a specified terminal of the plurality of terminals which accessed the server as a terminal of a system manager, and treats a terminal other than the specified terminal of the plurality of terminals as a terminal of a typical user whose access to the server is limited by the system manager.

Abstract: According to the file access control method of the present invention, a read-only medium and read/write medium are prepared, and when a file update is issued from an application by way of a non-real-time OS, the file that is the object of this update is copied from the read-only medium to the read/write medium under a different name, the copied file is updated, and the name of the file is stored in a correspondence table with a correspondence to the different name of the file that has been copied. Then, when an update of a file is subsequently issued, the correspondence table is checked to find if the object file is listed, and if the object file is not listed, the update process is performed as before. However, if the object file is listed, based on the corresponding different name in the correspondence table, the object file in the read/write medium is updated.

Abstract: In an information transmission system, a first frequency dividing section divides a clock signal by 2X, where X is information to be transmitted, and a second frequency dividing section divides an inverted clock by 2Y, where Y is information to be transmitted. The exclusive-OR of the outputs of the first and second frequency dividing sections is output to a frequency divisor detection section, which measures the time interval between changes thereof at the rising edge of the clock and the falling edge of the clock, thereby reading the set values of the first and second frequency dividing sections via a data signal line.

Abstract: A memory mounting judgment circuit can improve reliability in detection whether ROM is mounted or not. In response to a power-ON reset signal, a signal from an output terminal of ROM is stored in a data storage portion. By pulling up a signal line electrically connecting the output terminal of ROM and the data storage portion, the signal line when ROM is not mounted, is fixed at all "1". When ROM is mounted, data read out from ROM is stored in the data storage portion. Depending upon the storage content of the data storage portion, judgment whether ROM is mounted or not, is made.

Abstract: A method of carrying out start-stop synchronous communications is disclosed in which, when improper synchronization takes place owing to the transmission of a recovery frame for improper synchronization having information bits all indicating "0" subsequent to an information frame for transmission, a framing error is produced and the improper synchronization is detected on a receiving side and proper or normal synchronization is established upon receipt of the next frame. Here, a recovery frame for improper synchronization having information bits that all indicate "0" is transmitted immediately after an information frame. When any "0" in a data bit section of the information frame immediately before the frame of all 0 bits is misrecognized as a start bit upon receipt, "0" of the recovery frame is always placed in the position of the stop bit of the misrecognized frame so that a framing error is produced.

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.

Abstract: A satellite packet communication system comprising a central station and VSAT stations. The central station generates chip-rate clock pulses and transmits a series of data on timeslots of a frame to a satellite transponder, and a plurality of terminal stations. Each VSAT station receives the frame from the transponder and recovers the chip-rate clock pulses from the received frame. A pseudorandom number (PN) sequence generator, provided in the terminal station is synchronized with the recovered chip-rate clock pulses for generating bits of a PN sequence with which packetized data bits are pseudorandomly modulated and transmitted in burst form to the transponder. The central station includes a correlator which is synchronized with the central station's chip-rate clock pulses to detect correlations between the pseudorandomly modulated data bits a sequence of pseudorandom numbers corresponding to the PN sequence bits of the terminal stations.