Nec Corporation

Seiji Kachi

Tomoki Osawa

Motoya Iwasaki

Susumu Otani

Shinichi Kono

Shoji Endo

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 terminalto wireless LAN terminal. Since the different subnets are allocated to respective wireless LAN terminals, wireless LAN terminalsare unable to communicate directly with each other. Wireless LAN terminalsends a packet destined for wireless LAN terminalto a default gateway (=access limiter). Since the packet received by the access limiter is destined for wireless LAN terminal, the access limiter transfers the packet to wireless LAN terminal

Method of limiting communication access between wireless LAN terminals

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.

Information transmission system and information transmission apparatus

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.

Memory mounting judgment circuit

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. Since an edge that falls from '1' to '0' does not exist in the recovery frame for improper synchronization, a start bit of the next frame can be accurately supplemented so that an improper synchronizing state is returned to a normal synchronizing state.

Start-stop synchronous communicating method capable of correcting

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. If the count value does not exceed the threshold value during that period, the sending station retransmits the request signal to repeat the count operation to elicit an acknowledgement response from those stations where the assigned link was not previously available.

Data communication using single logical link for broadcast session

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. Preferably, the portions are retransmitted to the failing stations concurrently and one after another when the failing stations are and are not greater in number than a predetermined threshold value.

Point-to-multipoint communication network capable of retransmitting a

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.

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Tokyo, Japan

Seiji Kachi