Hitachi, Ltd.

Hitachi Microcomputer Engineering, Ltd.

Hitachi, Ltd. and Hitachi Microcomputer System Ltd.

Hitachi, Ltd. and Hitachi Microcomputer Eng. Ltd.

Kazunori Nakamura

Mitsuhiro Yamaga

Yoshihiro Takiyasu

Osamu Takada

Hidehiko Jusa

Koichi Kimura

Eiichi Amada

Atsushi Takai

Norihiko Sugimoto

Naoya Kobayashi

Ryozo Yoshino

Kunio Hiyama

Atsushi Anzai

Katsuyoshi Onishi

Nagatoshi Usami

Satoru Hirayama

Tatsuhito Iiyama

A wireless LAN system which allows the transmission and reception of various data without lowering the transmission efficiency and the transmission quality even in an overlapping environment of areas of a plurality of wireless LANs and a base station apparatus therefor are provided. The wireless LAN system has a plurality of wireless LANs including base stations and wireless terminal devices, and the base stations and the wireless terminal devices in the wireless LANs communicate while sequentially hopping carrier frequencies to conduct the intercommunication between the base stations in the wireless LANs through inter-base station communication units. Each base station includes a unit for transmitting and receiving a specific frame to and from other base stations through the inter-base station communication unit to determine whether its own base station is a master base station or not and a unit for assigning different hopping start frequencies to its own base station and other base stations when its own base station is determined as the master base station.

Wireless LAN system and base station apparatus

Frontend LANs connecting plural stations are connected to plural nodes of a backbone LAN respectively. The backbone LAN is constituted by plural physical or logical links, and each node corresponds to each frontend LAN. A first data block is segmented into one or plural second data block units of fixed length and transferred to destination nodes, a bridge is provided in order to assemble the second data blocks into the first data block. The bridge can transmit the second data blocks to arbitrary links, and the receiving is performed through one link. The bridge a decoder also has a decoder for decoding whether the learning should be performed or not, based on the learning indication information existing in the second data block including the routing information.

Bridge apparatus and a communication system between networks using the

In a network having a plurality of node apparatus connected to a transmission line, each node apparatus segmenting a transmission message into information blocks of a predetermined length and transmitting them to the transmission line in the form of a fixed length packet (cell) having a source address, each node apparatus sequentially stores packets having different source addresses in vacant memory blocks of a buffer memory. There is written in each memory block the packet data as well as a next address pointer indicating a memory block in which the next received packet having the same source address is stored. When a packet containing the last information block of a message is received, stored in a read address queue is the address indicating the memory block which stores the first information block of the same packet. Reading the first block of a message from the buffer memory is executed in accordance with an address read from the read address queue, and reading the following blocks is executed in accordance with the next address pointer. Read/write of the buffer memory is alternately executed in units of memory block.

Communication apparatus for reassembling packets received from network

In a network system wherein a plurality of terminal devices communicates with each other via respective node devices over a ring transmission line, a transmitting node device can confirm whether a multicast information transmission has succeeded or failed. The transmitting node device send a response frame after a multicast information frame. A receiving node device relays the multicast information frame and a response frame from the upstream node device to the downstream one when the multicast information has been received successfully, or in case of a failure in receiving the multicast information, sends a response frame to the downstream node device by changing at least part of the response frame from the upstream node device. The transmitting node device can determine from a received response frame if there is one or more of the receiving node devices which cannot receive the multicast information.

Ring network system for transmission of multicast information

A decoding circuit is operative to decode a differential Manchester code consisting of four symbols 'J', 'K', '1' and '0' each composed of two consecutive signal elements. For detection of the symbol 'J' and consequent determination of the symbol boundary, the decoding circuit has a circuit configuration which takes advantage of the fact that the symbol 'K' immediately follows the symbol 'J' and three consecutive signal elements, two of which are included in the symbol 'J' and one of which is for a symbol immediately preceding the symbol 'J', have the same polarity. To prevent an error that a second occurrence of the symbol 'J' is detected after completion of detection of the symbol 'J', the decoding circuit has an additional circuit configuration which inhibits the detection of the symbol 'J' until the symbol '0' or the symbol '1', for example, is detected.

Decoding circuit

Growing community of inventors

Hadano, Japan

Kazunori Nakamura