Hitachi, Ltd.

Hitachi Computer Engineering Co., Ltd.

Hitachi Microcomputer Engineering, Ltd.

Hitachi, Ltd. and Hitachi Microcomputer System Ltd.

Hidehiko Jusa

Tomoaki Ishifuji

Eiichi Amada

Yoshihiro Takiyasu

Shuichi Adachi

Genichi Ishii

Masaaki Shida

Hiroshi Yoshigi

Takahiko Fukinuki

Yasuhiro Hirano

Atsushi Anzai

Kazunori Nakamura

Kenichiro Orita

Takaharu Aoyama

Osamu Takada

Naoya Kobayashi

Mitsuhiro Yamaga

Masato Hirai

Satoru Hirayama

Tatsuhito Iiyama

A frequency hopping communication system having a plurality of wireless mobile stations and at least one base station. Each wireless mobile station is operated to communicate according to a communication frame format generated by a base station. The system performing slow frequency hopping by keeping a frequency hopping interval within each frame. The hopping pattern of a frequency is designated at a field located at the tail of each communication frame by the base station.

Frequency-hopping communication system and communication station

The wireless LAN system has an information-carrying capacity which is several times the transmission rate obtained by a single cell. The wireless LAN system properly notifies hopping information even if an error in transmission arises. Hopping control is carried out on a master base-station device 10a and slave base-station devices 10b and 10c based on a synchronizing frame generated from hopping timing of the master base-station device 10a. After completion of the hopping control, each base-station device 10 starts to send hopping information to radio terminals 2 present in the same cell. Radio terminals 2, which are in the same cell as one of the base stations 10, work under the base-station device 10.

Wireless LAN system

A frequency-hopped mobile communication system is disclosed, in which a mobile wireless station automatically becomes a base station in accordance with the surrounding conditions, thereby automatically reconfiguring a communication network. A control frame is generated by at least one master station, and frequencies are hopped by a plurality of slave stations in accordance with the control frame. Each slave station switches the master thereof to be tracked, in accordance with the receiving conditions of the control frame and the relation between the control frame received from the master station and the status of the slave station and decides in which mode, master station or slave station, the slave station is to operate. The cells are thus automatically reconfigured.

Frequency-hopped wireless communication system and mobile wireless

In a wireless LAN system, each wireless terminal device determines whether or not the wireless terminal device has entered into a wireless LAN domain established by a base station, and if it has entered, transmits an entry terminal identification information update control frame including identification information of its own device to the base station at a predetermined time interval. The base station receives the entry terminal identification information update control frame from the wireless terminal device, stores in a storage the identification information of the wireless terminal device entered into the wireless LAN domain established by its own base station, and when it receives an information frame from a wired transmission line connected to its own base station, relay-transmits only the information frame to the wireless terminal device having the identification information thereof stored in the storage by referring the information stored in the storage.

Wireless LAN system, base station device and wireless terminal device

In a wireless communication system having a plurality of base stations connected through a control line and a plurality of mobile terminals, one of base stations (a master base station) informs a carrier frequency hop timing to the other base stations (slave base stations) through the control line. Each slave base station generates a wireless communication frame used inside of each cell and switches the carrier frequency of the wireless communication frame in synchronous to the timing indicated by the master base station. Each movable terminal receives an identifier of a frequency hopping sequence from a control information field of the wireless communication frame, hops to one carrier frequency selected among a frequency hopping sequence corresponding to this identifier, and transmit or receive the data through the field following the control information field of the wireless communication frame.

Frequency hopping wireless communication system and communication

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

A wireless network is provided for restricting the number of mobile terminal devices which are managed by the base station device for wireless communication with one another. The base station device has a mobile terminal confirming database for registering mobile terminal devices allowed to be subscribers to the wireless network, and a mobile terminal managing database for registering presently-managed mobile terminal devices. The wireless transfer request from one of the mobile terminal devices is tested to determine whether the request-issuing mobile terminal device is one of the subscribers. If the request is accepted, then the identification of the request-issuing mobile terminal device is registered into the managing database.

Wireless LAN system capable of re-transmission under management of a

A wireless communication system includes a plurality of wireless terminals and a base station for periodically generating a fixed-length communication frame composed of an information field which includes a plurality of information slots, and first and second control fields which are arranged preceding the information field and each of which includes a plurality of time slots. Each time slot of the first control field of each communication frame is used for allowing the base station to send control data for designating a terminal which is to make the transmission or reception of data in one information slot of the information field, and each time slot of the second control field thereof is used for allowing one wireless terminal to send control data indicating a requirement for assignment of an information slot for data transmission. Each wireless terminal, when receiving control data inclusive of an address of that terminal in the i-th time slot of the first control field of each communication frame, makes the reception or transmission of data in the i-th information slot in the information field of that communication frame. When the control data is not found out in the first control field, the power source of a reception unit of the wireless terminal is turned off during a period of time until the next communication frame is generated.

Wireless communication system and wireless terminal device using fixed

In a communication system having a base station for controlling a transmission right and a plurality of substations, a substation having data to be transmitted transmits the number of necessary fragments and its address to a request field of a communication frame. The base station uses a plurality pair of fragment slots and reply slots following the request field in the communication frame to transmit an address of a substation permitted to transmit data, to each fragment slot. The substation permitted to transmit data transmits the address of a destination substation and the data to a predetermined field following the address in one fragment slot. The destination station transmits a reply signal indicating the reception state of the data to the reply slot paired with the fragment slot. If the base station detects from the reply signal that the destination station failed in receiving the data, the base station instead of the substation first transmitted the data transmits the destination address and data received at the fragment slot to the next fragment slot.

Method of wireless communication between base station and mobile station

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

A television signal transmission system having an improved receiver which system is capable of transmitting a wide-band television video signal in a frequency band narrower than the frequency band of the television video signal is a multiplex video signal and the receiver reproduces a luminance signal and color signal from the multiplexed video signal. The receiver includes a motion detector for detecting motion information of a picture from the multiplex video signal and a separator for separating signals in response to the detected motion information to thereby form a picture of high quality utilizing the motion information.

High resolution color television signal transmission system and receiver

In a color television signal processing system for converting a scanning signal sequentially scanned in the transmitting side into an interlace-scanned television signal in order to obtain a high-quality color television picture, said system is arranged to detect information related to picture motion and that concerning to a spatio-temporal frequency characteristic and to control a characteristic of a spatio-temporal filter for transmitting a luminance signal on the basis of this information and to transmit the signal expressing the information multiplied with the color television signal.

Growing community of inventors

Hadano, Japan

Hidehiko Jusa