Nec Corporation

Makoto Nishio

Naoya Henmi

Hitoshi Takeshita

Tatsuya Shiragaki

Hirofumi Shimomura

Kazuo Takagi

Tsuneo Nakata

Shuji Suzuki

Akira Arutaki

Syuji Suzuki

Hiromitsu Watanabe

Makiko Yoshida

Takahiro Numai

Sho-ichiro Nakai

A transmitter/receiveron a mobile bodyutilizes a plurality of antennas. It is assumed that a plurality of the antennasare distributed and arranged in a moving direction of the mobile body, and the antennas at both ends are away from each other at an extent that a distance between the antennas is not negligible as compared with an interval of the base station. A radio wave from the base station-is stronger in intensity in-than in the center, and the radio wave from the base station-is stronger in intensity in-than in the center, respectively, whereby the communication stabilization effect, which is larger as compared with the case that the antennas are locally located in the center, is expected. This enables the interval of the base station, which is broader than the conventional one, to be employed, yet both of a speed and a frequency of a hand-over process to be lowered, and in addition hereto, the bandwidth utilization efficiency, which is higher as compared with that of the conventional example, to be realized.

Mobile device and radio interface arrangement method

Multiple working paths are established on each working rings and multiple protection paths are established on each of multiple protection rings. A working path on a first working ring spans across first and second nodes for signal transmission in a first direction of the ring, and a working path on a second working ring spans across the first and second nodes for signal transmission in a second, opposite direction of the ring. A protection path on a first protection ring spans across the first and second nodes for signal transmission in said second direction, and a protection path on a second protection ring spans across the first and second nodes for signal transmission in said first direction. The first and second nodes normally use the working paths, respectively. When one of the working paths fails, the first and second nodes use a corresponding protection path.

Ring network for sharing protection resource by working communication paths

In a ring topology network, a number of nodes interconnect transmission links to form first and second working rings and first and second optical protection rings in a ring topology. Multiple working paths are established on each working ring and multiple protection paths are established on each protection ring corresponding to the working paths. A first working path spans across first and second nodes for transmission of a signal in a first direction of the ring topology, and a second working path of the second working rings spans across the first and second nodes for transmission of a signal in a second direction of the ring topology opposite to the first direction. A first protection path on the first protection ring spans across the first and second nodes for transmission of a signal in the second direction of the ring topology, and a second protection path of the second protection ring spans across the first and second nodes for transmission of a signal in the first direction of the ring topology. The first and second nodes normally use the first and second working paths, respectively. Responsive to a failure of one of the first and second working paths, the first and second nodes use a corresponding one of the first and second protection paths, instead of the failed working path.

Optical signals having arbitrary wavelengths of wavelength-multiplex optical signals are separated in an optical add-dorop multiplexer . Switching of the signals after separation and an external signal that is input outside is conducted in an ATM switch . The signals after the switching by the ATM switch is combined with wavelength-multiplex signals in the optical add-dorop multiplexer

Optical communication network node

Traffic characteristics of virtual paths 140 through 142 are monitored. A network node 120 notifies a network management system 170 that the traffic characteristics exceeds a predetermined threshold value, if it happens. The network management system 170 establishes an optical path 220 between certain network nodes 100 and 130 and use the optical path to transfer the virtual paths 141 and 142 multiplexed with optical paths 160 through 162 previously established for the individual transmission paths. On the other hand, the virtual paths 141 and 142 transferred on the optical path 220 are inverse switched into the optical paths 160 through 162, when the traffic characteristics for the virtual paths 141 and 142 are within the threshold value.

Electro/optical combined type network node control system

In a video server used for a video-on-demand system, a special video program, such as a commercial video program, is transmitted from a special video storage unit of the video server to each subscriber terminal within a nontransmission time which takes place during a searching time for a video program requested by the subscriber and/or during an execution time of a specific reproduction control command, such as a 'FAST-FORWARD' command, a 'FAST-REWIND' command. The transmission of the special video program is not stopped even when a reproduction control command is given from the subscriber to the special video storage unit by judging the reproduction control command to be invalid while a reproduction control command related to video programs different from the special video program is executed by judging the commands to be valid.

Video server and video-on-demand system capable of effectively

In an ATM virtual path switching node, upon being notified of a current virtual path by a virtual path monitoring unit, a link fault determination unit compares the number of faulty current virtual paths with a predetermined threshold value. When the number of faulty current virtual paths is equal to or larger than the threshold value, a link fault is determined, and a message communication unit transmits/receives a link fault notification signal to/from another ATM virtual path switching node. When the number of faulty current virtual paths is smaller than the threshold value, a current virtual path fault is determined, and the message communication unit transmits/receives a virtual path fault notification signal to/from another ATM virtual path switching node. The message communication unit transmits a switching control signal for designating switching from the current virtual path to a stand-by virtual path. A current virtual path information management unit manages correspondence between the current virtual path having, as one switching terminal, a self ATM virtual path switching node and a plurality of links in an ATM network.

ATM virtual path switching node

In an ATM switching system, bi-directionally coupling devices establish connections between corresponding interface units and an ATM switching module. The switching module includes a self-routing switch, an input distribution network for establishing connections between the bi-directionally coupling devices and the input ports of the self-routing switch, and an output distribution network for establishing connections between the output ports of the self-routing switch and bi-directionally coupling devices. The bi-directionally coupling devices and the input and output distribution networks are controlled in accordance with data supplied from the interface units indicating the directions of signals passing through the interface units and the operating speed of the interface units.

ATM switching system with distribution networks for varying traffic

A video-on-demand system provides video signals from a video information provider to any one of subscriber terminals. The system comprises video storage devices distributed over a network area for storing a video program supplied from the video information provider. A video gateway receives a subscriber request from a subscriber terminal and produces a control signal according to the information stored in a database. A service request monitor analyzes subscriber requests received by the video gateway to produce a list of recorded calls. A program relocator analyzes the list to determine first and second video storage devices between which the video program is to be transferred. A transfer command generator is responsive to the determined video storage devices for supplying a program transfer command signal to the video gateway for updating the database. A switched telecommunication network is responsive to the program transfer command signal for transferring the video program from the first video storage device to the second video storage device and responsive to the control signal for establishing a connection between the subscriber terminal and the second video storage device,

Video-on-demand system with program relocation center

An optical wavelength selection control system in an optical network includes an optical center node device and a plurality of terminal devices each comprised of a work station and an interface. The optical center node device includes a control circuit, a plurality of optical switches and a plurality of tunable wavelength filters. When there occurs a collision among the plurality of terminal devices wherein a plurality of terminal devices send simultaneously optical packets to the same terminal device, the control circuit operates to control the optical switches and the tunable wavelength filters such that they select only one optical packet, based on information relating to, for example, a data length to be transferred. The control circuit sends out an acknowledgment (ACK) signal to the terminal device whose optical packet has been selected. To each of the terminal devices whose optical packets have not been selected, the control circuit sends out, in addition to a not-acknowledgement (NACK) signal, a signal indicating a resending time schedule. There are no possibilities any more for at least these optical packets to be involved in the collision problems, and this ensures an enhancement of the throughput of the network system.

Optical wavelength selection control system in optical networks

In an optical ATM switching system, an optical ATM cell is produced in response to an incoming ATM cell so that it contains an optical routing bit in a timeslot corresponding to the destination of the cell. A first switching stage is provided for routing the cell from one of its inlets to one of its outlets in accordance with the routing bit contained in the cell and generating a routing signal indicative of the position of the outlet to which the cell is routed. A second switching stage is connected to the outlets of the first switching stage for routing the cell to one of optical buffers in response to the routing signal from the first switching stage. Optical combiners are provided, each corresponding to a group of the optical buffers for combining outputs of the corresponding group of optical combiners.

Optical ATM self-routing switching system with reduced routing header

An optical switching system for optical wavelength-division and time-division multiplexed signals includes a plurality of tunable wavelength filters each of which selects a signal having a desired wavelength from an optical wavelength-division and time-division multiplexed signal, a plurality of optical memory elements each of which is supplied with an output signal of each of the plurality of tunable wavelength filters. Each optical memory element memorizes a light intensity of the output signal by being applied with a first control voltage and supplies an output port with the output signal which is converted to have a predetermined wavelength in a desired time slot. The tunable wavelength filters and optical memory elements may by replaced by wavelength filters and tunable wavelength optical memories.

Optical switching system for optical wavelength-division and

In an optical self-muting network, N optical splitters are associated respectively, with N inlet terminals for splitting an optical signal from the associated inlet terminal into M replicas of the optical signal. M optical combiners, associated respectively with M outlet terminals, combines N optical signals incident thereon into a combined optical signal and couples it to the associated outlet terminal. M sets of N optical gates are connected between the N optical splitters and the M optical combiners. Each optical gate allows passage of an optical signal incident thereon when it timely coincides with an electrical signal applied thereto. A controller supplies a gate control electrical signal to the optical gates of each set during M successive intervals. Contention between optical packets simultaneously incident on the optical gates of the same set is resolved by the controller.

Self-routing network using optical gate array driven by control voltages

An optical switching network comprises a plurality of optical splitters coupled respectively to inlet highways for receiving wavelength-time division multiplex (WTDM) signals through the respective inlet highways, each of the multiplex signals comprising a series of WTDM signals each being identified by a unique wavelength and a unique time slot. A like plurality of sets of tunable wavelength filters are provided. The filters of each set are coupled to respective outputs of the splitters for selecting one of the WTDM signals. A like plurality of time-space switches are associated respectively with the sets of the tunable wavelength filters. Each of the time-space switches has input ports and output ports, the input ports of the time-space switch being coupled respectively to outputs of the filters of the associated set for interchanging the time slot of the selected WTDM signal with another time slot and establishing a path for the selected wavelength between the input ports and the output ports. A like plurality of sets of wavelength tunable lasers are provided, the wavelength tunable lasers of each set being coupled to the output ports of an associated one of the time-space switches for generating an optical output according to the WTDM signal from the established path, the optical output having a wavelength different from the wavelength of the selected WTDM signal. A like plurality of optical combiners are provided for coupling the output of the wavelength tunable lasers of different sets to a respective one of outlet highways.

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Tokyo, Japan

Makoto Nishio