| Hitachi Communication Technologies, Ltd. Patent applications |
| Patent application number | Title | Published |
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| 20110096865 | Digital predistortion transmitter - There is a need for effectively compensating distortion when a predistortion transmitter is subject to not only a memory effect due to nonlinearity of an amplifier, but also a modulator's DC offset, IQ unbalance, or local quadrature error. A predistortor to be used is a polynomial predistortor including a polynomial basis generation portion and an inner product calculation portion. The polynomial basis generation portion delays a real part and an imaginary part of a complex input signal Sx=Ix+jQx for up to M samples to generate 2(M+1) signals, duplicately combines these signals to generate monomials having maximum degree N, and outputs, as a basis vector, all or part of the monomials depending or needs. The inner product calculation portion performs an inner product calculation using a coefficient vector, i.e., a set of complex numbers sized equally to the basis vector to find a polynomial value and outputs the value as a complex signal. | 04-28-2011 |
| 20110096794 | Packet transfer apparatus - A packet transfer apparatus connects two networks of different protocols. The packet transfer apparatus, connected to a first communication network and a second communication network, performs the steps of: storing first destination correspondence information; receiving a packet of the first communication protocol; based on the first destination correspondence information, determining destination information of a packet of the second communication protocol corresponding to destination information of the received packet of the first communication protocol; generating the header of the packet of the second communication protocol, based on the determined destination information of the packet of the second communication protocol; converting the received one or more packets of the first communication protocol into one or more packets of the third communication protocol; and adding the generated header of the packet of the second communication protocol to the packets of the third communication protocol. | 04-28-2011 |
| 20100226244 | Network System - Provided is a multicast path management method for a connectionless communication. Also provided is a path protection function which is effective when a path has failed. A network is formed by a trunk and a branch path. The multicast path is managed by end-to-end and when a failure has occurred, an instruction is issued from the apex of the multicast tree to respective end-to-end paths so as to switch from the currently used channel to a backup path. Thus, upon failure, an individual path protection can be performed without affecting other parts of the tree to which the same multicast flow as the defective path is distributed or the distribution state of the multicast flow. | 09-09-2010 |
| 20100113071 | CELLULAR PHONE AND MOBILE SWITCHING CONTROLLER - In a case where a cellular phone exists outside a WOS system service area, the cellular phone receives a not-connectable signal and an audio message from a mobile switching controller. The cellular phone conducts disconnection processing with the not-connectable signal as a turning point. Moreover, the cellular phone stores an extension number and converts a dedicated special number into an external number for retransmission, thus establishing connection to a PBX. After the reception of a connection-accepted signal and an automatic exchange answer message from the PBX, the cellular phone automatically transmits the stored extension number. | 05-06-2010 |
| 20100086304 | OPTICAL COMMUNICATION SYSTEM - A transmitting apparatus includes a plurality of code spreaders different in spreading code, a reception processing unit that selectively distributes transmission data to the plurality of code spreaders, a plurality of optical transmitters each of which that transmit a code-spread signal to an optical fiber as a CDMA optical signal of a carrier wavelength different from that of the other optical transmitters, and a signal multiplexing unit that selectively supplies outputs of the plurality of code spreaders to the plurality of optical transmitters, and a receiving apparatus includes an optical receiver that receives a wavelength-division-multiplexed CDMA optical signal from the optical fiber, and a plurality of despreaders connected to the optical receiver and different in spreading code, wherein each of the despreaders reproduces a CDMA signal corresponding to its spreading code from an output signal of the optical receiver. | 04-08-2010 |
| 20100067910 | PON SYSTEM AND OPTICAL NETWORK UNIT - Provided is an ONU that suppresses transmission of a useless multicast control message to a PON section and enables a communication bandwidth of the PON section to be effectively used. The ONU of the PON system has a multicast group management table that shows a correspondence between a multicast group identifier and an address of a user terminal participating in a multicast group. When the ONU receives a request message of participation in the multicast group from the user terminal, the ONU registers the correspondence between the multicast group identifier indicated by the received message and the user terminal address. A new received message is deleted without being sent to the OLT if another user terminal address is registered already, along with a correspondence with the same multicast group identifier, in the multicast group management table. | 03-18-2010 |
| 20100062787 | COMMUNICATION QUALITY CONTROL SYSTEM - The present invention implements communication control with user's service subscription information reflected in a mobile communication network. A QoS control server for providing a communication quality control function of a network, a user information management server for managing user's service information, a service proxy server for transferring a service control message transmitted by a user to a service control server, a service relay server for relaying a message between service control servers in two different networks, and a service control server for exercising service control based on user service information are included. In user service start processing, the service control server or service relay server transmits a service control message inclusive of service subscription information acquired beforehand to the service proxy server. The QoS control server acquires the service subscription information from the service proxy server. Thus, subscriber information is reflected to communication quality control processing. | 03-11-2010 |
| 20100039977 | RADIOCOMMUNICATION SYSTEM AND MULTICAST DATA DISTRIBUTION METHOD IN THE RADIOCOMMUNICATION SYSTEM - Radio resources are utilized efficiently and the communication quality is improved by flexibly adapting to the state of radio waves at a base station varying every moment or the topology of the distribution area of contents in multicast communication. The base station ( | 02-18-2010 |
| 20100034205 | COMMUNICATION NETWORK SYSTEM, PATH CALCULATION DEVICE, AND COMMUNICATION PATH ESTABLISHMENT CONTROL METHOD - In an MPLS or GMPLS network, links for hops of a communication path and adaptation to be implemented on the border of management domains or layers are automatically appropriately selected based on a service type or a requirement for maintenance. First, a unit that appends an identifier of a service to be provided and an attribute of the service to a communication path establishment control message, and requests path establishment is installed in a source node. Secondly, a unit that determines a requirement for maintenance of the communication path and adaptation on the basis of the service identifier and/or service attribute is installed in each node. Thirdly, maintenance attributes of network resources are compared with the requirement for maintenance in order to determine links and nodes through which the communication path passes. The determined links, nodes, and adaptation are designated as action parameters for a switching unit and/or interface unit. | 02-11-2010 |
| 20100021161 | PON SYSTEM - Disclosed herewith is a PON system and a bandwidth controlling method capable of controlling congestion with use of an upstream bandwidth in a PON section efficiently when congestion occurs in a gateway (GW) connected to an OLT. An OLT connected to a plurality of ONUs through a passive optical network (PON) and to a gateway (GW) through a communication line, when receiving a congestion occurrence notice indicating a congestion occurred output number from a GW, identifies the identifier of the ONU that is using a GW output line having the congestion output port number and shifts the bandwidth controlling of the PON section in a normal mode for allocating a bandwidth to each ONU normally to that in a bandwidth suppression mode for allocating a congestion time allowable bandwidth that is less than the current bandwidth to the ONU having the identified ONU identifier and a bandwidth to each of other ONUs according to its transmission queue length. | 01-28-2010 |
| 20090324247 | OPTICAL MODULATOR - The present invention relates to an optical modulator that generates quaternary amplitude modulated light without inter-symbol-interference by splitting input light into three optical paths, generating a continuous wave signal in a first optical path, generating binary phase modulated lights using a single drive MZ type optical phase modulator in second and third optical paths, and interfering them at in-phase and at field amplitude 1:a:b. | 12-31-2009 |
| 20090317078 | OPTICAL TRANSMISSION DEVICE AND OPTICAL TRANSMISSION METHOD - The signal quality of ultra high-speed signals such as 40 Gbit/s and 100 Gbit/s are significantly degraded due to wavelength dispersion and nonlinear effects in an optical fiber. Thus, there is provided a transponder unit in which a light source is polarization multiplexed in a direction mutually orthogonal to a signal direction, in order to reduce the nonlinear effects in the optical fiber and improve the signal quality. At the same time, it is possible to monitor an amount of the wavelength dispersion in the optical fiber, allowing for more precise dispersion compensation design. | 12-24-2009 |
| 20090303996 | COMMUNICATION DEVICE WITH A PATH PROTECTION FUNCTION, AND NETWORK SYSTEM USING THE COMMUNICATION DEVICE - Provided is a network system including a start device and multiple end devices. A point-to-point (P-to-P) logical path is set to be used for unicast communication between the start device and each of the end devices. A first point-to-multipoint (P-to-M) logical path and a second P-to-M logical path are set to be used for multicast communication from the start device to the multiple end devices. The start device transmits data over the first P-to-M logical path. When one of the end devices detects a defect along the first P-to-M logical path, the end device that has detected the defect transmits a switch request over the P-to-P logical path set between this end device and the start device. The start device receives the switch request and transmits data over the second P-to-M logical path. | 12-10-2009 |
| 20090300454 | TRANSMISSION APPARATUS, ACCESS POINT AND SYMBOL TRANSMISSION METHOD - In a transmission apparatus in a MIMO-OFDM communication system employing a cyclic diversity, a cyclic delay controller sets plural delay magnitudes different for respective antennas, in cyclic delayers for each predetermined timing. The cyclic delayers receive symbols subjected to orthogonal frequency division multiplexing, for the respective ones of plural allotted antennas. Besides, the cyclic delayers bestow cyclic delays on the individual symbols of the respective antennas in accordance with plural set delay magnitudes. The symbols cyclically delayed are outputted from the antennas. As the delay magnitudes, a first delay magnitude at a first transmission timing and a second delay magnitude at a second transmission timing are different for one antenna, and the delay magnitudes differ in the respective antennas for one transmission timing. Thus, in a MIMO-OFDM transmission scheme, a frequency diversity and a time diversity are enhanced to heighten a retransmission efficiency in a data retransmission mode. | 12-03-2009 |
| 20090270111 | WIRELESS COMMUNICATION SYSTEM AND BASE STATION ACCOMMODATION SERVER - To appropriately set the location registration area according to the installation location of the femto base station. Provided is a base station accommodation server that is coupled to a location management server accommodating at least one of first base station coupled to a first communication network, and accommodates at least one of second base station connected to a second communication network. The base station is configured to determine a location management group identifier of the second base station based on a location management group identifier of the first base station that is present at a location from which the second base station can receive the location management group identifier broadcast by the first base station. | 10-29-2009 |
| 20090257758 | OPTICAL RECEIVING APPARATUS - In an optical receiving apparatus for receiving an optical DQPSK signal, a phase difference between both arms of an optical interferometer is controlled to an optimum value. The optical DQPSK signal is incident on two optical interferometers in each which a delay-time difference between two arms is set to be equal to a 1-symbol time of the optical DQPSK signal and which are orthogonal to each other. The optical receiving apparatus converts the optical DQPSK signal into an intensity signal and receives it. A differential amplifier obtains a difference signal between outputs of a pre-amplifier and a discriminator connected thereto. The difference signal includes, as an amplitude, a phase shift in a phase section. A control circuit adjusts the phase of the phase section in the optical interferometers to reduce this difference signal, and changes the phase difference between the two arms to a desired phase difference. | 10-15-2009 |
| 20090252133 | MOBILE COMMUNICATION SYSTEM AND ACCESS GATEWAY HAVING PLURAL USER PLANE AGWS - In a mobile communication system including an access gateway (AGW) comprising a C-AGW for handling control messages and a plurality of U-AGWs for forwarding data packets, the C-AGW is provided with a management table indicating an address of U-AGW to be an endpoint of tunnel, in association with each of mobile station IDs. When a tunnel setup request message including a mobile station ID is received from one of base stations, the C-AGW searches the management table for the address of U-AGW corresponding to the mobile station ID and notifies the base station of the U-AGW address, and if the mobile station ID is not found in the management table, the C-AGW notifies the base station of an address of a particular U-AGW selected out of the U-AGWs, so that the base station establishes a tunnel for forwarding data packets toward the notified U-AGW. | 10-08-2009 |
| 20090245210 | CDMA COMMUNICATION SYSTEM AND METHOD - In CDMA communications, a base station detects a difference between a reference phase of a spreading code and a phase of a received signal of each terminal station, and feeds a phase jump signal PJ-i representative of the phase difference back to each terminal station. After timing acquisition, the reception operation is performed using the reference phase, and a shift amount between the phase of a received signal and the reference phase is fed back to each terminal station as phase synchronization control information PC-i. Each terminal station coarsely adjusts the phase of the spreading code in accordance with the phase jump signal PJ-i, and thereafter finely adjusts the phase of its transmitting signal in accordance with the phase synchronization control information PC-i. It is therefore possible to synchronize the phases of the signals transmitted from terminal stations and received at the base station. Accordingly, an orthogonal code is used for spreading on the reverse links. | 10-01-2009 |
| 20090214211 | APPARATUS OF ADJUSTING OPTICAL SIGNAL TRANSMISSION TIMING - In a light reception element such as an APD (Avalanche Photo Diode) used for receiving a high-speed and weak optical signal, it is possible to prevent the phenomenon of distortion of a signal inputted after a large-level light is received. A PON (Passive Optical Network) system includes an OLT (Optical Line Terminal) which can impartially and effectively transmit light reception data to each ONU (Optical Network Unit). According to a light reception amplitude received by each ONU, an inter-frame gap of an appropriate length is assigned for each ONU. The OLT includes a unit for measuring and accumulating the reception light amplitude and data on the inter-frame gap of an appropriate length decided in advance according to the characteristic of the light reception device and generates a grant value for assuring an inter-frame gap of an appropriate length by using the both information. | 08-27-2009 |
| 20090208224 | OPTICAL FIELD RECEIVER, OPTICAL MULTILEVEL SIGNAL RECEIVER, AND OPTICAL TRANSMISSION SYSTEM - An optical field receiver comprises an optical branching circuit for branching a received optical multilevel signal into first and second optical signals, a first optical delayed demodulator for performing delayed demodulation on the first optical signal at a delay time T (T=symbol time), a second optical delayed demodulator for performing delayed demodulation on the second optical signal at the delay time T with an optical phase difference deviating from the first optical delayed demodulator by 90°, first and second optical receivers for converting each of the delayed demodulation signals representing x and y components of complex signals output from the first and second delayed demodulators into first and second electrical signals, and a field processing unit fort generating a first reconstructed signal representing an inter-symbol phase difference or a phase angle of a received symbol from the first and second electrical signals for each symbol time T. | 08-20-2009 |
| 20090191879 | WIRELESS COMMUNICATION SYSTEM AND SOFT HANDOFF CONTROL METHOD IN WIRELESS COMMUNICATION SYSTEM - When measurement results of received radio wave intensities of wireless base stations, which demands a soft handoff, are received from a wireless terminal in a wireless communication system and when a base station controller attempts to acquire a traffic channel in a wireless base station, via which a wireless communication path will be added, in the state in which the channel resource usage rate of that wireless base station is over a threshold, a traffic channel may be acquired only if the ratio between the radio wave intensity of the wireless base stations establishing communication paths and the radio wave intensity of the wireless base station via which a communication path will be added is higher than a threshold or if the difference between the radio wave intensity of the wireless base stations and the radio wave intensity of the wireless base station smaller than a threshold. | 07-30-2009 |
| 20090131043 | WIRELESS COMMUNICATION SYSTEM AND TEST METHOD THEREOF, AND ACCESS TERMINAL FOR TESTING WIRELESS COMMUNICATION SYSTEM - A wireless communication system and its test method capable of executing a test of the wireless communication apparatus from a remote place by using a terminal generally used in wireless communication systems are implemented with a low-cost configuration and a simple procedure. A terminal obtained by installing a test AP on a general terminal that is used in general wireless communication systems and that can execute APs via a communication network is placed in a coverage area of a wireless communication apparatus. A maintenance center for the wireless communication system activates the terminal. The terminal executes the test AP and conducts communication with the maintenance center by using control signals and test signals for testing wireless communication system. A test is executed by measuring an actual communication state of the wireless communication system. | 05-21-2009 |
| 20090123160 | BIT SYNCHRONIZATION CIRCUIT WITH PHASE TRACKING FUNCTION - A bit synchronization circuit comprising an initial phase determining unit for rapidly determining, during a period of receiving a preamble of burst data, a clock with a phase synchronized with received burst data from among multi-phase clocks having the same frequency as an internal reference clock and a phase tracking unit for modifying the synchronized phase clock responsive to phase variation of received data during a period of receiving a payload of burst data by taking the synchronized phase clock determined by the initial phase determining unit as an initial phase. The bit synchronization circuit retimes burst data with a data retiming clock having a predetermined phase relation with the synchronized phase clock and outputs the burst data in synchronization with the internal reference clock. | 05-14-2009 |
| 20090110400 | WDM TYPE PASSIVE OPTICAL NETWORK - In a WDM type PON system, each ONU comprises an optical transmitter capable to transmit optical signals with variable wavelengths, an optical signal receiving filter variable its receiving wavelength, and a control unit. An OLT selects in response to a wavelength allocation request from each ONU, a transmitting wavelength and a receiving wavelength out of currently free wavelengths and allocates these wavelengths to the requester ONT. The control unit of the ONU switches the transmitting wavelength of the optical transmitter and the receiving wavelength of the optical signal receiving filter to the wavelengths specified in a response message from the OLT and starts data communication. | 04-30-2009 |
| 20090087185 | OPTICAL TRANSMISSION APPARATUS AND CONTROL METHOD THEREFOR - An optical transmission apparatus comprising a first detector for detecting the power of the supervisory signal light separated from received wavelength-division multiplexed signal lights; a second detector for detecting the power of the wavelength-division multiplexed signal lights after the separation of the supervisory signal light; a gain-controlled type optical amplifier for amplifying the wavelength-division multiplexed signal lights; an optical attenuator coupled to the amplifier; and a control unit for controlling the optical amplifier and the optical attenuator so as to keep the output level of the wavelength-division multiplexed signal lights to a predetermined target value, wherein the control unit restrains automatic output level control by the optical attenuator when the supervisory signal light power fluctuates within its permissible range and fluctuations in the signal light power have deviated from its permissible range. | 04-02-2009 |
| 20090080889 | WDM TYPE PASSIVE OPTICAL NETWORK - In a WDM type PON system, each ONU comprises an optical transmitter capable to transmit optical signals with variable wavelengths, an optical signal receiving filter variable its receiving wavelength, and a control unit. An OLT selects in response to a wavelength allocation request from each ONU, a transmitting wavelength and a receiving wavelength out of currently free wavelengths and allocates these wavelengths to the requester ONT. The control unit of the ONU switches the transmitting wavelength of the optical transmitter and the receiving wavelength of the optical signal receiving filter to the wavelengths specified in a response message from the OLT and starts data communication. | 03-26-2009 |
| 20090052897 | PASSIVE OPTICAL NETWORK SYSTEM AND RANGING SYSTEM THEREOF - A station-side communication device connected to subscriber-side communication devices via an optical combining device; sending, to the subscriber-side communication devices, a distance measurement request signal; computing transmission delay times of optical signals from the individual subscriber-side communication devices by receiving distance measurement signals, and including: a threshold control part identifying the level of distance measurement signals; a signal detection part detecting breaks in the distance measurement signals from the threshold control part; a transmission granting part determining the timing at which transmission of optical signals is granted, and a reset timing generation part that, there is notification of detection of a break in the distance measurement signal from the signal detection part while it is being notified that distance measurement is carried out to and from the subscriber-side communication devices from the transmission granting part, sends a reset signal indicating that the voltage level is reset to the threshold control part. | 02-26-2009 |
| 20090052896 | PASSIVE OPTICAL NETWORK SYSTEM AND RANGING SYSTEM THEREOF - A station-side communication device connected to subscriber-side communication devices via an optical combining device; sending, to the subscriber-side communication devices, a distance measurement request signal; computing transmission delay times of optical signals from the individual subscriber-side communication devices by receiving distance measurement signals, and including: a threshold control part identifying the level of distance measurement signals; a signal detection part detecting breaks in the distance measurement signals from the threshold control part; a transmission granting part determining the timing at which transmission of optical signals is granted, and a reset timing generation part that, there is notification of detection of a break in the distance measurement signal from the signal detection part while it is being notified that distance measurement is carried out to and from the subscriber-side communication devices from the transmission granting part, sends a reset signal indicating that the voltage level is reset to the threshold control part. | 02-26-2009 |
| 20090047020 | ONU MANAGEMENT METHOD AND OPTICAL LINE TERMINATION - In a PON system, a PON-ID assigned to a connected ONU before replacement is assigned to a newly connected ONU after the replacement and, setting data before the replacement is succeeded also after the replacement. An OLT includes a PON-ID state where a management state of the PON-ID is stored, a PON-ID management table where the PON-ID and an ONU serial number of the connected ONU and setting data are correspondingly stored and, a delete ONU table where the PON-ID and an ONU serial number of a replacement object are correspondingly stored. When the OLT receives an ONU replacement instruction from an operation system, the PON-ID assigned to the ONU of the replacement object is assigned to an ONU newly connected during the ONU replacement. | 02-19-2009 |
| 20090041461 | ONU MANAGEMENT METHOD AND OPTICAL LINE TERMINATION - In a PON system, a PON-ID assigned to a connected ONU before replacement is assigned to a newly connected ONU after the replacement and, setting data before the replacement is succeeded also after the replacement. An OLT includes a PON-ID state where a management state of the PON-ID is stored, a PON-ID management table where the PON-ID and an ONU serial number of the connected ONU and setting data are correspondingly stored and, a delete ONU table where the PON-ID and an ONU serial number of a replacement object are correspondingly stored. When the OLT receives an ONU replacement instruction from an operation system, the PON-ID assigned to the ONU of the replacement object is assigned to an ONU newly connected during the ONU replacement. | 02-12-2009 |
| 20090023382 | Radio Communication System and Base Station - A radio communication system includes a grouping unit for grouping a plurality of base stations into a plurality of groups (Soft Handoff Groups) and a determining unit for selecting base stations belonging to one and the same group selected from the groups produced by the grouping unit and for determining the base stations as base stations to send communication packets to an access terminal. | 01-22-2009 |
| 20090022059 | Optical Cross Connect Apparatus and Network - An optical signal connection apparatus for connecting first and second optical signal transmission lines to first and second routers, respectively, is disclosed. The first and second routers are configured to handle both optical signals and electrical signals. The optical signal connection apparatus comprises a first node and a second node. The first node includes a first port that is coupled to the first router via the first optical signal transmission line, the first port being configured to handle a first type of optical signals associated with the first router, the first optical signal transmission line defining a first communication link; a first line-setting unit configured to couple the first and second nodes to enable data communication between the first and second nodes using optical signals; a first control unit to control the first line-setting unit in setting an optical communication link between the first and second nodes; and a first signal-type storage unit configured to store first information on the first type of optical signals that the first port is configured to handle. The second node includes a second port that is coupled to the second router via the second optical signal transmission line, the second port being configured to handle a second type of optical signals associated with the second router, the second optical signal transmission line defining a second communication link, wherein the first information is compared with second information on the second type of optical signal to determine whether or not the first and second communication links are compatible to each other. | 01-22-2009 |
| 20080317469 | PASSIVE OPTICAL NETWORK SYSTEM AND RANGING SYSTEM THEREOF - A station-side communication device connected to subscriber-side communication devices via an optical combining device; sending, to the subscriber-side communication devices, a distance measurement request signal; computing transmission delay times of optical signals from the individual subscriber-side communication devices by receiving distance measurement signals, and including: a threshold control part identifying the level of distance measurement signals; a signal detection part detecting breaks in the distance measurement signals from the threshold control part; a transmission granting part determining the timing at which transmission of optical signals is granted, and a reset timing generation part that, there is notification of detection of a break in the distance measurement signal from the signal detection part while it is being notified that distance measurement is carried out to and from the subscriber-side communication devices from the transmission granting part, sends a reset signal indicating that the voltage level is reset to the threshold control part. | 12-25-2008 |
