Abstract: 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.

Abstract: An optical switch is provided with: an optical matrix switch; and an optical path decision section which divides input light into two branches, supplies the input light of one divided branch to the optical matrix switch, demultiplexes the input light of the other divided branch into the light of individual wavelengths, subjects the demultiplexed optical signals to photoelectric conversion and generates electric signals corresponding to individual wavelengths, outputs connection request signals to SW connection request adjustment circuits for O1 to O4 which are set beforehand for individual wavelengths by receiving the generated electric signals, supplies, to the optical matrix switch, input port information JP corresponding to connection request transmitters from which the connection request signals are output, and decides optical paths in the optical matrix switch.

Abstract: 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.

Abstract: An IPv4-IPv6 multicast address translation table is dynamically created, so that it is unnecessary to register multicast servers in advance. When an IPv4 MC group address exists as a response of a DNS server to a DNS request of an IPv6 MC client or when an IPv6 MC group address exists as a response of the DNS server to a DNS request of the IPv4 MC client H1 to H4, DNS Proxy D3 requests an MC adaptive translator T1 to generate a virtual IPv6 MC group address or a virtual IPv4 MC group address, and the MC adaptive translator T1 generates a virtual IPv6 MC group address or a virtual IPv4 MC group address from an address pool, and also creates an MC address translation table, whereby the MC address translation of IPv4-IPv6 can be dynamically performed.

Abstract: When a trouble is developed in an IP exchange (TM) 2 or a circuit (network) 5, a backup exchange 6 (backup TM) is switched over from a waiting system to an operating system, and all IP terminals Eqi inside lodgments A, B, . . . N also log out from the IP exchange (TM) 2, and transmit the IP addresses to the backup exchanges 6 (backup TM) inside own lodgment, respectively, and log in there with a result that the extension telephone calls inside own lodgment is made possible by a control of the backup exchange 6 (backup TM), and therefore, even when a fault occurs in the IP exchange or the circuit, the IP terminals inside the lodgment are backed up and the actuations of the IP terminals are continuously operated, and for example, the extension phone calls inside the lodgment can be realized.

Abstract: 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.

Abstract: In a packet transmission router used in a VRRP (Virtual Router Redundancy Protocol) network having a VR (Virtual Router) function, when virtual routers VR are realized by the VRRP, the routing control information that each VR manages is prevented from being mixed with that of other VR. When an active packet transmission router transmits a VRRP packet to a standby packet transmission router, an identifier indicating which virtual router belongs to the VRRP packet is added to the VRRP packet before the transmission of the VRRP packet.

Abstract: A television phone adapter which permits an ordinary analog telephone to switch between being a telephone with a video function and a telephone without a video function. The television phone adapter includes a telephone adapter unit that detects dial operation of an analog telephone connected to a router with an IP telephone function, a video adapter unit that connects and disconnects a video connection using an IP network, sends a video taken by a camera to a communication partner and outputs a video received from the communication partner to a display 4 through the video connection in the connected state. A translation table stores correspondence between dial operation and a setting content.

Abstract: Disclosed are a delay locked loop circuit capable of accurately extracting nonlinear distortion superimposed on an output of a digital predistortion type transmitter, the digital predistortion type transmitter, and a wireless base station using the same. The delay locked loop circuit outputting a smoothed signal to the variable delay element, in which delay control is implemented for checking distortion occurring to the output IQ signals due to the same passing through the analog circuit by means of the variable delay element. Either the first input IQ signals or the second input IQ signals are signals generated as a result of output IQ signals Io, Qo undergoing digital-to-analog conversion, and again undergoing analog-to-digital conversion after passing through an analog circuit. In particular, an IIR filter may be used for the variable delay element.

Abstract: Disclosed is an optical transmission device with a simple configuration that can attenuate an input optical power only when it is necessary so that it falls within a predetermined range, and can suppress insertion loss when it is unnecessary. A variable optical attenuator is configured pluggable. A pluggable variable optical attenuator is equipped with an optical connector that is an interface of an optical signal and an electrical signal connector for receiving an electrical signal that specifies the amount of control used for feedback-controlling the attenuation, and controls the attenuation depending on the input optical power of the optical transmission board. Moreover, an optical through that has the same shape as the variable optical attenuator being configured pluggable and that is configured pluggable is prepared.

Abstract: A radio communication system for enabling control of a modulation scheme following variation in the propagation channel and control of a coding rate in a small amount of delay and arithmetic operation. In order to attain the object explained above, a transmitter station and a receiver station use in common the information of the maximum number of bits used for communication of each symbol. The transmitter station generates codeword by previously encoding the communication signal with the code having sufficient error correcting capability, assigns, to each symbol, the codeword to result in the maximum number of bits per symbol, and modulates and transmits the bits using the modulation scheme in which the number of bits per symbol is equal to or less than the maximum number of bits per symbol.

Abstract: In an electronic apparatus in which plural substrates are arranged in a perpendicular direction between plural cooling fans in a lower part of a case and plural temperature sensors in an upper part of the case, any temperature variation by 2° C. in three seconds detected by any one of the temperature sensors is determined to be abnormal, and thermal energy is caused to be discharged from surfaces of substrates on two sides of a flame by raising air flow rates of fans. Expansion of the flame to other substrates is thereby prevented.

Abstract: 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.

Abstract: To provide a communication apparatus which is used in a VoIP telephone system and which can make connections with the minimum partners even in case an access cannot be made to a server managing a call connection. In case a call control unit 401 of a communication apparatus 4 acquires a telephone number by a call-initiate and requests the communication connection with a communication partner apparatus corresponding to said telephone number for the server, the call control unit 401 requests a communication connection addressed to an IP address corresponding to said telephone number, when no response is obtained from said server and when the IP address corresponding to said telephone number is stored in a correspondence storage unit 403b, so that the call control unit 401 performs a call connection processing directly with the connection partner thereby to make a communication connection by the VoIP.

Abstract: 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.

Abstract: 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.

Abstract: When wireless terminal A and wireless terminal B respectively transmit signals (T123, T133), and Access Point (AP) in the wireless LAN system recognizes occurrence of contention, if AP successfully recognizes an address of sending source of this signal and a duration of this signal as a result of analyzing any signal from the wireless terminal A, AP transmits a CTS signal which gives a clearance for transmission to the wireless terminal A which is the source of sending the signal (T113). The wireless terminal A which is given the clearance for transmission by the CTS signal, resends a signal identical to the one previously sent (T127), whereas the wireless terminal B which is not given the clearance for transmission by the CTS signal withholds a signal transmission during the duration indicated by the CTS signal.

Abstract: 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.

Abstract: 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.

Abstract: When multicast distribution is performed on a network where a point-to-point connection is made between user terminals and a multicast router, the multicast router is protected from load due to response reports, join requests, or leave statements sent from the user terminals simultaneously. If the user terminals send response reports simultaneously, a Layer 2 switch disposed between the user terminals and the multicast router limits response reports sent to the multicast router. The Layer 2 switch prevents response reports sent from the same user terminal from being discarded consecutively, by sending a response report sent from the same user terminal to the multicast router 200 with priority in the next join confirmation event. If the user terminals send join requests or leave statements simultaneously, the Layer 2 switch limits the join requests or leave statements sent to the multicast router 200 in the same manner.