Abstract: A communications device 100, which performs data communication, includes an AC cycle sensor 30 which is connected to a power line 106 supplied with an a.c. voltage and generates a synchronous signal SS at timing of an a.c. voltage waveform AC of the power line 106; a data communicator 10 for performing data communication; and a communications controller 20 which performs communication of a control signal including information showing at least one of a communications device and a communications standard and controls the data communicator 101. When the a.c. voltage supplied to the power line 106 is an N-phase and when the cycle of the a.c. voltage waveform is T, data communication to be performed in a communication period subsequent to the period is controlled on the basis of the control signal included in the period of T/2M on condition that M is a natural multiple of N.

Abstract: PLC modems and a PLC communication system that includes the PLC modems receive a multicast packet from a video server of a multicast group. When a MAC address table is set therein, the PLC modems and the PLC communication system convert the multicast packet into a unicast packet and transmit the converted packet to a power line. When no MAC address is set, the PLC modems and the PLC communication system transmit the multicast packet to the power line.

Abstract: A communication system includes a synchronizing signal generator that generates a synchronizing signal based on a timing of an alternating waveform in a power line, a data communicating circuit that performs the data communication, and a communication controller that controls to acquire a transmitting right utilizing a timing of the synchronizing signal and to control the communication circuit in accordance with whether or not the communication apparatus acquires the transmitting right.

Abstract: In-home communication systems 110 and 130 and an access communication system 120 are caused to coexist by TDM in synchronization with a power cycle, and a communication system which needs to secure AV-QoS assigns transmission timing to a slave station in itself by synchronizing a beacon cycle with a cycle of a power line.

Abstract: A communication apparatus and a method are provided for easily enabling two communication systems having different communication schemes and using the same communication medium to coexist. An access coexistence signal for notifying an in-home communication system 110 and 130 of the presence of an access communication system 120, and an in-home coexistence signal for sharing frequency and time resources between a plurality of in-home communication systems 110 and 130, are used. Further, by transmitting the two coexistence signals asynchronously, a process of synchronizing the access communication system 120 and the in-home communication system 110 and 130 is no longer required.

Abstract: An in-home-system master station of an in-home communication system detects a frequency band (a channel number corresponding to a data communication subchannel) or a time slot used by each station of an access communication system, using a coexistence signal subchannel. Based on the detected information, the in-home-system master station determines a frequency band or a time slot to be used in the in-home communication system to which the in-home-system master station belongs, so as not to avoid overlapping the frequency or time slot used in the access communication system, and informs each in-home-system slave station of the determined frequency band or time slot.

Abstract: A coexistence controller which performs management and control of time division for coexistence, is provided in a power line communication modem which has a function as a QoS controller for a QoS type communication system and a power line communication modem for a best-effort type communication system. In the QoS type communication system, by controlling allocation of a communication band in accordance with priorities given to the communication systems by cooperation of the coexistence controller and the QoS controller, the power line communication systems having different schemes can coexist.

Abstract: A frequency band is divided into N subchannels. Sub-channels are first allocated for a power line communication system having a higher priority, such as public communication or the like. Sub-channels for a power line communication system having a relatively low priority, such as in-home communication or the like, are allocated from free subchannels. In this case, the subchannels used by the power line communication system having the high priority are limited to a plurality of consecutive subchannels from an upper side or a lower side of the frequency band.

Abstract: A relay apparatus includes a plurality of connecting terminals, such as a modem connecting terminal, a power line connecting terminal, an electric appliance connecting terminal and an antenna line connecting terminal; a selector that selects at least one connecting terminal from among the plurality of connecting terminals to transmit and receive a communication signal; and a control circuit that controls the selector. The relay apparatus further includes a first communication filter that passes signals in a frequency band used for communication by a power line communication modem and that blocks signals in other frequency bands, and a second communication filter that passes signals in a frequency band used for communication by another electric appliance and that blocks signals in other frequency bands.

Abstract: A display device comprises an inspection circuit for inspecting a data reception related circuit to generate inspection information, an inspection result image generation circuit for generating image data indicating the inspection information, a display switching circuit for superimposing inspection result image data on test video data, and a display unit for displaying the test video data superimposing the inspection result image data. As a result, it is possible to carry out inspection after assembly of the display device without disassembling the display device. This in turn makes it possible to carry out a test in a simple manner on the data reception related circuit inside the display device without changing noise environment inside the display device.

Abstract: A communication system includes a synchronizing signal generator that generates a synchronizing signal based on a timing of an alternating waveform in a power line, a data communicating circuit that performs the data communication, and a communication controller that controls to acquire a transmitting right utilizing a timing of the synchronizing signal and to control the communication circuit in accordance with whether or not the communication apparatus acquires the transmitting right.

Abstract: A communication apparatus includes a transmission signal generation section 1, a transmission signal control section 2, a transmission section 3, a leakage electric power detection section 4, and an electric power control judgment section 5. The transmission signal generation section 1 generates a transmission signal for carrying out transmission using a plurality of sub-carriers, under control of the transmission signal control section 2, and has a transmission electric power control function with respect to each sub-carrier. The leakage electric power detection section 4 detects electric power which is leaked from a transmission line 9 among transmission electric power.

Abstract: In a multicarrier communication using a balanced transmission line such as a power line, a multicarrier communication method operable to select carriers on the basis of an SN-ratio and balancing of the transmission line is provided. Available carriers are selected in accordance with the balancing of the balanced transmission line, in which the balancing is measured at either a sending terminal or a receiving terminal or alternatively at both of them, and the SN-ratio measured between the sending terminal and the receiving terminal. More specifically, any frequency domain having poor balancing and a poor SN-ratio is treated as a non-carrier-employing domain, and consequently the available carriers are selected at other frequency domains. In addition, a modulation method having the greatest permissible multivalue is selected for each of the carriers. The carriers are selected in light of the SN-ratio and balancing, or alternatively in highest-to-lowest order of frequency.

Abstract: There is provided a communication network system which can set communication parameters which enable an operation under a maximum possible communication rate in a situation where a transmission path has cyclic noise/impedance fluctuations, without being influenced by such local noise/impedance fluctuations. A transmission/reception apparatus 100 transmits training packets for checking the state of the power line at two distinct points in time. Each time a training packet is received, a transmission/reception apparatus 101 analyzes SNR at each carrier frequency, and stores an SNR evaluation result. The transmission/reception apparatus 101 compares two SNR evaluation results which are obtained through two instances of a channel estimation algorithm, selects an SNR evaluation result which dictates a faster PHY rate, and transmits it to the transmission/reception apparatus 100. The transmission/reception apparatus 100 changes modulation/demodulation rules based on the received SNR analytical result.

Abstract: Two or more synchronous words are arranged to a section as long as a noise cycle “t” regarding a frame. Or, one or more synchronous words are arranged such that a section not being influenced by the noises is long enough considering the noise cycle. When information that cyclical noises occur is given and/or the noise cycle can be measured, probability that the synchronous word is influenced by the noises is reduced so that reliability of frame synchronization establishment can be improved.

Abstract: In a transmitter, either the voltage or the current, or both applied to each of a pair of conductors is monitored. In a receiver either the voltage or the current, or both outputted from each conductor are monitored, thereafter the status will be outputted. Using the outputted status, either the voltage or the current, or both applied to the conductors in a transmitter will be controlled. This makes it possible to improve the degree of balance in the receiver while keeping the balance in the transmitter, which results in reducing EMC problems both in the transmitter and the receiver.

Abstract: Impedance values of a common mode choke coil, an impedance element disposed anterior to the common mode choke coil and an impedance element disposed posterior to the common mode choke coil are determined in such a manner that a common mode current flowing into the common mode choke coil does not exceed a value of rated current. Excessive common mode current is prevented from flowing into the common mode choke coil, and saturation and damage of the common mode choke coil is prevented.

Abstract: The status of communications by a specific metallic cable set among a number of metallic cables and that are arranged close to each other in a transmission line is inspected. An inspection signal is supplied to flow in one metallic cable, an interference signal flowing in another metallic cable is measured in response to the flow of this inspection signal, and based on the relationship between the inspection signal and the interference signal, it is judged whether or not the status of communications by the specific metallic cable set is fine. A measuring device measures components other than a descending carrier to be received by a transmitter-receiver from a repeater, and includes information on the components in an ascending carrier.

Abstract: A display device comprises an inspection circuit for inspecting a data reception related circuit to generate inspection information, an inspection result image generation circuit for generating image data indicating the inspection information, a display switching circuit for superimposing inspection result image data on test video data, and a display unit for displaying the test video data superimposing the inspection result image data. As a result, it is possible to carry out inspection after assembly of the display device without disassembling the display device. This in turn makes it possible to carry out a test in a simple manner on the data reception related circuit inside the display device without changing noise environment inside the display device.

Abstract: To use high noise transmission lines, such as an electric wire, as the lines to transmit signals, it is imperative to reduce the level of signals. The present invention is provided with a sending signal generating means 10, which outputs converted data after converting an input signal into a plurality of carrier signals assuming values at such intervals on the axis of frequency that the frequencies may not interfere with each other. If an interfering noise with any one of the plurality of frequencies arises on the transmission line, removal of only a carrier of the noise frequency would leave the communication in a good condition.