Abstract: A radio communication system is formed of a plurality of radio communication terminals and a radio communication control terminal for controlling radio communication. Data communication is performed between each radio communication terminal and the radio communication control terminal by the orthogonal frequency division multiplexing (OFDM) method. Data is multiplexed with a frame structure having the specified number of symbols by the TDMA method. The radio communication control terminal transmits a synchronization acquisition code to the plurality of radio communication terminals in each frame. Each radio communication terminal receives the synchronization acquisition code, sets a timer according to the receiving timing of the synchronization acquisition code, and sets the transmission timing and the receiving timing with the timer being used as the reference. With the use of the OFDM method, demodulation is performed without an error even if jitter occurs.

Abstract: A spectrum spread signal spread by a spread code synchronized with a synchronous signal accompanying to an information signal is superimposed on the information signal and is then transmitted and the spectrum spread signal is then detected using the spread code for detection synchronized with the synchronous signal from the information signal on which the spectrum spread signal is superimposed. A value of the information signal on which the spectrum spread signal is superimposed is added or subtracted depending on the chip value of the relevant spread code for detection in each chip of the spread code for detection. The spectrum spread signal is detected by determining whether the added/subtracted value has exceeded the predetermined threshold value or not.

Abstract: A playback device 10 generates a pseudo random noise (PN) code with a start timing based on a video sync signal, and generates a PN inverse code which has a reverse polarity to that of the PN code with a timing based on the video sync signal. An anti-duplication control signal is spectrally spread using this PN code, superimposed on the video signal and supplied to a recording device. A PN inverse code which is the same as the PN inverse code used in the playback device is also generated in the recording device based on the video sync signal, and reverse spectral spread is performed using this PN inverse code.

Abstract: The level of the spectrally spread anti-duplication control signal to be superimposed on an information signal such as a video signal is changed by using a random number RD generated by a random number generation unit 163. Since it is difficult to follow after the change of the level of the spectrally spread anti-duplication control signal, elimination of the anti-duplication control signal from the information signal is made further difficult. This can reliably provide the anti-duplication control signal to the receiving side.

Abstract: A radio communication system where data is transferred by TDMA in one frame. A frame is formed of a control-data transfer time region and an information-data transfer time region. In the control-data transfer time region, polling is performed for each terminal and a transfer rate and whether transfer data exists are returned to a control station as an ACK. The control station assigns a channel to each terminal according to this information a time period for data transfer in the information-data transfer time region is assigned to each terminal which has made a transmission request. In the region, asynchronous data and isochronous data can be transferred together. Since data is transferred in the time period assigned in advance in a frame, a constant transfer rate is obtained without being affected by an increase or decrease of traffic.

Abstract: A method and apparatus for ensuring wireless transmission among respective communicating apparatuses when constructing a local area network with a plurality of wireless communicating apparatuses. Under the control of a control station (10), a wireless signal of a frame structure is transmitted between communicating stations (20) and (30). The wireless signal of a frame structure has a managing region and a data transmitting region. In the managing region, a test signal for checking quality of communication among a plurality of communicating stations and communication quality information representative of quality of communication among the plurality of communicating stations are transmitted. In the data transmitting region, isochronous data or asynchronous data is transmitted under the access control of the control station.

Abstract: A correlation detecting apparatus is capable of securely detecting a M sequence code forming a reference for timing even when a plurality of signals with different amplitudes are time division multiplexed includes matched filter (82) for detecting a predetermined code from a received signal, an average amplitude detector circuit (83) for detecting an average amplitude of the received signal, and a divider circuit (84) for normalizing an output of the matched filter (82) by an output of the average amplitude detector circuit 83 are provided. The output of the matched filter (82) normalized by the divider circuit (84) is compared with a threshold value for outputting a correlation detecting signal. When a received signal level is large, the output level of the matched filter (82) becomes large.

Abstract: A spread code generation section outputs selectively one of a plurality of different spectral spread codes corresponding to an anti-duplication control signal for indicating the content of the duplication prevention control such as duplication permission, duplication inhibition, and duplication of generation restriction of a video signal in a recording medium. The plurality of spectral spread codes is different in phase or series, or generated by multiplying a specified spread code by the plurality of different orthogonal codes. An additional information signal is spectrally spread using the selected spread code, and superimposed on the video signal to output a combined information signal.

Abstract: A playback device generates a Pseudo-random noise (PN) code sequence repeatedly with a predetermined period in synchronism with a video sync signal. An anti-duplication control signal is spectrally spread using this generated PN code sequence, is superimposed on the video signal, and is output. A PN code sequence having the same timing and code pattern as the PN code sequence used in the playback device is similarly generated based on the video sync signal on the receiving side which receives the output video signal. Using this PN code sequence, reverse spectral spread is performed, the anti-duplication control signal superimposed on the video signal is extracted, and anti-duplication control is performed according to the extracted anti-duplication control signal.

Abstract: A playback device 10 generates a PN code with a start timing based on a video sync signal, and generates a PN inverse code which has a reverse polarity to that of the PN code with a timing based on the video sync signal. An anti-duplication control signal is spectrally spread using this PN code, superimposed on the video signal and supplied to a recording device. A PN inverse code which is the same as the PN inverse code used in the playback device is also generated in the recording device based on the video sync signal, and reverse spectral spread is performed using this PN inverse code.

Abstract: The invention intends to secure the control of duplicating information signals. In the duplication control method according to the invention, a main information signal containing a duplication control information transformed into a spread spectrum signal to be superimposed and a duplication control information superimposed by a processing different from the spectrum spreading is transmitted. The duplication control information transformed into a spread spectrum signal is extracted from the main information signal by the reverse spectrum spreading, and the duplication control information superimposed by the different processing is extracted from the main information signal. One information most closest to duplication prohibition is selected as an output duplication control information out of the plural extracted duplication control information. On the basis of the selected output duplication control information, the main information signal is controlled on duplication.

Abstract: The invention intends to secure the control of duplicating information signals. In the duplication control method according to the invention, a main information signal containing a duplication control information transformed into a spread spectrum signal to be superimposed and a duplication control information superimposed by a processing different from the spectrum spreading is transmitted. The duplication control information transformed into a spread spectrum signal is extracted from the main information signal by the reverse spectrum spreading, and the duplication control information superimposed by the different processing is extracted from the main information signal. One information most closest to duplication prohibition is selected as an output duplication control information out of the plural extracted duplication control information. On the basis of the selected output duplication control information, the main information signal is controlled on duplication.

Abstract: An additional information is spectrally spread and superimposed on a video signal over a plurality of fields, and the superimposed additional information is detected easily. A time code information is spectrally spread using the first spectrally spreading code string synchronous to the video signal, and the spectral spread signal of the time code information is superimposed on the video signal. An additional information is spectrally spread using the second spectrally spreading code string generated synchronously to the sync signal of the video signal and having a different period or different content corresponding to the time code information, and the spectral spread signal of the additional information is superimposed on the video signal.

Abstract: A communication apparatus which is in a wireless network is characterized by comprising a communication means transmitting information among the other communication devices, a means receiving priority order information representing stand-by times different in each communication device from the control station and setting communication devices as control station candidates in a memory, and a means performing communication control as a control station in the wireless network when the stand-by time elapses.

Abstract: This invention provides an image transmission method, image anti-duplication method, image anti-duplication device, and image recording medium in which the information for anti-duplication control is superimposed on the video signal without deterioration of the resultant video signal and the information is extracted accurately and quickly to perform anti-duplication control.

Abstract: A superimposing position setting unit uses a video synchronizing signal from a synchronization separating unit as a reference signal, and generates a superimposing position indicating signal S4 for indicating an effective image plane interval of a video signal as a superimposing interval during which an SS duplication control signal is superimposed. An SS duplication control signal generator generates a PN code sequence repeating every one vertical interval, and spreads the spectrum of a duplication control signal S3 by using the PN code sequence to form an SS duplication control signal. The SS duplication control signal is outputted to the effective image plane interval on the basis of the superimposing position indicating signal S4, and is superimposed on the video signal during the effective image plane interval of the video signal by an adder.

Abstract: The invention provides an information duplication prevention method and an information duplication prevention device capable of performing correct and proper duplication prevention. Prior to transmission of the information signal such as video signal, an anti-duplication control signal for preventing duplication of the information signal is transmitted. The reception side for receiving the information signal can arrange the condition for performing duplication prevention control based on the previously received anti-duplication control signal prior to reception of the information signal.

Abstract: To provide a radio transmission method and a radio transmission apparatus capable of performing a highly-efficient radio transmission depending on the number of communicating stations, a predetermined frame period is prescribed, a management information transmitting field being provided within the frame period, a station sync transmit/receive interval being provided within the management information transmitting field and an arbitrary communicating station being designated to transmit a station sync at plural frame period intervals during the station sync transmit/receive interval. Thus even if only the station sync transmitting area corresponding to the number which is less than the number of communicating stations forming a network exists within one frame, the station sync can be transmitted and received.

Abstract: The present invention relates to a radio transmission method and apparatus for a radio network using a plurality of communication stations. More specifically, the apparatus defines a radio transmission frame based on a signal sent from a control station. A management information transmission region and an information transmission region are set in the defined frame period. A station synchronous section for transmitting a signal for every communication station constituting the radio network is set in the management information transmission region. The length of the station synchronous section is variable in accordance with the number of communication stations in the network. Using this frame format, it is possible to efficiently conduct radio transmission.

Abstract: When many buses are provided, addition/omission of a bus frequently occurs. Whenever the addition/omission of the bus occurs, a configuration process of the overall network system must be performed. Thus, interruption of data communication occurs frequently. Second bridges are provided that are bridges each having a function of performing a configuration process for assigning individual identification numbers to a lower network. The second bridges are used to connect buses to one another.