Abstract: A system including a central unit 10, a terminal 20, and a relay device 30 relay transmission of isochronous data effectively, in a time-sharing manner. The central unit 10 cyclically carries out the polling. In response to the polling, the terminal 20 transmits a plurality of frames. The relay device 30 detects that the plurality of frames transmitted from the terminal 20 via a transmission path 40 are completely received based on carrier-sensing by a carrier detecting portion 308 incorporated in the relay device 30. The relay device 30, at the time of detection, transmits frames received thereby without error to the central unit 10.

Abstract: The present invention provides a terminal apparatus connectable to a communication network capable of comprising a plurality of different communication systems.

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: A communication terminal device of the present invention includes: a packet classification section 103 for classifying the packets by stream types and destinations; a packet accumulation section 104-107 for accumulating the packets classified by the packet classification section, so as to be separately stored based on classification by the stream types and the destinations; a QoS control section 113 for determining a transmission start requirement based on a QoS parameter which defines a transmission quality of a stream; a transmission control section 108 for determining whether the transmission start requirement is satisfied; a framing section 109 for generating the frame by concatenating the packets accumulated in the packet accumulation section if it is determined by the transmission control section that the transmission start requirement is satisfied; and a transmission section 110 for transmitting the frame generated by the framing section to a destination communication terminal device.

Abstract: A medium access control method is provided in which a control station 11 transmits one specific frame to terminal stations 21 through 2n, thereby arranging a schedule of a data transmission time of the control station 11 and each of the terminal stations 21 through 2n and allowing a time zone unused by a station for data transmission to be allocated to another station. The control station 11 transmits a schedule frame having defined therein a time occupied by each of the terminal stations 21 through 2n, thereby reducing overhead. Also, the completion of the preceding communication performed by another station is detected, thereby effectively using an idle time of a medium and improving transmission efficiency.

Abstract: A transmitting/receiving apparatus 100 includes a packet construction section 9 for dividing continuous data into a plurality of subpackets, and constructing a packet by concatenating the plurality of subpackets; a modulation transmission section 1,2,3 for modulating the constructed packet, and transmitting the modulated packet to another apparatus; a training session execution section 1, S115 for checking channel conditions, when a predetermined condition is satisfied, and changing a modulation rule; and a subpacket transmission confirmation section 1, S110 for confirming whether or not a subpacket included in the transmitted packet is transmitted successfully to the transmission destination apparatus.

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: A communication device capable of correcting a burst error exceeding a correcting capability of an error correcting code by only transmitting one packet. With respect to data to be transmitted, a frame generating section 22 generates a frame for which an error detecting process, etc., is performed. A frame dividing section 23 divides the generated frame, by a predetermined number, into a plurality of divided frames. A transmission control section 24 generates a packet in which the plurality of divided frame are copied predetermined times. A transmitting section 25 sends the packet to a receiver. A receiving section 35 receives the packet transmitted from a transmitter. A reception control section 34 divides the received packet by the predetermined number. A frame reconstructing section 33 reconstructs the frame by assembling the divided frames in predetermined order. A frame processing section 32 performs an error correcting process, etc., for the reconstructed frame.

Abstract: In a relay transmission method and system, and a device used therefor, efficiently realizing relay transmission on a half-duplex transmission path while controlling retransmission, a transmitter on the transmission side receives a polling from a transmitter on the reception side, and then transmits a frame-numbered data frame to a relay transmitter. If a data frame is not normally received, the transmitter on the reception side generates a retransmission request asking for retransmission thereof, and outputs the request for the relay transmitter. If storing the requested data frame in its retransmission frame buffer, the relay transmitter deletes the data frame's frame number from the retransmission request, and then transfer the request. Thereafter, the relay transmitter adds, to the retransmitted data frame, the data frame whose frame number has been deleted during last transfer.

Abstract: There is provided a vacant channel searching method for use in a wireless communication system, capable of finding a optimum vacant channel which is under least influence of the disturbance by taking also into account the periodicity and burst properties of disturbance waves. The short-term fluctuation (short cycle T1) of disturbance waves is observed over each observation interval length T2. Through repetitive observations up to a repetition number N, the long-term fluctuation (long cycle T3) of the disturbance waves is observed. As a result, constant observations of disturbance generation are realized in such a manner as to account for the periodicity and burst properties of the disturbance waves. By determining a channel which is under least influence of the disturbance based on the results of such observations, it becomes possible to find an optimum vacant channel.

Abstract: In a coding control apparatus deciding, when coding of motion picture data on the basis of a generated information amount Aig of coded data generated by coding one frame, a quantization characteristic to be used for coding a next frame, a threshold comparison part compares the generated information amount Aig with upper bound and lower bound thresholds Th_U and Th_L, and on the basis of the comparison result, a quantization characteristic decision part decides the quantization characteristic to be used for coding the next frame.

Abstract: Video data coded in a coding device 12 is temporarily stored in a temporary buffer 13 before transmitted to a transmission buffer 171. A frame dropping/quantization control device 16 cancels the video data in the temporary buffer 13 if the amount of information of the video frame stored in the temporary buffer 13 is larger than a predetermined threshold, and further, sets a quantization step size with a quantization step size larger than the quantization step size used to code the video frame stored in the temporary buffer 13 and outputs it to the coding device 12.

Abstract: In a video coding apparatus coding a motion picture while switching a coding mode between an INTER coding mode and an INTRA coding mode, a motion information management part determines whether or not there is motion exceeding a prescribed threshold in an object in each region of m groups of blocks in each frame of the motion picture during a lapse of a prescribed time T from a prescribed point. On the basis of the result of this determination, a whole-group refresh part performs whole-group refresh (INTRA coding in one frame) on a group of blocks of a region having motion exceeding the threshold, and a dispersed refresh part performs dispersed refresh (INTRA coding in frames varying with the block) on a group of blocks of a region having no motion exceeding the threshold. Thus, appearance of a disturbance line is avoided and influence by a transmission error is eliminated in a short time while reducing increase of a coding quantity resulting from refresh.

Abstract: A multiplex frame is of a fixed length and includes a header and a fixed-length field. The fixed-length field is divided into variable-length slots 1 and 2. The length of the variable-length slot 1 is a predetermined fixed length when data to be stored exists and is zero with no data to be stored. The length of the variable-length slot 2 is increased/decreased depending on the length of the variable-length slot 1. Fixed-length data not employing retransmission (e.g., an audio frame) is transmitted in the first variable-length slot and one complete variable-length data employing retransmission (e.g., a data link frame of video) is transmitted in the second variable-length slot.

Abstract: A highly efficient retransmission control method is achieved by preventing the order of data from being changed by one revolution of a modulo without adding extra overhead. The transmitting side continues to continuously transmit frames assigned frame numbers circulating by a modulo M to the receiving side. Upon detecting an error in the received frame, the receiving side returns a reject provided with the frame number of the frame. The transmitting side retransmits the frame to the receiving side in response to the reject. In a case where such retransmission control is carried out, the maximum number of times Nr a reject of the same frame is returnable is previously determined. The receiving side discontinues the return of the reject of the same frame until the number of times of the return exceeds the maximum number of times Nr. Consequently, the return of the reject of the same frame can be discontinued before the modulo of the frame number revolves once.

Abstract: Disclosed is a decentralized data-processing star network with a contention system having a plurality of terminal devices and a concentrator to interconnect the terminal devices via a transmission medium. Any of the terminal devices can start to transmit a packet immediately after a pause disposed to prohibit all transmissions, the pause occurring every time a packet has been transmitted. The concentrator has a start bit generation device for generating a start bit in accordance with the timing that the terminal devices should transmit their start bits and a relay device for ORing the generated start bit with each bit of a packet modulated as predetermined with a first frequency, converting it into a packet modulated as predetermined with a second frequency, and sending it out.

Abstract: A coding rate upper limit value storing unit and a coding rate lower limit value storing unit store a pair of a preset quantization accuracy and an upper limit value and a lower limit value on a coding rate corresponding to the preset quantization accuracy respectively. A coding rate calculating unit calculates a coding rate based on a code amount generated for a frame which was coded the last time. A first comparator and a second comparator compare a coding rate calculated by the coding rate calculating unit with an upper limit value and a lower limit value on a coding rate corresponding to a quantization accuracy with which a frame was coded the last time respectively. If the coding rate from the coding rate calculating unit is greater than the upper limit value or is smaller than the lower limit value, a quantization accuracy which is more accurate or less accurate than the quantization accuracy with which a frame was coded the last time is selected from quantization accuracies respectively.

Abstract: According to the picture data coding apparatus of the present invention, the picture data storage unit stores each frame inputted from the pre-process unit, and the frame memory stores the latest-transmitted decoded frame. The frame selection unit judges whether or not a frame under transmission can be displayed. If the frame has been judged to be incapable of being displayed, the frame selection unit judges whether or not each frame stored in the picture data storage unit 103 can be displayed or not, and selects the smallest numbered frame among frames which have been judged to be capable of being displayed. The coding unit predictive codes the selected frame by using the latest-transmitted frame stored in the frame memory 131 as a reference frame, thereby outputting it to the transmission buffer 127. These features can minimize frame skipping even when a frame under transmission becomes incapable of being displayed due to a burst error.

Abstract: This invention provides a start-stop synchronous data transmitter and a start-stop synchronous data receiver for transmitting a code consisting of a start bit, data, and a stop bit, wherein the data in a 1-bit interval is divided into a number of slots, to each of which different data are set so as to multiplex the data as many data as the number of the slots.

Abstract: A transmitter and a receiver for an unbalanced transmission line are constituted by omitting pulse transformers, but in the transmitter by installing switching circuits (S.sub.1, S.sub.4) directly coupled to the unbalanced transmission line (306 or 306') through respective switching devices (305, 310), and in the receiver by installing a pair of input circuits comprising D.C. isolating capacitors (503, 505) and bias circuits (502, 504) for uninverted and inverted input terminals (+,-), in receiver parts (525, 526) for positive polarity pulses and negative polarity pulses, respctively.