Abstract: The present invention provides a management table that uses only specific symbols for upstream signals and other symbols for downstream signals, within a hyperframe (ADSL communication unit). Communication is performed by switching streams between the upstream and downstream, in accordance with the symbols stored in the management table. Upon transmitting a predetermined number of hyperframes, a processor transmits a SEGUE signal instead of a REVERB signal in the beginning of the next hyperframe.

Abstract: A center side transmits a downstream signal by using a specified carrier preset by a communication standard, when a handshake sequence is initiated, and retransmits a downstream signal by using an alternate carrier shifted toward a higher frequency instead of a specified carrier in the proximity of carriers used for the upstream, when a line connection with an opposing ADSL modem apparatus fails during the signal transmission using the specified carrier. Further, a remote side detects a signal of a specified carrier preset by a communication standard from downstream, when a handshake sequence is initiated, and detects an alternate carrier signal in accordance with a carrier change made by the transmitter side, when the signal of the specified carrier fails to be received within a predetermined time since the initiation of the handshake sequence.

Abstract: An ADSL modem apparatus that serves as an ATU-R receives a signal in the hyperframe format having FEXT and NEXT parts, when an initialization sequence is started, the signal configured with a known number of symbols. The received signal is sampled by an AFE and stored in a buffer memory of an FFT unit. A processor establishes a symbol synchronization and a hyperframe synchronization, upon receiving an original signal, based on sample data of the original signal, the original signal having REVERB signals during a FEXT period and non-REVERB signals (distinguishable from REVERB signals) during a NEXT period.

Abstract: A host manages a ROM that stores a handshake program for executing a handshake sequence and an initialization program for executing an initialization sequence. During the handshake sequence, the handshake program is retrieved from the ROM to download the program to a non-resident memory of a program area. Upon completing the handshake sequence, the initialization program is retrieved from the ROM, to download the program to the non-resident memory, replacing the handshake program.

Abstract: A constellation encoder provides carrier data with a topology inverted at 180 degrees every 8 symbols to an IFFT unit to transmit the topology inversion signal to a line. Upon receiving the signal from the line during the transmission, an FFT unit performs a fast Fourier transformation on the signal in order to obtain constellation data. Then, an AGC controller performs an AGC on the data. Further, a CAPC unit performs a CAPC, and a timing regenerator monitors whether a timing regeneration is necessary. During a period of signal hybrid echo due to the carrier topology inversion transmission, processes of the AGC, CAPC and timing regeneration are frozen.

Abstract: An ADSL communication apparatus includes a transceiver that executes an initialization sequence, a host that is connected to a user terminal, an AFE unit, a driver that transmits an analog signal (converted by the AFE unit) to a line, and a receiver that receives the analog signal from the line. The transceiver retrieves a signal component of a known carrier from the front-end of a hyperframe, based on an arbitrary symbol breakpoint. By calculating outer product values between the previously retrieved signal component and the currently retrieved signal component, the symbol breakpoint is adjusted in accordance with the patterns of the outer product values.

Abstract: A receiver receives an analog signal that is modulated from transmission data using a multi-carrier method, and a gain controller controls a gain of the received analog signal. An AD converter samples the received analog signal processed by the gain controller so that an FFT unit can perform a Fourier transform on the sampling data and demodulate the data into carrier units. Then, a sync symbol, which is transmitted from an opposing side after the data communication is initiated using the multi-carrier method, is retrieved from the demodulated data. By analyzing individual signal value of a plurality of carriers within the retrieved sync symbol, an appropriate gain control is instructed for the gain controller.

Abstract: The present invention monitors communication status during a data communication, determines whether the current communication status needs a re-initialization, requests a re-initialization of an opposing ADSL modem apparatus by transmitting ClearEOC when a re-initialization is needed, receives a response to a re-initialization request from the opposing ADSL modem apparatus, and performs a re-initialization after a predetermined time period.

Abstract: A communication control method detects whether an opposing apparatus is capable of performing an abbreviated procedure during a handshake step, declares an initiation of the abbreviated procedure if the opposing apparatus is capable of performing the abbreviated procedure, omits a negotiation prior to transmitting a MEDLEY signal, allows a remote side to transmit capacity information and reception result once to a center side after exchanging the MEDLEY signal, and further allows the center side to transmit the final capacity and transmission speed information to the remote side, in order to complete the initialization sequence.

Abstract: A center and remote sides are connected via a line and perform an initialization sequence to set a transmission speed and to detect gain characteristics of a signal received during the initialization sequence at both sides. Both center and remote sides then inform each other of the detected gain characteristics and correct gain characteristics of future transmission signals based on the informed gain characteristics. Therefore, it is possible for a sender side to perform a gain correction that raises gain amounts of transmission signals according to a decay rate, and for a receiver side to maintain the reception level, which is more than a predetermined value, thereby providing a high-speed data rate.

Abstract: A control monitors communication status during a data communication and determines a re-initialization is necessary in the current communication status. If the re-initialization is necessary, a pre-selected sub-carrier topology is inverted to request the re-initialization to an ADSL modem apparatus, which is installed by a central system. Upon receiving a reply to the re-initialization request from the ADSL modem apparatus, the re-initialization is performed after an expiration of a predetermined time period.

Abstract: In multi-carrier communication, error amounts, which are deviations between the coordinate points of eye patterns detected from actual reception signals of each sub-carrier, and the target coordinate points of eye patterns from the reception signals are calculated by an eye pattern display controller and displayed on an oscilloscope.

Abstract: A maximum amount searcher searches maximum carrier energy amount, among the energy amounts of multiple carriers that comprise REVERB signals, and a main controller performs a gain control to bring the maximum energy amount to a target gain amount. At the same time, the same gain control for the maximum energy amount is performed for other carrier energy amounts across the board.

Abstract: It is decided whether or not the reception is performed with respect to signals of 1650 Hz, 1750 Hz and 185O Hz passed through band pass filter (BPF) 4031 up to 4033 and processed for the energy calculation in energy calculating circuit 4041 up to 4043 respectively. Low speed signals that are processed for the energy calculation in energy calculation circuit 4041 up to 4043 respectively are added in adding section 405. At this time, a timer in decision circuit 406 starts. When a predetermined time passes in the timer in decision circuit 406 with a predetermined energy level of signals of 1650 Hz, 1750 Hz and 1850 Hz kept, the signals are identified as EOP signal that comes after PIX signal. Thereby the apparatus is controlled to shift to the low speed signal reception mode.

Abstract: When a communication is started through a control channel in a half-duplex communication compliant with the Recommendation V.34, the modem apparatus of the present invention demodulates reception symbols subjected to quadrature amplitude modulation and thereby finds their coordinates on a signal space diagram. Then, the modem apparatus calculates a cross product of two vectors from the origin to the coordinates of two consecutive symbols and identifies a control signal from a polarity array configured by polarities of the calculation result arrayed over a span of a plurality of consecutive symbols.

Abstract: A training circuit for training a tap coefficient of an adaptive equalizer that performs error calculations in a training process and updating of the tap coefficient in a time area and thereby makes the tap coefficient converge stably in a short time.

Abstract: When carrying out pre-processing of image signal transmission using the control channel of a full-duplex modem and switching image signal transmission to the primary channel of a half-duplex modem, the answer modem stops the transmission carrier upon confirmation that all “1” signals with 40 bit or more have been received from the calling modem, restarts the reception of all “1” signals after the elapse of a certain period of time, confirms the end of all “1” signals and switches to the primary channel.

Abstract: The present invention calculates a product of the present sampling data by the sampling data 1 data unit ahead through multiplier 14, adds up product values calculated for every sampling by going back to the time point 1 data unit ahead through adder 16 and detects a reference timing with regard to a CP signal using the addition value.

Abstract: The present invention calculates a difference between present sampling data and sampling data 1 data unit ahead, cumulatively adds up difference values calculated for every sampling by going back to the time point ahead by the number of samples of a CP signal inserted into an initializing signal and confirms the position of the CP signal from the sample number for which this cumulative value indicates a minimum value.

Abstract: When the present modem control apparatus detects that the receive level of a probing signal in phase 2 of the pre-communication procedure or a tone signal with a specific frequency in phase 2 of the pre-communication procedure is lower than a prescribed value, it sets the transmission rate of the control channel to a low rate of 1200 bps. In this case, the modem control apparatus sets the transmission rate to 1200 bps through a prescribed bit of the MPh signal in the communication control procedure and performs the setting that will not permit communications with the answer modem at different transmission rates, through the second prescribed bit of said MPh signal, and notifies those settings to the answer modem, thus carrying out communications at a lower transmission rate.