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 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 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 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: An encoding (or decoding) method, by which raw data of 1 line is converted into, for example, modified Huffman (MH) code (or MH code is converted into raw data) by obtaining a cumulative run-length code every transition point, at which there occurs a transition or change between a run of white pixels to another contiguous run of black pixels, from the beginning of the line and then converting the cumulative run-length code to the MH code (or converting the MH code to the cumulative run-length code). The cumulative run-length code is defined by both of data, which indicates that a pixel of a run just prior to the transition point is black or white, and data representing a cumulative run-length of the run up to the pixel thereof just prior to the transition point. Thus, an encoding or decoding processing can be performed at a high speed.

Abstract: A Viterbi decoding method, in which consecutive input data bits Q.sub.6n .about.Q.sub.1n are first converted into consecutive code bits Q.sub.6n .about.Q.sub.3n Y.sub.2n Y.sub.1n Y.sub.0n at a time instant n by use of a Trellis encoder. Then, a branch metric, which is a minimum Euclidean distance between a reception signal point and each of signal points (namely, Trellis codes Q.sub.6 .about.Q.sub.3 Y.sub.2 Y.sub.1 Y.sub.0) in a signal space diagram, corresponding to each of eight states 0 to 7 and a corresponding signal point are obtained. Further, a sum of the branch metric corresponding to each state and a corresponding path metric at a time instant (n-1), which is a sum of corresponding branch metrics since a time instant 1 to the time instant (n-1) is calculated. Then, the path metric corresponding to each state is updated by replacing it with the calculated sum of the corresponding branch metric and the corresponding path metric obtained at the time instant (n-1).