Adtran Gmbh

Universal Data Systems, Inc.

Norman R Harris

John S McGary

Clifford L Hall

Jeffrey B Wells

Stephen T Killian

Roger W Cain

Clint S Coleman

Don A Waring

Non-intrusive performance monitoring of a DS0 channel between a customer premises interface and a D4 channel bank includes an augmentation of existing channel bank equipment and a digital services communication device terminating the DS0 link at the customer site. An auxiliary signalling and performance monitoring arrangement is remotely accessible by a non-resident control site, for example by way of an RS-232 port of a line interface unit of the channel bank, thereby enabling the control site to perform prescribed network supervisory tasks with respect to one or more selected DS0 links, including provisioning of their associated loop equipment and performance monitoring of each DS0 loop. Office channel unit data port and line interface components of the channel bank are modified to provide bidirectional signalling capability via the receive segment of the channel bank's internal communications link. The signalling format on the bidirectional signalling link is defined so as to support both the transmission of incoming (received DS1) signalling traffic from the line interface unit to an office channel unit, and the bidirectional exchange of performance-monitoring command and response messages. A performance monitoring arrangement, installed in the channel unit and the digital communications network interface, monitors at least one prescribed performance aspect of the DS0 channel and forwards performance signals to the line interface unit over the bidirectional signalling link.

Performance monitoring of DSO channel via D4 channel bank

Non-intrusive performance monitoring of a DS0 channel between a customer premises interface and a D4 channel bank includes an augmentation of existing channel bank equipment and a digital services communication device terminating the DS0 link at the customer site. An auxiliary signalling and performance monitoring arrangement is remotely accessible by a non-resident control site, thereby enabling the control site to perform prescribed network supervisory tasks with respect to one or more selected DS0 links. Office channel unit data port and line interface components of the channel bank are modified to provide bidirectional signalling capability via the receive segment of the channel bank's internal communications link. The signalling format on the bidirectional signalling link is defined so as to support both the transmission of incoming (received DS1) signalling traffic from the line interface unit to an office channel unit, and the bidirectional exchange of performance-monitoring command and response messages. A performance monitoring arrangement, monitors at least one prescribed performance aspect of the DS0 channel.

Performance monitoring of DS0 channel via D4 channel bank

To prevent the occurrence of an anomaly on a single data-sourcing slave channel from causing continuous transmission on that channel and thereby tying up the entirety of a multipoint network, a signal transmission quality monitoring mechanism is incorporated into the office channel unit of each data-sourcing channel. The signal transmission quality monitoring mechanism controls the participation of each monitored digital communications channel on the basis of a measure of the quality of digital signals received from each monitored channel. The control software of each slave channel's office channel unit is configured to include a bipolar violation detector which monitors the channel for the presence of errors exhibited as bipolar violations of alternate mark inversion (AMI)-formatted digital signals. In response to the occurrence of a prescribed number of illegal bipolar violations within a predetermined number of received signals (e.g. three errored seconds within a sliding ten second window), the channel is declared to be of 'BAD' quality, and the office channel unit sends an `ABNORMAL` station code upstream to a multipoint junction unit. Thereafter, during continued monitoring of the channel, in response to the lapse of a predetermined period of time (e.g. 30 seconds) during which the prescribed number of illegal bipolar violations has not occurred within the predetermined number of received digital signals, the channel is declared to be 'GOOD', so that participation of the channel for the transmission of digital signals to the master site may be resumed.

Mechanism for monitoring quality of digital telephone link based upon

The need to equip a digital data service termination with the ability to decode digital loopback commands is obviated by a relatively simple hardware modification of a four wire telephone circuit connecting an office channel unit and customer premises equipment. In addition, the signal processing and test control firmware of the office channel unit equipment (OCU DP) is modified so as to realize a simplified circuit configuration for performing loopback testing of the four wire circuit. The hardware modification of the four wire circuit connecting the office channel unit and the customer premises involves the use of a sealing current-dependent relay circuit that responds to respectively different sealing current flow states: normally; interrupted; and reversed, as converted by the OCU DP. The present invention is particularly useful in subscriber loop circuits that are less than 10,000 feet in length, whereby the need for additional amplifier and noise reduction components is obviated.

Digital data loopback device

An all rate equalizer provides direct equalization of a data signal which is automatically adjusted based on data rate and transmission line. The equalizer is embodied in a closed loop circuit in which the amplitude of the data signal is the controlled parameter. The DC amplitude of the data signal is restored by an adjustable gain circuit and the bandwidth of the data signal is restored by an adjustable frequency circuit. The signal processing circuits are adjusted by a control processor in accordance with pre-determined tables of control signals corresponding to frequency and gain values required to provide equalization of the data signal for virtually any given data rate and transmission line. The all rate equalizer thereby automatically provides equalization of the data signal that is optimized for any combination of data rate and transmission.

Digitally controlled, all rate equalizer

A high-speed modem which acquires receiver operating parameters and equalizer coefficients, stores the parameters and coefficients after an initial modem communication having an initial training sequence, and reinitializes the modem equalizer and receiver at the beginning of subsequent modem transmissions with the previously stored coefficients and parameters to be followed by a shortened training sequence. The modem according to the present invention acquires the above-mentioned parameters and coefficients with improved accuracy by extending the initial training period before the transmission of data. The particular stored receiver parameters include carrier frequency offset and data timing frequency offset parameters. According to the present invention, an additional .DELTA. parameter is determined and stored which optimizes the receiver timing according to a difference between parameters acquired at different portions of the initial training sequence. During subsequent modem transmissions and after restoration of several of the previously used equalizer coefficients and receiver parameters, the modem further acquires the remaining receiver parameters during a very brief training period. The parameters acquired during the brief training period are adjusted by the previously determined .DELTA. parameter to achieve a high data accuracy with a minimum (brief) training period, which maximizes data transfer during the subsequent transmissions.

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Madison, AL, United States of America

Norman R Harris