Abstract: A method for testing subscriber loop conditions includes receiving test signal data from a test signal provider, receiving a request for transmitting a test signal described by the test signal data, and transmitting the test signal over a subscriber loop. The test signal may correspond to a pre-qualification test signal, a qualification test signal, or an in-service test signal. Test results may be transmitted to the test signal provider or to some other designated.

Abstract: In a communications environment wherein data terminal equipment (DTE) transmits a data signal to data communication equipment (DCE) synchronously with a clocking signal provided by the DCE to the DTE, a circuit and method are configured to automatically detect a condition in which the data signal is sampled near a transition in the data signal, which may result in system clocking errors. Upon detecting this condition, the clocking signal used to sample the data signal is automatically inverted relative to the data signal to ensure that that the data signal is sampled near the midpoint between transitions in the data signal. In this manner, data clocking errors may be significantly reduced.

Abstract: The power budgeter controls the rate of data flow in one or more transceivers among a plurality of transceivers. The power budgeter monitors aggregate transceiver activity (data flow) during a predefined period, and limits transceiver data transmit and receive rates during times when the aggregate transceiver activity would otherwise exceed a predefined threshold. If total data flow during the monitored time period exceeds the threshold, data flow through the active transceiver during the next (second) time period is limited. Data flow rates are limited in a transceiver by shutting off transceivers (receiver and/or transmitter) for a specified portion of the second time period. In other types of transceivers, the transmitter and/or receiver may be forced into a low-power idle state or similar operating condition for a specified portion of the second predefined time period.

Abstract: A symbol timing derivation system derives receiver timing from received symbols which avoids the need for a pilot tone, thereby reducing power consumption and expanding usable bandwidth. The system is implemented by using a calculation that finds the timing phase error. The timing phase error is then averaged and controls a phase locked loop (PLL). This PLL in turn controls a voltage-controlled oscillator, which handles the modem receiver timing. A centroid calculation can be included to bias the voltage-controlled oscillator to push the equalizer coefficients back to the ideal position. The system can be implemented in either a point-to-point modem environment or a multi-point environment, for example, but not limited to, MVL or DMT. The voltage-controlled oscillator may also be implemented to control transmitter timing, so that the central office modem and the remote modem will operate more-or-less synchronously, reducing the need for large equalizer corrections at either end.

Abstract: A plain old telephone system (POTS) device, for example but not limited to, a telephone, facsimile machine, analog modem, caller identification (ID) system, speaker phone, cordless phone, etc., employs an on-board transistor-based linear polarity guard to enable decoupling of a POTS channel from one or more xDSL channels on a telephone connection (subscriber loop associated with a public service telephone network), while reducing undesirable interference, such as intermodulation distortion imposed upon the POTS and xDSL channels. Transistors associated with the polarity guard are operated in the ohmic region, or in a nonsaturated linear mode, to achieve a substantially linear transfer function through the transistors and through the overall linear polarity guard. Current that is input to the polarity guard and the voltage drop across the transistors that conduct the current in the polarity guard exhibit a substantially linear relationship, or linear VI transfer function.

Abstract: A plain old telephone system (POTS) device, for example but not limited to, a telephone, facsimile machine, analog modem, caller identification (ID) system, speaker phone, cordless phone, etc., employs an on-board POTS filter to enable reliable and efficient decoupling of a POTS channel from one or more xDSL channels on a telephone connection, while permitting and not interfering with the xDSL channels. The POTS device, which connects to a subscriber loop associated with the public service telephone system, includes a subscriber loop connection switch (for example, a hook switch), a POTS transmitter, receiver, or transceiver, and a low pass filter interconnecting the subscriber loop connection switch with the transmitter, receiver, or transceiver. The switch effectively isolates the POTS filter from the telephone line when the POTS device is disconnected, or is on hook, and interfaces the telephone line through the POTS filter to the POTS transceiver when the POTS device is connected, or is off hook.

Abstract: A network congestion control system and method facilitate the transmission of information on a communication network by monitoring the data streams coming out of the communication network for congestion notifications, and actively rate controlling the end user application sessions based on such congestion notifications to alleviate the network congestion. This provides congestion control for the network and can be used to avoid congestion reaching the point where the network has to discard data. The end user sessions can be divided into mission critical sessions and non-mission critical sessions. These session types can be prioritized so that non-mission critical sessions are rate controlled during periods of congestion, while mission critical sessions remain unaffected. Mission critical sessions are effectively reserved a specific amount of bandwidth with the rest of the available bandwidth (up to the congestion point) being allocated dynamically to the non-mission critical sessions.

Abstract: A discrete multi-tone (DMT) digital subscriber line (DSL) communication device employs a linear block interleaver for mathematically combining multiple tones into n-tone combinations in order to efficiently suppress or eliminate correlated noise or impulse noise generated in the communication channel. In architecture, the linear block interleaver includes logic configured to combine multiple signaling constellations into n-tone combinations. The multiple constellations are mathematically combined such that noise energy present in at least one of the n-tone combinations is spread among each of the multiple tones, thus reducing the energy of the noise on each of the multiple tones.

Abstract: A system and method for the measurement of communication network performance over a secondary communication channel sends an inquiry signal containing information pertaining to network performance from a near end communication device to a far end communication device. From the inquiry signal the far end communication device can determine the number of packets of information lost through the network. Once received the inquiry signal is modified by the far end communication device with additional information and sent as a reply signal to the near end communication device. The near end communication device receives the reply signal and can determine therefrom the network latency.

Abstract: A subscriber line driver (SLD) is provided for the continuous and automatic transformation of the characteristics of a communication system signal so that the signal conforms to a power spectral distribution (PSD) standard. The signal is transformed by the SLD which may increase (amplify) portions of the signal to a predefined specification, decrease (attenuate) portions of the signal to a predefined specification, and/or frequency modulate or filter the transmit signal frequencies to fit within the communication channel frequency bandwidth as defined by a predefined frequency band. After modification by the SLD, the transformed communication signal is injected (transmitted) into a communication transmission line. An SLD device can be employed in a variety of communication systems such as a public telephony system, a private branch exchange (PBX), a coaxial cable system, a fiber optic system, a microwave system, a radio communication system or the like.

Abstract: A system for providing a backup network is disclosed that includes a glare detection circuit, an arbitration circuit, and a line control circuit. The glare detection circuit receives a dial signal associated with the call control circuit and a cause value from a backup circuit, and asserts a glare present signal responsive to the dial signal and the cause value being asserted. The arbitration circuit receives the glare present signal and produces an arbitration signal responsive to an arbitration procedure. The line control circuit receives the arbitration signal and determines whether the call control circuit will discontinue an outgoing call on the backup circuit and wait a specified period of time for an incoming call on the backup circuit or wait for the outgoing call on the backup circuit to be answered. Methods and other systems are also provided.

Abstract: The eavesdropping prevention system and method of the present invention provides a mask signal generator which generates a mask signal superimposed over a leakage signal. The mask signal prevents meaningful detection and amplification of the leakage signal. The amplitude of the mask signal is low enough so as not to interfere with the transmission of analog POTS signals over the communication line on which the mask signal is superimposed. In the preferred embodiment, the amplitude of the mask signal exceeds the amplitude of any anticipated leakage signals which may be manifested on the communication line. Alternative embodiments of a mask signal are described.

Abstract: The eavesdropping prevention system and method of the present invention provides a controllable line selection unit which couples a receiver and a transmitter to a selected one of a plurality of subscriber loops according to the current channel of a time-multiplexed communication signal. The controllable line selection unit prevents meaningful detection and amplification of the leakage signal by physically isolating communication connections from each other. In the preferred embodiment, the controllable line selection unit actuates a plurality of switches coupled to a plurality of communication connections. Alternative embodiments of a controllable line selection unit are described.

Abstract: A central office (CO) filter system connects between a CO telephone switch and a telephone connection (subscriber loop) that can communicate voice and digital data channels. The CO filter system suppresses transients and harmonics on the connection caused by a telephone ring signal (typically, 90 to 150 Vrms at 15 to 68 Hz) generated by the switch in order to minimize adverse effects on the digital data channel on the connection. Architecturally, the CO filter system includes a first filter designed to implement a first low pass filter function to attenuate frequencies higher than a ring signal so that transients and harmonics produced from the ring signal are suppressed, a second filter designed to implement a second low pass filter function to attenuate frequencies higher than a voice channel, and a current detector designed to detect when a telephone is off-hook.

Abstract: A thresholding noise estimator detects and samples an error signal during a sampling period. When the magnitude of a noise sample, also known as an error sample, is at least equal to a predefined threshold, the power of that error sample is calculated. At the end of the sampling period, the computed powers of the error samples (only those data samples having a magnitude at least equal to the predefined threshold) are averaged. This average power corresponds to an error indicator which quantitatively indicates the power for that portion(s) of an error signal which is at least equal to the threshold. Alternative embodiments provide for magnitude hysteresis, time hysteresis, or both magnitude and time hysteresis in the determination of an error indicator.

Abstract: A filter system (and associated filtering method) is disclosed, the filter system being connected between a large-amplitude, high-frequency noise source and a frequency-division multiplexed communications channel. The large-amplitude, high-frequency noise commonly being a POTS (plain old telephone service) ring signal generated by a CO (central office) telephone switch. The frequency-division multiplexed communications channel generally used to carry digital signals at frequencies above the POTS baseband in order to implement a digital subscriber line (DSL). Large-amplitude, high-frequency signal components from the POTS ring signal impair the performance of frequency-division multiplexed channels on a transmission line such as a subscriber loop. The filter system of the present invention utilizes amplitude and also may utilize frequency to selectively suppress the transients and harmonics on the transmission line caused by a telephone ring signal.

Abstract: A communication system containing a constellation encoder, a feedback precoder, and an interleaver that is coupled to the feedback precoder, enables efficient trellis encoding by preventing adjacent transmit symbols from having the same trellis symbol. Consequently, the adverse impact of quantization noise that may occur over adjacent transmitted symbols is minimized. The constellation encoder uses redundant bits that are generated by a trellis encoder connected to the interleaver, the redundant bits being added to an input stream of data bits being provided to the communication system for transmission. The trellis encoder generates the redundant bits based on the interleaved storage of trellis symbols bits in the interleaver.

Abstract: Apparatus and method for providing simultaneously multiple telephone-type services to any/all POTS-type devices on a single wire pair at a user premises. The present invention provides for the ability to add separately addressable POTS devices on a single service loop.

Abstract: A system and method for transmission over a bus between ATM layer devices and PHY layer devices which exist on different printed circuit boards use a ATM-PHY layer interface connected to the ATM and PHY layers across a bus. Data and control signals are transmitted across the ATM-PHY interface consisting of a single clock and one or more pairs of data leads. Asynchronous cell transmission without flow control, with cell level flow control and with byte/octet level flow control as well as cell synchronization are possible. The number of signals required to connect the PHY/ATM layer devices are dramatically reduced by transporting the data and control information using in-band signaling.

Abstract: A method and apparatus for communicating both packet data and time division multiplexed (TDM) transmissions over a shared bus. An apparatus is providing having a shared data communication bus and first and second control signals. The first control signal indicates the transmission of time division multiplexed data on the shared data communication bus, while the second control signal indicates the transmission of packet data on the shared data communication bus. A plurality of packet modules are provided, wherein each packet module is responsive to the state of the first and second control signals, and each packet module is further configured to transmit and receive data across the shared data communication bus. A plurality of synchronous interfacemodules are further provided, wherein each synchronous interface module is configured to transmit and receive data across the shared data communication bus.