Lucent Technologies Inc.

At+t Corp.

At&t Bell Laboratories

Nuri Ruhi Dagdeviren

Andreas Constantine Papanicolaou

Lujing Cai

Khashayar Mohammadi

Rajiv Laroia

Jin-Der Wang

Ender Ayanoglu

George John Kustka

Burton R Saltzberg

James E Mazo

Mahendra Pratap

Cheng D Yu

Herbert B Cohen

Walter Patrick Binns

Deirdre T Ryan

Jerome Prestinario

Kenneth R Klein

An Asymmetric Digital Subscriber Loop (ADSL) Discrete Multi-Tone system has disjoint and adjacent upstream and downstream channels. During the training phase of an ADSL connection, an ADSL DMT transmitter first determines a round trip propagation delay by transmitting a ranging signal to a far-end ADSL endpoint. During the subsequent communications phase, the ADSL transmitter synchronizes transmission of DMT symbols to a reference clock. In addition, the cyclic extensions of each DMT symbol are increased as a function of the propagation delay.

Reduction of interference in discrete multi-tone (DMT) based communications systems

The present invention provides a method and apparatus for minimizing quantization noise in signal transmissions between modems coupled together via a digital network resulting from the performance of digital loss insertion in &mgr;-law encoded signal transmissions when the receiving modem is coupled to the digital network via an analog subscriber loop. In a preferred embodiment, the minimization of quantization noise is effected by providing a digital modem capable of &mgr;-law encoding and decoding a signal transmission; and capable of scaling the amplitude levels of signals generated by the modem; and capable of performing an inversion mapping.

Method and apparatus compensating for effects of digital loss insertion in signal transmission between modems

A method is presented to enable the impulse response of a channel to be identified when the received signal contains a large amount of quantization noise. A probabilistic estimate of the distribution of the quantization noise is subtracted from the summation of the products of the received training signal samples and tap coefficients to provide a more accurate error signal for the adjustment of the tap coefficients.

Digital equalization in the presence of quantization noise

For use with a central communications device digitally-coupled to a digital telecommunications network that includes an analog interface having an analog-to-digital converter ('ADC'), a system and method for iteratively determining quantization intervals of the ADC and a modulator/demodulator ('modem') employing the system or the method. The system includes: (1) a signal generator, coupled to an input of the ADC, that generates a sequence of analog signals to be quantized by the ADC to yield resulting symbols for reception into the central communications device and (2) an analyzer, that receives a return signal from the central communications device, the return signal indicating comparisons by the central communications device of the resulting symbols with expected symbols, the comparisons allowing the analyzer to determine threshold values between the quantization intervals of the ADC, the quantization intervals being a function of the threshold values.

System and method for iteratively determining quantization intervals of

For use with an analog communications device coupled to an analog interface of a digital telecommunications network, the analog interface having signal conversion values corresponding to an n-level symbol table, a system and method that dynamically selects a constellation of symbols from the n-level symbol table, and a modulator/demodulator ('modem') employing the system or the method. The system includes (1)a logic circuit that selects m symbols, m being less than or equal to n, from the n-level symbol table, the m symbols being a function of the signal conversion values, and (2) a transmission circuit adapted to transmit data identifying the m symbols to a remote device digitally-coupled to the digital telecommunications network, the data allowing the analog communications device and the remote device to communicate with a common symbol table dynamically adapted to the signal conversion values of the analog interface of the digital telecommunications network.

System and method for dynamically optimizing a symbol table and modem

A telephone system simultaneously transmits voice and data through a public switched telephone network and over one telephone line between a calling party location having an ISDN connection and a destination party location having a POTS analog connection. The calling party location determines if the destination party location has an analog POTS connection and then creates a connection between the calling party and the destination party. Data and voice band signals are packetized and multiplexed and transmitted through the public switched telephone network to a modem located at the destination party location. The packets are demultiplexed into separate voice band and digital signal components and the digital signal components demodulated within the modem. The demodulated data signals are forwarded to a data terminal and a voice band signals forwarded to an analog terminal.

Method and system for interoperating between ISDN and PSTN transport for

The general problem of conveying a particular meaning in a message so that the meaning is most understandable when an abridged version of the message is displayed is solved by supplying as the message a 'tagged' string in which all characters in the unabridged version of the sting are tagged with respective priority indicator each having a value indicating a particular priority level. In a station set an abridged version of the string for a particular priority level is determined by selecting all characters from the received, unabridged version having a priority indicator value equal to or greater than that particular priority level. A priority level is elected such that the corresponding abridged string fits within the available display length. In accordance with a feature of the invention, the message may further include one or more supplementary characters each also tagged with a priority indicator, and the abridged version of the string for a particular priority level includes not only the characters selected as aforesaid, but also any supplementary, characters whose priority indicator has that particular value. This, advantageously, allows the version of the string for each priority level to include characters that a) do not even appear in the unabridged version of the string, or b) arm not displayed as part of some abridged, but longer version(s) of the message, even though they appear in the unabridged version

Abridgment of text-based display information

The present invention provides a method and apparatus for minimizing quantization noise in signal transmissions between modems coupled together via a digital network resulting from the performance of digital loss insertion in .mu.-law encoded signal transmissions when the receiving modem is coupled to the digital network via an analog subscriber loop. In a preferred embodiment, the minimization of quantization noise is effected by providing in a digital modem means for .mu.-law encoding and decoding of signal transmissions, means for scaling the amplitude levels of signals generated by the first modem down by a predetermined reduction factor to obtain factored signals in addition to means for performing an inversion mapping comprising a scaling of the amplitude level of the factored, .mu.-law encoded signals up by a predetermined inversion factor to obtain a gain in the amplitude level of the factored signals corresponding to the predetermined loss inserted in the amplitude levels of the transmitted .mu.-law encoded signals. In accordance with an alternate embodiment, the minimization of quantization noise is effected independently of the transmitting modem through an inversion mapping of .mu.-law encoded signals forming .mu.-law code words when transmitted through an interexchange (IEC) digital network. The inversion mapping is performed by scaling the amplitude levels of .mu.-law code words up by a predetermined inversion factor to obtain a gain corresponding to the predetermined loss subsequently inserted in the amplitude levels of the .mu.-law code words. This is accomplished by providing within a digital switch of the IEC network means for detecting one of the existence of a terminating analog subscriber loop and the occurrence of loss insertion over the digital network, means for determining the amount of loss inserted in the signal transmissions, means for performing a .mu.-law code word-to-code word inversion mapping.

Method and apparatus compensating for effects of digital loss insertion

Techniques are disclosed for providing interoperability between a first modem and a calling identity delivery on call waiting (CIDCW) service. According to an embodiment disclosed herein, a first modem is coupled to an alerting signal receiver and a communications re-establishment device. The alerting signal receiver receives an alerting signal generated in response to an incoming call from a third party line if the first modem is communicating with a second modem. The communications re-establishment device reestablishes communications between the first modem and the second modem after the alerting signal receiver receives an alerting signal. The first modem is equipped to receive the alerting signal and reestablish communications with the second modem independent of the specific capabilities of the second modem, so that these techniques can be utilized in conjunction with a second modem not constructed in accordance with the embodiments disclosed herein.

Modem communications interoperability with services equipped to provide

The general problem of conveying a particular meaning in a message so that the meaning is most understandable when an abridged version of the message is displayed is solved by supplying as the message a 'tagged' string in which all characters in the unabridged version of the string are tagged with respective priority indicators each having a value indicating a particular priority level. In a station set, an abridged version of the string for a particular priority level is determined by selecting all characters from the received, unabridged version having a priority indicator value equal to or greater than that particular priority level. A priority level is selected such that the corresponding abridged string fits within the available display length. In accordance with a feature of the invention, the message may further include one or more supplementary characters each also tagged with a priority indicator, and the abridged version of the string for a particular priority level includes not only the characters selected as aforesaid, but also any supplementary characters whose priority indicator has that particular value. This, advantageously, allows the version of the string for each priority level to include characters that a) do not even appear in the unabridged version of the string, or b) are not displayed as part of some abridged, but longer version(s) of the message, even though they appear in the unabridged version.

A tagged string is developed by setting the value of a current priority variable to the maximum priority level, selecting a shortest length string of the plurality the characters of which have not all been incorporated into the tagged string as the current string, selecting a character of the current string that is not found in the string that was processed for incorporation into the tagged string immediately prior to the current string, adding the selected character to the tagged string and setting the value of the priority indicator for the just added character to the value of the current priority value. Character selection, addition and priority setting are repeated until the characters of the current string are all incorporated into the tagged string. Thereafter, the value of the current priority variable is decreased. The process, except for the setting of the current priority level, is repeated until all strings have been incorporated into the tagged string. The message may also include one or more supplementary characters, in which case each character is tagged with a priority indicator and a supplement indicator. If so, characters are selected if they are not found in the immediately preceding processed string or if they are not in the longest string. The supplement indicator for each selected character is set if the selected character is not in all strings having a length greater than the current string when the current string is not the longest string.

An approach for operating modems in synchronism with the A/D and D/A converters of the network limits the analog signals transmitted to the modem to low levels and concurrently restricts the received signals to large steps. This set of apparently conflicting signal limitations is achieved with a signal conversion process interposed in the communication path between the two hybrids. In one embodiment of this invention, the code conversion is implemented in an adjunct processor that is associated with a switch that participates in the communication path between the two modems. In operation, a call that needs the conversion process is identified by virtue of the calling party's number and service associated service provision information. When it is established that both the calling party's modem and the receiving party's modem operate in the manner that requires signal conversion, conversion is executed. Echo cancellation may be applied to the signal in the code conversion apparatus to further improve performance.

Modem with received signals and transmitted signals comprising signal

A modem that operates reliably at a symbol rate that corresponds to twice its bandwidth even when it is coupled to a receiving A/D converter that operates under control of a clock is realized by synchronizing the modem's operation to the A/D's clock. The superior operation of this modem advantageously extends to A/D clock frequencies beyond the frequency of twice the modem's bandwidth. To minimize quantization noise, the modem's output is conditioned to minimize intersymbol interference by adjusting the modem's output to the A/D converter's sampling times and slicing levels. When the A/D's clock is higher than twice the bandwidth of the modem's output signal, some intersymbol interference cannot be avoided. In accordance with this invention, the position and value of this interference is computed at the receiver and subtracted from the received signal.

High-speed modem synchronized to a remote CODEC

A single medium (audio) voice grade call initiated by an ISDN video phone and directed to another ISDN video phone is converted into a multimedia (audio and video) ISDN call by a) maintaining the connection for the voice grade call while the ISDN audio and video connection is being established over a bearer channel of the ISDN subscriber loop different from the bearer channel being used by the voice grade connection, b) switching the audio signals from the voice grade call to the ISDN audio and video connection, once the ISDN audio and video connection is established, and c) tearing down the initial voice grade call.

ISDN-based system for making a video call

In a video telephony system, a coaxial cable network, which is preferably a part of an existing cable television system, provides a local link for the transmission of the video telephone signals between each originating and destination location and a respective 'head end' located on the cable company premises. Each of the head ends is connected to a 'point of presence' of a telephone interexchange carrier so that a connection between pairs of head ends, and thus between a pair of video telephone locations, can be made via a switched digital network maintained by the carrier. Certain of originating and destination locations comprise a standard television set, serving as the audio/video display, and a consumer-type camera or camcorder, serving as the audio/video source. Others of the originating and destination locations comprise ISDN video telephones which are connected to the various points of presence of the interexchange carrier via local exchange carrier telephone networks. The video telephone number for cable subscriber locations are administered to be the same as the standard ten-(i.e., area code plus seven-) digit telephone number used for regular telephone calls directed to those locations.

Growing community of inventors

Red Bank, NJ, United States of America

Nuri Ruhi Dagdeviren