Abstract: A communications switch communicates a message to a particular access network endpoint by forwarding an identification of that endpoint along with the message, link-by-link, through the access network, the forwarding being accomplished by using previously stored routing information identifying, at the switch and at each cross-connection point, a particular downstream link over which the endpoint can ultimately be reached. The links connecting the cross-connection points are multiplexed links supporting digital loop carrier and fiber-in-the-loop communications. The routing information is generated and stored automatically by having each network element report information about itself upstream into the network.

Abstract: Network elements in a telecommunications network, such as toll switches, databases and the like, are provided with redundant SS7 signaling interfaces based on different software designs. At least one of the interfaces, referred to as a network endpoint signaling transfer point, or NESTP, is loosely coupled to its host and has signaling transfer point (STP) capabilities. In a routing table within the NESTP, a plurality of prioritized route lists are provided for at least some destinations, the list that is used to route a particular message to such a destination being a function of the route by which that message arrived at the NESTP.

Abstract: A communications switch communicates a message to a particular access network endpoint by forwarding an identification of that endpoint along with the message, link-by-link, through the access network, the forwarding being accomplished by using previously stored routing information identifying, at the switch and at each cross-connection point, a particular downstream link over which the endpoint can ultimately be reached. The links connecting the cross-connection points am time-division-multiplexed links supporting digital loop carrier and fiber-in-the-loop communications. The routing information is generated and stored automatically by having each network element report information about itself upstream into the network.

Abstract: 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.

Abstract: A unified and automated system for providing, restoring and optimizing special services is continually aware of the state of all the equipment and facilities in the network. The unified system responds automatically to a request for a special service by 1) designing a circuit required to support the requested special service, 2) identifying network facilities and configurations for implementing the designed circuit, 3) assigning those facilities to the circuit, 4) causing the various equipment providing the facilities to be interconnected to implement the service, 5) verifying the integrity of the special service, and 6) delivering the service to the customer.

Abstract: In order to mitigate against the multiplicative noise effects caused by known non-linearities in a trellis coded data transmission system, a signal constellation is formed by starting with a base constellation whose number of signal points and whose geometry are selected in accordance with conventional criteria and then warping that constellation by adjusting the positions of its signal points in accordance with a warp function which is the inverse of the known component of the non-linear characteristic of the transmission system. Because the constellation warping is deterministic, it is possible for the receiver to "unwarp" the received signal points prior to applying them to the Viterbi decoder. In preferred embodiments, the trellis code is of a type in which the dominant error event is a trellis path error.

Abstract: Congestion control is implemented at the resources that actually suffer from congestion and, moreover the congestion control is performed within the network as well as at its access points. In a particular embodiment, congestion control is continuously performed at each resource. Use of each resource is controlled according to a head-of-the-line weighted round-robin service discipline thereby assuring fairness and full use of bandwidth for all active channels. Also, in order to control conditions of congestion, the queue of data elements waiting for service at each resource is regulated by a global congestion indicator for the entire queue. The data elements of each channel that are waiting for service are further regulated in response to specific local congestion indicators that are individualized for each channel. The global and local congestion indicators are used to guarantee predetermined levels of service for each channel.

Abstract: The standard exchange message interface (EMI) message record generated for interexchange telephone toll calls is enhanced via the addition of a primary interexchange carrier (PIC) indicator, whose value provides an indication as to whether a terminating subscriber has a particular interexchange carrier as his/her PIC. The PIC indicator may be used by the interexchange carrier when bills are rendered for its subscribers--for example, to provide different billing treatment for calls that were made over that carrier's network to terminating subscribers whose PIC is, in fact, that very carrier, as opposed to calls that were made to subscribers with a different PIC.

Abstract: A multilevel coded modulation scheme trellis encodes a portion of the input data and the resulting encoded stream is used to identify a particular one of a predetermined number of subsets of symbols of a predetermined signal constellation. The remaining input data is coded using a Reed-Solomon (RV) code whose output is used to select for transmission a particular symbol from the identified subset. In applications in which phase hits or other channel phenomena may cause the received signal points to be phase-rotated versions of the signal points that were transmitted, differential encoding is included in the overall coded modulation scheme. In different embodiments, the differential encoding/decoding and RV encoding/decoding are in different orders. In one such embodiment, overlapped multilevel codes are used to preserve the advantages afforded by taking a multilevel coding approach.

Abstract: 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.

Abstract: A telephone call initiated from a first network and directed to a second network at which network resources are temporarily unavailable to route and/or switch that call, is completed by a) estimating the anticipated time before these resources can become available, b) offering the caller the option of being called back, based on that estimation, c) calling back the caller when network resources are expected to become available, d) establishing a connection from the first network to the called party at the second network, and e) merging the two calls.

Abstract: Digital data is transmitted over partial-response channels using a precoding technique which allows for the use of a wide variety of transmit constellations. A sequence of signal points is selected from a predetermined base constellation meeting particular criteria. A so-called combined signal point is developed for a present symbol interval by a) selecting a signal point from the base constellation as a function of input bits associated with the present symbol interval and b) combining the signal point thus selected with a feedback signal which is a function of one or more combined signal points that were developed for previous symbol intervals, that function being determined by the characteristic of the partial-response channel. A transmit signal which represents the combined signal points is then provided. In one implementation, the processing steps are performed explicitly using an integrated precoder/constellation mapper. In another implementation those steps are performed implicitly using table look-up.

Abstract: The problem of being unable to supply prescribed fair amounts of telephone traffic to each carrier in a foreign country is overcome by a) assigning a call to one of the carriers in a foreign country at the switch where the call originated b) including an indication of the identity of the assigned carrier with the call as the call is routed from the originating switch to an egress switch and c) retaining at the originating switch an indication of the carrier to which the call is currently assigned. The indication of the assigned carrier stays with the call until either the call is completed to the assigned carrier or it is determined that the call cannot be completed to the assigned carrier. This allows the originating switch to retain control over the assignment of a call to a carrier. Furthermore, the originating switch can cause all the routes from the originating switch to the originally assigned carrier to be tried before it allows another carrier to complete the call.

Abstract: Digital signals, such as digitized television signals, are subjected to a source coding step followed by a channel mapping step. The source coding step causes the signal to be represented by first and second data streams. The first stream carries data regarded as more important and the second carries data regarded as less important. In the channel mapping step, the mapping is such that the data elements of the various data streams have differing probabilities of being erroneously detected at the receiver. The channel mapping step includes at least one multi-level coding step. The signal constellations used in the channel mapping step are partitioned into supersymbols, in which the distance between the symbols of at least ones of the supersymbols is less than a parameter referred to as the maximum intra-subset distance (MID).

Abstract: A modem which represents the transmitted primary data stream using signal points selected via a trellis code is provided with the further capability of transmitting secondary data. In particular, a standard constellation of signal points is expanded to include a number of signal points which is greater than that needed to transmit the primary data. Particular primary data word values are representable by either of a predetermined pair of signal points associated with that value--one signal point of the pair being a standard signal point and the other being an expanded signal point. The specific one of the two signal points of the pair that is transmitted at any given time is chosen as a function of whether the value of the next bit in the secondary data stream waiting to be transmitted is a "0" or a "1".

Abstract: When a telephone caller charges a call to a commercial credit card, an announcement which includes the name of the credit card issuer is supplied to the caller after the validation of the credit card. In a preferred embodiment, the issuer of the commercial credit card is identified, for purposes of announcing its name, by examining the prefix code of a credit card number supplied by the calling party. Also, in the preferred embodiment, not only the issuer of the commercial credit card but also the name of the telephone carrier is supplied as part of the announcement given prior to connecting the calling station to the called station after validation of the credit card. An illustrative such announcement is "Thank you for using AT&T and for charging this call to your American Express card".

Abstract: Fractional rate modulation is accomplished by separating incoming data into frames of bits. Each frame in partitioned into bit words of unequal lengths. The words are divided by a modulus to obtain remainders. The remainders are transmitted using, for example, QAM modulation. At the receiving end, the process is reversed. The ratio of baud rate of the system to the incoming bit rate defines the modulus as well as the number of QAM modulation points. A "data rate throttling" technique takes advantage of the capabilities provided by the foregoing to allow the rate at which data is channel mapped and transmitted over a communication channel to be easily varied in small increments.

Abstract: 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.

Abstract: The penalties and drawbacks associated with encrypting information in a portable device having a microprocessor are avoided by, in advance of the time for encryption to begin, having the microprocessor develop portions of a key sequence during periods of time that the microprocessor is not engaged in performing any function necessary for the operation of the portable device and storing each developed portion of the key sequence for later use in encrypting information. In one embodiment, at least one entire key sequence of sufficient length to encrypt a string of information that has a predetermined maximum possible length is developed and stored in advance of the beginning of any encrypting.

Abstract: A process that disallows any bridging onto the signal to be broadcast from any switch of the input stage of the Clos switching network and that further disallows any requests for point-to-multipoint broadcast connections in excess of the number of switches in the center stage of the network avoids the perceived problems with maintaining point-to-multipoint broadcast connections in a Clos switching network. Such a process causes rearranging to occur only when the broadcast connection is established or added to. It also guarantees that paths for point-to-point connections can always be found, when they are requested, without spending time to rearrange any other connection.