Abstract: A Voronoi signal constellation with ties includes those points of a lattice .LAMBDA. (or a coset .LAMBDA.+c) that lie within a Voronoi region of a sublattice .LAMBDA.' of .LAMBDA., .LAMBDA.' being other then a scaled version of .LAMBDA., and the constellation includes more than .vertline..LAMBDA./.LAMBDA.'.vertline. points, where .vertline..LAMBDA./.LAMBDA.'.vertline. is the order of the lattice partition .LAMBDA./.LAMBDA.'. In order aspects, the lattices .LAMBDA. and .LAMBDA.' are of dimension greater than two; the sublattice .LAMBDA.' is a version of a binary lattice of depth at least two and normalized informativity less than one; a method is provided of mapping from m data bits to a point drawn from a Voronoi constellation of more than 2.sup.m points, based on an N-dimensional lattice partition .LAMBDA./.LAMBDA.'; and Voronoi constellations are provided comprising points of a lattice .LAMBDA. (or a coset .LAMBDA.+c) that lie within a Voronoi region of a sublattice .LAMBDA.' of .LAMBDA., the sublattice .

Abstract: A data communication networking system for carrying messages among a plurality of data handling devices in accordance with a plurality of different networking modes, each device being compatible with at least one of the networking modes, the networking system including networking circuitry for interconnecting the devices effectively in accordance with different ones of the networking modes, and concentrator circuitry having control circuitry for providing signals indicative of the networking modes with which different devices are compatible, and routing circuitry responsive to the control circuitry for routing messages between a given device and the networking circuitry in accordance with one of the networking modes with which the given device is compatible.

Abstract: A decoder including first and second decoding stages for selecting a codeword near to a given N-tuple r which is a sequence of N real values r.sub.i representing signals. The first stage includes substages associated respectively with sections r.sub.j of N-tuple r, each substage for evaluating distances between multiple sets of possible partial codewords and the section r.sub.j and for selecting a survivor from each of the multiple sets based on the distances. The second stage includes n-1 substages, each of which operates with respect to a supersection made up of a combination of two parts, each part being a section or a supersection combined in an earlier substage of the second stage and it includes a final substage which operates with respect to a final supersection whose parts make up the complete N-tuple r.

Abstract: The modem communicates with a variety of modem types employing differing initial handshake signals. The multimode modem sends a sequence of signals corresponding to the variety of modem type handshake signals and the sequence terminates when the multimode modem receives an appropriate response identifying a particular one of the variety of modem types.

Abstract: Apparatus for testing the performance of a communication line that carries customer data between two modems, including a programmable processor (for example, a digital signal processor) in each modem that either performs modulation or demodulation of customer data or tests the line, and a controller (for example, a programmable host processor) that switches the programmable signal processor selectively between processing customer data and line testing. The communication line carries both customer data and network control commands that include a test command for initiating testing, and each host processor responds to the test command by switching the signal processor to the test mode. There are a plurality of modems forming a data network and a central network control system connected to the network for providing the test command. The test command names two of the modems to participate in the testing and the controller identifies whether a given modem is one of the participants.

Abstract: Data flow in a communications network is controlled by a downstream node specifying the maximum average speeds of a plurality of data streams sent from an upstream node on a plurality of data paths.

Abstract: A Voronoi signal constellation includes those points of a coset of a lattice .LAMBDA. that lie within a Voronoi region of a sublattice .LAMBDA.' of .LAMBDA., where .LAMBDA.' is other than a scaled version of .LAMBDA.. The Voronoi signal constellation is combined with a coset code. A method of mapping data words to Voronoi constellation points is described.

Abstract: A data communication networking system for carrying messages among a plurality of data handling devices in accordance with a plurality of different networking modes, each device being compatible with at least one of the networking modes, the networking system including networking circuitry for interconnecting the devices effectively in accordance with different ones of the networking modes, and concentrator circuitry having control circuitry for providing signals indicative of the networking modes with which different devices are compatible, and routing circuitry responsive to the control circuitry for routing messages between a given device and the networking circuitry in accordance with one of the networking modes with which the given device is compatible.

Abstract: In a communication system, the combined advantages of decision feedback equalization and delayed decoding are achieved in a receiver by interleaving the signal points at the transmitter, and deinterleaving them at the receiver so that sufficiently reliable delayed decoder decisions can be used in estimating the distortion component of the received signal presently being processed in the decision feedback circuit.

Abstract: Echo cancellation to remove, from a locally received data communication signal, an echo signal component having a changing phase difference relative to the phase of a locally transmitted data communication signal, said locally transmitted communication signal are generated by modulating a carrier based on sequences of complex data signal points, is accomplished by correcting the phase of an input sequence of complex samples of the modulated carrier based on the changing phase difference to generate complex phase corrected samples, and generating a real-valued simulation of the echo signal based on the complex, phase corrected samples.

Abstract: In a modulation system for sending digital symbols over a band-limited channel in accordance with a sequence of multi-dimensional points each composed of a plurality of two-dimensional modulation signal points, and each selected from an available alphabet of the multi-dimensional points by an encoder on the basis of a group of the digital symbols, the improvement which includes circuitry for accumulating the symbols of each group, and circuitry for thereafter selecting the multi-dimensional point for the group, and in which the available alphabet includes a plurality of subsets of the multi-dimensional points, and the subset from which the multi-dimensional point is selected for each group depends on the subset from which the multi-dimensional point is selected for another one of the groups.

Abstract: In a modem that transmits signals to and receives signals from a remote device at a multiplicity of communication rates, the quality of the channel is monitored, a communication rate is selected based on the channel quality, the desire for an increased rate is indicated, and the increased rate is implemented by the modem when the remote device concurs.

Abstract: A technique for regulating the transmission of messages initiated simultaneously by a plurality of nodes of a network, in which clock intervals are established for the network, a sequence of digital values is included in each message and is transmitted to the medium at the rate of one digital value per clock interval, the sequences included in messages that are initiated at the same time by more than one node are transmitted in the same sequence of clock intervals, the presence on the medium of a selected digital value during any clock interval in which a node is transmitting a different digital value within the sequence of a message is detected, and the transmission of the message is interrupted by the node upon such detection, without corrupting another node's transmission.

Abstract: The unknown time when a transition in a signal point sequence has occurred is determined by a trellis technique based on known subsequences of symbols that preceded and followed the transition.

Abstract: A family of multi-dimensional convolutionally coded modulation systems achieves enlarged minimum distance between possible sequences of signal points, reduced number of error events with the minimum distance, acceptable peak-to-average power ratio, reduced number of signal points in each constituent two-dimensional constellation, immunity to rapid carrier phase changes, and reduced complexity, resulting in a reduced error probability when maximum likelihood decoding is used.These advantages are achieved by the construction and by the partitioning into subsets of the multi-dimensional constellation, by the design of convolutional codes using those multi-dimensional subsets, by using a bit converter and a block encoder to convert a multi-dimensional constellation mapping into multiple two-dimensional constellations mappings, and by a simplified decoding technique.

Abstract: A receiver for deciding which signal points were sent from a transmitter based on corresponding noise affected signals received via a distorting channel, the noise affected signals carrying information about a particular sequence of encoding states occupied in a succession of time intervals by a finite state process having a finite number of possible encoding states, the receiver including modifying circuitry for generating a plurality of different modified versions of each received signal, and a decoder for deciding which signal points were sent based on estimating a particular sequence of decoder states by storing a number of path histories of previous signal points and using the modified versions to extend the path histories, the different modified versions of each received signal numbering fewer than the number of stored path histories.

Abstract: In a modulation system for sending digital symbols over a band-limited channel in accordance with a sequence of multi-dimensional points each composed of a plurality of two-dimensional modulation signal points, and each selected from an available alphabet of the multi-dimensional points by an encoder on the basis of a group of the digital symbols, the improvement which includes circuitry for accumulating the symbols of each group, and circuitry for thereafter selecting the multi-dimensional point for the group, and in which the available alphabet includes a plurality of subsets of the multi-dimensional points, and the subset from which the multi-dimensional point is selected for each group depends on the subset from which the multi-dimensional point is selected for another one of the groups.

Abstract: Backup power is provided for primary power supplies that serve several loads by providing fewer backup power supplies than the number of primary power supplies, generating power fault information indicative of the failure status of the primary power supplies, and connecting the backup power supplies each in parallel to one of the failed primary power supplies in response to power fault signals.

Abstract: A Complementary Metal Oxide Semiconductor (CMOS) input buffer circuit is provided which accepts Transistor-Transistor Lock (TTL) input signal levels without generating any significant DC current path. A reference voltage circuit (1, FIG. 1) provides first and second reference voltages (V.sub.A and V.sub.B, FIG. 1) which are coupled to first and second stages, respectively, of the input buffer circuit (3, FIG. 1), and which are of predetermined magnitudes and scaled relative to each other to permit the P-channel devices of the input buffer circuit to turn off completely when the input to the circuit is "high", while allowing a successively higher output at each successive stage of the input buffer circuit. The reference circuit 1 is compensated for power supply and process window variations.

Abstract: Double side band-quadrature carrier modulation signal points as mapped on the complex plane are drawn from an alphabet consisting of at least 8 points, and are set up in concentric rings each rotated by 45.degree. with respect to adjacent rings. Differential encoding is shown encoding the phase components of the transmitted signals.