Abstract: In a full-duplex modem, correlation of an echo estimate signal with an echo-canceled signal is used to determine the presence or absence of a remote signal.

Abstract: A secure cellular telephony arrangement where the mobile unit maintains a secret that is assigned to it by the service provider, and which is known to the provider (home cellular geographic service are--CGSA) but not to any other base station. A shared secret datum is generated by the home CGSA with the aid of the secret and some other data. That data is transmitted to the mobile unit to enable it to also generate the shared secret datum. A mobile unit wishing to communicate with a base station creates an authentication string with the aid of the shared secret datum and sends it and the unit's identity to the base station. A base station which does not have the shared secret datum is unable to immediately authenticate the mobile unit. It therefore contacts the home CGSA, receives the shared secret datum and the other data, and proceeds to authenticate the mobile unit's authentication string.

Abstract: Effective control of impedance values in integrated circuit applications is achieved with an integrated circuit transistor whose size is digitally controlled. The digitally controlled size is achieved, for example, with a parallel interconnection of MOS transistors. In one application, the digitally controlled transitor serves as a controlled impedance connected to an output terminal of an integrated circuit. In that application, a number of transistors are enabled with control signals, and the collection of enabled transistors is responsive to the input signal that normally is applied to a conventional transistor. In another application, where the digitally controlled transistor serves as a controlled impedance at the input of a circuit, only the control signals that enable transistors and thereby determine the effective developed impedance are employed.

Abstract: Signal distortion in fiber optic systems is compensated for by forming decisions as to the transmitted information as a joint function of the received signal and of a feedback signal. The latter, in turn, is a function of decisions made for at least one signal transmitted over the fiber. The feedback signal determines the value of a threshold to which the received signal is compared in order to generate the decisions.

Abstract: An enhanced "800" service automatically provides a second communications path between a customer and a business in order to provide additional product information, such as video information, to the customer. For example, upon receipt of a customer telephone call on a B-channel of an ISDN facility, premise switching equipment, of the business, automatically receives the customer's network address. This address is used to automatically setup the second communications path to the customer.

Abstract: A new class of circuit simulation methods comprises a homotopy that is constructed by employing particular models of the nonlinear elements of the circuit and by including a randomizing component in the homotopy equation. In particular, the models of the non-linear elements are passive, in the sense that they contain no negative resistors and no voltage dependent sources. Also, the models are smooth enough to at least have well-defined first and second order derivatives. One such homotopy is (1-t)(Bx+a)+tF(x)=0, where B is a randomizing matrix and a is a randomizing vector, t is the continuation parameter, x is a vector of the circuit's node voltages, and F(x) is a set of equations such that F(x)=0 describes the circuit. Another is the homotopy (1-t)(F.sub.A (x)+a)+tF.sub.B (x)+.sigma.(t)(x-a) where F.sub.B (x)=0 describes the circuit whose dc operating point is sought, F.sub.A (x)=0 describes a circuit whose dc operating point is known, and .sigma.(t) is a function that is 0 at t=0 and t=1.

Abstract: Designs are created through a high-level to low-level transformation in the form of a formal top-down development procedure based upon successive refinement. Starting with a high-level (abstract) model, such as a formal abstraction of a protocol standard, successively more detailed models are created through successive refinement, in a fashion which guarantees that properties verified at one level of abstraction hold in all successive levels of abstraction. The successive refinements end with a low-level "model" which forms the ultimate implementation of the protocol. In one embodiment of this invention, the analysis/development apparatus creates a unique C language code representation of the specified system that is guaranteed to carry out the tasks specified when executed in a stored program controlled machine. In another embodiment, the code is used to create a "net list" for manufacturing the specified system.

Abstract: A high definition television system that is characterized by low transmission bandwidth is achieved by removing redundancies in the signal, encoding the remaining signals, and transmitting the encoded signal in a manner that is most compatible with the applicable standards. The dynamic range of the encoded signal is reduced by combining groups of adjacent samples that are smaller than a "floor" threshold to form larger samples, and by splitting samples that are larger than a "ceiling" threshold to form a plurality of smaller samples. Encoding of the combined samples is carried out in a conforming manner to minimize deleterious effects of transmission noise.

Abstract: A motion compensated encoder where motion vectors are selected based on the prediction error generated in localized areas of the encoded image and based on an available bit budget. The motion vectors are created by dividing the image into blocks of two sizes and by considering the best mix of large and small size blocks, and their associated motion vectors, that minimize the overall prediction error, within the constraints of the bit budget. For convenience, the image division is arranged so that a given number of small sized blocks forms one large sized block (e.g. 16:1). Also, the block sizes are arranged so that employing only large sized blocks does not exceed the given bit budget, while employing only the small sized blocks does exceed the given bit budget.

Abstract: An arrangement for a television receiver to attenuate correlated noise injected by the transmission medium. Recognizing that there is substantial line to line correlation of the transmission noise injected by interfering television stations, this arrangement enhances noise immunity by inserting in the receiver a de-emphasis stage that includes a circuit for removing the correlated noise. To account for the modifications to the desired signal that are introduced by the de-emphasis circuit, a pre-emphasis circuit is included in the transmitter. In accordance with one embodiment, the receiver's circuit comprises a feed-forward arrangement where the received signal of a scan line is subtracted from a fraction of the received signal of the previous scan line. At the transmitter, a feedback loop develop a scan line to be transmitted that corresponds to a video scan line subtracted from a fraction of the previous scan line to be transmitted.

Abstract: A quantizer, with quantization control that is sensitive to input signal characteristics and to output buffer fullness responds to an input signal that is divided into blocks and DCT transformed. The transformed signal is analyzed to develop a brightness correction and to evaluate the texture of the image and the change in texture in the image. Based on these, and in concert with the human visual perception model, perception threshold signals are created for each subband of the transformed signal. Concurrently, scale factors for each subband of the transformed signal are computed, and a measure of variability in the transformed input signal is calculated. A measure of the fullness of the buffer to which the quantizer sends its encoded results is obtained, and that measure is combined with the calculated signal variability to develop a correction signal. The correction signal modifies the perception threshold signals to develop threshold control signals that are applied to the quantizer.

Abstract: Apparatus for optimizing the operational state of a system, which follows the Karmarkar method, and which in the course of carrying out this method, obtains a solution to the linear system of equations AD.sup.2 A.sup.T u=p in accordance with a modified conjugate gradient method that incorporates a preconditioning operation. The preconditioning operation includes pre-drop and post-drop procedures that reduce the number of non-zero terms in the matrix to be preconditioned by judiciously discarding values that are smaller than a certain threshold. Use of the preconditioned conjugate gradient method reduces the processing time required for carrying out each iteration in the Karmarkar method.

Abstract: An HDTV receiver design includes a reconstruction section and an inner loop section. The reconstruction section comprises a receiving section for accepting the television receiver's antenna signals, for separating out the component signals from the received signals and for decoding the separated signals. The decoded signals are applied to a quantization decoder that is responsive to vector codebook and to applied quantized vector signals, and the output signals of the quantization decoder are applied to an inverse DCT circuit. The inner loop comprises an adder for adding an estimate signal to the output of the DCT circuit, a frame buffer, a motion compensation circuit that is capable of translating large blocks as well as small blocks and a leak circuit that modulates the output of the motion compensator circuit in accordance with a received leak control signal.

Abstract: A programmable memory system that interfaces with a computer's control and data manipulation units, and is capable of performing the manipulation, bookkeeping, and checking that would normally be performed by the computer. The memory system comprises active structure modules that are interconnected in a network to form clusters. The clusters are interconnected to form an aggregate memory system. Each ASE contains a processor section and a conventional memory section.

Abstract: In a differential PCM encoder, the problem of error perpetuation is solved by leaking a changing, rather than a fixed, fraction of the input signal to the differential PCM. The fraction leaked is sensitive to the characteristics of the signal. In one embodiment the fraction leaked is fixed for a frame in accordance with a chosen characteristic of the frame signal. In another embodiment, the fraction leaked is set in accordance with one function when a chosen characteristic of the frame signal exceeds a given level, and follows another function when the chosen characteristic does not exceed the chosen level. In a still another embodiment, the fraction leaked is set to one of two levels, based on a chosen characteristic of the frame signal.

Abstract: Bandwidth balancing is accomplished to DQDB networks that handle multi-priority traffic by causing each node to throttle its own rate of transmission in accordance with the priority of the data that the node transmits. In accordance with one approach, each node limits its throughput to the product of a bandwidth balancing factor (which is a fraction that varies according to the priority level of data) and the unused bus capacity. When parcels of different priorities are received within each node, the parcels are processed in priority order. In accordance with another approach, all active parcels within a node are handled concurrently and receive some bandwidth. The throughput of each parcel in a node is limited to the product of the bandwidth balancing factor and the unused bus capacity. In accordance with still another approach, each traffic parcel limits it throughput to the product of the bandwidth balancing and the bus capacity unused by parcels of equal or higher priority.

Abstract: Making use of the conceptual and computational similarities between the Karmarkar method and the Kalman filter a controller system is capable of handling the observer function, the minimum time controller function and the minimum energy controller function. The system includes an element that has the computational structure of a Kalman filter. The inputs of this element are qualitatively controlled to deliver the desired results to the remaining computation elements. In a controller for an LP control task, the element develops the dual vector signal used in the affine scaling algorithm by applying information to it as if its task were to estimate the states of a system whose observable output is D.sub.x(k) c, the input is O, the observation noise covariance matrix R is close to zero, the transition matrix is I and the matrix that describes the relationship between the measurable parameters and the observable output is A.sup.T D.sub.x(k).

Abstract: An arrangement for teleconferencing voice and data is provided through an arrangement that includes a voice bridge that offers individual control of the conferencing setup. The voice bridge comprises a crossbar with crosspoints that include a series connection of two switches and a resistor. One switch of each crosspoint is associated with the row of the crosspoint while the other switch of the crosspoint is associated with the column of the crosspoint. A user, connected to a selected row and column of the crossbar for the "talk" and "listen" functions, respectively, controls the row switches in the crosspoints connected to the user's row and the column switches in the crosspoints connected to the user's column.

Abstract: A communications protocol that communicates absolute state information, as contrasted to incremental information, on a regular basis to achieve high throughput by reducing the need for retransmissions. The protocol exchanges control messages that contain all of the relevant state information between the receiver and the transmitter on a frequent, routine and periodic basis, independent of any significant event that may have taken place in the receiver or the transmitter. The periodic rate of state exchange depends on the activity on the logical channel. The data communication from the transmitter to the receiver is in blocks of packets, with each block carrying a sequence number. Selective retransmission procedures are initiated by the transmitter whenever a control packet from the receiver identifies a failed reception. When a packet in a block fails to be received properly, the entire block, but only that block, is retransmitted.

Abstract: A high definition television system that is characterized by low transmission bandwidth is achieved by removing much of the redundancies in the signal, efficiently encoding the remaining signals, and transmitting the encoded signal in a manner that is most compatible with the applicable standards. To enhance noise immunity a number of techniques are employed. One is to encode adjacent low-amplitude signals into larger signal samples, another one is the introduction of a controllable gain feature, a third one is the introduction of both fixed and variable leak, and still another one is the incorporation of signal scrambling.