Abstract: In a receiver for signals in a multilevel partial response class-IV communication system, the coefficients of a digital adaptive equalizer need to be updated to minimize the error due to noise and signal distortion. After initial convergence of the equalizer coefficients to near-optimum settings, an estimate of the mean-square error gradient for coefficient updating can be obtained in decision-directed mode from an estimate of the error signal. In the absence of a reference signal, initial convergence must be achieved in self-training mode. The decision-directed error signal is then replaced by a pseudo-error signal for the computation of an approximation of the mean-square error gradient. The invention provides a particular self-training procedure which outperforms known methods in terms of speed of convergence and achieved mean-square error values, and does not require timing recovery prior to equalizer convergence.

Abstract: A flow control method is practiced in a first node in a computer network having one or more upstream nodes, each of which can provide data cells to the first node over a connection. Cells are transmitted over a connection during an established transmission period for that connection and at a data rate not exceeding a peak data rate. To determine whether a buffer is sufficient during a given time period starting at the current time, the potential buffer requirements during that time period are established as a function of the current buffer occupancy and the maximum number of cells which may be received during the given time period. If the potential buffer requirements exceed a predetermined buffer threshold, one or more stop signals is sent to upstream sources to limit the number of cells to be provided to the first node.

Abstract: A packet communications network includes a route management system in which routes can be remotely changed by using a simple set command to set a data value in the originating or terminating node of the route. Storage tables in the originating and destination nodes record the route changes and administrative data concerning the route. This administrative data can be retrieved from the originating node by simple get or get-next commands. The administrative data can include the specific specification of the route in links, the time of creation of the route, the route replaced and the reason for initiating the change in route. Together these capabilities permit centralized management of route changes in the entire network from a single manager node, and using only simple set, get and get-next command structures.

Abstract: Variable length LAN frames can be segmented into fixed length cells to allow the data in the frames to be transported through an intermediate cell-based system, such as an ATM network. Where transport through the intermediate system results in time gaps between data units extracted from the cells, special symbol combinations can be inserted into the time gaps to permit frame-representing data to be forwarded toward its destination as a "stretched frame" without waiting for all the cells representing the frame to arrive. When a stretched LAN frame is received at a "stretch-aware" LAN station, the special symbol combinations are detected and removed to recover at least the data payload of the original LAN frame.

Abstract: In case of a failure in a high speed packet switching network, the failure information provided by the multiplicity of resources is registered in the access nodes of the network. The failure information can be retrieved by the network management on request for fault correlation. A plurality of alarms flooding the network management when a failure occurs is thus avoided.

Abstract: The present invention is related to high speed packet switching networks and, more particularly, to a process for selecting an optimal path for packets transmission without bandwidth reservation in communication systems supporting both bandwidth-reserved and non-bandwidth-reserved connections. Non-reserved network connections do not have bandwidth set aside either implicitly or explicitly. The lowest delay priority is assigned to non-reserved traffic and the networks drops non-reserved packets when their buffer overflow at intermediate links. Because the data profile over the connections is bursty and non deterministic, reserved traffic does not lead to a full links utilization except on peaks. Therefore, non-reserved traffic can be transmitted when some bandwidth is available on the links.

Abstract: An enhanced adaptive rate-based congestion control system for packet transmission networks uses the absolute rather than the relative network queuing delay measure of congestion in the network. Other features of the congestion control system include test transmissions only after a predetermined minimum time, after the receipt of an acknowledgment from the previous test, or transmission of a minimum data burst, whichever takes longest. The congestion control system also provides a small reduction in rate at low rates and a large reduction in rates at high rates. A logarithmic rate control function provides this capability. Rate damping is provided by changing all of the values in a rate look-up tables in response to excessive rate variations. Finally, the fair share of the available bandwidth is used as the starting point for rates at start-up or when a predefined rate damping region is exited.

Abstract: A data processing method for efficiently transporting multimedia data packets of fixed and/or variable length over an Assynchronous Transfer Mode (ATM) network made to transport fixed length ATM cells including a fixed length user data payload and a fixed length ATM header. The data processing method includes concatenating said fixed and/or variable length user data and appending said concatenated data with a so-called trailer defining the various concatenated user data lengths and identifications, for being further split into ATM cells payloads before being transmitted over said ATM network.

Abstract: A data processing system having a client system, a server system for connection to the client system, and a remote user terminal for connection to the server system. The client stores application code which is executed on receipt of a remote access request to generate output requests which are communicated to the server. The terminal issues the remote access request to the server. The output requests are display requests directed to manipulating the display screen, and non-display requests which can be processed independently of the terminal. The server forwards the remote access request to the client, stores decoding code, sends the decoding code to the terminal on detection of the remote access request, receives the output requests from the client, generates responses to the non-display requests on behalf of the terminal, returns the responses generated to the client and forwards the display requests to the terminal.

Abstract: A process and an apparatus to calculate the FCS (Frame Check Sequence) error checking code of a message sent over a connection and segmented into a finite number of packets in a fixed size packets network. The process is implemented in the adapter cards of the ATM network access nodes (2, 4) located at the boundary of the ATM network. These nodes, when supporting AAL5 type ATM connections, reassemble messages which have been segmented at the entry of the network and to calculate the FCS of the message cell payloads for data integrity checking. The process of the invention starts at each reception of a cell with the calculation of a partial FCS (10) performed in parallel to the connection control block fetching phase (40); these 2 parallel operations allow FCS checking during the cell processing time of connections established over medium and high speed lines.

Abstract: An explicit rate algorithm is disclosed for use in an end-to-end closed loop flow control algorithm for an ATM network which carries at least constant bit rate (CBR) traffic, variable bit rate (VBR) traffic and adjustable bit rate (ABR) traffic. The algorithm determines how much additional bandwidth is available for ABR traffic on an output link from a node and produces an explicit rate variable that can be forwarded to a source for the ABR traffic. Both the maximum and minimum bandwidths already reserved for all connections on the output link are determined. A single reserved bandwidth value is chosen within the range defined by the maximum and minimum reserved bandwidth values. The current utilization of the ABR input buffer for the node is also determined. The explicit rate variable is generated as a function of the link capacity, the reserved bandwidth value and the current utilization of the ABR input buffer.

Abstract: This invention is an implementation of a congestion control mechanism, especially for ATM networks supporting data services or other nonreserved bandwidth traffic, e.g. in multimedia applications. It reacts immediately upon detection of a traffic bottleneck by selectively and temporarily holding back the data traffic that is to pass the bottleneck (5). A congested node (3) transmits congestion notifications (36) containing routing label information and deferment information to upstream nodes (2), thus enabling selective, temporary throttling action. If congestions persist, further notifications may be spread backwards step by step, eventually reaching the sources. A specific implementation is given for PRIZMA type switching nodes.

Abstract: A process for computing the coefficients C(i) of an adaptive filter (206) used in an echo-cancellation structure for a telecommunication apparatus. The process is based on the Least Mean Squared (L.M.S.) or gradient algorithm for computing the coefficients of the filter in accordance with the formula: ##EQU1## where e(i) is the estimation error and .alpha. is the step size used for performing an adjustement of the convergence of the filtering process. The process uses two different estimations of the power of the analog signal, a former short-term estimation and a latter long-term estimation in order to derive the appropriate value of the stepsize .alpha. which is used for computing the new coefficients. In the preferred embodiment the value of .alpha. is determined by dividing a constant .alpha..sub.0 being slightly lower than the maximum value ensuring stability of the convergence process by the greater of the two different estimations of the power of the analog signals.

Abstract: A method and an apparatus for removing the silence from the digitalized voice signals conveyed through packets or cells switching networks. The silence samples are neither packetized nor sent over the network but are regenerated at the output of the network. The silence samples generated are white noise samples, where the level is adapted to the background noise of the silence samples received at the input node of the network. For long periods of silence, the white noise level is periodically refreshed to be adapted to the last silence samples received at the input node of the network. The method provides also a control of packet or cell loss. The method uses are not control packets; in the later case, it can be used for ATM networks with AAL1. The method is implemented as a program executed in a Digital Signal Processor located on adapter cards dedicated to voice processing in the network access nodes.

Abstract: A magnetoresistive spin valve sensor is described. Such a sensor is also known as a GMR sensor or giant magnetoresistive sensor. The layers (24, 26, 28) of the sensor are mounted on a substrate (20) having steps or terraces on one of its face. The steps or terraces on the substrate's surface cooperate with one or more of the ferromagnetic layers (24, 28) of the sensor to determine the layers' magnetic properties. Specifically, the thickness of one or more of the sensor's layers can be set above or below a critical thickness which determines whether the easy direction of uniaxial magnetization of a layer of that particular material is fixed or "pinned". If pinned, the layer has a high coercive field. Thus, the new device avoids a biasing layer to pin any of the magnetic layers. Preferably the easy axes of the first two ferromagnetic layers (24, 28) are set at 90.degree. to one another in the zero applied field condition by appropriate choice of layer thickness.

Abstract: A method and an apparatus for shaping the output traffic in the transmit part of a network node adapter. The network node supports fixed length cell switching user information traffic between a source unit and a destination unit. The method and apparatus use two lookup tables called an active and a standby calendar per output line. Each entry in the calendars represents the position of one cell in the output cell stream. Three parameters tables are used to store the information on user traffic in the descending order of the user bandwidth share negotiated at traffic establishment time for the calendars. The active calendar is continuously read by a transmit device and the corresponding cells are sent onto the output line. Under control of a control device, a placement device places entries in the standby calendar reserved as changes occur in the traffic. Once filled up, the standby calendar is swapped to the active calendar and is read by the transmit device.

Abstract: To efficiently diagnose local and remote adapters without using dedicated hardware in a communication network to which a plurality of terminals are connected through associated adapters, a local logical address which is different from logical addresses reserved for communication between the terminals, is assigned to communication with a local adapter, and a frame including the local logical address and a diagnostic command is transmitted to the local adapter. When a remote adapter is to be diagnosed, a frame including a logical address assigned to communication with a remote terminal associated with that remote adapter, a diagnostic command, and at least one invalid character, is sent out from the local adapter to the network.

Abstract: To enhance the security provided by data encryption in a data communication network, the encryption/decryption keys are changed periodically at the source and destination nodes for an established connection. A destination node must know not only the value of any new key but also when to begin using that key to decrypt received data packets. Synchronization (making sure a data packet is decrypted using a decryption key correlated with the encryption key used to encrypt the same packet) is achieved by defining a single bit in each packet header as a key synchronization bit. As long as key synchronization bit value remains unchanged from one received packet to the next, a receiving node will continue to use the same decryption key it has been using. When a change in the key synchronization bit value is detected, the receiving node will begin using a previously-received, new decryption key.

Abstract: A communication system comprises a plurality of nodes interconnected by links comprising a plurality of connections. The traffic between the nodes is set up by a reserved bandwidth service and/or a non reserved bandwidth service. The non reserved bandwidth service is controlled by a hop by hop backpressure mechanism. When the traffic entering a node exceeds a high threshold, the backpressure mechanism generates stop backpressure primitives in order to throttle the entering traffic. In case of congestion the mechanism is either able to selectively interuppt the connection contributing to the congestion without affecting the rest of the link traffic, or to globally stop all link traffic. Traffic can be resumed if traffic rates fall below the low threshold values.

Abstract: In a data processing system having a host computer running an application that communicates with a terminal device through an optimizer, a terminal data stream is created in response to an operator input sequence at the terminal device. Thereafter, a selected combination of an operator input sequence and a selected terminal data stream, is identified at the terminal wherein such a selected combination will result in an incorrect representation in an optimizer presentation space memory of data stored in a terminal presentation space memory. In response to identifying the selected combination described above, terminal status data is added to the selected terminal data stream to create a modified terminal data stream, wherein the modified data stream includes information necessary for the optimizer to correctly represent in the optimizer presentation space memory data that is stored in the terminal presentation space memory.