Abstract: A method and apparatus for improving the performance of coding systems in the presence of frame erasures or lost packets. The encoded signal is modified after transmission but prior to decoding by a decoder preprocessor. The preprocessor recognizes that a given frame has been corrupted and modifies the encoded signal so that the decoding thereof will result in improved coding system performance. Specifically, based on the decoding process and on a predetermined target signal, the encoded signal is modified so that the decoding thereof will generate an approximation to the target signal. In a first illustrative embodiment, a CELP speech coder is used and the target signal is an excitation signal comprised of all-zero excitation vectors. In this case, the portion of the corrupted excitation signal indices which identify the corresponding gain factors are set to values which represent a low gain factor.
Abstract: Disclosed is a telecommunications equipment terminal for outdoor mounting. The terminal housing includes a removable hood which reveals a top surface including sealing means around the periphery thereof and appropriate apertures to permit the terminal to be vertically stacked with another terminal of the same type.
Abstract: In accordance with the invention, an optical four-wave mixer for producing a phase-conjugated signal comprises a source of optical input signals, a fiber laser for receiving the signals, and a detector for selectively detecting the frequency-shifted signals produced by four-wave mixing. The laser can be a rare-earth doped fiber laser with a fiber cavity phase matched to the input signals. The frequency-shifted output signals have an inverted spectral waveform as compared with the input signals. The mixer can be made in compact form with a cavity length as small as 100 m and can provide inverted signals at the same intensity as the input signals, making the mixer particularly useful for providing spectral inversion in an optical communications system.
Type:
Grant
Filed:
March 2, 1995
Date of Patent:
August 27, 1996
Assignee:
Lucent Technologies Inc.
Inventors:
Jay R. Simpson, Jefferson L. Wagener, Kenneth L. Walker
Abstract: An intelligent terminal (which can be a telephone, a facsimile machine, or similar device) is arranged so that (a) it can store information indicating when (e.g., date and time) a particular subscriber last was present at the terminal, and (b) the stored information can be retrieved from the terminal remotely, preferably without completing a conventional call to the terminal. A central processor contains, for each subscriber, a list of the intelligent terminals that have been pre-designated for use by that subscriber, and has the ability to query terminals on the list. In response to a call placed to the subscriber by dialing the subscriber's unique personal number, specific intelligent terminals on that subscriber's list are queried by the central processor to determine when the subscriber was last present at each terminal. The central processor then generates a control signal such that the call is then completed to the particular terminal that was most recently visited by the subscriber.
Abstract: The recovery of each signal in a transmitted signal including a pair of superimposed signals is improved by the use of linear prediction. The pair of signals includes various combinations of analog and digital signals, e.g., an analog signal sample superimposed upon a digital signal sample, or a digital signal sample superimposed upon another digital signal sample. In a first embodiment, prediction coefficients for the analog signal are generated from the received signal. These coefficients are then used to recover the analog and digital signals from the received signal. In a second embodiment, the analog signal recovered, pursuant to the first embodiment, is considered a tentative estimate of the analog signal, and prediction coefficients for this tentative analog signal estimate are formed and used to generate final estimates of the analog and digital signal.
Abstract: A method is disclosed for forming a self-aligned optical subassembly for supporting an optical fiber and associated optical component(s). In particular, sequential masking layer/silicon substrate etch operations are performed so as to etch, in series, the largest opening first and the narrowest opening last. By following this procedure, axial alignment between tandem grooves is maintained.
Abstract: The disclosed integrated modulator/laser (I-MOD/DFB) combination comprises an active region that extends the full length of the combination without variation of layer thickness and/or composition. Because of this constancy of the active region parameters the relevant bandgap energy is the same in the laser portion of the combination as in the modulator portion thereof. The combination typically comprises a distributed feedback structure (e.g., a "grating"). In preferred embodiments the feedback structure is selected such that .lambda..sub.e >.lambda..sub.o (typically .lambda..sub.e -.lambda..sub.o in the range 20-70 nm), where .lambda..sub.e is the laser output wavelength, and .lambda..sub.o is the wavelength of the gain peak of the laser medium. The active region can be a bulk active region but preferably is a quantum well active region. Optionally an I-MOD/DFB combination according to the invention can comprise an absorbing region, e.g.
Abstract: Disclosed is a low bit rate audio and video communication system which employs an integrated encoding system that dynamically allocates available bits among the audio and video signals to be encoded based on the content of the audio and video information and the manner in which the audio and video information will be perceived by a viewer. A dynamic bit allocation and encoding process will evaluate the current content of the audio and video information and allocate the available bits among the audio and video signals to be encoded. In addition, an appropriate audio encoding technique is dynamically selected based on the current content of the audio signal. A face location detection subroutine will detect and model the location of faces in each video frame, in order that the facial regions may be more accurately encoded than other portions of the video frame.
Abstract: This transmission system for transmitting data by a link comprising intermediate equipments (I.sub.1 to I.sub.N) is provided for connecting a transmitting side of a first user equipment (TE) with a receiving side of a second user equipment (TR). In the intermediate equipment situated on the receiving side, thus the most downstream equipment, there is provided a disturbance circuit (30) which disturbs bits at its output as a function of an error information signal that represents the quality of the received information signals in the intermediate equipments.
Abstract: A hierarchical network management system is described which includes concentrators (2A to 5A) on the individual levels (E1 to E3) of the hierarchy as well as adjustable interfaces in the concentrators for point-to-point and bus connections. An interface is provided for a bus connection on a master side. The interface takes delays into consideration. A transmission channel can be connected to the interface. The channel includes a forward bus and return line (a5, b5). Parallel addressable apparatus (8A, 8B, 8C) can be connected to the forward and return lines. A controllable change-over switch (A8, B8, C8), inserted in the return line (b5) of the transmission channel, is provided for each addressable apparatus (8A, 8B, 8C) of the parallel combination.
Type:
Grant
Filed:
September 7, 1995
Date of Patent:
August 6, 1996
Assignee:
Lucent Technologies Inc.
Inventors:
Johannes Fuchsreiter, Konrad Schmidt, Rudolf Kasseckert, Walter Neumann
Abstract: The invention relates to a transmission system comprising a synchronizer for forming a multiplex signal, comprising at least a device for conveying the multiplex signal, and a desynchronizer. The desynchronizer comprises at least a buffer store for buffering transport unit data contained in the signal, a write address generator for controlling the writing of the data in the buffer store, a control arrangement for forming a control signal for the write address generator from the signal, a read address generator for controlling the reading of the data from the buffer store, a difference circuit for forming difference values between the addresses of write and read address generators and a generating circuit for generating from the difference values a read clock signal applied to the read address generator.