Abstract: A method of concealing errors in picture header information within H.263-encoded video compares current group-of-block frame identification (GFID) information to GFID information from the previous frame. If the GFID values are equal, the picture header information from the previous frame is used to decode the current frame. Otherwise, a selected parameter in the previous picture header information (for example, “picture type”) is altered and decoding proceeds with the altered picture header information. Preferably, only a portion of the current frame is initially decoded and validated prior to decoding the remainder of the frame. If the decoded portion is error-free, the decoding continues with the selected picture header information. If errors are found in the decoded portion, the picture header information is modified and the decoding process continues accordingly.

Abstract: An Asymmetric Digital Subscriber Loop (ADSL) Discrete Multi-Tone system has disjoint and adjacent upstream and downstream channels. During the training phase of an ADSL connection, an ADSL DMT transmitter first determines a round trip propagation delay by transmitting a ranging signal to a far-end ADSL endpoint. During the subsequent communications phase, the ADSL transmitter synchronizes transmission of DMT symbols to a reference clock. In addition, the cyclic extensions of each DMT symbol are increased as a function of the propagation delay.

Abstract: The specification relates to a method and apparatus supporting multiple access, bi-directional data and multimedia transfer described over a hybrid fiber/coax (HFC) network, though applicable to transmissions over other media as well. The protocol associated with the present invention supports downstream broadcast transmission from headend to cable modem, and also provides for allocation of bandwidth for cable modems to transmit back to the headend. The protocol supports different access modes such as STM, ATM, and VL; within each subframe of a subframe/frame/masterframe structure. The protocol is utilized over a system which provides for forward error correction (FEC) and scrambling/descrambling, while eliminating the deleterious effects on the error correcting capability of the FEC due to the bit error spreading associated with a scrambling/descrambling function.

Abstract: The specification relates to a broadband multiple access protocol for bi-directional hybrid fiber/coax (HFC) networks. The protocol supports downstream broadcast transmission from headend to cable modem, and also provides for allocation of bandwidth for cable modems to transmit back to the headend. Although the present invention is described in relation to an HFC network, it is also equally applicable to a wireless communications environment. The protocol supports different access modes such as synchronous transfer mode, asynchronous transfer mode, and variable length data. The protocol adapts to changing demands for a mix of circuit and packet mode applications and allocates upstream and downstream bandwidth in response to the a variety of bursty and isochronous traffic sources.

Abstract: The specification relates to a broadband multiple access protocol for bi-directional hybrid fiber/coax (HFC) networks. The protocol supports downstream broadcast transmission from headend to cable modem, and also provides for allocation of bandwidth for cable modems to transmit back to the headend. Although the present invention is described in relation to an HFC network, it is also equally applicable to a cellular wireless communications environment. The protocol supports different access modes such as STM, ATM, and VL; within each subframe of a subframe/frame/masterframe structure. The protocol adapts to changing demands for a mix of circuit and packet mode applications and allocates upstream and downstream bandwidth in response to the a variety of bursty and isochronous traffic sources.

Abstract: Digital streams are converted into analog signals for recording by analog recorders, such as conventional video cassette recorders, onto analog storage media, such as conventional video cassette tapes. The recorded analog signals are then retrieved from the analog storage media using an analog player, such as a conventional video cassette player, and converted back into the original digital streams. The present invention allows conventional analog-based recording and playing equipment, like video cassette recorders/players, to be used for storing and retrieving digital data. In one embodiment, the digital streams correspond to digital audio/video data and the retrieved digital streams can be further processed to playback the audio/video streams using conventional television sets. In other embodiments, the digital streams correspond to other digital data streams that can be converted into analog signals for storage and retrieval using conventional video cassette recorders and conventional video cassette tapes.

Abstract: A temporally-pipelined predictive encoder/decoder circuit for encoding or decoding an input signal containing a sequence of data frames received at a particular frame rate and frame data rate into an output signal having an equal frame rate employs a plurality of N predictive encoders/decoders. An input buffer may be used to extract the information for each data frame in the input signal and supply such information to a corresponding one of the encoders/decoders at rate of 1/N of the particular frame data rate. Each encoder/decoder generates corresponding encoded/decoded information as it is received as well as provides digitized frame information to the encoder/decoder processing the next received image frame. The encoded/decoded information is provided to corresponding frame buffers which temporarily store such information.

Abstract: A sample timing recovery arrangement for synchronous amplitude and phase modulated digital data transmission systems correlates present and delayed samples of received digital data signals to obtain a spectral line at the sampling rate using digital techniques. Conventional methods of timing recovery generally perform analog operations on the envelope of a received data signal.

Abstract: A demodulator for differentially coherent phase-shift keyed data signals correlates samples taken in consecutive baud intervals. Received digital data signals are hardlimited to preserve zero-crossings only and samples of such hardlimited signals are temporarily stored in a delay structure. Polarity correlations are made between two pairs of samples relatively delayed by a baud interval less 45.degree., and a baud interval plus 45.degree., of carrier wave phase. These direct correlations control the counting direction of separate reversible counters. A further indirect correlation is made between the direct correlations and this third correlation is used to inhibit or not the operation of the reversible counters. The count-up, count-down and inhibit pattern constitutes ternary processing of binary data. The resultant counts are decoded at the end of each baud interval by observing whether the net count has been up or down. The counters are reset.