Lucent Technologies Inc.

Digital Fountain, Inc.

Vivek K Goyal

Jelena Kovacevic

Gavin Bernard Horn

Amin Shokrollahi

Michael G Luby

Martin Vetterli

Soren Bogh Lassen

Jens Rasmussen

Barry Dobyns

Francois Masson

Jonathan Adam Kelner

Ramon Arean

A method for communicating the content of a live data stream to a receiver using a plurality of channels comprising two encoder channels used to encode the live data content prior to transmission. Initially a plurality of segments of a live data stream are received, wherein each segment contains segment data. A forward error correction algorithm is applied to each segment's data, thereby producing FEC-encoded segment data. The FEC-encoded segment data is contained within an FEC-encoded block, resulting in a corresponding plurality of FEC-encoded blocks being generated. Each FEC-encoded block is copied to a sub-channel on both a first encoder channel and a second encoder channel, resulting in a plurality of FEC-encoder blocks residing on the first and second encoder channels. The first and second encoder channels differ in the number of sub-channels they contain (interleaving depth), and accordingly the arrangement of the FEC-encoded blocks in the first and second encoder channels are different. A first cross-section of the FEC-encoded segment data contained within the FEC-encoded blocks resident in the first encoder channel is added to a first transmit block T. Similarly, A first cross-section of the FEC-encoded segment data contained within the FEC-encoded blocks resident in the second encoder channel is added to a second transmit block T. The first and second transmit blocks are then communicated to the receiver.

System and method for reliably communicating the content of a live data stream

A signal processing device utilizes a stochastic approximation of a gradient descent algorithm for updating a transform. The signal processing device is configured to implement the transform for producing a desired transformed output signal, and the transform is updated using the stochastic approximation of the gradient algorithm based on received data associated with the signal being processed. The transform is represented in a reduced-parameter form, such as a Givens parameterized form or a Householder form, such that the reduced-parameter form for an N&#xd7;N transform comprises fewer than Nparameters. The updating process is implemented using computations involving the reduced-parameter form, and an adaptation of the transform is represented directly as one or more changes in the reduced-parameter form. The gradient algorithm may be configured to minimize a negative gradient of a pairwise energy compaction property of the transform. Advantageously, the gradient algorithm may be made locally convergent in mean for a specified step size. The invention can also be implemented in a backward adaptive form in which the updating process is driven by quantized data.

Methods and apparatus for adaptive signal processing involving a Karhunen-Lo&#xe8;ve basis

A multiple description coder generates a number of different descriptions of a given portion of a signal in a wireless communication system, using multiple description scalar quantization (MDSQ) or another type of multiple description coding. The different descriptions of the given portion of the signal are then arranged into packets such that at least a first description of the given portion is placed in a first packet and a second description is placed in a second packet. Each of the packets are then transmitted using a frequency hopping modulator, and the hopping rate of the modulator is selected or otherwise configured based at least in part on the number of descriptions generated for the different portions of the signal. For example, in an embodiment in which two descriptions are generated for each portion of the signal, a first description for a current one of the portions of the signal is placed in a current packet along with a second one of the descriptions for a previous portion of the signal, and the frequency hopping rate of the modulator is doubled relative to a hopping rate used for single description transmission.

Methods and apparatus for wireless transmission using multiple description coding

A lattice-structured multiple description vector quantization (LSMDVQ) encoder generates M descriptions of a signal to be encoded, each of the descriptions being transmittable over a corresponding one of M channels. The encoder is configured based at least in part on a distortion measure which is a function of a central distortion and at least one side distortion. For example, if M&equals;2, the distortion measure may be an average mean-squared error (AMSE) function of the form &fnof;(D , D , D ), where D is a central distortion resulting from reconstruction based on receipt of both a first and a second description, and D and D are side distortions resulting from reconstruction using only a first description and a second description, respectively. Further performance improvements may be obtained through perturbation of the lattice points. The LSMDVQ techniques of the invention can also be extended to cases of M greater than two, for which the encoder may utilize an ordered set of M codebooks &Lgr; , &Lgr; , . . . , &Lgr; of increasing size, with the coarsest codebook corresponding to a lattice. In such cases, for each number k of descriptions received, there may be a single decoding function that maps the received vector to a corresponding one of the codebooks &Lgr; , such that reconstruction of the signal requires no more than M such decoding functions.

Methods and apparatus for lattice-structured multiple description vector quantization coding

A multiple description (MD) joint source-channel (JSC) encoder in accordance with the invention encodes n components of a signal for transmission over in channels of a communication medium. In illustrative embodiments, the invention provides optimal or near-optimal transforms for applications in which at least one of n and m is greater than two, and applications in which the failure probabilities of the m channels are non-independent and non-equivalent. The signal to be encoded may be a data signal, a speech signal, an audio signal, an image signal, a video signal or other type of signal, and each of the m channels may correspond to a packet or a group of packets to be transmitted over the medium. A given n&times;m transform implemented by the MD JSC encoder may be in the form of a cascade structure of several transforms each having dimension less than n&times;m. The transform may also be configured to provide a substantially equivalent rate for each of the m channels.

Multiple description transform coding using optimal transforms of arbitrary dimension

A multiple description (MD) joint source-channel (JSC) encoder in accordance with the invention encodes n components of an image signal for transmission over m channels of a communication medium. In an illustrative embodiment which uses statistical redundancy between the different descriptions of the image signal, the encoder forms vectors from transform coefficients of the image signal separated both in frequency and in space. The vectors may be formed such that the spatial separation between the transform coefficients is maximized. A correlating transform is then applied, followed by entropy coding, grouping as a function of frequency, and application of a cascade transform. In an illustrative embodiment which uses deterministic redundancy between the different descriptions of the image signal, the encoder may apply a linear transform, followed by quantization, to generate the multiple descriptions of the image signal. For example, vectors may be formed from transform coefficients of the image signal so as to include coefficients of like frequency separated in space. The vectors are expanded by multiplication with a frame operator, and then quantized using a step size which may be a function of frequency.

Multiple description transform coding of images using optimal transforms of arbitrary dimension

A multiple description (MD) joint source-channel (JSC) encoder in accordance with the invention encodes n components of an audio signal for transmission over m channels of a communication medium, where n and m may take on any desired values. In an illustrative embodiment, the encoder combines a multiple description transform coder with elements of a perceptual audio coder (PAC). The encoder is configured to select one or more transform parameters for a multiple description transform, based on a characteristic of the audio signal to be encoded. For example, the transform parameters may be selected such that the resulting transformed coefficients have a variance distribution of a type expected by a subsequent entropy coding operation. The components of the audio signal may be quantized coefficients separated into a number of factor bands, and the transform parameter for a given factor band may be set to a value determined based on a transform parameter from at least one other factor band, e.g., the previous factor band. As another example, the transform parameter for one or more of the factor bands may be selected based on a determination as to whether the audio signal to be encoded is of a particular predetermined type. A desired variance distribution may also be obtained for the transformed coefficients by, e.g., pairing or otherwise grouping coefficients such that the coefficients of each pair or group are required to be in the same factor band.

Multiple description transform coding of audio using optimal transforms of arbitrary dimension

Transform encoding techniques are disclosed which permit reductions in entropy coding memory requirements. In an illustrative embodiment, a selected discrete linear transform is applied to a discrete-valued version of an information signal to be encoded. The transform is selected such that it produces a transformed output that can be entropy coded using a reduced codeword memory without a substantial increase in entropy coding rate. The entropy coding may be, for example, scalar entropy coding which independently codes each of the components of the transformed discrete-valued version of the information signal, using a single entropy codebook for all of the components to be encoded. As another example, the entropy coding may utilize scalar entropy coding for a first subset of the components of the transformed discrete-valued version of the information signal, using a first codebook for each of the subset of components to be encoded, and vector entropy coding for a second subset of the components, using a second, larger codebook for each of the vectors to be encoded. Other types of entropy coding can also be improved through appropriate selection of the discrete transform.

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Hoboken, NJ, United States of America

Vivek K Goyal