Lucent Technologies Inc.

Agere Systems Inc.

Agere Systems Guardian Corp.

Alcatel Lucent

Hui-Ling Lou

Vijitha Weerackody

Carl-Erik Wilhelm Sundberg

Christine Irene Podilchuk

Sae-Young Chung

Rudiger L Urbanke

Raghavan Anand

Harish Viswanathan

Zulfiquar Sayeed

Deepen Sinha

Markus Rupp

Rajeev Krishnamoorthy

Edith Cohen

Gerald Dietrich Thomas Schuller

Jihwan Patrick Choi

Gerald Dietrich Schuller

Techniques for multilevel coding of a stream of information bits in a communication system. The stream of information bits is separated into portions, and each of the portions is associated with a different level of the multilevel coding. At least one code is applied to the portion of the information bits of each level in a designated subset of the full set of levels, such that the portions of the information bits for levels in the designated subset are coded while the portions of the information bits for levels not in the designated subset are uncoded. Both the coded portions of the information bits and the uncoded portions of the information bits are used to select modulation symbols for transmission in the system. Advantageously, the invention provides improved coding gain relative to conventional techniques, and can be configured to provide unequal error protection as well as time diversity for transmissions in the system.

Multilevel coding with unequal error protection and time diversity for bandwidth efficient transmission

A video signal is encoded in a progressive video coder so as to generate a progressive coded video bit stream for transmission over a heterogeneous network. The progressive coded video bit stream is configured so as to be decodable at any one of a series of increasing bit rates up to a maximum bit rate, depending on which of a number of corresponding portions of the progressive coded video bit stream are received by a decoder. Each of the portions is associated with a different bit rate, and one or more of the portions may each also be associated with different values of other parameters such as frame rate, spatial resolution, and peak signal-to-noise ratio. Each of the series of increasing bit rates produces progressively better reconstructed video quality at an output of the decoder. The progressive coded bit stream is transmitted over a first part of the heterogeneous network at a first one of the bit rates. One or more selected portions of the progressive coded video bit stream are then transmitted from the first part of the heterogeneous network to a second part of the heterogeneous network. The selected portions are associated with a second one of the bit rates lower than the first bit rate, and may be selected based on an error detected in the transmission over the first part of the heterogeneous network, and/or a characteristic of the second part of the heterogeneous network. The invention provides efficient bit rate scalability and adaptability and is particularly well-suited for use in conjunction with transmission over heterogeneous wired-to-wireless networks.

Method and apparatus for video transmission over a heterogeneous network using progressive video coding

Signal processing operations are performed in a digital communication system receiver on a sequence of received symbols, each representing a number of information bits. The symbols correspond to points in a given modulation constellation generated by applying a predetermined rotation, e.g., a 45&#xb0; rotation, to an otherwise conventional modulation constellation, e.g., a QPSK constellation, a 16-QAM constellation, etc. The use of the rotated constellation allows certain signal processing operations, such as filtering, Least-Mean-Squares (LMS) estimation, and Maximum-Likelihood (ML) sequence detection via the Viterbi algorithm, to be performed without the need for multipliers. By eliminating or substantially reducing the number of required multiplication operations, the invention significantly reduces the complexity and delay associated with the corresponding signal processing circuitry. Advantageously, this reduction in complexity and delay is accomplished without the use of any approximation or other reduction in precision.

Multiplier-free methods and apparatus for signal processing in a digital communication system

A CDM satellite transmission system is disclosed that broadcasts programming content, such as audio and video information, using one or more geo-synchronous satellites based on Code Division Multiple Access technology. Forward error correction coding and interleaving are used prior to broadcasting the signals over the CDM channel to account for signal loss due to short-term fading. The CDM satellite transmission system provides a tuning channel corresponding to each program channel that reduces the delay when a mobile receiver is first tuned to a selected program channel. The tuning channel utilizes a shorter interleaver length, if any, than the corresponding primary program channel. The CDM satellite transmission system transmits a delayed version of a program signal with the on-time version of the audio output to accommodate uninterrupted reception in the event of such a blockage. In one implementation of the invention, the core layer, C(n), of the delayed version of the audio output of a scalable audio coding scheme is utilized as the tuning channel. The core layer, C(n), and enhancement layers, E(n), of the on-time signal and the enhancement layers, E(n), of the delayed-time signal employ a representative block interleaver having a duration of four seconds. The tuning channel (C(n), of the delayed-time signal) employs a representative block interleaver having a duration of 500 milliseconds.

Tuning scheme for code division multiplex broadcasting system

A method and apparatus which reduces the start-up delay that may occur when switching programs in audio and/or video streaming applications while maintaining high quality steady-state performance thereof. A program source (e.g., an audio and/or video data stream) is encoded and transmitted as two or more separate bit streams (e.g., sequences of data packets), the transmission of one of these bit streams being delayed by a given amount of time relative to the transmission of the other bit stream(s). At the receiving end of the transmission channel, the two or more bit streams are buffered by receive buffers having different sizes (thereby resulting in different time delays when the contents thereof are decoded), wherein the time delay difference corresponds (inversely) to the relative delay times prior to transmission. Advantageously, either a multiple descriptive source coding scheme or an embedded coding scheme may be employed, in which at least one of the individual bit streams is sufficient to obtain a satisfactory decoded signal, but wherein the addition of the other bit stream(s) will improve the quality of the decoded signal. Alternatively, the data streams may comprise multiple encodings of the program source having different bit rates, wherein the lower bit rate encodings are transmitted with the correspondingly larger delays.

Method and apparatus for reducing start-up delay in data packet-based network streaming applications

Error flags are generated for use in source decoding of a source-coded bit stream transmitted through a channel of a communication system. The source-coded bit stream is channel coded using at least one channel code, and the channel code is decoded in a soft-decision channel decoder to generate a received version of the source-coded bit stream and one or more reliability measures associated with a designated portion of the received version of the source-coded bit stream. The reliability measures are processed to generate one or more error flags indicative of the presence of an error in the corresponding portion of the received version of the source-coded bit stream. The invention allows different detection capabilities to be used for different portions of the received version of the source-coded bit stream, and further allows these detection capabilities to be changed dynamically at the receiver. The error flags may be used to trigger an error mitigation/concealment algorithm in the source decoder. Advantageously, the error flags can be matched to frames or subframes of the source-coded bit stream, such that the performance of the error mitigation/concealment algorithm is substantially improved relative to its performance when using error flags generated from a conventional outer block code.

Method and apparatus for generating channel error flags for error mitigation and/or concealment in source decoders

Channel error protection is provided for a source coded bit stream in a communication system by a combination of outer channel coding and inner channel coding implemented across different network layers of the system. One or more of a number of different portions of the source coded bit stream are outer channel coded in a first network layer of the system, e.g., an application layer, using a designated outer channel code, so as to provide an outer channel coded bit stream having different levels of error protection for each of the different portions of the source coded bit stream. The outer channel coded bit stream is then inner channel coded in a second network layer of the system, e.g., a physical layer, using a designated inner channel code to thereby generate a channel coded bit stream. The channel coded bit stream may then be subject to further processing operations prior to transmission in the communication system. Advantageously, the invention allows unequal channel error protection to be provided for source coded audio, image, video or multimedia bit streams in a standard second generation (2G) or third generation (3G) wireless system in a manner which is independent of the physical layer coding infrastructure of the system.

Channel error protection implementable across network layers in a communication system

A method and apparatus for reducing deep fading of signals in satellite-based communications systems employing terrestrial repeater stations by shifting the phase of the signals transmitted from each terrestrial repeater station by a different amount so that the signals are transmitted from each terrestrial repeater station and received at a receiver at different phases, thereby effectuating time diversity in such signals to reduce deep fading of the signals. The method and apparatus can be used in CDMA and OFDM systems.

Method and apparatus for reducing signal interference in satellite broadcast systems employing terrestrial repeater stations

A method for providing packet loss recovery in a data packet-based network used for real-time multimedia communications. In accordance with a first illustrative embodiment of the present invention, the information payload associated with a given data packet k is identically copied and appended to data packet k&plus;w (i.e., the information payload is repeated with a delay of w transmitted packets). More generally, the present invention provides a method of coding a sequence of data packets representing a contiguous stream of information, with each data packet comprising, a set of payload information representative of a segment of the stream of information corresponding thereto. The method comprises the steps of coding a first data packet for transmission (wherein the encoded first data packet comprises a first set of payload information representative of a first segment of the stream of information), and coding a second data packet subsequence to the first data packet in the sequence for transmission (wherein the encoded second data packet comprises a second set of payload information representative of a second segment of the stream of information subsequent to the first segment of the stream of information). The encoded second data packet further comprises an additional set of payload information, the additional set of payload information also representative of the first segment of the stream of information, but not representative of other segments of the stream of information.

Packet loss control method for real-time multimedia communications

Unequal channel error protection is provided for a bit stream, e.g., a progressive source coded bit stream, by puncturing of a channel code. The channel code has a specified rate associated with a corresponding level of error protection, and is used to code a first portion of the bit stream. The channel code is subsequently punctured for at least a second portion of the bit stream so as to provide a rate higher than that of the designated rate. Commencement of the puncturing is deliberately delayed by an amount determined based at least in part on a memory of the channel code. Advantageously, the delay prevents propagation of errors in a channel decoder used to decode the channel coded bit stream. The progressive bit stream may be a progressive source coded video or audio bit stream, any other type of progressive information bit stream, or a partitioned source coded bit stream.

Method and apparatus for providing channel error protection for a source coded bit stream

In a communications system implementing, e.g., an in-band on channel AM (IBOC-AM) (also known as &ldquo;hybrid IBOC-AM&rdquo;) scheme, multiple bit streams are used to represent an audio signal to be transmitted over one or more frequency bands including, e.g., parts of an AM frequency band for radio broadcast. These bit streams contain various and/or equivalent amounts of audio information. In an illustrative embodiment, at least one of the bit streams is a core bit stream containing core audio information. The remaining bit streams are enhancement bit streams containing enhancement audio information. The core bit stream is necessary for recovering the audio signal with minimal acceptable quality. Such quality is enhanced when the core bit stream, together with one or more of the enhancement bit streams, is used to recover the audio signal. In accordance with the invention, the AM frequency band is divided into subbands. Each of the core and enhancement bit streams is assigned to a respective one of the subbands for transmission. The assignment is conducive to an effective treatment of interference affecting the IBOC-AM system. Other embodiments may include, e.g., communications of the multiple bit streams in accordance with the invention in an IBOC-FM system, a satellite broadcasting system, etc.

Technique for effectively communicating multiple digital representations of a signal

First and second source signal streams each associated with a program source are produced. A first error correction code having a first correction delay is applied to the first source signal stream, thus producing a first error-corrected source signal stream that is transmitted for reception by a receiver. A tuning signal stream corresponding to the second source signal stream is transmitted for reception by the receiver at a determined timing relative to transmission of the first error-corrected signal stream. When first tuning to a program transmission channel, the receiver initially processes the tuning signal to obtain at least a recognizable reproduction of the program source, with little if any delay attributable to error correction coding of the first source signal stream.

Tuning scheme for error-corrected broadcast programs

Parallel Decision-Feedback Decoding (PDFD) techniques which provide joint Decision Feedback Equalization (DFE) and decoding of a sequence of transmitted symbols. In an illustrative embodiment, branch metrics associated with transitions between states of a multi-stage trellis are computed. For a given stage t of the trellis, the branch metrics are computed for each of the states, using a different input value y (s) for each state. The input values y (s) correspond to extended survivor paths computed for each state using a DFE process. The branch metrics are utilized to determine a global most-likely path through the trellis, and the path is used to generate a decoded output signal representative of the transmitted symbol sequence. The PDFD techniques of the invention provide significant performance gains relative to conventional techniques, and are suitable for use with both PSK and QAM modulation constellations.

Methods and apparatus for parallel decision-feedback decoding in a communication system

A communication system decoder in which branch metrics are represented using linear distance. An illustrative embodiment for decoding a sequence of received symbols of a QPSK or QAM constellation includes a branch metric calculation unit, an add-compare-select unit, and a traceback unit. The branch metric unit computes branch metrics associated with transitions between states of a multi-stage trellis representation of a state machine. In accordance with the invention, each of the branch metrics correspond to a linear distance between a given one of the received symbols and its nearest codeword in a given stage of the trellis. The add-compare-select unit utilizes the branch metrics of a current stage, along with a previously-generated path metric, for comparison purposes in determining a survivor path and corresponding updated path metric for a current stage of the multi-stage trellis. The traceback unit utilizes the updated path metric to generate a corresponding decoded output. Advantageously, the add-compare-select unit of the decoder is configured such that it achieves a level of performance using the linear distance branch metrics which is equivalent to that achieved using squared distance branch metrics, while also substantially reducing the decoder complexity through the elimination of multiplication operations.

Methods and apparatus for representation of branch metrics in a communication system decoder

Digital data is stored in an analog memory device using coded modulation techniques. The memory device includes a number of memory cells, each capable of storing one of a number of different levels. A given set of b information bits to be stored in the memory device is first coded in a convolutional or block coder to generate a set of coded bits which includes more than b bits. The set of coded bits is then mapped to one or more corresponding levels, and the one or more levels are each stored in a separate cell of the memory device. In a one-dimensional embodiment, the coding may involve applying a rate 1/2 convolutional code to i least significant bits, i&equals;1, 2, . . . , and mapping the resulting b&plus;i coded bits to one of 2,distinct levels in a one-dimensional AM signal set. In embodiments of the invention which utilize multidimensional signal sets, a given set of bits is mapped to a signal in an m-dimensional signal set, with or without coding of the bits, and each of the m dimensions of the selected signal is then stored as a level in a separate cell of the analog memory device. The invention increases the storage capacity of the memory device for a given readout error probability, or alternatively improves the error probability for a given storage capacity. Readout performance may be further improved by using a multiple read-and-sum unit to generate a readout value for a given stored level based on a sum or average of several different readouts of the stored level.

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Murray Hill, NJ, United States of America

Hui-Ling Lou