Abstract: Improved error screening techniques are used in processing digital audio or other types of information received in a digital communication system. Control information associated with a given packet of the received information is identified and compared with a decoding requirement of the packet, in order to control the generation of an error indicator for the packet. More particularly, the error indicator may be generated in response to an inconsistency between the control information and the decoding requirement. For example, the control information may include an indication of packet length that can be compared to a number of bits required to decode the corresponding packet, with any inconsistency between the packet length indication and the number of required bits leading to the generation of an error flag for the packet.

Abstract: Improved channel code configurations for use in transmission of digital audio or other types of information in a digital communication system. The channel code may include an outer channel code, e.g., a cyclic redundancy code (CRC), and an inner channel code, e.g., a complementary punctured pair convolutional (CPPC) code. In accordance with the invention, multiple code words of the outer code are associated with a given packet of the digital information, in accordance with a particular outer code configuration, so as to provide partial error flagging for different portions of the given packet. An information encoder, e.g., a PAC encoder, interacts with an outer code encoder to determine a bit allocation for transmission of packets at a particular bit rate, based at least in part on the outer code configuration.

Abstract: Source-coded information from a multi-mode source encoder is channel coded for transmission in a communication system. A multi-mode channel encoder associates a different channel coding error protection profile with each of the modes of the multi-mode source encoder. The channel encoder determines a mode used by the multi-mode source encoder to source code a given frame or other designated portion of the information, and channel codes the source-coded portion of the information utilizing an error protection profile identified at least in part based on the determined mode. A multi-mode channel decoder is operative to hypothesize that a particular one of the modes of the multi-mode source encoder was used to source code the designated portion of the information.

Abstract: In a communications system implementing an in-band on channel AM (IBOC-AM) (also known as “hybrid IBOC-AM”) scheme, digitally modulated signals are transmitted in a 30 kHz digital band centered at an analog host AM carrier frequency fc. The host AM carrier is assigned to the geographic area served by the communications system for AM radio broadcast. It is likely that a similar IBOC-AM scheme is implemented in an adjacent area which is assigned a second analog host AM carrier having a frequency which is either 20 kHz higher or lower than fc. In that case, the transmission of the digitally modulated signals are interfered by a similar transmission in the adjacent area. The interference is known as “second adjacent channel interference.” To reduce such interference, selected power profiles in accordance with the invention are used to allocate the relative transmission power to the digitally modulated signals in the digital band.

Abstract: In a communications system implementing, e.g., an in-band on channel AM (IBOC-AM) (also known as “hybrid IBOC-AM”) 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.

Abstract: Techniques for processing received information in a communication system, such that performance is significantly improved in the presence of certain types of interference. In an illustrative embodiment, first and second digital sidebands are transmitted on either side of an FM or AM host carrier signal in a hybrid in-band on-channel (HIBOC) digital audio broadcasting (DAB) system. The compressed digital audio information in the sidebands is encoded using an outer code, e.g., a cyclic redundancy code (CRC), and an inner code, e.g., a complementary punctured pair convolutional (CPPC) code. A receiver generates an error indicator based at least in part on a first decoding of the received information. The error indicator characterizes interference associated with at least one of the digital sidebands. The receiver then generates at least one alternative decoding of the received information if the error indicator has a designated characteristic.

Abstract: Methods and apparatus for decoding multiple program information, e.g., audio, video or image information, in a communication system are disclosed. In an illustrative embodiment, a multiple program decoder includes a deinterleaver for deinterleaving information corresponding to a set of frames, using a specified deinterleaving length. A given one of the frames includes information from each of at least a subset of the programs, and the frames are encoded using an outer code, e.g., a CRC code, RS code, BCH code or other type of linear block code, and an inner code, e.g., a convolutional code, turbo code or trellis coded modulation. The multiple program decoder includes an inner code decoder for decoding the inner code over one or more of the programs, and an outer code decoder for decoding the outer code for a selected one of the programs.

Abstract: In a communications system implementing an in-band on channel AM (IBOC-AM) (also known as “hybrid IBOC-AM”) scheme, digitally modulated signals are transmitted in a 30 kHz digital band centered at an analog host AM carrier frequency fc. The host AM carrier is assigned to the geographic area served by the communications system for AM radio broadcast. It is likely that a similar IBOC-AM scheme is implemented in an adjacent area which is assigned a second analog host AM carrier having a frequency which is either 20 kHz higher or lower than fc. In that case, the transmission of the digitally modulated signals are interfered by a similar transmission in the adjacent area. The interference is known as “second adjacent channel interference.” To reduce such interference, selected power profiles in accordance with the invention are used to allocate the relative transmission power to the digitally modulated signals in the digital band.

Abstract: Methods and apparatus for processing information, e.g., audio, video or image information, for transmission in a communication system are disclosed. In an illustrative embodiment, a multiple program coder encodes a bitstream for each of the programs, in accordance with a specified bit allocation. An outer code encoder receives the encoded bitstreams from the multiple program coder, and jointly applies an outer code, e.g., a CRC code, RS code, BCH code or other type of linear block code, to subblocks of a subset of the resulting encoded bitstreams. The outer code is applied such that subblocks of each of the encoded bitstreams in the subset of the encoded bitstrcams are associated with a single outer code block. The number of subblocks associated with a given outer code block may be an integer or non-integer number of code blocks.

Abstract: Methods and apparatus for processing information, e.g., audio, speech, video or image information, for transmission in a communication system. In an illustrative embodiment, a set of bit streams are generated from an audio information signal. The set of bit streams may be, e.g., a total of four bit streams generated by separating each of two multiple description bit streams, corresponding to separate representations of the audio information signal, into first and second class bit streams. The first and second class bit streams associated with the first multiple description bit stream may then be transmitted in respective first and second subbands of a first sideband of an FM host carrier, while the first and second class bit streams associated with the second multiple description bit stream are transmitted in respective first and second subbands of a second sideband of the FM host carrier.

Abstract: The invention provides optimal complementary punctured convolutional codes for coding information bits in a communication system. In an illustrative embodiment, an optimal pair of complementary punctured codes is selected from a set of potential code pairs. The set of potential code pairs includes all non-catastrophic complementary punctured code pairs which combine to produce to a specified full-bandwidth code, and thus includes both equivalent and non-equivalent complementary codes. The optimal code pair may be selected, for example, as the pair of equivalent or non-equivalent codes which has the best free Hamming distance and minimum information error weight of all the pairs in the set. In addition, the invention provides both rate-compatible and rate-incompatible codes suitable for use in providing unequal error protection (UEP) for different classes of information bits.

Abstract: The invention provides methods and apparatus for processing information, e.g., audio, video or image information, for transmission in a communication system. In an illustrative embodiment, interference characteristics are determined for a set of n channels to be used to transmit audio information bits, where n is greater than or equal to two. The audio information bits are separated into n classes based on error sensitivity, for example, the impact of errors in particular audio data bits on perceived quality of an audio signal reconstructed from the transmission. The classes of bits are then assigned to the n channels such that the classes of bits having the greatest error sensitivity are transmitted over the channels which are the least susceptible to interference.

Abstract: The likelihood of significant errors in a decoded sequence is determined based on at least one criterion that is both extrinsic and intrinsic to the decoded sequence. In particular, this determination is preferably made by comparing a signal corresponding to the decoded sequence with a so-called error mitigation signal.

Abstract: The invention provides methods and apparatus for processing information, e.g., audio, video or image information, for transmission in a communication system. In an illustrative embodiment, the value of a single-bit or multiple-bit criticality flag is determined for each of the programs in a set of multiple programs to be transmitted in the system. The information bits for each of the programs are then separated into n classes, where n is greater than or equal to two, based on the values of the criticality flags for the programs. Each of the classes is provided with a different level of error protection, e.g., through the use of different convolutional codes or other suitable techniques. The program or programs having the highest criticality flag values in a given frame or other designated time interval thus have a larger percentage of their information bits assigned to the class that is provided with the highest level of error protection.

Abstract: In a system for simulcasting digitally modulated and analog FM signals over the same FM frequency band, the effect of the analog FM signal on the digitally modulated signal in the simulcast is calculated and canceled from the latter signal before its transmission. As a result, the digital transmission is free from interference from the analog FM signal. Moreover, the digital transmission is achieved by adaptively inserting a time varying number of carriers modulated by digital data into the FM band. The carriers are selected frame by frame to control their interference with the analog FM signal. In accordance with the invention, the carriers are selected in a predetermined order, and in a preferred embodiment grouped contiguously with one another in the FM band. As a result, the rate of control information required to identify the inserted carriers to a receiver is advantageously low.

Abstract: 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=1, 2, . . . , and mapping the resulting b+i coded bits to one of 2b+i distinct levels in a one-dimensional AM signal set.

Abstract: For a transmission system in which (a) a received sequence of symbols is processed by an inner decoder followed by an outer decoder and (b) the inner decoder is capable of providing to the outer decoder more than one output sequence corresponding to the received sequence, the decoded sequence released by the outer decoder is screened for errors undetected by the outer decoder, if a predetermined criterion is satisfied.

Abstract: List Viterbi decoding of a block of data that has been encoded with a tailbiting convolutional code is provided for in a manner that takes advantage of decoder knowledge that starting and terminating states are identical but data-dependent and thus unknown to the receiver.

Abstract: In a system for simulcasting digitally modulated and analog FM signals over the same FM frequency band, the effect of the analog FM signal on the digitally modulated signal in the simulcast is calculated and canceled from the latter signal before its transmission. As a result, the digital transmission is free from interference from the analog FM signal. Moreover, the digital transmission is designed in such a manner that the interference caused thereby to the analog FM signal is kept at a minimal level.

Abstract: List Viterbi algorithms are provided for decoding blocks or frames of convolutional coded information transmitted and received in a continuous mode, i.e., without blockwise termination with a tail. Viterbi decoding is utilized to estimate, for each respective one of a sequence of blocks of symbols, a terminating (and optionally a starting) state which is(are) used in subsequent application of a List Viterbi algorithm. The path memory should be sufficient to enable both the starting state and the terminating state used by the subsequent List Viterbi decoding to be estimated with reasonable accuracy and at the same time to keep track of the best paths between those states.