Lucent Technologies Inc.

Alcatel Lucent

Alcatel-lucent USA Inc.

Agere Systems Guardian Corp.

Mohammad Hossein Zarrabizadeh

Mohsen Sarraf

Robert Louis Cupo

Mojtaba Shariat

Muhammad R Karim

Xin Wang

Ahmed A Tarraf

Masoud Sajadieh

Mahmoud Sherif

Marek Milbar

Jian Yi

Watermark data is effectively placed in at least one of the bit positions, e.g., of the integer portion, of the average value of at least a selected one of the chrominance portions of up to each block, on up to a frame-by-frame basis. Values of the selected chrominance portion of individual pixels in a block may be adjusted if necessary in order to cause the resulting substitution of the selected bit of the average. The bit position replaced may be a function of the block's busyness. A 'margin' value may also be added to the average value in order to better ensure that the bit of watermark data survives any MPEG encoding, while minimizing resulting artifacts. A receiver extracts the bit of watermark data from the selected bit position of the average value of the chrominance portion.

Watermarking scheme for digital video

A system and method for digital watermarking a video signal with an increased bit rate is achieved by inserting the additional information which constitutes the watermarking signal within the video signal on the chrominance signal. Thus, the additional information is 'impressed' upon the chrominance component of the video signal. The human visual system is much less sensitive to chrominance than to luminance, and therefore, additional distortion which results from the higher bit rate can be allowed on the chrominance signal and yet such distortion will not be detected by the human visual system.

Each bit of information that is impressed upon a video signal is impressed upon each pixel of a block of pixels of the video signal a video signal so as to reduce errors in transmission of the additional information. Prior to impression, the additional information may be further coded, e.g., using channel coding, interleaving, and differential encoding. A receiver performs complimentary processes to recover the additional data.

A video analysis technique includes correlating frames from a processed video with frames from a pre-processed, original video. A linear approximation of a relationship between the correlated frames is determined. A disclosed example includes determining a linear approximation that maximizes the number of processed video frames that fit into the linear approximation. The linear approximation and whether any frames do not fit within the linear approximation is then used to provide quality information for analyzing a quality of the processed video.

Video quality analysis using a linear approximation technique

A method and apparatus increase the time and frequency diversity of a multi-stream signal in a DAB system. A plurality of audio streams are divided into four (4) digital sub-streams, C, C, C, and C. Each sub-stream C, C, C, and Cis assigned a unique frequency band, and time slot. A first core sub-stream Cis mapped to one frequency partition and a second core sub-stream Cis mapped to another frequency partition and delayed relative to the first core sub-stream. Similarly, two enhancement sub-streams Cand Care mapped to different frequency partitions and are time delayed relative to each other and the core sub-streams. The two core sub-streams Cand Ccan have a maximum separation across both the time and frequency axes.

Method and apparatus for multi-stream transmission with time and frequency diversity in an orthogonal frequency division multiplexing (OFDM) communication system

Data to be impressed upon the average value of a chrominance portion of a block, is replicated at least once. The original and each replica is impressed on blocks in the same block position of separate frames. The frames that have like-positioned blocks that are carrying the same data are considered to be a group. Specific blocks of the frame may be embedded with a particular known data sequence rather than user data. Each group may employ a different known sequence. Instead of simply repeating the data for each like-positioned block of a group, the amount added to the average value for each such block may be changed slightly from frame to frame in group, even when the complexity of the blocks is the same. At a receiver, the multiple instances of the same data bit are extracted and combined to form a single received bit.

Determining a chrominance portion to be watermarked employs a perception-based table that indicates for various pixel values which of the chrominance portions, if any, should be selected for watermarking. Only the Y, U, and V values of a pixel are needed to access the table and determine which chrominance portion should be selected. However, the table may be represented such that it may be accessed using only R, G, and B values. The table may be modified so that it may indicate which of U or V should be selected, or that neither should be selected, indicating that this pixel should not be watermarked at all. Advantageously, the table may be simplified by employing some processing, because a large section of the table may be replaced by a simple test on the pixel values, e.g., U&#x3c;128, to determine the selected chrominance portion.

Color selection scheme for digital video watermarking

Interleaving methods and apparatus are disclosed for an in-band on-channel digital audio broadcasting system. The guard periods that separate any two adjacent symbols in a conventional OFDM system can provide a mechanism for OFDM frame synchronization. The guard period of successive OFDM frames is utilized to establish one or more unique positive or negative patterns and thereby provide a mechanism for interleaver synchronization. By proper positioning of the guard period patterns, one or more particular portions of each interleaver block are identified, such as the beginning and midpoint of each interleaver block. The present invention identifies the beginning of each interleaver block, for example, by positioning the fourth negative cyclic prefix with OFDM frame zero (). The present invention can optionally identify the midpoint of each interleaver block, for example, by positioning the fourth negative cyclic prefix with OFDM frame. The beginning of an interleaver block can be distinguished from the midpoint using a unique cyclic prefix pattern. A receiver monitors the incoming data stream for a synchronization pattern to (i) establish interleaver synchronization, (ii) detect when synchronization is lost, and (iii) detect and correct a false synchronization.

Method and apparatus for establishing interleaver synchronization in an orthogonal frequency division multiplexing (OFDM) communication system

A method and apparatus are disclosed for frequency offset estimation and interleaver synchronization, using periodic signature sequences, such as Barker codes. The periodic signature sequence is used for interleaver synchronization or frequency offset estimation or both. The periodic signature sequence is transmitted over a certain number of bins in both the upper and lower sides of the DAB signal. Since the signature sequences are assigned to specific bins known to the receiver, any shift of the correlated peak from the expected location due to frequency offset errors can be estimated by the frequency offset algorithm. If the Barker sequence is placed, for example, in the last column of the DAB interleaver, the location of the Barker sequence upon correlation of the received digital signal identifies the beginning of an interleaver block. A Barker sequence is transmitted over a signature frame every L data frames on each side band, where L is generally the number of OFDM frames that can fill the interleaver memory. If the maximum frequency offset is M, then the frequency offset algorithm utilizes a search window of size n+2M (between bins N&#x2212;M through N+n+M), and attempts to maintain the Barker sequence in the center of the search window. At the receiver, the Barker sequence is mapped to the OFDM signature bins that do not belong to uncertainty regions (the group of bins that can fall out of the receiver processing range for maximum positive and negative frequency offset values). Thus, the Barker sequence bins are processed by the disclosed receiver as long as the frequency offset does not exceed the specified maximum frequency offset.

Method and apparatus for frequency offset estimation and interleaver synchronization using periodic signature sequences

Frame synchronization of a received OFDM signal (such as that used in a hybrid FM DAB system) is provided by filtering out significant outer frequency portions of the digital channels, and then using cyclic extension and correlation of the cyclically extended bits (or samples). The received OFDM signal is passed through a bandpass filter to remove outer digital subcarriers (i.e., those farthest from a center frequency) from a received OFDM signal before correlating to locate the OFDM frame boundaries. By filtering out digital subcarriers within each of the digital channels, particularly those closest to adjacent channels and thus most likely to be interfered with by an adjacent first channel OFDM (or FM) signal, correlation between cyclically extended bit (or sample) patterns and thus frame synchronization of OFDM signals can be improved significantly.

Frame synchronization of an OFDM signal

A novel antenna diversity technique for OFDM receivers is disclosed. A method and apparatus are disclosed for combining in the frequency domain the various signals received on each of the multiple antennas in an OFDM communication system. At the OFDM transmitter, the transmitted signal is differentially encoded over frequency, as opposed to time, to differentially encode the transmitted signal in the frequency domain with respect to consecutive bins (OFDM sub-carriers). The OFDM receiver processes a signal received on a number of diversity branches and combines the received signals using a post-detection combining technique after differential decoding. Each frame is independently processed by a differential decoder and then delayed to align each symbol in a given frame. The post-detection combining of the frame data inherently scales the received samples and thereby implements an optimal maximum ratio combining mechanism. Unlike conventional maximum ratio combining techniques, the faded bins are scaled individually by the differential decoder, based on their own power levels rather than the overall power of the OFDM frame. Thus, bins with higher magnitudes will be weighted more heavily than bins having severe channel fading.

Method and apparatus for post-detection maximum ratio combining with antenna diversity in an orthogonal frequency division multiplexing (OFDM) communication system

A method and apparatus are disclosed for frequency offset estimation in a hybrid in-band on-channel (HIBOC) digital audio broadcasting (DAB) system. The frequency offset estimation algorithm first determines the coarse frequency offset, in terms of integer number of OFDM bin separations between an actual and measured location of a correlated peak, followed by estimation and tracking of the partial (residual) offset in a continuous fashion. A frame is correlated at a first frequency, and then the frequency is shifted by a predefined amount, such as half of the inter-bin frequency amount, &Dgr;f, before correlating again. The measurement with the highest peak of the plurality of frequency values is utilized to obtain the course frequency offset estimate. The partial frequency offset estimation algorithm utilizes phase information contained in reference frequency points in the frequency domain. The phase rotation of the reference vector is proportional to the frequency error, and the frequency error is extracted and filtered in the time domain. The initial partial frequency offset estimation is corrected and used for continuous frequency tracking. Following the course frequency offset estimation, the unmodulated pilot bins (and all other bins), are within at least half the of the OFDM bin separation. In the presence of a frequency offset, the complex bins start rotating. The rate of the rotation is a function of the extent of the partial frequency offset. The change in phase from one frame to the next is proportional to the rate of rotation, and the sign of the rotation indicates the direction of the shift.

Method and apparatus for partial and course frequency offset estimation in a digital audio broadcasting (DAB) system

Interleaving methods and apparatus are disclosed for an in-band on-channel digital audio broadcasting system. The guard periods that separate any two adjacent symbols in a conventional OFDM system can provide a mechanism for OFDM frame synchronization. The guard period of successive OFDM frames is utilized to establish one or more unique positive or negative patterns and thereby provide a mechanism for interleaver synchronization. By proper positioning of the guard period patterns, one or more particular portions of each interleaver block are identified, such as the beginning and midpoint of each interleaver block. The present invention identifies the beginning of each interleaver block, for example, by positioning the fourth negative cyclic prefix with OFDM frame zero ( ). The present invention can optionally identify the midpoint of each interleaver block, for example, by positioning the fourth negative cyclic prefix with OFDM frame . The beginning of an interleaver block can be distinguished from the midpoint using a unique cyclic prefix pattern. A receiver monitors the incoming data stream for a synchronization pattern to (i) establish interleaver synchronization, (ii) detect when synchronization is lost, and (iii) detect and correct a false synchronization.

Method and apparatus for interleaver synchronization in an orthogonal frequency division multiplexing (OFDM) communication system

In accordance with the principles of the present invention, in addition to conventional use of frequency division multiplexed upper and lower side bands, the spectral area occupied by the analog host will be utilized by applying a one-dimensional modulation, e.g., pulse amplitude modulation (PAM) as opposed to the conventional use of a two-dimensional modulation, e.g., quadrature amplitude modulation (QAM). Furthermore, the analog and digital information within the analog host bandwidth may be combined in quadrature to keep the signals orthogonal. Thus, should one side band under the analog carrier be deteriorated or obliterated by adjacent channel interference, the other side band under the analog carrier can still provide useful data and hence better digital audio codec performance. By transmitting one or two digital data streams asymmetrically with respect to the center frequency, particular digital side bands can be rendered useless as environmental conditions warrant (e.g., as they become detrimentally affected by adjacent channel interference), reducing bandwidth capacity but not affecting the quality of the received digital data transmitted in any of the remaining digital side band regions.

Asymmetric pulse amplitude modulation transmission of multi-stream data embedded in a hybrid IBOC channel

A method and a receiver for reducing adjacent-channel interference to a digitally modulated receive signal evaluates error rates of the receive signal associated with different receive bandwidths of the receive signal. The receiver selects a preferential bandwidth among the different bandwidths based on a suitably low error rate associated with the preferential bandwidth. The selection of the different bandwidths is achieved by digital signal processing that weighs desired data bits representing a desired bandwidth differently than rejected data bits representing a rejected bandwidth.

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Woodbridge, NJ, United States of America

Mohammad Hossein Zarrabizadeh