At+t Corp.

AT&T Intellectual Property I, LP

Lucent Technologies Inc.

Other

William Turin

James David Johnston

Naofal Mohammed Al-Dhahir

Schuyler Reynier Quackenbush

Shyh-Shiaw Kuo

Christine Fragouli

Jianying Hu

Michael Kenneth Brown

Winston Lowell Nelson

Stephen Charles Glinski

Ramanujan S Kashi

Robert A Boie

The burden of designing multiple training sequences for systems having multiple transmit antennas, is drastically reduced by employing a single sequence from which the necessary multiple sequences are developed. The single sequence is selected to create sequences that have an impulse-like autocorrelation function and zero cross correlations. A sequence of any desired length Ncan be realized for an arbitrary number of channel taps, L. The created sequences can be restricted to a standard constellation (that is used in transmitting information symbols) so that a common constellation mapper is used for both the information signals and the training sequence. In some applications a training sequence may be selected so that it is encoded with the same encoder that is used for encoding information symbols. Both block and trellis coding is possible in embodiments that employ this approach.

Training-based channel estimation for multiple-antennas

The burden of designing multiple training sequences for systems having multiple transmit antennas, is drastically reduced by employing a single sequence from which the necessary multiple sequences are developed. The single sequence is selected to create sequences that have an impulse-like autocorrelation function and zero cross correlations. A sequence of any desired length Ncan be realized for an arbitrary number of channel taps, L. The created sequences can be restricted to a standard constellation (that is used in transmitting information symbols) so that a common constellation mapper is used for both the information signals and the training sequence. In some applications a a training sequence may be selected so that it is encoded with the same encoder that is used for encoding information symbols. Both block and trellis coding is possible in embodiments that employ this approach.

A system and method of generating a watermarked signal are disclosed. The system segments the signal into overlapping blocks using a window function and processes the overlapping blocks according to whether each block is odd- or even-numbered. The system windows the odd-numbered blocks, modulates the phase of each block in the frequency domain, transforms each modulated block in the time domain, windows each block transformed into the time domain and overlap-adds each odd-numbered block with each even-numbered block to generate the watermarked signal.

System and method of watermarking a signal

This invention provides an iterative process to maximum a posteriori (MAP) decoding. The iterative process uses an auxiliary function which is defined in terms of a complete data probability distribution. The auxiliary function is derived based on an expectation maximization (EM) algorithm. For a special case of trellis coded modulators, the auxiliary function may be iteratively evaluated by a combination of forward-backward and Viterbi algorithms. The iterative process converges monotonically and thus improves the performance of any decoding algorithm. The MAP decoding minimizes a probability of error. A direct approach to achieve this minimization results in complexity which grows exponentially with T, where T is the size of the input. The iterative process avoids this complexity by converging on the MAP solution through repeated maximization of the auxiliary function.

Iterative decoding

A system, method and computer readable medium that processing a watermarked signal using the phase S(f) of an original signal. The watermarked signal includes odd and even overlapped blocks where the watermark is contained in the even blocks. The method comprises test-decoding the watermarked signal and, if the watermarked signal contains errors, recoding the watermarked signal with a higher redundancy code. The steps of test-decoding and recording may be performed until all errors are corrected.

System and method of retrieving a watermark within a signal

A training sequence is created for space-time diversity arrangement, having any training sequence length, while limiting the training sequence to a standard constellation. Given a number of channel unknowns that need to be estimated, L, a training sequence can be creates that yields minimum means squared estimation error for lengths N=kN+L&#x2212;1, for any positive integer k&#x2267;1, where Nis a selected perfect roots-of-unity sequence (PRUS) of length N. The training sequence is created by concatenating k of the length N perfect roots-of-unity sequences, followed by L&#x2212;1 initial symbols of that same PRUS. Good training sequences can be created for lengths Nthat cannot be obtained through the above method by concatenating a requisite number of symbols found through an exhaustive search.

Creating training sequences for space-time diversity arrangements

A system and method of retrieving a watermark in a watermarked signal are disclosed. The watermarked signal comprises odd and even overlapped blocks where the watermark is contained in the even blocks. The method comprises, for each k-th even block, subtracting the two adjacent odd numbered blocks from the k-th even block of the watermarked signal to retrieve*(n), transforming*(n) into the frequency domain to generate(f), calculating a phase of(f) as(f) and a phase of S(f) as &#x3c6;(f), calculating the difference &#x3a8; (f) between(f) and &#x3c6;(f), unwrapping &#x3a8; (f) to obtain the phase modulation {tilde over (&#x3a6;)}(f), and using a Viterbi search to retrieve the watermark embedded in {tilde over (&#x3a6;)}(f).

A training sequence is created for space-time diversity arrangement, having any training sequence length, while limiting the training sequence to a standard constellation. Given a number of channel unknowns that need to be estimated, L, a training sequence can be creates that yields minimum means squared estimation error for lengths N=kN+L&#x2212;1, for any positive integer k&#x2266;1, where Na selected perfect roots-of-unity sequence (PRUS) of length N. The training sequence is created by concatenating k of the length N perfect roots-of-unity sequences, followed by L&#x2212;1 initial symbols of that same PRUS. Good training sequences can be created for lengths Nthat cannot be obtained through the above method by concatenating a requisite number of symbols found through an exhaustive search.

A system and method of retrieving a watermark in a watermarked signal are disclosed. The watermarked signal comprises odd and even overlapped blocks where the watermark is contained in the even blocks. The method comprises, for each k-th even block, subtracting the two adjacent odd numbered blocks from the k-th even block of the watermarked signal to retrieve*(n), transforming*(n) into the frequency domain to generate(f), calculating a phase of(f) as(f) and a phase of S(f) as &#x3c6;(f), calculating the difference &#x3a8;(f) between(f) and &#x3c6;(f), unwrapping &#x3a8;(f) to obtain the phase modulation {tilde over (&#x3c6;)}(f), and using a Viterbi search to retrieve the watermark embedded in {tilde over (&#x3a6;)}(f).

A method of retrieving a watermark in a watermarked signal involves processing a signal having odd- and even-overlapped blocks and where the watermark is contained in the even blocks. For each k-th block, the method comprises subtracting the odd-numbered blocks from the k-th block of the watermarked signal to generate*(n), applying an FFT to*(n) to generate a phase(&#x192;), calculating a phase of(&#x192;) as(&#x192;) and a phase of an original signal S(&#x192;) as &#x3c6;(&#x192;), calculating the difference &#x3a8;(&#x192;) between(&#x192;) and &#x3c6;(&#x192;); and retrieving the watermark embedded in &#x3a8;(&#x192;). A Viterbi search may be the algorithm used to retrieve the watermark.

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East Brunswick, NJ, United States of America

William Turin