At+t Corp.

Other

At&t Intellectual Property I, L.p.

Lockheed Martin Corporation

Qatar University

General Electric Company

Martin Marietta Corporation

Naofal Mohammed Al-Dhahir

William Turin

Christine Fragouli

Ali H Sayed

John Erik Hershey

Suhas Nagraj Diggavi

Ridha Hamila

Anastasios Stamoulis

Gary Jude Saulnier

Waheed U Bajwa

Jeffrey Michael Ashe

Mohamed Awadin

Nick Andrew Van Stralen

Mark Lewis Grabb

Richard Louis Frey

Richard Charles Gaus, Jr

Khalil John Maalouf

Abubakr O Al-Abbasi

Ozgur Ozdemir

A method and apparatus may include receiving a transmission. The method can also include determining a sparsifying dictionary that sparsely approximates a data vector of the transmission. The determining the sparsifying dictionary includes performing a fast Fourier transform and/or an inverse fast Fourier transform. The method also includes configuring a filter based on the determined sparsifying dictionary.

Method and apparatus for implementing sparse finite-impulse-response equalizers

The method of identifying faulty antenna elements in massive uniform linear antenna arrays is a compressive sensing-based method that takes advantage of the reduction of the measurement matrix for a uniform linear antenna array to a partial discrete Fourier transform (DTF) matrix, whose rows correspond to the measurements' locations. Particularly, the method of identifying faulty antenna elements in massive uniform linear antenna arrays allows the measurements to be taken to reduce the measurement matrix's worst-case coherence, a factor which affects the detection probability of the defective antenna elements. The method constructs a measurement matrix with fewer distinct inner product values to reduce the worst-case coherence. In an alternative embodiment, the method focuses on bounding the inner product between any pair of measurement matrix columns.

Method of identifying faulty antenna elements in massive uniform linear antenna arrays

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

Disclosed are an system and method for compensation of I/Q imbalance in a beamforming OFDM system. The system comprises: a TX beamformer configured at a transmitter end of the beamforming OFDM system; a noise whitener configured at a receiver end of the beamforming OFDM system; and a RX MMSE configured at the receiver end of the beamforming OFDM system. At least one of the TX beamformer, the noise whitener and the RX MMSE receiver, or any combination thereof are capable of jointly processing a carrier and its image subcarrier to compensate the I/Q imbalance in the beamforming system.

System and methods for compensation of I/Q imbalance in beamforming OFDM systems

A multi-input, multi-output pre-filter improves operation of a multi-input receiver by shortening the effective memory of the channel with a set of FIR filters. The coefficients of these FIR filters can be fashioned to provide a variety of controls by the designer, for example, the value of the effective memory.

Method and apparatus for designing finite-length multi-input multi-output channel shortening pre-filters

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 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 MIMO Decision Feedback Equalizer improves operation of a receiver by canceling the spatio-temporal interference effects caused by the Multiple-Input-Multiple-Output (MIMO) channel memory with a set of Finite Impulse Response (FIR) filters in both the feed-forward and the feedback MIMO filters. The coefficients of these FIR filters can be fashioned to provide a variety of controls by the designer.

Finite-length equalization over multi-input multi-output (MIMO) channels

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 Multiple-Input Multiple Output (MIMO) Decision Feedback Equalizer improves operation of a receiver by canceling the spatio-temporal interference effects caused by the MIMO channel memory with a set of (Finite Impulse Response (FIR) filters in both the feed-forward and the feedback MIMO filters. The coefficients of these FIR filters can be fashioned to provide a variety of controls by the designer.

Space-time block coding is combined with single-carrier, minimum-mean-square-error, frequency-domain equalization for wireless communication through a medium characterized by multi-paths. The transmitter encodes incoming symbols into two or more streams that are transmitted over a corresponding number of transmitting antennas. The encoding employs modulo arithmetic. Decoding in the receiver proceeds by converting received signals to frequency domain, linearly combining the signals to separate contribution of the signals from the two or more transmitting antennas equalizing the separated signals, converting the equalized signals to time domain, and applying the converted signals to a decision circuit.

Frequency-domain method for joint equalization and decoding of space-time block codes

In an environment where a block transmission takes place via a frequency selective channel that is characterized by channel parameters that change with time in the course of the transmission of a block, an arrangement employs pilot signals to ascertain some of the parameters, and estimates the remaining parameters through an interpolation process. In some embodiments, channel coefficients estimates are improved by employing estimates from previous blocks. In an OFDM system, the pilot signals are advantageously selected to be in clusters that are equally spaced from each other in the time or the frequency domains. This approach applies to multiple antennae arrangements, as well as to single antenna arrangements, and to arrangements that do, or do not, use space-time coding.

Method for communicating via a channel characterized by parameters that vary in time within a transmission block

A MIMO Decision Feedback Equalizer improves operation of a receiver by cancelling the spatio-temporal interference effects caused by the MIMO channel memory with a set of FIR filters in both the feedforward and the feedback MIMO filters. The coefficients of these FIR filters can be fashioned to provide a variety of controls by the designer.

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Niskayuna, NY, United States of America

Naofal Mohammed Al-Dhahir