The Directv Group, Inc.

Weimin Sun

Matthew C Bromberg

Dale A Branlund

Methods and systems that enhance interference cancellation in communication channels are described. Specialized time domain training sequences and simple cross correlation are used to obtain a channel estimate for use in stacked carrier beamforming and OFDM based spatial beamforming. In certain embodiments, a time domain preamble sequence is provided as an alternative to the conventional frequency domain preamble sequence. The use of a time domain preamble can increase channel estimation performance, facilitating cancellation of co-channel interference. Embodiments include generating a training sequence preamble in the time domain, computing a frequency domain response of the channel using an estimate of its time domain impulse response, and using the frequency domain response of the channel to calculate channel estimation from a cross correlation of data received from the channel against the training sequence.

Wireless communications systems and methods

Methods and systems that enhance interference cancellation in communication channels are described. Samples are obtained from stacked carriers in a received signal and a data vector is created from the samples. Stacked carriers are selected using a steering vector received during synchronization of the receiver. The steering vector is calculated to obtain cancellation of interference from another receiver and is calculated based on time domain channel estimation. Specialized time domain training sequences and simple cross correlation are used to obtain a channel estimate for use in stacked carrier beamforming and/or for use in OFDM based spatial beamforming. State space or filter-based modeled interpolators or whitening matrix-filters in the frequency or time domain are used for interpolation of the channels to maintain linear beamforming weights as a function of time or frequency. Space time adaptive processing facilitates beamforming of communications signals for OFDM and 802.16 (WiMax) systems.

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Boxborough, MA, United States of America

Weimin Sun