Hemanth T Sampath from 3745 Carmel View Rd, San Diego, CA 92130, age 49, Phone: 8587925877

Us Patents

Method And System For Mode Adaptation In Wireless Communication
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US Patent:

6922445, Jul 26, 2005
Filed:

Jun 30, 2000
Appl. No.:

09/609591
Inventors:

Hemanth Sampath - Palo Alto CA, US
Arogyaswami J. Paulraj - Stanford CA, US
Assignee:

Intel Corporation - Santa Clara CA
International Classification:

H04B007/02
H04L001/02
US Classification:

375267, 455132, 455101, 375299, 375347
Abstract:

A method and system for selective mode adaptation for transmitting data by spatial multiplexing applicable in communications systems with a transmit unit having multiple transmit antennas or multiple transmit units and a receive unit having multiple receive antennas. A channel descriptor, such as channel matrix H or a channel matrix filter , with has sub-descriptors corresponding to the transmit antennas is determined and a quality parameter, such as signal-to-interference and noise ratio, signal-to-noise ratio or power level are chosen. The quality parameter is assigned a threshold and the sub-descriptor or sub-descriptors whose quality parameters do not meet the threshold are identified and deactivated.

Synchronization Of A Pilot Assisted Channel Estimation Orthogonal Frequency Division Multiplexing System
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US Patent:

7023928, Apr 4, 2006
Filed:

Aug 6, 2001
Appl. No.:

09/922885
Inventors:

Rajiv Laroia - Basking Ridge NJ, US
Junyi Li - Bedminster NJ, US
Sundeep Rangan - Hoboken NJ, US
Hemanth T. Sampath - Bethesda MD, US
Assignee:

Lucent Technologies Inc. - Murray Hill NJ
International Classification:

H04K 1/10
US Classification:

375260, 375344, 370210
Abstract:

A synchronization of a pilot assisted channel estimation orthogonal frequency division multiplexing can be achieved by receiving a signal containing pilot symbols, providing an initial time and frequency synchronization to the signal, phase rotating the signal across time, transforming the signal with a fast Fourier transformation, phase rotating the signal across frequency, extracting the pilot symbols and generating a channel estimator. The phase rotating across time and the phase rotating across frequency are controlled by a phase rotation controller in accordance with the channel estimator. The initial time and frequency synchronization synchronizes the signal such that intercarrier interference effects and intersymbol interference effects are negligible. The signal may include plural carrier frequencies each having an arrival timing offset and a frequency offset. The signal may also include delay spread or Doppler spread.

Method And Apparatus For Time And Frequency Synchronization Of Ofdm Communication Systems
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US Patent:

7027429, Apr 11, 2006
Filed:

Jun 19, 2001
Appl. No.:

09/884581
Inventors:

Rajiv Laroia - Basking Ridge NJ, US
Junyi Li - Bedminster NJ, US
Sundeep Rangan - Hoboken NJ, US
Hemanth T. Sampath - Bethesda MD, US
Assignee:

Flarion Technologies, Inc. - Bedminster NJ
International Classification:

H04J 3/06
US Classification:

370350, 370503, 375260, 375316
Abstract:

A method and apparatus for joint time and frequency synchronization for orthogonal frequency division multiplexing (OFDM) systems. A multitone pilot signal is sent in a designated OFDM symbol period. The receiver synchronizes to the pilot signal in a two-stage procedure. The first stage estimates the frequency offset coarsely with a frequency-domain correlation method and estimates the time offset with smoothed time-domain correlation. In a multipath channel, the smoothed time offset estimate is used to locate a cyclic prefix interval which captures the maximum total signal energy. The second stage improves the frequency estimate with a computationally efficient numerical optimization method.

System And Method For Multiple Signal Carrier Time Domain Channel Estimation
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US Patent:

7058134, Jun 6, 2006
Filed:

Dec 17, 2001
Appl. No.:

10/023632
Inventors:

Hemanth Sampath - Palo Alto CA, US
Assignee:

Intel Corporation - Santa Clara CA
International Classification:

H04K 1/10
H04L 27/28
US Classification:

375260, 375340
Abstract:

The present invention provides a method of characterizing a frequency response of a transmission channel between a transceiver and a subscriber unit. The method includes once per predetermined interval of time, the transceiver transmitting a signal including multiple carriers, a plurality of the carriers including training symbols, a plurality of the carriers including information symbols. The subscriber unit generates frequency response estimates at the frequencies of the carriers including training symbols, each interval of time. The frequency response estimates are converted into a time domain response generating an impulse response once per interval of time. The impulse responses are filtered over a plurality of intervals of time. A channel profile is determined from the filtered impulse responses. The channel profile is converted to the frequency domain generating a channel interpolator.

Transmit Signal Preprocessing Based On Transmit Antennae Correlations For Multiple Antennae Systems
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US Patent:

7149254, Dec 12, 2006
Filed:

Sep 6, 2001
Appl. No.:

09/948204
Inventors:

Hemanth Sampath - Palo Alto CA, US
Assignee:

Intel Corporation - Santa Clara CA
International Classification:

H04B 7/02
US Classification:

375267, 375296
Abstract:

The present invention provides a method and system for preprocessing transmit signals in spatial multiplexing and diversity systems that include multiple transmit antennae. The method includes generating a representative correlation matrix based upon estimates of a correlation between each pair of the plurality of antennae. An equivalent eigenvalue decomposition of the representative correlation matrix is determined. A preprocessing matrix based upon the equivalent eigenvalue decomposition is generated. Finally, a preprocessor preprocesses the transmit signals by multiplying blocks of data of the transmit signals with the preprocessing matrix. The representative correlation matrix can be an exact estimate of the correlation between each pair of the multiple antennae, or the representative correlation matrix can be an approximate estimate of the correlation between each pair of the multiple antennae.

Mimo-Ofdm Receiver Processing With Frequency And Channel Estimation
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US Patent:

7408976, Aug 5, 2008
Filed:

Aug 5, 2004
Appl. No.:

10/912829
Inventors:

Ravi Narasimhan - Los Altos CA, US
Hemanth Sampath - Sunnyvale CA, US
Hsiao-Cheng Tang - Milpitas CA, US
Assignee:

Marvell International Ltd. - Hamilton
International Classification:

H04B 1/69
H04B 1/04
US Classification:

375148, 375299, 455132
Abstract:

A receiver in a MIMO-OFDM system may process OFDM symbols received on a number (M) of receive antennas. The system may utilize a MIMO-OFDM frame format that includes additional long training OFDM symbols, for training additional antennas and for link adaptation, and a header with an additional SIGNAL symbol to indicate MIMO-OFDM-specific information.

Cqi And Rank Prediction For List Sphere Decoding And Ml Mimo Receivers
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US Patent:

7428269, Sep 23, 2008
Filed:

May 31, 2006
Appl. No.:

11/445098
Inventors:

Hemanth Sampath - San Diego CA, US
Tamer Kadous - San Diego CA, US
Assignee:

QUALCOMM Incorporated - San Diego CA
International Classification:

H04B 7/02
US Classification:

375267, 375295, 375299, 455513
Abstract:

Systems and methodologies are described that facilitate integrating a list-sphere decoding design in a multiple input-multiple output (MIMO) wireless communication environment. According to various aspects, optimal rank selection and CQI computation for an optimal rank can be performed in conjunction with a non-linear receiver, such as a maximum likelihood (ML) MMSE receiver, a non-linear receiver with a list-sphere decoder, and the like. Optimal rank selection can be performed using a maximum rank selection protocol, a channel capacity-based protocol, or any other suitable protocol that facilitates rank selection, and CQI information can be generated based in part on effective SNRs determined with regard to a selected optimal rank.

Mechanism To Improve Quality Of Channel Estimates In Ofdm Transmissions
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US Patent:

7532563, May 12, 2009
Filed:

Mar 11, 2004
Appl. No.:

10/799548
Inventors:

Kedar Shirali - Sunnyvale CA, US
Hemanth Sampath - Sunnyvale CA, US
Assignee:

Marvell International Ltd. - Hamilton
International Classification:

H04J 9/00
H04L 5/04
US Classification:

370205, 370203, 370204, 370208, 370209, 370210, 379343, 375260, 375261, 375264, 375348, 375349
Abstract:

An OFDM (Orthogonal Frequency Division Multiplexing) system may utilize pilot symbol structures including two or more pilot symbols with pilot information on alternate tones. The pilot information in one symbol is transmitted on mirror tones in another of the symbols. The pilot symbol structure may include a copy of one of the pilot symbols to aid in frequency offset estimation.