Patents by Inventor Narayan Prasad

Narayan Prasad has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 8270918
    Abstract: A multi-rank beamforming (MRBF) scheme in which the downlink channel is estimated and an optimal precoding matrix to be used by the MRBF transmitter is determined accordingly. The optimal precoding matrix is selected from a codebook of matrices having a recursive structure which allows for efficient computation of the optimal precoding matrix and corresponding Signal to Interference and Noise Ratio (SINR). The codebook also enjoys a small storage footprint. Due to the computational efficiency and modest memory requirements, the optimal precoding determination can be made at user equipment (UE) and communicated to a transmitting base station over a limited uplink channel for implementation over the downlink channel.
    Type: Grant
    Filed: October 6, 2011
    Date of Patent: September 18, 2012
    Assignee: NEC Laboratories America, Inc.
    Inventors: Mohammad Ali Khojastepour, Narayan Prasad
  • Patent number: 8255778
    Abstract: A method for decoding of multiple wireless signals by a chase combining hybrid-automatic-repeat-request CC-HARQ receiver includes demodulating wireless signals received from respective mobile sources using an effective channel matrix and decision statistics; updating log-likelihood-ratios LLRs and decoding the received codewords using the corresponding updated LLRs; determining set of correctly decoded codewords using a cyclic redundancy check; updating the effective channel matrix and decision statistics responsive to the step of determining; and resetting the effective channel matrix and decision statistics in the event that the number of decoding errors for a codeword exceeds its maximum limit after storing the updated LLRs of all remaining erroneously decoded codewords for which the number of decoding errors is below the respective maximum limit.
    Type: Grant
    Filed: May 4, 2009
    Date of Patent: August 28, 2012
    Assignee: NEC Laboratories America, Inc.
    Inventors: Narayan Prasad, Xiaodong Wang
  • Patent number: 8254859
    Abstract: A multi-rank beamforming (MRBF) scheme in which the downlink channel is estimated and an optimal precoding matrix to be used by the MRBF transmitter is determined accordingly. The optimal precoding matrix is selected from a codebook of matrices having a recursive structure which allows for efficient computation of the optimal precoding matrix and corresponding Signal to Interference and Noise Ratio (SINR). The codebook also enjoys a small storage footprint. Due to the computational efficiency and modest memory requirements, the optimal precoding determination can be made at user equipment (UE) and communicated to a transmitting base station over a limited uplink channel for implementation over the downlink channel.
    Type: Grant
    Filed: May 19, 2011
    Date of Patent: August 28, 2012
    Assignee: NEC Laboratories America, Inc.
    Inventors: Mohammad A. Khojastepour, Narayan Prasad
  • Patent number: 8238854
    Abstract: A multi-rank beamforming (MRBF) scheme in which the downlink channel is estimated and an optimal precoding matrix to be used by the MRBF transmitter is determined accordingly. The optimal precoding matrix is selected from a codebook of matrices having a recursive structure which allows for efficient computation of the optimal precoding matrix and corresponding Signal to Interference and Noise Ratio (SINR). The codebook also enjoys a small storage footprint. Due to the computational efficiency and modest memory requirements, the optimal precoding determination can be made at user equipment (UE) and communicated to a transmitting base station over a limited uplink channel for implementation over the downlink channel.
    Type: Grant
    Filed: May 19, 2011
    Date of Patent: August 7, 2012
    Assignee: NEC Laboratories America, Inc.
    Inventors: Mohammad A. Khojastepour, Narayan Prasad
  • Patent number: 8238366
    Abstract: The invention provides a sequential rate allocation process which assigns excess rates to variable-rate users in a sequential fashion according to specified priorities and yields a strongly pare-to-optimal rate allocation. The invention also provides two parallel rate allocation techniques for where all variable-rate users have the same priority. The first is a parallel symmetric rate and the second is an iterative rate allocation.
    Type: Grant
    Filed: November 19, 2008
    Date of Patent: August 7, 2012
    Assignee: NEC Laboratories America, Inc.
    Inventors: Narayan Prasad, Xiaodong Wang
  • Patent number: 8218422
    Abstract: System and methods are disclosed for optimizing wireless communication for a plurality of mobile wireless devices. The system uses beamforming vectors or precoders having a structure optimal with respect to the weighted sum rate in a multi-cell orthogonal frequency division multiple access (OFDMA) downlink. A plurality of base stations communicate with the mobile devices and all base stations perform a distributed non-convex optimization exploiting the determined structure.
    Type: Grant
    Filed: June 3, 2009
    Date of Patent: July 10, 2012
    Assignee: NEC Laboratories America, Inc.
    Inventors: Luca Venturino, Xiaodong Wang, Narayan Prasad
  • Publication number: 20120170676
    Abstract: Methods and systems for optimizing the utilities of receiver devices in a wireless communication network are disclosed. Precoder design formulations that maximize a minimum worst-case rate or a worst-case sum rate are described for both full base station, cooperation and limited base station cooperation scenarios. In addition, optimal equalizers are also selected to optimize the worst-case sum rate.
    Type: Application
    Filed: March 7, 2012
    Publication date: July 5, 2012
    Applicant: NEC LABORATORIES AMERICA, INC.
    Inventors: Ali Tajer, Narayan Prasad, Xiaodong Wang, Sampath Rangarajan
  • Publication number: 20120170677
    Abstract: System and methods are disclosed for optimizing wireless communication for a plurality of mobile wireless devices. The system uses beamforming vectors or precoders having a structure optimal with respect to the weighted sum rate in a multi-cell orthogonal frequency division multiple access (OFDMA) downlink. A plurality of base stations communicate with the mobile devices and all base stations perform a distributed non-convex optimization exploiting the determined structure.
    Type: Application
    Filed: March 7, 2012
    Publication date: July 5, 2012
    Applicant: NEC LABORATORIES AMERICA, INC.
    Inventors: Luca Venturino, Narayan Prasad, Xiaodong Wang
  • Publication number: 20120170530
    Abstract: A method for LTE or WiMAX scheduling includes collecting, by a basestation BS, channel feedback from multiple mobiles with downlink traffic. The channel feedback enables the BS to determine an achievable rate or block error probability if transmitting to a mobile with a given modulation and coding scheme MCS and multiple-input multiple-output MIMO mode. The method includes determining, by the BS, which of the mobiles is scheduled on each resource block RB and what the MCS and MIMO mode is selected for each scheduled mobile, and allocating bits on the set of the RBs assigned to each scheduled mobile.
    Type: Application
    Filed: January 4, 2012
    Publication date: July 5, 2012
    Applicant: NEC Laboratories America, Inc.
    Inventors: Honghai Zhang, Narayan Prasad, Sampath Rangarajan
  • Publication number: 20120170531
    Abstract: Methods and systems for allocating resources in a cellular uplink include iteratively allocating uplink resource blocks (RBs) to a plurality of user devices in a multiple-input multiple-output network. Allocation is performed subject to constraints and incremental utility maximization according to an approximation that has a worst-case guarantee.
    Type: Application
    Filed: January 4, 2012
    Publication date: July 5, 2012
    Applicant: NEC LABORATORIES AMERICA, INC.
    Inventors: Narayan Prasad, Honghai Zhang, Meilong Jiang, Guosen Yue, Sampath Rangarajan
  • Publication number: 20120163332
    Abstract: System and methods are disclosed for optimizing wireless communication for a plurality of mobile wireless devices. The system uses beamforming vectors or precoders having a structure optimal with respect to the weighted sum rate in a multi-cell orthogonal frequency division multiple access (OFDMA) downlink. A plurality of base stations communicate with the mobile devices and all base stations perform a distributed non-convex optimization exploiting the determined structure.
    Type: Application
    Filed: March 7, 2012
    Publication date: June 28, 2012
    Applicant: NEC LABORATORIES AMERICA, INC.
    Inventors: Luca Venturino, Narayan Prasad, Xiaodong Wang
  • Publication number: 20120114030
    Abstract: A method includes obtaining a precoder for retransmission of one codeword responsive to known precoding matrix P of rank r and modulation and coding scheme MCS assignments used in an original transmission, and a desired retransmission rank r?; and scaling power in the retransmission responsive to at least two of 1) information parameters Index of UL precoder in previous transmission, 2) rank r of uplink UL precoder in previous transmission, 3) MCS assignments in previous retransmission (MCSi), 4) rank r? UL retransmission 5) number of retransmit antennas used thr codeword to be retransmitted x in previous transmission, 6) number of retransmit antennas x? used for retransmission, 7) precoder for UL retransmission, 8) UL precoders and channel information for previous transmission, and 8) latest channel measurements.
    Type: Application
    Filed: November 9, 2011
    Publication date: May 10, 2012
    Applicant: NEC LABORATORIES AMERICA, INC.
    Inventors: Guosen Yue, Narayan Prasad, Meilong Jiang, Sampath Rangarajan
  • Patent number: 8174959
    Abstract: Systems and methods to assign one or more resources in a multi-user cellular Orthogonal Frequency-Division Multiple Access (OFDMA) uplink includes specifying a resource allocation problem for one or more resources; converting the resource allocation problem into an assignment problem; solving the assignment problem through an auction; and allocating one or more resources to cellular users to maximize a system utility.
    Type: Grant
    Filed: March 6, 2009
    Date of Patent: May 8, 2012
    Assignee: NEC Laboratories America, Inc.
    Inventors: Kai Yang, Narayan Prasad, Xiaodong Wang
  • Publication number: 20120082259
    Abstract: A method includes obtaining a precoder for retransmission of one codeword responsive to a known precoding matrix of a certain rank and modulation and coding scheme assignments used in an original transmission, and a desired retransmission rank', forming an approximate channel covariance matrix; stimating an a minimum mean square error receiver signal-to-noise-interference-ratio for each layer to be retransmitted responsive to the prior forming; and finding a precoding matrix from a preceding codebook that maximizes a sum-rate for enabling precoding selections for retransmissions in uplink multiple-input multiple-output MIMO hybrid automatic repeat request HARQ.
    Type: Application
    Filed: October 4, 2011
    Publication date: April 5, 2012
    Applicant: NEC LABORATORIES AMERICA, INC.
    Inventors: Guosen Yue, Narayan Prasad, Meilong Jiang, Sampath Rangarajan
  • Publication number: 20120069928
    Abstract: A system and method for providing at least one transmit precoder includes transforming at least one of a weighted sum-rate and max-min rate objective into two or more sub-problems by introducing at least one slack variable. The two or more sub-problems are iterated on a computer readable storage medium to provide at least one transmit precoder for each transmitter.
    Type: Application
    Filed: September 16, 2011
    Publication date: March 22, 2012
    Applicant: NEC Laboratories America, Inc.
    Inventors: Jubin Jose, Narayan Prasad, Mohammad A. Khojastepour, Sampath Rangarajan
  • Publication number: 20120069757
    Abstract: An inventive method for link adaptation for an LTE/LTE-A uplink with a turbo SIC receiver includes the steps of determining a precoding matrix index PMI and rank index RI selection for an LTE/LTE-A uplink when precoding of the uplink is enabled, responsive to channel state information of a subcarrier in the uplink; determining a decoding order for codewords in the uplink i) when the precoding of the uplink is not enabled and ii) if needed when the precoding of the uplink is enabled; performing modulation and coding scheme MCS assignment for the uplink based on a hard decision successive interference cancellation SIC rule (without intra-CW cancellation) or a partial hard decision successive interference cancellation SIC rule (with intra-CW cancellation), responsive to the determined PMI and RI selection; and influencing data transmission in the uplink responsive to the MCS assignment for detection by a turbo SIC receiver.
    Type: Application
    Filed: September 16, 2011
    Publication date: March 22, 2012
    Applicant: NEC LABORATORIES AMERICA, INC.
    Inventors: Meilong Jiang, Narayan Prasad, Guosen Yue, Sampath Rangarajan
  • Patent number: 8140024
    Abstract: Systems and methods for joint training of beam patterns in a system having a transmitter and a receiver. Initial transmit and receive beam pattern vectors are first selected. The beam pattern vectors are perturbed to produce a plurality of perturbed transmit and receive beam pattern vectors. A received signal power between the transmitter and the receiver is estimated for each combination of the perturbed transmit and the perturbed receive beam pattern vectors. The transmit and receive beam pattern vectors having a highest received signal power are applied to the transmitter and the receiver respectively. The perturbation, estimation, and application steps are iterated until the received signal power meets a convergence criterion.
    Type: Grant
    Filed: June 29, 2010
    Date of Patent: March 20, 2012
    Assignee: NEC Laboratories America, Inc.
    Inventors: Narayan Prasad, Kishore Ramachandran
  • Publication number: 20120057657
    Abstract: A multi-rank beamforming (MRBF) scheme in which the downlink channel is estimated and an optimal precoding matrix to be used by the MRBF transmitter is determined accordingly. The optimal precoding matrix is selected from a codebook of matrices having a recursive structure which allows for efficient computation of the optimal precoding matrix and corresponding Signal to Interference and Noise Ratio (SINR). The codebook also enjoys a small storage footprint. Due to the computational efficiency and modest memory requirements, the optimal precoding determination can be made at user equipment (UE) and communicated to a transmitting base station over a limited uplink channel for implementation over the downlink channel.
    Type: Application
    Filed: October 6, 2011
    Publication date: March 8, 2012
    Applicant: NEC LABORATORIES AMERICA, INC.
    Inventors: Mohammad A. Khojastepour, Narayan Prasad
  • Publication number: 20120057558
    Abstract: Methods and systems for conveying or transmitting to any given user in an OFDMA-MU-MIMO system scheduling information of other co-scheduled users to permit the user to perform error-correction on received data and/or interference reduction on its received signals. The scheduling information can include resource block assignment, modulation constellations employed, coding rates employed, power levels utilized and precoder matrix indices used. Further, the scheduling information can be conveyed in part through dedicated reference symbol layers or pilot streams. Moreover, a base station may transmit a preliminary estimate of the total number of users the base station expects to schedule, or an upper-bound on the total number of users, to the MU-MIMO users to permit the MU-MIMO users to determine preferred precoder matrix indices and indications of channel quality indices.
    Type: Application
    Filed: November 15, 2011
    Publication date: March 8, 2012
    Applicant: NEC LABORATORIES AMERICA, INC.
    Inventors: Narayan Prasad, Mohammad Ali Khojastepour, Meilong Jiang, Xiaodong Wang, Sampath Rangarajan
  • Publication number: 20120057557
    Abstract: Methods and systems for conveying or transmitting to any given user in an OFDMA-MU-MIMO system scheduling information of other co-scheduled users to permit the user to perform error-correction on received data and/or interference reduction on its received signals. The scheduling information can include resource block assignment, modulation constellations employed, coding rates employed, power levels utilized and precoder matrix indices used. Further, the scheduling information can be conveyed in part through dedicated reference symbol layers or pilot streams. Moreover, a base station may transmit a preliminary estimate of the total number of users the base station expects to schedule, or an upper-bound on the total number of users, to the MU-MIMO users to permit the MU-MIMO users to determine preferred precoder matrix indices and indications of channel quality indices.
    Type: Application
    Filed: November 15, 2011
    Publication date: March 8, 2012
    Applicant: NEC LABORATORIES AMERICA, INC.
    Inventors: Narayan Prasad, Mohammad Ali Khojastepour, Meilong Jiang, Xiaodong Wang, Sampath Rangarajan