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).

  • Signaling of mixture combination sets
    Patent number: 8472554
    Abstract: Systems and methods for conveying and determining modulations schemes employed by co-scheduled users are disclosed. In addition, methods and systems for designing signaling schemes that convey such information are also disclosed. In accordance with one method, an index is received and a table of indices in which the received index denotes a plurality of different sets of modulation schemes is referenced. Further, one or more modulation schemes of at least one co-scheduled user is determined based on the referencing. In addition, data signals are received and are processed by utilizing the one or more modulation schemes.
    Type: Grant
    Filed: April 18, 2011
    Date of Patent: June 25, 2013
    Assignee: NEC Laboratories America, Inc.
    Inventors: Mohammad A. Khojastepour, Narayan Prasad, Sampath Rangarajan
  • Max-log stack decoder
    Patent number: 8432989
    Abstract: A method for demodulating signals in a multi-input multi-output (MIMO) receiver includes obtaining a transformed vector by a coordinate transformation of a received observation vector using a unitary matrix determined through QR decomposition of an estimated channel matrix; maintaining a list containing nodes along with a cost metric for each node; using the list to generate soft-outputs in the form of log-likelihood ratios (LLRs) for selected symbols of interest, based on the transformed vector and a lower triangular matrix determined through QR decomposition of the estimated channel matrix and the constellations to which the input symbols belong.
    Type: Grant
    Filed: August 28, 2009
    Date of Patent: April 30, 2013
    Assignee: NEC Laboratories America, Inc.
    Inventors: Narayan Prasad, Xiaodong Wang, Sampath Rangarajan
  • LTE and LTE-Advanced UL Power Control
    Publication number: 20130072210
    Abstract: A method for LTE and LTE-A uplink power control includes open loop power control where user equipment UE measures downlink pathloss which is sent to an eNodeB that determines uplink UL transmit power based on the downlink pathloss.
    Type: Application
    Filed: September 14, 2012
    Publication date: March 21, 2013
    Applicant: NEC LABORATORIES AMERICA, INC.
    Inventors: Honghai Zhang, Narayan Prasad, Sampath Rangarajan
  • Distributed message-passing based resource allocation in wireless systems
    Patent number: 8385364
    Abstract: Systems and methods are disclosed to allocate resources in discrete Fourier transform spread orthogonal frequency division multiple access (DFT-S-OFDMA) networks, which involve determining a reward for each user when assigned a frequency chunk (FC) of subcarriers, where each FC is a set of contiguous subcarriers; splitting each user into one or more sub-users, with each sub-user having identical rewards; and assigning resources with a message-passing based FC allocation.
    Type: Grant
    Filed: August 28, 2009
    Date of Patent: February 26, 2013
    Assignee: NEC Laboratories America, Inc.
    Inventors: Kai Yang, Xiaodong Wang, Narayan Prasad
  • Robust linear precoder designs for multi-cell downlink transmission
    Patent number: 8385454
    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: Grant
    Filed: September 9, 2010
    Date of Patent: February 26, 2013
    Assignee: NEC Laboratories America, Inc.
    Inventors: Ali Tajer, Narayan Prasad, Xiaodong Wang, Sampath Rangarajan
  • Codebook with nested structure
    Patent number: 8374562
    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: June 15, 2012
    Date of Patent: February 12, 2013
    Assignee: NEC Laboratories America, Inc.
    Inventors: Mohammad Ali Khojastepour, Narayan Prasad
  • Codebook with nested structure
    Patent number: 8346193
    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: July 12, 2012
    Date of Patent: January 1, 2013
    Assignee: NEC Laboratories America, Inc.
    Inventors: Mohammad Ali Khojastepour, Narayan Prasad
  • Distributed inter-cell interference mitigation in OFDMA multi-carrier wireless data networks
    Patent number: 8335534
    Abstract: Systems and methods are disclosed for transmission with a plurality of base stations (BSs) in a wireless cellular data network where one BS communicates with neighboring BSs by determining a binary or discrete new power level on each subchannel to determine a weighted sum modified rates of a BS and in-neighbor BSs; and resolving concurrent power update in each BS in a distributed manner.
    Type: Grant
    Filed: February 18, 2009
    Date of Patent: December 18, 2012
    Assignee: NEC Laboratories America, Inc.
    Inventors: Hoonghai Zhang, Sampath Rangarajan, Luca Venturino, Narayan Prasad
  • Multi-User Multiple Input Multiple Output Wireless Communications
    Publication number: 20120294381
    Abstract: A method implemented in a user equipment used in a multi-user multiple input multiple output (MU-MIMO) wireless communications system is disclosed. The method includes receiving from a base station an indication of a first modulation type for the user equipment, receiving a first data signal for the user equipment, receiving a second data signal for a co-scheduled user equipment, where a second modulation type for the co-scheduled user equipment is unknown to the user equipment, and deciding the second modulation type. Other methods, systems, and apparatuses also are disclosed.
    Type: Application
    Filed: July 31, 2012
    Publication date: November 22, 2012
    Applicant: NEC LABORATORIES AMERICA, INC.
    Inventors: NARAYAN PRASAD, GUOSEN YUE, MOHAMMAD A. KHOJASTEPOUR, MEILONG JIANG, SAMPATH RANGARAJAN
  • Scheduling Information of Overlapping Co-Scheduled Users in an OFDMA-MU-MIMO System
    Publication number: 20120281662
    Abstract: A user equipment (UE) used in a multi-user (MU)-multiple input multiple output (MIMO) orthogonal frequency division multiple access (OFDMA) system is disclosed. The UE includes a receiving unit to receive from a base station an indication of an estimate of or an upper-bound on the total number of MU-MIMO user equipments (|S|) that are scheduled on a sub-band by the base station, wherein the sub-band includes one or more resource units, a calculation unit to calculate channel quality based on the indication of the estimate of or the upper-bound on the total number of MU-MIMO user equipments, and a transmission unit to transmit to the base station an indication of the channel quality. Other methods and apparatuses also are disclosed.
    Type: Application
    Filed: July 16, 2012
    Publication date: November 8, 2012
    Applicant: NEC LABORATORIES AMERICA, INC.
    Inventors: Narayan Prasad, Mohammad Ali Khojastepour, Meilong Jiang, Xiaodong Wang, Sampath Rangarajan
  • RESOURCE ALLOCATION IN MIMO MULTI-CELLULAR NETWORKS VIA SUBMODULAR OPTIMIZATION
    Publication number: 20120275402
    Abstract: A method to allocate resources in a wireless MIMO system, by enforcing per-cell orthogonality to avoid intra-cell interference; and allocating resources based on interference handling.
    Type: Application
    Filed: April 27, 2012
    Publication date: November 1, 2012
    Applicant: NEC LABORATORIES AMERICA, INC.
    Inventors: Narayan Prasad, Honghai Zhang, Luca Venturino, Jubin Jose, Sampath Rangarajan
  • Codebook With Nested Structure
    Publication number: 20120275536
    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: July 12, 2012
    Publication date: November 1, 2012
    Applicant: NEC Laboratories America, Inc.
    Inventors: Mohammad A. Khojastepour, Narayan Prasad
  • Enhancement of Download Multi-User Multiple-Input Multiple-Output Wireless Communications
    Publication number: 20120275314
    Abstract: A method implemented in a user equipment configured to be used in a multi-user (MU) multiple-input multiple-output (MIMO) wireless communications system is disclosed. In an aspect, the user equipment transmits to a base station a first channel state information (CSI) report determined according to a single-user (SU) MIMO rule and a second CSI report determined according to an MU-MIMO rule.
    Type: Application
    Filed: April 26, 2012
    Publication date: November 1, 2012
    Applicant: NEC LABORATORIES AMERICA, INC.
    Inventors: Narayan Prasad, Guosen Yue, Meilong Jiang, Mohammad A. Khojastepour, Sampath Rangarajan
  • Enhancement of Download Multi-User Multiple-Input Multiple-Output Wireless Communications
    Publication number: 20120275313
    Abstract: A method implemented in a user equipment configured to be used in a multi-user (MU) multiple-input multiple-output (MIMO) wireless communications system is disclosed. In an aspect, the user equipment transmits to a base station a first channel state information (CSI) report determined according to a single-user (SU) MIMO rule and a second CSI report based on a residual error.
    Type: Application
    Filed: April 26, 2012
    Publication date: November 1, 2012
    Applicant: NEC LABORATORIES AMERICA, INC.
    Inventors: Narayan Prasad, Guosen Yue, Meilong Jiang, Mohammad A. Khojastepour, Sampath Rangarajan
  • Polmux-OFDM-DD Transmitter and Receiver for Reduced Complexity and Overhead in Optical Access/Metro Transmission
    Publication number: 20120263467
    Abstract: An optical communication system includes a polarization multiplexed orthogonal frequency-division multiplexing POLMUX-OFDM transmitter for generating a POLMUX-OFDM double sideband signal, an optical processing path for processing the double sideband signal from the transmitter; an analog-to-digital convert ADC-OFDM receiver coupled to the optical processing path for receiving the double sideband signal processed by the optical path; and a block-diagonal multiple-input multiple-output MIMO equalizer responsive to the receiver for enabling correct operation for a completely random incoming signal polarization state without adaptive polarization control at said receiver, which enables complexity.
    Type: Application
    Filed: April 13, 2012
    Publication date: October 18, 2012
    Applicant: NEC Laboratories America, Inc.
    Inventors: Neda Cvijetic, Yue-Kai Huang, Narayan Prasad, Ting Wang
  • Codebook With Nested Structure
    Publication number: 20120257685
    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: June 15, 2012
    Publication date: October 11, 2012
    Applicant: NEC LABORATORIES AMERICA, INC.
    Inventors: Mohammad A. Khojastepour, Narayan Prasad
  • Method for Improving Multiuser MIMO Downlink Transmissions
    Publication number: 20120257664
    Abstract: A method for improving multiple-input multiple-output MIMO downlink transmissions includes obtaining a channel state information CSI report including preferred matrix index PMI for precoding, channel quality index CQI and rank index RI at a base station from user terminals through a channel feedback; applying selectively a signal-to-interference-plus-noise-ratio SINR offset to a SINR of said CSI report; applying selectively a rate matching responsive to SINR offset or the CSI report; and controlling or adjusting the SINR offset.
    Type: Application
    Filed: April 6, 2012
    Publication date: October 11, 2012
    Applicant: NEC LABORATORIES AMERICA, INC.
    Inventors: Guosen Yue, Narayan Prasad, Meilong Jiang, Mohammad A. Khojastepour, Sampath Rangarajan
  • Codebook with nested structure
    Patent number: 8285232
    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: October 9, 2012
    Assignee: NEC Laboratories America, Inc.
    Inventors: Mohammad A. Khojastepour, Narayan Prasad
  • Efficient Square-Root Free 2 Symbol Max-Log Receiver
    Publication number: 20120250804
    Abstract: The present invention employs a look up table based implementation for the metric computations which eliminate redundancy and substantially reduce the number of multiplications. Moreover, inventive method exploits the fact that the un-normalized constellation symbols are complex integers so that the product of a real-number and an un-normalized constellation symbol can be implemented by only additions. The inventive method also enables a greater efficiency for whitening colored noise prior to demodulation, one of which involves no square-root operation.
    Type: Application
    Filed: March 29, 2012
    Publication date: October 4, 2012
    Applicant: NEC LABORATORIES AMERICA, INC.
    Inventors: Narayan Prasad, Neda Cvijetic, Sampath Rangarajan, Ting Wang
  • COMPUTATIONALLY-EFFICIENT EQUALIZATION IN POLMUX OFDM TRANSMISSION WITH DIRECT-DETECTION VIA JOINT TRANSMITTER AND RECEIVER PROCESSING
    Publication number: 20120251110
    Abstract: A method for joint transmitter and receiver processing for computationally efficient equalization in polarization multiplexed (POLMUX) optical orthogonal frequency division multiplexed (OFDM) transmission with direct detection.
    Type: Application
    Filed: March 31, 2011
    Publication date: October 4, 2012
    Applicant: NEC Laboratories America, Inc.
    Inventors: Neda CVIJETIC, Narayan PRASAD, Dayou QIAN, Ting WANG