Showing papers by "Timothy A. Thomas published in 2004"

Method and apparatus for multi-antenna transmission

Abstract: In a multiple-input, multiple-output (MIMO) communication system, a method and apparatus for multi-antenna transmission In accordance with the preferred embodiment of the present invention a reduced number of transmit weight matrices are fed back to the transmitter Each transmit weight matrix is then applied to a plurality of subcarriers Because each transmit weight matrix is applied to more than one subcarrier, the amount of weight matrixs being fed back to the transmitter is greatly reduced

Method and apparatus for reducing interference within a communication system

Abstract: A method for reducing interference within a communication system is provided herein. A receiver (100), and method for operating a receiver are provided. The receiver operates by utilizing a filter bank (103-104) to partition a wide-band signal into smaller sub-bands. Interference suppression takes place individually on the sub-bands (frequency bands) instead of on the wideband signal as a whole. By using interference suppression on smaller sub-bands, interference suppression techniques can be utilized with less computational complexity than when performing interference suppression on the broadband signal as a whole.

OFDM channel estimation in the presence of interference

Abstract: We develop a frequency-domain channel estimation algorithm for single-user multiantenna orthogonal frequency division multiplexing (OFDM) wireless systems in the presence of synchronous interference In this case, the synchronous interferer's signal on each OFDM subcarrier is correlated in space with a rank one spatial covariance matrix In addition, the interferer's spatial covariance matrix is correlated in frequency based on the delay spread of the interferer's channel To reduce the number of unknown parameters we develop a structured covariance model that accounts for the structure resulting from the synchronous interference To further reduce the number of unknown parameters, we model the covariance matrix using a priori known set of frequency-dependent functions of joint (global) parameters We estimate the interference covariance parameters using a residual method of moments (RMM) estimator and the channel parameters by maximum likelihood (ML) estimation Since our RMM estimates are invariant to the mean, this approach yields simple noniterative estimates of the covariance parameters while having optimal statistical efficiency Hence, our algorithm outperforms existing channel estimators that do not account for the interference, and at the same time requires smaller number of pilots than the MANOVA method and thus has smaller overhead Numerical results illustrate the applicability of the proposed algorithm

PAPR reduction via a fixed frequency-domain weighting across multiple OFDM bauds

Abstract: The paper introduces a PAPR reduction technique for OFDM that uses the same PAPR reduction weights over multiple OFDM bauds. The PAPR reduction weights are applied on each subcarrier in the frequency domain and are designed to be either fixed over a group of subcarriers (in addition to multiple bauds) or parameterized by time taps. The advantage of these methods is to simplify channel estimation by not destroying the channel frequency correlation (for weights fixed over groups of subcarriers) or by increasing the effective length of the channel to be estimated (for the weights parameterized by time taps). Simulation results show up to a 6.0 dB decrease in PAPR where PAPR is measured over an OFDM baud.

Title GCL Sequences for Uplink Channel Sounding in TDD OFDMA Date Submitted

Abstract: This contribution proposes GCL sequences for use by the uplink channel sounding methodology described in Contribution C802.16e-04/263r1: “Uplink Channel Sounding for TDD-OFDMA”. Purpose Adoption of proposed changes into P802.16e Notice This document has been prepared to assist IEEE 802.16. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.16. Patent Policy and Procedures The contributor is familiar with the IEEE 802.16 Patent Policy and Procedures , including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.16 Working Group. The Chair will disclose this notification via the IEEE 802.16 web site .

Title Signaling Methodologies to Support Closed-Loop Transmit Processing in TDD-OFDMA Date Submitted

Abstract: Optional signaling enhancements to support downlink closed-loop transmission techniques in TDD OFDMA systems. Purpose Adoption of proposed changes into P802.16e Notice This document has been prepared to assist IEEE 802.16. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.16. Patent Policy and Procedures The contributor is familiar with the IEEE 802.16 Patent Policy and Procedures , including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.16 Working Group. The Chair will disclose this notification via the IEEE 802.16 web site .