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Journals and Conferences
This paper proposes a blind channel estimation method in the context of a multiuser orthogonal-frequency-domain-multiplexing (OFDM) system, where each user transmits utilizing all available subcarriers. A linear nonredundant block precoding scheme is applied at the input of the OFDM system. The precoding spreads the symbols of each user over all… (More)
Radio Interferometry is an essential method for astronomical observations. Self-calibration techniques have increased the quality of the radio astronomical observations (and hence the science) by orders of magnitude. Recently, there is a drive towards sensor arrays built using inexpensive hardware and distributed over a wide area acting as radio… (More)
Cosmic rays are the highest-energy particles found in nature. Measurements of the mass composition of cosmic rays with energies of 10(17)-10(18) electronvolts are essential to understanding whether they have galactic or extragalactic sources. It has also been proposed that the astrophysical neutrino signal comes from accelerators capable of producing cosmic… (More)
The main objective of this work is to accelerate the MaximumLikelihood (ML) estimation procedure for radio interferometric direction dependent self-calibration. We introduce the OS-SAGE radio interferometric calibration method, as a combination of the Ordered-Subsets (OS) method with the Space Alternating Generalized Expectation maximization (SAGE)… (More)
Existing calibration algorithms in radio interferometry implicitly assume the noise to be Gaussian. However, outliers in the data due to interference or due to errors in the sky model would have adverse effects on processing based on a Gaussian noise model. Most of the shortcomings of calibration such as the loss in flux or coherence, and the appearance of… (More)
We present an efficient method to generate large simulations of the Epoch of Reionization (EoR) without the need for a full 3-dimensional radiative transfer code. Large dark-matteronly simulations are post-processed to produce maps of the redshifted 21cm emission from neutral hydrogen. Dark matter haloes are embedded with sources of radiation whose… (More)
We consider user cooperation under multipath channels using OFDM modulation. We propose and analyse the performance of an amplify and forward cooperation scheme using OFDM. We show the performance improvement in terms of channel capacity and diversity both analytically and using simulations.
We consider the problem of MIMO channel estimation subject to a given error and delay constraints. Our objective is to minimize the energy spent during the channel estimation phase, which includes transmission of training symbols, storage of those symbols at the receiver, and also channel estimation at the receiver. We develop a model that is independent of… (More)
We consider a multiuser OFDM system, and propose a novel approach for blind channel estimation. Each user information signal is linearly precoded before OFDM modulation. The receiver uses an antenna array. Using cross-correlations of the blocks received at the array elements leads to the estimation of the underlying channels within a scaling ambiguity.
Cooperative transmission schemes have recently been proposed to improve the uplink performance of wireless communications systems by increasing diversity without requiring use of multiple transmit antennas. We here propose a novel cooperative scheme that performs distributed coding of user data, uses only one channel per user and allows a flexible tradeoff… (More)