1,061 research outputs found
Generalized Signal Richness Preservation Problem and Vandermonde-Form Preserving Matrices
In this paper, a theoretical problem arising in digital communications, namely the generalized signal richness preservation problem, is addressed and studied. In order to solve the problem, a special class of square matrices, namely the "Vandermonde-form preserving" (VFP) matrices, is introduced and found to be highly relevant to the problem. Several properties of VFP matrices are studied in detail. The necessary and sufficient conditions of the problem have been found, and a systematic proof is also presented
Low Complexity Blind Equalization for OFDM Systems with General Constellations
This paper proposes a low-complexity algorithm for blind equalization of data
in OFDM-based wireless systems with general constellations. The proposed
algorithm is able to recover data even when the channel changes on a
symbol-by-symbol basis, making it suitable for fast fading channels. The
proposed algorithm does not require any statistical information of the channel
and thus does not suffer from latency normally associated with blind methods.
We also demonstrate how to reduce the complexity of the algorithm, which
becomes especially low at high SNR. Specifically, we show that in the high SNR
regime, the number of operations is of the order O(LN), where L is the cyclic
prefix length and N is the total number of subcarriers. Simulation results
confirm the favorable performance of our algorithm
A Generalized Algorithm for Blind Channel Identification with Linear Redundant Precoders
It is well known that redundant filter bank precoders can be used for blind identification as well as equalization of FIR channels. Several algorithms have been proposed in the literature exploiting trailing zeros in the transmitter. In this paper we propose a generalized algorithm of which the previous algorithms are special cases. By carefully choosing system parameters, we can jointly optimize the system performance and computational complexity. Both time domain and frequency domain approaches of channel identification algorithms are proposed. Simulation results show that the proposed algorithm outperforms the previous ones when the parameters are optimally chosen, especially in time-varying channel environments. A new concept of generalized signal richness for vector signals is introduced of which several properties are studied
Quantifying identifiability in independent component analysis
We are interested in consistent estimation of the mixing matrix in the ICA
model, when the error distribution is close to (but different from) Gaussian.
In particular, we consider independent samples from the ICA model , where we assume that the coordinates of are independent
and identically distributed according to a contaminated Gaussian distribution,
and the amount of contamination is allowed to depend on . We then
investigate how the ability to consistently estimate the mixing matrix depends
on the amount of contamination. Our results suggest that in an asymptotic
sense, if the amount of contamination decreases at rate or faster,
then the mixing matrix is only identifiable up to transpose products. These
results also have implications for causal inference from linear structural
equation models with near-Gaussian additive noise.Comment: 22 pages, 2 figure
Jordan cells in logarithmic limits of conformal field theory
It is discussed how a limiting procedure of conformal field theories may
result in logarithmic conformal field theories with Jordan cells of arbitrary
rank. This extends our work on rank-two Jordan cells. We also consider the
limits of certain three-point functions and find that they are compatible with
known results. The general construction is illustrated by logarithmic limits of
(unitary) minimal models in conformal field theory. Characters of
quasi-rational representations are found to emerge as the limits of the
associated irreducible Virasoro characters.Comment: 16 pages, v2: discussion of three-point functions and characters
included; ref. added, v3: version to be publishe
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