Showing 2 results for M. Khademi
A.-R. Zirak, M. Khademi, M.-S. Mahloji,
Volume 4, Issue 1 (April 2008)
Abstract
We present an efficient method for the reduction of model equations in the
linearized diffuse optical tomography (DOT) problem. We first implement the maximum a
posteriori (MAP) estimator and Tikhonov regularization, which are based on applying
preconditioners to linear perturbation equations. For model reduction, the precondition is
split into two parts: the principal components are considered as reduced size
preconditioners applied to linear perturbation equations while the less important
components are marginalized as noise. Simulation results illustrate that the new proposed
method improves the image reconstruction performance and localizes the abnormal section
well with a better computational efficiency.
H. Ghanei Yakhdan, M. Khademi, J. Chitizadeh,
Volume 5, Issue 1 (March 2009)
Abstract
The performance of video transmission over wireless channels is limited by the
channel noise. Thus many error resilience tools have been incorporated into the MPEG-4
video compression method. In addition to these tools, the unequal error protection (UEP)
technique has been proposed to protect the different parts in an MPEG-4 video packet with
different channel coding rates based on the rate compatible punctured convolutional
(RCPC) codes. However, it is still not powerful enough for the noisy channels. To provide
more robust MPEG-4 video transmission, this paper proposes a modified unequal error
protection technique based on the mutual information of two video frames. In the proposed
technique, the dynamic channel coder rates are determined online based on the mutual
information of two consecutive video frames. With this technique, irregular and high
motion areas that are more sensitive to errors can get more protection. Simulation results
show that the proposed technique enhances both subjective visual quality and average peak
signal to noise ratio (PSNR) about 2.5 dB, comparing to the traditional UEP method.
