562 research outputs found
Low-Complexity Puncturing and Shortening of Polar Codes
In this work, we address the low-complexity construction of shortened and
punctured polar codes from a unified view. While several independent puncturing
and shortening designs were attempted in the literature, our goal is a unique,
low-complexity construction encompassing both techniques in order to achieve
any code length and rate. We observe that our solution significantly reduces
the construction complexity as compared to state-of-the-art solutions while
providing a block error rate performance comparable to constructions that are
highly optimized for specific lengths and rates. This makes the constructed
polar codes highly suitable for practical application in future communication
systems requiring a large set of polar codes with different lengths and rates.Comment: to appear in WCNC 2017 - "Polar Coding in Wireless Communications:
Theory and Implementation" Worksho
Optimizing MDS Codes for Caching at the Edge
In this paper we investigate the problem of optimal MDS-encoded cache
placement at the wireless edge to minimize the backhaul rate in heterogeneous
networks. We derive the backhaul rate performance of any caching scheme based
on file splitting and MDS encoding and we formulate the optimal caching scheme
as a convex optimization problem. We then thoroughly investigate the
performance of this optimal scheme for an important heterogeneous network
scenario. We compare it to several other caching strategies and we analyze the
influence of the system parameters, such as the popularity and size of the
library files and the capabilities of the small-cell base stations, on the
overall performance of our optimal caching strategy. Our results show that the
careful placement of MDS-encoded content in caches at the wireless edge leads
to a significant decrease of the load of the network backhaul and hence to a
considerable performance enhancement of the network.Comment: to appear in Globecom 201
Pareto Smoothed Importance Sampling
Importance weighting is a general way to adjust Monte Carlo integration to
account for draws from the wrong distribution, but the resulting estimate can
be noisy when the importance ratios have a heavy right tail. This routinely
occurs when there are aspects of the target distribution that are not well
captured by the approximating distribution, in which case more stable estimates
can be obtained by modifying extreme importance ratios. We present a new method
for stabilizing importance weights using a generalized Pareto distribution fit
to the upper tail of the distribution of the simulated importance ratios. The
method, which empirically performs better than existing methods for stabilizing
importance sampling estimates, includes stabilized effective sample size
estimates, Monte Carlo error estimates and convergence diagnostics.Comment: Major revision: 1) proofs for consistency, finite variance, and
asymptotic normality, 2) justification of k<0.7 with theoretical
computational complexity analysis, 3) major rewrit
Performance Monitoring in Depression: Behavioural and Neurophysiological Correlates of Feedback Processing
Unipolar major depressive disorder (MDD) is a common mental health disorder which has a lifetime prevalence of about 19% in the Netherlands (De Graaf et al., 2010). This means that almost 1 out of 5 persons will experience a depressive episode at some point in their lives. Women are almost twice as often affected as men (Bijl et al., 1997, De Graaf et al., 2010). Worldwide, about 121 million of people are affected by depression, and it is one of the leading causes of disability (WHO, 2011)
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