2,919 research outputs found
On Path Memory in List Successive Cancellation Decoder of Polar Codes
Polar code is a breakthrough in coding theory. Using list successive
cancellation decoding with large list size L, polar codes can achieve excellent
error correction performance. The L partial decoded vectors are stored in the
path memory and updated according to the results of list management. In the
state-of-the-art designs, the memories are implemented with registers and a
large crossbar is used for copying the partial decoded vectors from one block
of memory to another during the update. The architectures are quite area-costly
when the code length and list size are large. To solve this problem, we propose
two optimization schemes for the path memory in this work. First, a folded path
memory architecture is presented to reduce the area cost. Second, we show a
scheme that the path memory can be totally removed from the architecture.
Experimental results show that these schemes effectively reduce the area of
path memory.Comment: 5 pages, 6 figures, 2 table
Low Complexity Belief Propagation Polar Code Decoders
Since its invention, polar code has received a lot of attention because of
its capacity-achieving performance and low encoding and decoding complexity.
Successive cancellation decoding (SCD) and belief propagation decoding (BPD)
are two of the most popular approaches for decoding polar codes. SCD is able to
achieve good error-correcting performance and is less computationally expensive
as compared to BPD. However SCDs suffer from long latency and low throughput
due to the serial nature of the successive cancellation algorithm. BPD is
parallel in nature and hence is more attractive for high throughput
applications. However since it is iterative in nature, the required latency and
energy dissipation increases linearly with the number of iterations. In this
work, we borrow the idea of SCD and propose a novel scheme based on
sub-factor-graph freezing to reduce the average number of computations as well
as the average number of iterations required by BPD, which directly translates
into lower latency and energy dissipation. Simulation results show that the
proposed scheme has no performance degradation and achieves significant
reduction in computation complexity over the existing methods.Comment: 6 page
An Implementation of List Successive Cancellation Decoder with Large List Size for Polar Codes
Polar codes are the first class of forward error correction (FEC) codes with
a provably capacity-achieving capability. Using list successive cancellation
decoding (LSCD) with a large list size, the error correction performance of
polar codes exceeds other well-known FEC codes. However, the hardware
complexity of LSCD rapidly increases with the list size, which incurs high
usage of the resources on the field programmable gate array (FPGA) and
significantly impedes the practical deployment of polar codes. To alleviate the
high complexity, in this paper, two low-complexity decoding schemes and the
corresponding architectures for LSCD targeting FPGA implementation are
proposed. The architecture is implemented in an Altera Stratix V FPGA.
Measurement results show that, even with a list size of 32, the architecture is
able to decode a codeword of 4096-bit polar code within 150 us, achieving a
throughput of 27MbpsComment: 4 pages, 4 figures, 4 tables, Published in 27th International
Conference on Field Programmable Logic and Applications (FPL), 201
Gradient Descent with Random Initialization: Fast Global Convergence for Nonconvex Phase Retrieval
This paper considers the problem of solving systems of quadratic equations,
namely, recovering an object of interest
from quadratic equations/samples
, . This
problem, also dubbed as phase retrieval, spans multiple domains including
physical sciences and machine learning.
We investigate the efficiency of gradient descent (or Wirtinger flow)
designed for the nonconvex least squares problem. We prove that under Gaussian
designs, gradient descent --- when randomly initialized --- yields an
-accurate solution in iterations
given nearly minimal samples, thus achieving near-optimal computational and
sample complexities at once. This provides the first global convergence
guarantee concerning vanilla gradient descent for phase retrieval, without the
need of (i) carefully-designed initialization, (ii) sample splitting, or (iii)
sophisticated saddle-point escaping schemes. All of these are achieved by
exploiting the statistical models in analyzing optimization algorithms, via a
leave-one-out approach that enables the decoupling of certain statistical
dependency between the gradient descent iterates and the data.Comment: Accepted to Mathematical Programmin
Female media use behavior and agreement with publicly promoted agenda-specific health messages.
This study set out to explore the relationship between female media use behavior and agreement with agenda-specific publicly promoted health messages. A random digit dial telephone cross-sectional survey was conducted using a nationally representative sample of female residents aged 25 and over. Respondents' agreement with health messages was measured by a six-item Health Information Scale (HIS). Data were analyzed using chi-square tests and multiple logistic regression. This survey achieved a response rate of 86% (n = 1074). In this study the longest duration of daily television news watching (OR = 2.32), high self-efficacy (OR = 1.56), and greater attention to medical and health news (OR = 5.41) were all correlates of greater agreement with the selected health messages. Surprisingly, Internet use was not significant in the final model. Many women that public health interventions need to be targeting are not receptive to health information that can be accessed through Internet searches. However, they may be more readily targeted by television campaigns. Agenda-specific public health campaigns aiming to empower women to serve as nodes of information transmission and achieve efficient trickle down through the family unit might do better to invest more heavily in television promotion
Parvovirus B19 infection presenting with severe erythroid aplastic crisis during pregnancy in a woman with autoimmune hemolytic anemia and alpha-thalassemia trait: a case report
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