778 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
Protein Kinase C-beta Dictates B Cell Fate by Regulating Mitochondrial Remodeling, Metabolic Reprogramming, and Heme Biosynthesis
PKCĪ²-null (Prkcbā/ā) mice are severely immunodeficient. Here we show that mice whose B cells lack PKCĪ² failed to form germinal centers and plasma cells, which undermined affinity maturation and antibody production in response to immunization. Moreover, these mice failed to develop plasma cells in response to viral infection. At the cellular level, we have shown that Prkcbā/āB cells exhibited defective antigen polarization and mTORC1 signaling. While altered antigen polarization impaired antigen presentation and likely restricted the potential of GC development, defective mTORC1 signaling impaired metabolic reprogramming, mitochondrial remodeling, and heme biosynthesis in these cells, which altogether overwhelmingly opposed plasma cell differentiation. Taken together, our study reveals mechanistic insights into the function of PKCĪ² as a key regulator of B cell polarity and metabolic reprogramming that instructs B cell fate. Lymphocyte activation is associated with major changes in metabolism. Tsui and colleagues demonstrate that PKCĪ² promotes metabolic reprogramming to drive effector fate decision in B cells
Non-Equilibrium Edge Channel Spectroscopy in the Integer Quantum Hall Regime
Heat transport has large potentialities to unveil new physics in mesoscopic
systems. A striking illustration is the integer quantum Hall regime, where the
robustness of Hall currents limits information accessible from charge
transport. Consequently, the gapless edge excitations are incompletely
understood. The effective edge states theory describes them as prototypal
one-dimensional chiral fermions - a simple picture that explains a large body
of observations and calls for quantum information experiments with quantum
point contacts in the role of beam splitters. However, it is in ostensible
disagreement with the prevailing theoretical framework that predicts, in most
situations, additional gapless edge modes. Here, we present a setup which gives
access to the energy distribution, and consequently to the energy current, in
an edge channel brought out-of-equilibrium. This provides a stringent test of
whether the additional states capture part of the injected energy. Our results
show it is not the case and thereby demonstrate regarding energy transport, the
quantum optics analogy of quantum point contacts and beam splitters. Beyond the
quantum Hall regime, this novel spectroscopy technique opens a new window for
heat transport and out-of-equilibrium experiments.Comment: 13 pages including supplementary information, Nature Physics in prin
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