1,095 research outputs found
Threshold-Based Fast Successive-Cancellation Decoding of Polar Codes
Fast SC decoding overcomes the latency caused by the serial nature of the SC
decoding by identifying new nodes in the upper levels of the SC decoding tree
and implementing their fast parallel decoders. In this work, we first present a
novel sequence repetition node corresponding to a particular class of bit
sequences. Most existing special node types are special cases of the proposed
sequence repetition node. Then, a fast parallel decoder is proposed for this
class of node. To further speed up the decoding process of general nodes
outside this class, a threshold-based hard-decision-aided scheme is introduced.
The threshold value that guarantees a given error-correction performance in the
proposed scheme is derived theoretically. Analysis and hardware implementation
results on a polar code of length with code rates , , and
show that our proposed algorithm reduces the required clock cycles by up
to , and leads to a improvement in the maximum operating frequency
compared to state-of-the-art decoders without tangibly altering the
error-correction performance. In addition, using the proposed threshold-based
hard-decision-aided scheme, the decoding latency can be further reduced by
at ~dB.Comment: 14 pages, 8 figures, 5 tables, submitted to IEEE Transactions on
Communication
A Split-Reduced Successive Cancellation List Decoder for Polar Codes
This paper focuses on low complexity successive cancellation list (SCL)
decoding of polar codes. In particular, using the fact that splitting may be
unnecessary when the reliability of decoding the unfrozen bit is sufficiently
high, a novel splitting rule is proposed. Based on this rule, it is conjectured
that, if the correct path survives at some stage, it tends to survive till
termination without splitting with high probability. On the other hand, the
incorrect paths are more likely to split at the following stages. Motivated by
these observations, a simple counter that counts the successive number of
stages without splitting is introduced for each decoding path to facilitate the
identification of correct and incorrect path. Specifically, any path with
counter value larger than a predefined threshold \omega is deemed to be the
correct path, which will survive at the decoding stage, while other paths with
counter value smaller than the threshold will be pruned, thereby reducing the
decoding complexity. Furthermore, it is proved that there exists a unique
unfrozen bit u_{N-K_1+1}, after which the successive cancellation decoder
achieves the same error performance as the maximum likelihood decoder if all
the prior unfrozen bits are correctly decoded, which enables further complexity
reduction. Simulation results demonstrate that the proposed low complexity SCL
decoder attains performance similar to that of the conventional SCL decoder,
while achieving substantial complexity reduction.Comment: Accepted for publication in IEEE Journal on Selected Areas in
Communications - Special Issue on Recent Advances In Capacity Approaching
Code
Improved Successive Cancellation Decoding of Polar Codes
As improved versions of successive cancellation (SC) decoding algorithm,
successive cancellation list (SCL) decoding and successive cancellation stack
(SCS) decoding are used to improve the finite-length performance of polar
codes. Unified descriptions of SC, SCL and SCS decoding algorithms are given as
path searching procedures on the code tree of polar codes. Combining the ideas
of SCL and SCS, a new decoding algorithm named successive cancellation hybrid
(SCH) is proposed, which can achieve a better trade-off between computational
complexity and space complexity. Further, to reduce the complexity, a pruning
technique is proposed to avoid unnecessary path searching operations.
Performance and complexity analysis based on simulations show that, with proper
configurations, all the three improved successive cancellation (ISC) decoding
algorithms can have a performance very close to that of maximum-likelihood (ML)
decoding with acceptable complexity. Moreover, with the help of the proposed
pruning technique, the complexities of ISC decoders can be very close to that
of SC decoder in the moderate and high signal-to-noise ratio (SNR) regime.Comment: This paper is modified and submitted to IEEE Transactions on
Communication
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