543 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
Fast-SSC-Flip Decoding of Polar Codes
Polar codes are widely considered as one of the most exciting recent
discoveries in channel coding. For short to moderate block lengths, their
error-correction performance under list decoding can outperform that of other
modern error-correcting codes. However, high-speed list-based decoders with
moderate complexity are challenging to implement. Successive-cancellation
(SC)-flip decoding was shown to be capable of a competitive error-correction
performance compared to that of list decoding with a small list size, at a
fraction of the complexity, but suffers from a variable execution time and a
higher worst-case latency. In this work, we show how to modify the
state-of-the-art high-speed SC decoding algorithm to incorporate the SC-flip
ideas. The algorithmic improvements are presented as well as average
execution-time results tailored to a hardware implementation. The results show
that the proposed fast-SSC-flip algorithm has a decoding speed close to an
order of magnitude better than the previous works while retaining a comparable
error-correction performance.Comment: 5 pages, 3 figures, appeared at IEEE Wireless Commun. and Netw. Conf.
(WCNC) 201
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