621 research outputs found
Reduced Path Successive Cancellation List Decoding for Polar Codes
Polar codes have already been adopted in 5G systems to improve error performance. Successive cancellation list (SCL) decoding is usually used at the decoder and involves lengthy processing. Therefore, different methods have been developed to reduce an SCL decoder’s complexity. In this paper, a reduced path successive cancellation list (RP-SCL) decoder is presented to reduce this complexity, where some decoding paths are pruned. The pruning is achieved by using three different thresholds: two for the path metric and one for the pruning depth in the decoding tree. An optimization procedure is considered to determine the optimum settings for these thresholds. The simulation tests are carried out over models of an additive white Gaussian noise channel and a fading channel by using 5G environments. The results reveal that the proposed RP-SCL decoder provides the complexity reduction in terms of the average number of processed paths at high SNR. Additionally, the computational complexity and the memory requirements decrease
Symbol-Based Successive Cancellation List Decoder for Polar Codes
Polar codes is promising because they can provably achieve the channel
capacity while having an explicit construction method. Lots of work have been
done for the bit-based decoding algorithm for polar codes. In this paper,
generalized symbol-based successive cancellation (SC) and SC list decoding
algorithms are discussed. A symbol-based recursive channel combination
relationship is proposed to calculate the symbol-based channel transition
probability. This proposed method needs less additions than the
maximum-likelihood decoder used by the existing symbol-based polar decoding
algorithm. In addition, a two-stage list pruning network is proposed to
simplify the list pruning network for the symbol-based SC list decoding
algorithm.Comment: Accepted by 2014 IEEE Workshop on Signal Processing Systems (SiPS
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
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
A Reduced Latency List Decoding Algorithm for Polar Codes
Long polar codes can achieve the capacity of arbitrary binary-input discrete
memoryless channels under a low complexity successive cancelation (SC) decoding
algorithm. But for polar codes with short and moderate code length, the
decoding performance of the SC decoding algorithm is inferior. The cyclic
redundancy check (CRC) aided successive cancelation list (SCL) decoding
algorithm has better error performance than the SC decoding algorithm for short
or moderate polar codes. However, the CRC aided SCL (CA-SCL) decoding algorithm
still suffer from long decoding latency. In this paper, a reduced latency list
decoding (RLLD) algorithm for polar codes is proposed. For the proposed RLLD
algorithm, all rate-0 nodes and part of rate-1 nodes are decoded instantly
without traversing the corresponding subtree. A list maximum-likelihood
decoding (LMLD) algorithm is proposed to decode the maximum likelihood (ML)
nodes and the remaining rate-1 nodes. Moreover, a simplified LMLD (SLMLD)
algorithm is also proposed to reduce the computational complexity of the LMLD
algorithm. Suppose a partial parallel list decoder architecture with list size
is used, for an (8192, 4096) polar code, the proposed RLLD algorithm can
reduce the number of decoding clock cycles and decoding latency by 6.97 and
6.77 times, respectively.Comment: 7 pages, accepted by 2014 IEEE International Workshop on Signal
Processing Systems (SiPS
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