7 research outputs found
Belief Propagation Decoding of Polar Codes on Permuted Factor Graphs
We show that the performance of iterative belief propagation (BP) decoding of
polar codes can be enhanced by decoding over different carefully chosen factor
graph realizations. With a genie-aided stopping condition, it can achieve the
successive cancellation list (SCL) decoding performance which has already been
shown to achieve the maximum likelihood (ML) bound provided that the list size
is sufficiently large. The proposed decoder is based on different realizations
of the polar code factor graph with randomly permuted stages during decoding.
Additionally, a different way of visualizing the polar code factor graph is
presented, facilitating the analysis of the underlying factor graph and the
comparison of different graph permutations. In our proposed decoder, a high
rate Cyclic Redundancy Check (CRC) code is concatenated with a polar code and
used as an iteration stopping criterion (i.e., genie) to even outperform the
SCL decoder of the plain polar code (without the CRC-aid). Although our
permuted factor graph-based decoder does not outperform the SCL-CRC decoder, it
achieves, to the best of our knowledge, the best performance of all iterative
polar decoders presented thus far.Comment: in IEEE Wireless Commun. and Networking Conf. (WCNC), April 201
CRC-Aided Belief Propagation List Decoding of Polar Codes
Although iterative decoding of polar codes has recently made huge progress
based on the idea of permuted factor graphs, it still suffers from a
non-negligible performance degradation when compared to state-of-the-art
CRC-aided successive cancellation list (CA-SCL) decoding. In this work, we show
that iterative decoding of polar codes based on the belief propagation list
(BPL) algorithm can approach the error-rate performance of CA-SCL decoding and,
thus, can be efficiently used for decoding the standardized 5G polar codes.
Rather than only utilizing the cyclic redundancy check (CRC) as a stopping
condition (i.e., for error-detection), we also aim to benefit from the
error-correction capabilities of the outer CRC code. For this, we develop two
distinct soft-decision CRC decoding algorithms: a Bahl-Cocke-Jelinek-Raviv
(BCJR)-based approach and a sum product algorithm (SPA)-based approach.
Further, an optimized selection of permuted factor graphs is analyzed and shown
to reduce the decoding complexity significantly. Finally, we benchmark the
proposed CRC-aided belief propagation list (CA-BPL) to state-of-the-art 5G
polar codes under CA-SCL decoding and, thereby, showcase an error-rate
performance not just close to the CA-SCL but also close to the maximum
likelihood (ML) bound as estimated by ordered statistic decoding (OSD).Comment: Submitted to IEEE for possible publicatio
The Effect of Error Propagation on the Performance of Polar Codes Utilizing Successive Cancellation Decoding Algorithm
In this paper, we discuss and analyze the effect of error propagation on the performance polar codes decoded using the successive cancellation algorithm. We show that error propagation due to erroneous bit decision is a catastrophic issue for the successive cancellation decoding of polar codes. Even a wrong decision on a single bit may cause an abundance of successor bits to be wrongly decoded. Furthermore, we observe that the performance of polar codes is significantly improved if even single bit errors are detected and corrected before the decoding of successor bits