  Polar codes are the first provable capacity-achieving forward error
correction (FEC) codes. In general polar codes can be decoded via either
successive cancellation (SC) or belief propagation (BP) decoding algorithm.
However, to date practical applications of polar codes have been hindered by
the long decoding latency and limited error-correcting performance problems. In
this paper, based on our recent proposed early stopping criteria for the BP
algorithm, we propose a hybrid BP-SC decoding scheme to improve the decoding
performance of polar codes with relatively short latency. Simulation results
show that, for (1024, 512) polar codes the proposed approach leads to at least
0.2dB gain over the BP algorithm with the same maximum number of iterations for
the entire SNR region, and also achieves 0.2dB decoding gain over the BP
algorithm with the same worst-case latency in the high SNR region. Besides,
compared to the SC algorithm, the proposed scheme leads to 0.2dB gain in the
medium SNR region with much less average decoding latency. In addition, we also
propose the low-complexity unified hardware architecture for the hybrid
decoding scheme, which is able to implement SC and BP algorithms using same
hardware.
