  It is known that the bit errors of polar codes with successive cancellation
(SC) decoding are coupled. However, existing concatenation schemes of polar
codes with other error correction codes rarely take this coupling effect into
consideration. To achieve a better error performance of concatenated systems
with polar codes as inner codes, one can divide all bits in an outer block into
different polar blocks to completely de-correlate the possible coupled errors
in the transmitter side. We call this interleaving a blind interleaving (BI)
which serves as a benchmark. Two BI schemes, termed BI-DP and BI-CDP, are
proposed in the paper. To better balance performance, memory size, and the
decoding delay from the de-interleaving, a novel interleaving scheme, named the
correlation-breaking interleaving (CBI), is proposed. The CBI breaks the
correlated information bits based on the error correlation pattern proposed and
proven in this paper. The proposed CBI scheme is general in the sense that any
error correction code can serve as the outer code. In this paper, Low-Density
Parity-Check (LDPC) codes and BCH codes are used as two examples of the outer
codes of the interleaving scheme. The CBI scheme 1) can keep the simple SC
polar decoding while achieving a better error performance than the
state-of-the-art (SOA) direct concatenation of polar codes with LDPC codes and
BCH codes; 2) achieves a comparable error performance as the BI-DP scheme with
a smaller memory size and a shorter decoding delay. Numerical results are
provided to verify the performance of the BI schemes and the CBI scheme.
