Polar coded HARQ scheme with Chase combining

Abstract

Abstract-A hybrid automatic repeat request scheme with Chase combing (HARQ-CC) of polar codes is proposed. The existing analysis tools of the underlying rate-compatible punctured polar (RCPP) codes for additive white Gaussian noise (AWGN) channels are extended to Rayleigh fading channels. Then, an approximation bound of the throughput efficiency for the polar coded HARQ-CC scheme is derived. Utilizing this bound, the parameter configurations of the proposed scheme can be optimized. Simulation results show that, the proposed HARQ-CC scheme under a low-complexity SC decoding is only about 1.0dB away from the existing schemes with incremental redundancy (HARQ-IR). Compared with the polar coded HARQ-IR scheme, the proposed HARQ-CC scheme requires less retransmissions and has the advantage of good compatibility to other communication techniques.

Throughput-Based Design for Polar-Coded Modulation

“…Note that the complexity of BCJR with 5 iterations is more than that of SCLD. The comparison of the CC HARQ schemes proposed in [10] for SCD and [9] for SCLD and the CC HARQ design method introduced in Function CC-Binary-Design is provided in Fig. 8 for BPSK.…”

“…8 for BPSK. To construct the polar codes using algorithms provided in [9] and [10], the K at each SNR is considered the same as K found using Function CC-Binary-Design. The results indicate that the methods proposed in [9] and [10] with at least N − K times more complexity, cannot generate codes better than the Function CC-Binary-Design.…”

“…The comparison of NC-I and NC-D protocols with SCD and SCLD is presented in Fig. 9 Figure 8: Comparison of proposed NC, CC, and IR codes and code design methods in [10] and [9] for SCD and SCLD, respectively. SCD and SCLD achieves 69% and 73% of the capacity and NC-I with SCD and SCLD achieves 74% and 84% of the capacity, respectively.…”

“…In this case, limited feedback can be employed to achieve high throughput using AMC and HARQ protocols since the polar code graph is fixed and only the information-set should be modified when the SNR changes. Polar codes have also been designed to maximize the throughput of CC HARQ with SCD in [10] and with SCLD in [9] based on puncturing for a fixed message length and a BPSK constellation. These methods, given the message length K, require a full search over all puncturing lengths from 0 to N − K and thus require running the GA method for N − K times.…”

“…In addition, the LLR estimation for MSD is cheaper than for BICM which make it a promising technique for future wireless communication systems. Similar to BPSK modulation, designing multilevel polar codedmodulation (MLPCM) using the puncturing-based search methods in [9] and [10] is hard since they require a full search over all levels of a MLC. To design MLPCM, Trifonov in [7] suggested using the GA, but the full steps of design have not been presented in the literature.…”