Multiple-Block Combined Decoding for Cell Search with Polar Codes

Polar codes have been applied in many applications due to the excellent decoding performance as well as relatively low encoding and decoding complexity. In the cell search procedure for the fifth generation (5G) systems, part of the common information bits (CIBs) is transmitted in successive transmission blocks. In this paper, multiple-block combined decoding (MBCD) schemes are proposed for both non-systematic and systematic polar codes to enhance cell search. In the proposed MBCD schemes, the log-likelihood ratios (LLRs) of the CIBs are combined to improve the reliabilities of the corresponding sub-channels. The common information sets are further optimized. For both schemes, low-complexity optimization methods are proposed. Meanwhile, the closed-form expression of block error rate (BLER) performance is derived, which is verified by simulation results. The simulation results show that the proposed MBCD schemes can significantly improve the BLER performance, leading to a latency reduction in cell search.