Combination of Multiple PBCH Blocks in 5G NR Systems

Physical broadcast channel (PBCH) in 5G new radio (NR) systems transmits system informations required for the user equipment (UE) to access the cell. In the long term evolution (LTE) system, multiple PBCHs are usually combined to improve demodulation performances in the case of poor channel conditions. However, in 5G NR systems, the payload of PBCH includes the system frame number and the payloads of multiple frames are not exactly consistent. Hence, it is impossible to adopt the same combination approach as that in LTE. In this paper, there proposes a method to solve the problem of combining multiple PBCH blocks in 5G NR systems. The main idea is to convert log likelihood ratios (LLRs) of all transmitted PBCH blocks into that of the first block and accumulate all LLRs at the receiving end. Then, an improved combination algorithm is considered to reduce the complexity. The simulation results show that the proposed combination algorithm can correctly combine multiple PBCH blocks. Besides, the improved combination algorithm with sort can also reduce the complexity.