Performance Analyses of Hybrid-ARQ in Fifth Generation New Radio

The main design criteria of the Fifth-generation (5G) New Radio (NR) specifications are to improve the requirements that enable high-speed, high-reliability, and low-latency communications. To achieve these design requirements, 5G NR specifications have defined the use of Low Density Parity Check (LDPC) codes channel coding scheme for data channels. LDPC codes have been chosen specifically because of their support for wide range of block sizes and code rates as well as their compatibility with Hybrid Automatic Repeat Request (HARQ) protocol. HARQ combines ARQ retransmission scheme with LDPC Forward Error Correction (FEC). In HARQ, a retransmitted code block consists of a different set of parity bits belonging to the same transport block and soft combining of previous copy and retransmitted copy is performed at the receiver. The new set of parity bits effectively reduces the coding rate for the FEC and achieve higher reliability. The objective of this research is to analyse the block error rate (BLER) and throughput performance of the HARQ protocol in 5G NR. The study, first, introduces LDPC codes and explains how LDPC rate matching is combined with HARQ protocol to improve performance. Then, BLER and throughput simulation results for various coding rates and transport block sizes in Tapped Delayed Line (TDL) channel models are presented. The results show that incremental redundancy combining in HARQ improves throughput, reliability, and latency.