Analysis of 5G LDPC Codes Rate-Matching Design

This paper analyzes the rate-matching algorithms for LDPC codes in 5G New Radio (NR) framework. Key features of NR LDPC rate-matching design includes flexible bit-selection based on circular buffer operation, enhanced decoding latency via code construction based on a single-parity-check extension from a high rate code, systematic bit puncturing, and support for limited buffer rate-matching (LBRM). IR-HARQ is supported via several redundancy versions (RVs) defined non-uniformly over the transmit circular buffer, enabling possibility of multiple self-decodable RVs. This paper, discusses NR LDPC structure, design, and its key features, followed by an in-depth investigation of IR-HARQ functionality, rate-matching, and (re-)transmissions via different RV ordering selections. Performance of single transmissions, as well as re-transmissions using different schemes are studied and evaluated using throughput and BLER metrics. This study attests the flexibility and robustness of NR LDPC design in addition to efficient support of IR-HARQ operation.