Low density parity check (LDPC) codes are a class of error correction codes. A structured class of LDPC codes known as quasi cyclic LDPC (QC-LDPC) codes have been selected for the data channels of the new generation of cellular communication standards known as 5G New Radio (NR). LDPC codes are generally decoded using iterative message passing algorithms that yield performance that is close to capacity. Previous research has shown that iterative decoders are vulnerable to certain combinatorial objects in the code’s structure resulting in an error floor, a typically abrupt change of slope in the frame error rate performance curve. These substructures are called absorbing sets; specifically, elementary absorbing sets are found to be particularly impactful for structured LDPC codes. The main focus of this thesis is investigating the decoder performance curve of the 5G NR code and identifying the error prone elementary absorbing sets that contribute to its error floor. In this thesis, we introduce the 5G NR QC-LDPC code and its characteristics; we talk about the measures taken in the transmitter to improve the code’s performance such as puncturing and shortening. We will see how practical limitations such as finite precision (quantization) of LLR values affects the performance in the error floor. We also devise an algorithm to identify all the (elementary) absorbing sets in the code.
Absorbing Sets and Error Floor Performance of the 5G New Radio CodeMaster's Thesis
|Contributor||Thomas E. Fuja, Research Director|
|Degree Level||Master's Thesis|
|Degree Discipline||Electrical Engineering|
|Degree Name||Master of Science|
|Departments and Units|