Low-complexity, high-speed multi-size cyclic-shifter for quasi-cyclic LDPC decoder

Quasi-cyclic low-density parity check (QC-LDPC) codes are being widely used in communication standards, and the decoder of QC-LDPC codes requires a unique type of rotator. The unique rotator, called a multi-size cyclic-shifter (MSCS), should be able to rotate data with various sizes, and many structures have been proposed for the operation. A low-complexity, high-speed MSCS structure is proposed, in which a part of the previous smallest structure is replaced with a structure with less delay and comparable area. The synthesis results present that the proposed structure achieves not only the highest speed but also the lowest complexity after synthesis.