ntLDPC_SDAOCT IP implements a 5G-NR Base Graph 1 systematic Encoder/Decoder based on Quasi-Cyclic LDPC Codes (QC-LDPC), with lifting size Zc=384 and Information Block Size 8448 bits. The implementation is based on block-structured LDPC codes with circular block matrices. The entire parity check matrix can be partitioned into an array of block matrices; each block matrix is either a zero matrix or a right cyclic shift of an identity matrix. The parity check matrix designed in this way can be conveniently represented by a base matrix represented by cyclic shifts. The main advantage of this feature is that it offers high throughput at low implementation complexity.
The ntLDPCE_SDAOCT Encoder IP implements a systematic LDPC Zc=384 encoder. Input and Output may be selected to be 32-bit or 128-bits per clock cycle prior to synthesis, while internal operations are 384-bits parallel per clock cycle. Depending on code rate, the respective amount of parity bits are generated and the first 2xZc=768 payload bits are discarded. There are 5 code rate modes of operation available (8448,8448)-bypass, (9984,8448)-0.8462, (11136,8448)-0.7586, (12672,8448)-0.6667 and (16896,8448)-0.5.
The ntLDPCD_SDAOCT Base Graph Decoder IP may optionally implement one of two approximations of the log-domain LDPC iterative decoding algorithm (Belief propagation) known as either Layered Min-Sum Algorithm (MS) or Layered Lambda-min Algorithm (LMIN). Variations of Layered MS available are Offset Min-Sum (OMS), Normalized Min-Sum (NMS), and Normalized Offset Min-Sum (NOMS). Selecting between these algorithms presents a decoding performance vs. system resources utilization trade-off. The ntLDPCD_SDAOCT decoder IP implements a Zc=384 parallel systematic LDPC layered decoder. Each layer corresponds to Zc=384 expanded rows of the original LDPC matrix. Each layer element corresponds to the active ZcxZc shifted identity submatrices within the layer. Each layer element is shifted accordingly and processed by the parallel decoding datapath unit, in order to update the layers LLR estimates and extrinsic information iteratively until the required number of decoding iterations has been run.
The decoder IP also features a powerful optional early termination (ET) criterion, to maintain practically equivalent error correction performance, while significantly increasing its throughput rate and/or reducing hardware cost. Additionally it reports how many decoding iterations have been performed when ET is activated, for system performance observation and calibration purposes. Finally a simple, yet robust, flow control handshaking mechanism is included in both IPs, which is used to communicate the IPs availability to adjacent system components. This logic is easily portable into any communication protocol, like AXI4 stream IF.
