Layered Decoding of Non-Layered LDPC Codes

Abstract

The principle of "layered decoding" is extended to those codes not especially conceived for this practice, as to benefit of the increased convergence speed. Two different strategies are considered to solve the problem and the related architectures presented: one more straightforward, and based on the use for the soft output of the last value originated in a layer; the other based on the computation of the variation (or delta) of the soft output metrics to allow concurrent updates. Then, as in architecture-first approach, the performance are assessed for several widths of the layer, which remarks the robustness of the delta-mechanism to high parallelisation factors. As in the exact layered decoding, the average boost of two times in the convergence speed is shown.

Low Complexity LDPC Code Decoders for Next Generation Standards

“…a layer spanning multiple rows), but collision-free decoding can be achieved only for those codes where the rows of the parity matrix are grouped into subsets in which the column weight is at most one [11]. However, it is demonstrated in [19] that approximated layered decoding is very robust even in the support of highly non-layered codes.…”

“…This codeword size flexibility is the most challenging aspect of this standardized LDPC code family. The interest of the standardization committee in the improvement in throughput and communications performance achievable through layered decoding (see Section 3.1) is evident since an optimal sequence of layers [19] is specified for two of the code classes [2].…”

Improved synchronization, channel estimation, and simplified LDPC decoding for the physical layer of the DVB-T2 receiver

“…Thus, further efficient manipulation of the structure of the parity check matrix can make it suitable for layered decoding [27][28][29].…”

“…The employed decoder makes use of the concept of layered decoding [28,30,31]. Layered decoding approaches the parity check matrix as a sequence of elementary matrices or layers.…”

Architecture and Finite Precision Optimization for Layered LDPC Decoders

“…The FEC supports eleven code rates for the DVB-S2 standard and is reduced to six code rates for the DVB-T2 standards. The LDPC codes defined by the DVB-S2,-T2,-C2 standards are structured codes or architecture-aware codes (AA-LDPC [3]) and can be efficiently implemented using the layered decoder architecture [4], [5] and [6]. The layered decoder benefits from three architecture improvements: parallelism of structured codes, turbo message passing, and Soft-Output (SO) based Node Processor (NP) [4], [5] and [6].…”